Inorganic Chemistry

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Inorganic Chemistry

Content
INC: Inorganic Chemistry
Paper
Tittle
ID
24 PREPARATION OF CRYSTALLINE NANOSEEDS
OF BEA STRUCTURETO INDUCE FORMATION
OF ZEOLITE BETA
45 A COLORIMETRIC SENSOR BASED ON 3,5DIHYDROXYTOLUENE AND 4-NITROPHENYL
FOR ANION
81
102
128
147
151
SYNTHESIS AND CHARACTERIZATION OF
COPPER(II) AND NICKEL(II) COMPLEXES OF
HEXAAZA MACROCYCLIC LIGANDS
Cu(II) AND Zn(II) COMPLEXES OF
POLYDENTATE SCHIFF BASE LIGANDS:
SYNTHESIS, CHARACTERIZATION,
PROPERTIES AND BIOLOGICAL ACTIVITY
SOME FIRST ROW TRANSITION COMPLEXES
WITH ACETYLACETONATE AND
TETRAAZAMACROCYCLIC LIGANDS FOR
ANTIBACTERIAL ACTIVITY
Authors
Pages
Siriluck Tesana,
Aticha Chaisuwan
166-169
Paengkwan Jansukra,
Apisit Songsasen,
Thawatchai Tuntulan,
Boontana Wannalerse
170-173
Surachai Kongchoo,
Anob Kantacha,
Sumpun Wongnawa
Abdulaziz M. Ajlouni,
Ahmed. K. Hijazi,
Ziyad A. Taha ,
Waleed Al Momani
Tossapon Phromsatit,
Supakorn Boonyuen,
Natthakorn Phadugsak ,
Pornsan Luangsriprech
174-177
ONE POT SYNTHESIS OF FREE BASE MESOJantima Sukjan,
TETRA (SUBSTITUTED PHENYL) PORPHYRINS Supakorn Boonyuen,
Wootthiphan Jantayot
Wootthiphan Jantayot,
LONG CHAINED PORPHYRIN DERIVATIVES
Supakorn Boonyuen,
AND COBALT COMPLEXES
Jantima Sukjan,
Kamolnate Jansaeng
178-181
182-186
187-189
190-193
204
214
261
281
289
316
366
380
397
SYNTHESES OF MAGNETIC NANOCOMPOSITE
SIZE SERIES
PREPARATION OF PERCHLORTE ANION
SELECTIVE MEMBRANE ELECTRODES FROM
DONNAN EXCLUSION FAILURE
PHENOMENON INDUCED BY METAL IONS
BIMETALLIC ALUMINUM COMPLEXES
SUPPORTED BY METHYLENE BRIDGED
BIS(PHENOXY-IMINE) LIGANDS FOR THE ROP
OF RAC-LACTIDE
GOLD NANOPARTICLES WITH POLYANILINE
FOR SELECTIVE COUPLING AND OXIDATION
REACTIONS OF ARYL BORONIC AND ITS
SUBSTITUTES
CRYSTAL STRUCTURE OF SILVER(I)
CHLORIDE COMPLEX WITH
N-ALLYLTHIOUREA AND
TRIPHENYLPHOSPHINE
CADMIUM(II) COMPLEX WITH
4,4'-BIPYRIDINE AND CINNAMIC ACID
Wishulada Injumpa,
Numpon Insin
Sutida Jansod,
Praput Thavoryutikarn,
Wanwisa Janrungroatsakul,
Wanlapa Aeungmaitrepirom,
Thawatchai Tuntulani
Nattawut Yuntawattana,
Pimpa Hormnirun
194-196
197-200
201-204
Vithawas Tungjitgusongun,
Ekasith Somsook
205-207
Mareeya Hemman,
Chaveng Pakawatchai,
Saowanit Saithong ,
Sujittra Youngme
Sirinart Chooset,
Anob Kantacha,
Arunpatcha Nimthong,
Sumpun Wongnawa
Phatthareeya Suriya,
Ratchadaporn Puntharod
208-210
Uthaiwan Injarean,
Pipat Pichestapong,
Yoreeta Marnchareon,
Sarin Cheephat,
Boonnak Sukhummek
PREPARATION OF BaZr1-xYxO3-BASED PROTON Suttiruk Salaluk, Apirat
CONDUCTING ELECTROLYTE USING TEALaobuthee, Chatchai
217-220
SYNTHESIS OF CALCIUM SILICATE FROM
SHELL OF POMACEA CANALICULATA AND
RICE HUSK ASH BY MECHANOCHEMICAL
METHOD
EQUILIBRIUM EXTRACTION OF URANIUM
AND THORIUM MIXTURES IN 4 M HNO3
WITH 5 AND 10% TBP/KEROSENE
211-213
214-216
221-224
479
564
590
613
METAL PRECURSOR BY THE SOL-GEL
METHOD
DEVELOPMENT OF IMPROVED IRON
CHELATORS
ONE-POT SYNTHESIS OF CuO/ZnO
NANOSTRUCTURE WITH DISCRETE CuO
NANOPARTICLES ON ZnO HEXAGONAL
PLATE
OPTICAL SENSING PROPERTIES OF
PLASTICIZED POLYMERIC MEMBRANE
INCORPORATING N,N'ETHYLENEBIS(SALICYLIMINE) AS
TRANSITION METAL ION-SELECTIVE
IONOPHORE
PREPARATION OF PROTIC IONIC
LIQUID/POLYVINYLPYRROLIDONE
COMPOSITES WITH ENHANCED
HYDROPHOBICITY
Veranitisagul, Panitat Hasin
and Nattamon Koonsaeng
Filip Kielar
225-228
Karnrat Hongpo,
Karaked Tedsree
229-232
Jiraporn Pandoidan,
Phetlada Kunthadee
233-235
Nuttakarn Moolthong,
Natkritta Maipul ,
Phawit Putprasert
236-238
166
PREPARATION OF CRYSTALLINE NANOSEEDS OF BEA
STRUCTURETO INDUCE FORMATION OF ZEOLITE BETA
Siriluck Tesana and Aticha Chaisuwan*
Department of Chemistry, Faculty of Science, Chulalongkorn University, Pathumwan, Bangkok, 10330, Thailand
*E-mail:aticha.c@chula.ac.th,
Abstract: Crystalline nanoseeds were successfully
synthesized using mesoporous SBA-15 as silica source,
aluminium isopropoxide as aluminium source, and
tetraethylammonium hydroxide as organic template. The
TEAOH/SiO2/H2O mole ratio of 0.40/1/7.5 was used. The
starting mixture was sonicated thoroughly prior to
crystallization in an autoclave under autogenous pressure
at 135°C for 48 hours. The product was characterized by
XRD, N2 adsorption and SEM techniques. The XRD
results presented complete phase transformation from
SBA-15 to crystalline seeds. The SEM image showed
uniform shape and size of nanoseeds with the average
size of approximately 160 nm. Nitrogen adsorption data
showed the characteristic behavior of microporous
nanoseeds having specific surface area of 702 m2/g. A
small amount of calcined crystalline nanoseeds was used
successfully as a structure directing agent in the synthesis
of highly thermal stable zeolite beta. It was found that
the structure of zeolite beta was formed under
hydrothermal conditions. In the absence of the crystalline
nanoseeds, an amorphous phase was found with a trace
amount of zeolite Na-P1 but zeolite beta was not
obtained.
1. Introduction
Zeolite beta [1-2]has a three dimensional channel
system with 12-membered ring pore openings. It has
been widely used in several catalytic reactions due to
its large micropore volume, unique pore structure and
high specific surface area [3-6]. Zeolite beta was
usually synthesized by hydrothermal method using
tetraethylammonium hydroxide (TEAOH) as structure
directing agent or template to shorten crystallization
time and to obtain nanocrystals. Unfortunately, the
structure of zeolite beta always partially collapses
during the combustion of organic templatein order to
empty pores and make the zeolite available for
applications[7-8].There have been rare reports about
the synthesis of zeolite beta in the absence of organic
template. In 2008, Xie and coworkers reported the
preparation of zeolite beta without organic
template[9]; nevertheless, zeolite beta could not be
obtained in the absence of calcined zeolite beta as
seeds. The synthesis of zeolite beta via addition of
inorganic seeds has been attempted by several groups
[9-12]. The synthesis of aluminum-rich zeolite beta
(Si/Al ratios of 3.9-6.2) was carried out by adding assynthesized zeolite beta as seeds which contained
organic template [10]. Among various inorganic
cations, only sodium ions provided structure of zeolite
beta with the crystal size around 400 nm. Mordenite
Tel. +66 2218 7619
was thermodynamically more stable than zeolite beta
but in the presence of seeds, zeolite beta phase was
kinetically favored [11-12]. To obtain pure zeolite
beta, seeds were needed to initiate crystal growth of
zeolite beta phase prior to nucleation of mordenite
phase. The crystallization of zeolite beta proceeded on
the surface of seeds. Crystallinity of zeolite beta was
also affected by types of seeds [8].
From our experience, the exothermic combustion
of organic template at high temperature is believed to
cause aluminium leaching from the zeolite framework
to its surface, resulting in the decrease of its
crystallinity [3]. To overcome the degradation in
zeolite structure, the organic template-free synthetic
route has been attempted using our on-site prepared
zeolite beta nanoseeds to induce the structure of zeolite
beta.
2. Materials and Methods
2.1 Chemicals
Tetraethylorthosilicate
(Fluka,
98.0
wt%),
PluronicP123 (Aldrich), hydrochloric acid (Merck, 37
wt%), tetraethylammonium hydroxide (Fluka, 40
wt%), aluminium isopropoxide (Merck, 99.8 wt%),
fumed silica (SiO2,Aldrich, 0.007 µm), sodium
aluminate (Riedel-de Haën), and sodium hydroxide
(Merck,99 wt%) were used as purchased.
2.2 Synthesis
SBA-15 silica was prepared following the method
described in the literature [13].Tetraethylorthosilicate
was acidic hydrolyzed in the presence of Pluronic
P123 and 2M hydrochloric acid at 40°C before
crystallization at 100°C for 48 hours. After washing
and drying at 100 °C, SBA-15 obtained was calcined
at 550°C for 5hours. Aluminium isopropoxide was
dissolved in an aqueous solution of 30 wt%
tetraethylammonium hydroxide. The resulted solution
was added drop-wise to calcined SBA-15 with
vigorous agitation. The gel mixture containing Al2O3:
TEAOH: SiO2: H2O mole ratio of 0.008: 0.40:1.0:7.5
was crystallized at 135 °C for 48 hours.The fine
precipitate was centrifuged, washed and dried at 110
°C before the removal of organic template via
calcination at 550 °C for 5 hours. The calcined
crystalline nanoseeds were used as structure directing
agent for the synthesis of highly thermal stable zeolite
beta by modifying the organic template-free synthetic
Pure and Applied Chemistry International Conference 2015 (PACCON2015)
167
2.3 Characterization
X-ray powder diffraction (XRD) patterns were
collected using Rigaku D/MAX-2200 Ultima-plus
instrument with Cu Kα radiation source (40kV, 30mA)
over 2θ range from 0.7° to 5.0° for SBA-15 and 5.0° to
40.0°for crystalline nanoseeds.Nitrogen adsorptiondesorption experiments of calcined samples were
performed at 77 K on a BEL Japan, BEL-SORP mini
II nitrogen adsorptometer. The specific surface area
was determined using the BET method. The
distribution data of micropore sizes were analyzed by
the MP-plot method. The particle morphology was
determined by a JEOL JSM-6480 LV scanning
electron microscope (SEM).
3. Results and Discussion
Intensity (arbitrary unit)
The XRD patterns of as-synthesized and calcined
SBA-15 samples are shown in Figure 1. They are
similar to the typical pattern of hexagonal structure of
SBA-15 [13-14]. Three well-resolved characteristic
peaks observed at 2θ of 0.86°, 1.46° and 1.68°
wereassigned to (100), (110) and (200) lattice planes,
respectively. After the removal of the organic template
at 550 °C for 5 hours, all peaks shifted to higher angle
by 0.12°, indicating smaller d-spacing value which is
resulted from the unit cell contraction.
2,000 cps
(B)
(A)
2 Theta (degree)
Figure 1 XRD patterns of (A) as-synthesized and (B)
calcined SBA-15.
From Bragg’s theory, nλ = 2dsinθ, d-spacing is
inversely proportional to 2θ. The peak intensities of
calcined SBA-15 silica without the organic template
are obviously about two times of those belonging to
the as-synthesized sample. This phenomenon is normal
for porous material synthesized by using an organic
template as the structure directing agent.
The nitrogen adsorption-desorption isotherms of
calcined SBA-15 as shown in Figure 2 can be assigned
to Type IV which is a characteristic pattern of
mesoporous materials. The SBA-15 sample presented
BET specific surface area of 740 m2g-1 and pore
volume of 1.13 cm3g-1. SEM images of calcined SBA15 in Figure 3 illustrate bundles of rope-like particles
with the average size of particles 39.5 µm.
Volume adsorbed (cm3/gSTP)
route reported by Zhang and coworkers[8]. A solution
containing 3.60 g sodium hydroxide and 0.84 g sodium
aluminate in 87.25 g deionized water was mixed with
8.31 g fumed silica with agitation. To the milky gel
mixture, calcined crystalline nanoseeds were added at
the amount of 2.0 wt% of silica. The whole mixture
was transferred into an autoclave and heated in an
oven at 130 °C for 5 days. After filtration, washing
and drying in an oven at 100 °C, the solid product was
characterized for its structures and pore properties.
Relative pressure (P/P0)
Figure 2 Nitrogen adsorption-desorption isotherms
ofcalcined SBA-15 silica.
Crystalline nanoseeds were synthesized from onsite-prepared SBA-15 silica by incipient wetness
impregnation with the template solution of TEAOH
followed by crystallization at 135 °C for 48 hours. The
XRD patterns of the as-synthesized and the calcined
crystalline nanoseeds are shown in Figure 4. The XRD
pattern of the as-synthesized sample was similar to the
typical one of zeolite beta with the highest peak
located at 2θ of 22.5°. The broad peak at 2θ of 7.68°is
resulted from the convolution of peaks due to the
concurrence of zeolite beta polymorph A (2θ = 6.98°
and 7.74°) and polymorph B (2θ = 7.34° and 8.31°)
[15]. After calcination at 550 °C for 5 hours, the XRD
peak positions are unchanged but the intensity of the
peak at 2θ of 22.5° decreases to about one half due to
the partial decomposition of zeolite structure. No
peaks are observed at 2θ below 5° (not shown). It can
be concluded that phase transformation from SBA-15
to the crystalline nanoseeds of BEA structure can be
accomplished under the reported experimental
condition.
168
15 kV x1,000 10 µm
(A)
15 kV x5,0005 µm
(B)
Volume adsorbed (cm3/gSTP)
The behavior of mesoporous system is not observed
which is correspondent to the XRD result. From BET
calculation, a specific surface area of 702 m2g-1 and a
micropore volume of 0.37 cm3g-1 were found. The
pore size distribution of the crystalline nanoseeds was
found in a micropore range with an average pore size
of 0.6 nm, a typical value for zeolite beta [16-17].The
SEM image of crystalline nanoseeds presents a
uniform shape of spheres with an average particle size
of 160 nm as shown in Figure 6.
Relative pressure (P/P0)
Figure 5 Nitrogen adsorption-desorption
isothermsofthe crystalline nanoseeds.
Figure 3 SEM images of calcined SBA-15 (A)1,000X
magnification and (B) 5,000X magnification.
500 cps
(B)
20 kV x50,000 0.5µm
(A)
2 Theta (degree)
Figure 4 XRD patterns of (A) the as-synthesized and
(B) the calcined crystalline nanoseeds.
The nitrogen adsorption-desorption isotherms of
the crystalline nanoseeds as illustrated in Figure 5 can
be assigned to Type I which is typical for micropores.
Figure 6 SEM image of the calcined crystalline
nanoseeds.
Instead of organic template, a small amount of the
calcined crystalline nanoseeds was used as a structure
directing agent in the synthesis of zeolite beta in this
project. The XRD patterns of solid samples
synthesized in the absence and presence of crystalline
nanoseeds are illustrated in Figure 7. Without
crystalline nanoseeds, zeolite beta was not formed and
169
the solid product was composed of an amorphous
phase and a trace amount of zeolite Na-P1. With the
addition of nanoseeds, the product shows the
characteristic XRD peaks of zeolite beta. After the
calcinations at 550°C for 5 hours, little decrease in
intensity of the peak at 2θ of 22.5° was observed. This
is a good sign indicating the thermal stability of zeolite
beta product. This study indicates that the zeolite beta
prepared via organic free route exhibits more thermal
resistance than those prepared by the conventional
organic template route. This is a benefit of the use of
zeolite beta in industry because most zeolite catalysts
have to be activated at elevated temperatures.
3500
3000
500 cps
2500
(C)
2000
1500
(B)
1000
500
(A)
0
5
10
15
20
25
30
35
40
2 Theta (degree)
References
[1] Auerbach, S.M., Carrado, K.A. and Dutta, P.K., 2003,
Handbook of Zeolite Science and Technology, Marcel
Dekker, USA.
[2] Baerlocher, Ch., McCusker, L.B. and Olson, D.H.,
2007, Atlas of Zeolite Framework Types, Elsevier B.V.,
Netherlands.
[3] Wanchai, K. and Chaisuwan, A., 2013, Chem. Mat.
Res., 3, 31-41.
[4] Serafim, H., Fonseca, I.M., Ramos, A.M., Vital, J. and
Castanheiro, J.E., 2011, Chem. Eng. J., 178, 291-296.
[5] Siffert, S., Gaillard, L. and Su, B.-L., 2000, J. Mol.
Catal. A: Chem., 153, 267-279.
[6] Chen, N.Y., Garwood, W.E., Huang, T.J., Le, Q.N. and
Wing, S.S., 1990, US Pat.4,919,788.
[7] Otomo, R., Yokoi, T., Kondo, J.N. and Tatsumi, T.,
2041, Appl. Catal., A, 470, 318-326.
[8] Zhang, H., Xie, B., Meng, X., Muller, U., Yilmaz, B.,
Feyen, M., Maure, S., Gies, H., Tatsumi, T., Bao, X.,
Zhang, W., Vos, D.D. and Xiao, F.S., 2013, Micropor.
Mesopor. Mater., 180, 123-129.
[9] Xie, B., Song, J., Ren, L., Ji, Y., Li, J. and Xiao, F.S.,
2008, Chem. Mater., 20, 4533-4535.
[10] Majano, G., Delmotte, L.,Valtchev, V. and Mintova, S.,
2009, Chem. Mater., 21, 4184-4191.
[11] Kamimura, Y., Chaikittisilp, W., Itabashi, K.,
Shimojima, A. and Okubo, T., 2010, Chem. Asian J., 5,
2182-2191.
[12] Kamimura, Y., Tanahashi, S., Itabashi, K., Sugawara,
A., Wakihara, T., Shimojima, A. and Okubo, T., 2011,
J. Phys. Chem., 115, 744-750.
[13] Zhao, D., Feng, J., Huo, Q., Melosh, N., Fredrickson,
G.H., Chmelka, B.F., Stucky, G., 1998, Science, 279,
548-552.
[14] Thielemann, J.P., Girgsides, F., Schlögl, R., Hess, C.,
2011, Beilstein J. Nanotechnol., 2, 110-118.
[15] Sagarzazu, A. and González, G., 2013, Mater. Chem.
Phys., 138, 640-649.
[16] Ba´rcia, P.S., Silva, J.A.C., Rodrigues, A.E., 2005,
Micropor. Mesopor. Mater., 79, 145-163.
[17]Mohammadi-Manesh, H., Tashakor, S., Alavi, S., 2013,
Micropor. Mesopor. Mater., 181, 29-37.
Figure 7XRD patterns of the as-synthesized solid
samples (A) in the absence, (B) in the presence of
crystalline nanoseeds and the calcined sample (C) at
550°C for 5 hours.
4. Conclusions
In summary, crystalline nanoseeds of BEA
structure were synthesized from mesoporous SBA-15
silica in the presence of aluminium isopropoxide and
tetraethyl-ammonium hydroxide by crystallization of
the starting mixture at 135 °C for 48 hours. High
crystallinity, large specific surface area and uniform
spherical nanoseeds could be achieved. The highly
thermal stable zeolite beta catalyst was formed in the
presence of a small amount of crystalline nanoseeds.
In the absence of nanoseeds, the synthesis of zeolite
beta was unsuccessful. Therefore, it can be concluded
that the crystalline nanoseeds play an important role as
the structure directing agent in zeolite beta formation.
170
A COLORIMETRIC SENSOR BASED ON 3,5-DIHYDROXYTOLUENE
AND 4-NITROPHENYL FOR ANION
Paengkwan Jansukra1, Apisit Songsasen1, Thawatchai Tuntulani2, Boontana Wannalerse1*
1Department
*
of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Kasetsart University,
Chatuchak, Bangkok, 10900, Thailand
2Supramolecular Chemistry Research Unit, Department of Chemistry, Faculty of Science,
Chulalongkorn University, Patumwan, Bangkok, 10330, Thailand
Author for correspondence; E-Mail: fscibnw@ku.ac.th, Tel. +66 25625555 ext. 2203, Fax. +66 25793955
Abstract: 2,2′-(5-Methyl-1,3-phenylene)bis(oxy)bis(N-(4nitrophenyl)acetamide), L1, has been synthesized and
explored its properties as a colorimetric sensor.
Interactions of receptor L1 with various anions are
investigated by using 1H NMR and UV–vis spectroscopy.
From 1H NMR studies in DMSO, the signal of NH
protons of receptor L1 was found at 10.65 ppm. These
protons disappeared after addition of anions (fluoride,
acetate, phosphate and benzoate) via deprotonation
process. Moreover, the aromatic protons of receptor L1
showed the upfield shift due to enhancement of negative
charges in the system. From UV–vis titration in DMSO,
the absorption at 328 nm of receptor L1 gradually
decreased upon the increment of anions. In the case of
fluoride and acetate, a respective isosbestic point and
new absorption band were observed at 386 nm and 447
nm for fluoride ion and at 400 nm and 443 nm for acetate
ion. The solution color of receptor L1 in DMSO changed
from pale yellow to orange and dark yellow in the
presence of fluoride and acetate ions, respectively. These
results indicated that receptor L1 underwent the charge
transfer process upon interacting with anions. The
receptor L1 is highly selective to fluoride ion over other
anions. The ratio of 1:1 complex between receptor L1 and
fluoride ion was identified by Job’s method.
1.
Introduction
Anions play essential roles in the biological
fields, medical systems including environmental
processes [1-3]. In addition, anions can be used as
indicator for predicting the state of the disease.
Fluoride and acetate ions are vital reactive ions in
biological systems. Both of them are employed in
treatment of health problems such as hypnotics and
cockroach poisons. When they reach extreme levels,
they can contaminate water and soil. Fluoride also
causes diseases such as fluorosis and irregular bone
arrangement [4-6].
Basically, sensor systems are composed of
two units. One is the anion binding unit and another
unit is signalling unit [7]. Both parts are commonly
either linked covalently or associated with noncovalent interaction [8]. The design and synthesis of
anion receptors have used functional groups such as
amide [9], urea/thiourea [10-12] and hydroxyl groups
[13] for anion binding sites. Amide moieties (NH
group) are the most common unit used in anion
receptors due to excellent hydrogen bond donors of the
NH groups for anionic guests. In this work, we have
designed a new receptor L1 based on 3,5dihydroxytoluene and 4-nitrophenyl. Moreover,
receptor L1 is selectively bound to F− and CH3COO−.
The complexation between receptor L1 and various
anions is investigated by using 1H-NMR spectroscopy
and UV-vis spectroscopy.
2. Experimental
2.1 Materials
All reagents for synthesis obtained commercially
were used without further purification. Column
chromatography was performed using silica gel (70230 mesh). In the titration experiment, all anions were
added in the form of tetrabutylammonium (TBA) salts
which were purchased from Sigma-Aldrich Co.
2.2 Apparatus
1
H NMR spectra were obtained on 400 MHz NMR
spectrometer. Elemental analysis (CHNS/O) was
performed on Thermo Scientific TM FLASH 2000. UVvis spectra were recorded on Shimadzu spectrophotometer. MS was carried out on Agilent 1100 Series
LC/MSD Trap. Infrared spectra (4000-400 cm-1) were
obtained by a Perkin Elmer system 2000 Fourier
transform infrared spectrometer.
2.3 UV–vis titration studies
The sensing properties of receptor L1 toward
F−, Cl−, Br−, CH3COO−, C6H5COO− and H2SO4− (as
tetrabutylammonium salts) were investigated by UV–
vis spectroscopy in DMSO. Stock solutions of receptor
L1 and anions were prepared by dissolving in DMSO
(5.0×10−5 M). UV–vis titrations were performed with
steady concentration of receptor L1 and increasing
concentration of anions.
2.4 Synthesis
The synthesis of receptor L1 was shown in Scheme
1. 2-Chloro-N-(4-nitrophenyl)acetamide, (1) was
synthesized according to literature [14] with minor
modifications. 4-Nitroaniline (1.0 g) and triethylamine
(2.28 mL) in dichloromethane (3 mL) were stirred
under N2 for 30 min. Then, a solution of 2chloroacetylchloride (1.3 mL) in dichloromethane (2
mL) was added dropwise. The reaction mixture was
kept stirring until the product was formed as a solid
(24 h). The reaction mixture was extracted with water
and dichloromethane. The combined organic phase
was washed with brine, and dried with anhydrous
Na2SO4. After the solvent was removed, the residue
was purified by column chromatography (silica gel,
dichloromethane) to give a light yellow solid of 1
(0.84 g, 84%). mp:187.6°C. 1H NMR (400 MHz,
171
DMSO-d6, ppm): δ10.87 (s, 1H,-NH), 8.25 (d, 1H,
ArH), 7.85 (d, 1H, ArH), 4.33 (s, 2H, -CH2); FT-IR
(KBr/cm-1) ʋ: 3277 (N-H), 1689 (C=O), 1501, 1341
(N-O), 748(C−Cl). MS: m/z calcd for C8H7ClN2O3Na+ ([M-Na+]), 237.0; found, 237.5.
The receptor L1 was prepared from the
following procedure. 3,5-Dihydroxy-toluene (1.00 g)
and potassium carbonate (2.0 g) were dissolved in 20
mL of acetonitrile under N2 atmosphere. Compound 1
(2.5 g) and sodium iodide in acetonitrile was added
dropwise. The mixture was stirred and refluxed for 16
h. The reaction mixture was extracted with water and
dichloromethane and washed with water. The
combined organic phase was dried with anhydrous
Na2SO4. After the solvent was removed, the residue
was purified by column chromatography (silica gel,
dichloromethane and ethyl acetate = 9:1) to give a pale
yellow solid of L1 (0.54 g) in a yield of 54%. mp:
250.7°C. 1H NMR (400 MHz, DMSO-d6, ppm): δ
10.65 (s, 1H,-NH), 8.20 (d, 1H, ArH), 7.89 (d, 1H,
ArH), 6.47 (t, 1H, ArH), 4.74 (s, 2H, -CH2), 2.25 (s,
3H, -CH3); 13C NMR (DMSO-d6, ppm): 167.54,
158.72, 144.55, 142.47, 139.93, 124.89, 119.28,
108.44, 99.00, 67.11, 21.37; FT-IR (KBr/cm-1) ʋ: 3383
(N-H), 1709 (C=O), 1545,1341 (N-O). MS: m/z calcd
for C23H20N4O8-H+ ([M-H+]), 481.1; found, 481.5.
Anal. Calcd for C23H20N4O8: C 57.50; H 4.20; N
11.66; Found: C 57.52; H 4.24; N 11.65.
receptor L1 the color change from pale yellow to
orange and intense yellow were observed respectively,
as shown Fig.1. These processes occur via charge
transfer process [15].
a
b
c
Figure 1. Color changes of receptor L1 (5×10-5 M) in
DMSO on addition of 4 equiv. of various anions:
receptor L1 (a), F− (b) and CH3COO− (c)
3.1 1H NMR studies
1
H NMR spectra of receptor L1 upon addition
of various anions were carried out in DMSO-d6, as
shown in Fig.2. The receptor L1 exhibited a sharp
signal of NH amide protons at 10.65 ppm in the
spectrum. The NH protons of L1 located at the lower
downfield region due to the hydrogen bonding
interaction between NH protons (amide group) and
DMSO in the solution. Upon addition of acetate,
benzoate, dihydrogen phosphate and fluoride ions, the
NH amide protons at 10.65 ppm disappeared.
Moreover, the aromatic protons of receptor L1 moved
to upfield shift due to the enhancement of electron
density at aromatic region. These results indicated that
the interaction between receptor L1 with CH3COO−,
C6H5COO−, H2SO4− and F− involved the formation of
hydrogen bonding and deprotonation processes [16]. In
the presence of bromide and chloride, the NH protons
slightly shifted to downfield because of weak
hydrogen bonding interaction in Fig. 2C and 2D.
Scheme1. Synthesis of receptor L1
3.
Results and discussion
The colorimetric sensing and sensitivity of
receptor L1 (5×10-3 M) toward various anions such as
F−, Cl−, Br−, CH3COO−, C6H5COO− and H2SO4−
(tetrabutylammonium salt) are investigated. In DMSO
solutions of receptor L1, upon adding 4 equiv. of Cl−
and Br− anions, the solution of L1 did not display in
any color changes. In the case of C6H5COO− and
H2SO4−, the color of solution L1 changes from pale
yellow to light yellow. However, upon addition of
F−and CH3COO− with receptor L1 to the solution of
Figure 2. 1H NMR spectra of receptor L1 (A) in
DMSO-d6 (5 x 10-3 M) upon addition of 4 equivalent
of F− (B), Cl− (C), Br− (D), CH3COO− (E), C6H5COO−
(F) and H2SO4− (G).
172
Figure 3. UV-vis absorption spectra of receptor L1 (5×10−5 M) in DMSO upon addition of (a) F− and (b) CH3COO−
(0 to 20 equivalent).
3.2 UV-vis studies
The binding abilities of receptor L1 with
various anions (F-, Cl-, Br-, CH3COO-, C6H5COO− and
H2SO4-) were examined by using UV–vis spectroscopy
in DMSO at room temperature. The receptor L1
displayed strong absorption band at 328 nm. Upon the
addition 0-20 equiv. of fluoride ions, the absorption
band of receptor L1 gradually decreased and induced a
new absorption band at 447 nm and an isosbestic point
at 386 nm. In case of acetate ions, the receptor L1
displayed a new absorption band at 443 nm and an
isosbestic point at 400 nm, as shown in Fig. 3a and 3b.
These results suggest that the formations of the
complex between receptor L1 and fluoride ion and
acetate ion occur under the internal charge transfer
transition. However, the addition of Br−, Cl−,
C6H5COO− and H2SO4− into the solution of receptor
L1 would give slight decrements of the absorption
band at 328 nm in the spectra.
The ratio of complexation between receptor
L1 and fluoride ion was confirmed by Job's method, as
shown in Fig. 4. The maximum absorption appeared at
the 0.50 mole fraction of [receptor L1]/ ([receptor L1]
+ [F−]), indicating a 1:1 formation of receptor L1 and
fluoride ion.
From the UV–vis absorption titrations, the
association constants of the anion complexes of
receptor L1 were calculated using Benesi–Hildebrand
plot [17]. The association constants, Ka, were listed in
Table 1. The selectivity of receptor L1 exhibited in
order of CH3COO− > C6H5COO− > H2PO4−.
Unfortunately, we could not calculate the association
constants between receptor L1 and spherical anions
due to the deprotonation process (F− ion) and weak
interactions (Br− and Cl− ions).
Table 1: Association constants (Ka, M-1) of receptor
L1 with various anion in DMSO.
anions
Ka, M-1
−
NDa
F
−
ND
Cl
−
ND
Br
−
CH3COO
5.26×103
−
C6H5COO
5.00 ×103
−
H2SO4
1.42×102
a
The association constant could not be determined.
4.
Conclusions
We have successfully designed, synthesized
and characterized a new colorimetric receptor L1. The
receptor L1 utilizes amide NH moieties binding to
anions. Through deprotonation process, the receptor
L1 could act as naked eye sensors for fluoride and
acetate ions.
Acknowledgements
We would like to thank to the Thailand
Research Fund (MRG 5580182), Kasetsart University
Research and Development Institute and Department
of Chemistry, Kasetsart University and the Center of
Excellent for Innovation in Chemistry (PERCH-CIC),
Commission on Higher Education, Ministry of
Education are gratefully acknowledged for financial
support.
Figure4. Job’s plot of receptor L1 with fluoride ion.
173
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174
SYNTHESIS AND CHARACTERIZATION OF COPPER(II) AND
NICKEL(II) COMPLEXES OF HEXAAZA MACROCYCLIC LIGANDS
Surachai Kongchoo1, Anob Kantacha2, and Sumpun Wongnawa1*
1
Department of Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand
2 Department of Chemistry, Faculty of Science, Thaksin University, Patthalung, 93110, Thailand
*
E-mail for Corresponding Author; E-mail: sumpun.w@psu.ac.th, Tel. +66 7428 8443, Fax. +66 7455 8841
Abstract: Two new complexes, [CuL](ClO4)2 (1) and
[NiL](ClO4)2 (2), of the hexaaza macrocyclic ligand 3,10dioctyl-1,3,5,8,10,12-hexaazacyclotetradecane (L), were
synthesized by one-pot condensation of ethylenediamine,
formaldehyde, and octylamine in the presence of
copper(II) and nickel(II) salts, respectively. The
complexes were characterized by elemental analyses
(CHN/O), liquid chromatography-mass spectrometry
(LC-MS), Fourier-transformed infrared spectroscopy
(FT-IR), and UV-Vis spectroscopy. Data from these
techniques indicated that each metal ion combined with
one ligand L and two perchlorate anions. The structures
of these two complexes were then proposed to consist of
metal-ion center, Ni(II) or Cu(II), coordinated to a
square-planar geometry by four secondary amine
nitrogen donors of the hexaaza macrocyclic ligand with
two perchlorato ligands to counter ion molecule the
square planar geometry.
1. Introduction
N-donor atoms hexaaza macrocyclic complexes
bearing pendant arms connected by an additional
bridge (e.g. -(CH2)n-) at one or two pairs of nitrogen
atoms of a macrocycle have received much attention
[1] due to possible applications in catalysis [2-3],
photocatalytic [4], magnetic properties [5], and
antimicrobial activity [6]. Macrocyclic complexes of
transition metals, particular, nickel(II) and copper(II),
are currently widely used as building blocks for
construction of new materials. One of the obvious
advantages of such compounds along with their high
thermodynamic stability and kinetic inertness is the
possibility of synthetically convenient chemical
modification of macrocyclic framework using the onepot condensation methods [7]. The metal ions as
templates and many macrocyclic ligands have been
prepared by the condensation of formaldehyde with
amide. Template synthesis of macrocyclic complexes
is simple reaction as formaldehyde links between two
amine moieties to form methylenediamine linkages
(-N-CH2-N-). The methylenediamine linkage is
unstable when it contains primary amines, R-NH2, in
which R is either aromatic or aliphatic group which
can condense with formaldehyde to form a new N-C
bond [8].
In this work, we report the syntheses of the
complexes of Cu(II) and Ni(II) with hexaaza
macrocyclic ligand, and characterizations by
spectroscopy techniques.
2.1 Materials and physical measurements
All chemicals were obtained from commercial
sources and were reagent grade. Absolute ethanol was
used throughout this synthesis. Infrared spectra of
solid samples as KBr pellets were recorded on a
Perkin-Elmer Spectrum One FT-IR spectrophotometer
in the range 4000-400 cm-1. Electronic absorption
spectra were obtained on a Shimadzu Lambda-1600
UV-Vis spectrophotometer. Elemental analysis of
CHNO was performed using a CE instruments Flash
EA 1112 series, Thermo Quest analyzer. Mass spectra
were recorded by electro-spray ionization (ESI)
technique operating in the positive ion mode, the
solution was injected directly in mass spectrometer
(Waters micromass).
Caution! Perchlorate salts are potentially explosive
and should be handled in small quantities.
2.2 Synthesis of [CuL](ClO4)2 (1)
To a stirred solution of copper(II) chloride
dihydrate (1 mmol) and ethylenediamine (2 mmol) in
absolute ethanol added dropwise a solution of
formaldehyde (4 mmol) and octylamine (2 mmol) in
absolute ethanol (15 mL). The reaction mixture was
refluxed for 24 h. The hot solution was filtered, cooled
and perchloric acid was added slowly. The precipitate
formed was filtered off, washed with absolute ethanol,
and dried in air. Yield: ∼75%. Anal. Calc. for
C24H54N6O8Cl2Cu: C, 41.72; H, 7.88; N, 12.17; O,
17.78. Found C, 41.45; H, 7.81; N, 12.52; O, 17.88%.
2.3 Synthesis of [NiL](ClO4)2 (2)
Complex 2 was prepared similarly to that of
complex 1 except that nickel(II) chloride hexahydrate
was used instead of copper(II) salt. Yield: ∼50%. Anal.
Calc. for C24H54N6O8Cl2Ni: C, 41.92; H, 7.87; N,
12.25; O, 24.68. Found C, 41.62; H, 7.81; N, 12.36; O,
24.74%.
The hexaaza macrocyclic complexes were
synthesized in a one-pot condensation from the
starting materials: copper(II) chloride dihydrate (or
nickel(II) chloride hexahydrate), ethylenediamine,
formaldehyde, and octylamine with in molar ratio
1:2:4:2 according to Scheme 1. The powder products
175
were soluble in organic solvents such as DMSO,
MeCN, DMF, and acetone. Unfortunately, all efforts
failed to grow single crystal suitable for X-ray
crystallography.
macrocyclic complexes reported by Sujatha and coworkers [11-12].
Scheme 1. The preparation of 1 and 2 complexes
3.1 FT-IR spectra of 1 and 2
The preliminary investigation of the hexaazamacrocyclic complexes was done from their FT-IR
spectra (Figure 1.). The FT-IR of 1 and 2 showed the
absence of a strong band in the range 1720-1740 cm-1
assignable to carbonyl group of aldehydic moiety
confirming the condensation reaction [9]. However,
the both complexes a weak band at 1638 cm-1 was
assigned to δ(O-H) of the moisture. The complexes
showed the presence of sharp band around 3241 and
3206 cm-1 corresponding to ν(N-H) of the coordinated
secondary amine of the 1 and 2, respectively. A
medium intensity band appearing in the range 29272857 cm-1 was assigned to ν(sp3 C-H) [10]. In the
region 1100 cm-1, splitting to two peaks at 1121-1118
and 1093-1167 cm-1 could be assigned to perchlorate
ions. The splitting of this peak clearly explained the
presence of coordinated perchlorate. In both
complexes, a band seen at 485-471 cm-1 was probably
due to the formation of M-N bonds [6].
Figure 2. The mass spectra of 1
Figure 1. The FT-IR spectra of 1 and 2
3.2 Mass spectra of 1 and 2
The electro-spray ionization mass spectra of the
perchlorate salts of copper(II) and nickel(II)
complexes were studied in positive mode. Complex 1
showed an intense signal of m/z values at 588.3
(100%) and 590.3 (85%) corresponding to
[CuL(ClO4)]+ and [CuL(ClO4)-2H]+ (Figure 2.)
whereas complex 2 showed peaks at 583.3 (100%) and
585.3 (80%) corresponding to [NiL(ClO4)]+ and
[NiL(ClO4)-2H]+ (Figure 3.). Similar type of mass
spectra patterns have been observed in hexaaza
Figure 3. The mass spectra of 2
3.3 UV-Vis spectra of 1 and 2
The electronic spectra of 1 (Figure 4) showed a
broad band at 502 nm consistent with that reported for
square planar geometry and, thus, was assigned to the
2
Eg → 2T2g [6]. In general, due to Jahn-Teller distortion
Cu2+ complexes give absorption band between 599699 nm [13]. No absorption bands are observed in the
176
region near UV any complex under study which rules
out the possibility of tetrahedral geometry [14].
The electronic spectra of 2 (Figure 5) exhibited two
bands at 452 and 625 nm which could be assigned to
3
A2g (F) → 3T2g (F) and 3A2g (F) → 3T1g (P) transitions,
respectively [6], for the square planar Ni2+ complex
[13].
The electronic spectra found in 1 and 2 were of the
d-d transition type similar to those reported by Firdaus
and co-workers [15].
2E
g
nitrogen atoms of the hexaaza macrocyclic ligand and
two oxygen atoms from perchlorate anions. The
hexaaza macrocyclic occupies the equatorial sites to
form a square-planar geometry leaving the two oxygen
atoms (from two perchlorates) at the axial sites to
counter ion molecule. The macrocyclic itself contains
two each of five- and six-membered rings. A similar
structure was presented in previous research [16-18].
4. Conclusions
Copper(II) and nickel(II) complexes have been
synthesized by the one-pot condensation reaction. The
elemental analyses and LC-MS revealed the
stoichiometry and composition while FT-IR and UVvisible spectra confirmed the bonding features and
stereochemistry of the hexaaza macrocyclic
complexes.
→ 2T2g
Acknowledgements
Figure 4. Electronic absorption spectra of 1
This work was supported by the Songklanagarind
Scholarship for Graduate Studies from the Prince of
Songkla University.
References
3A
2g
3A
2g
→ 3T1g
→ 3T2g
Figure 5. Electronic absorption spectra of 2
From spectroscopic data the structure of both
complexes can be proposed as follows (Figure 6.).
O
O
Cl
O
O
H
N
H
N
N
M
N
N
H
N
H
O
O
Cl
O
O
Figure 6. The proposed structure for 1 and 2 (M =
Cu(II) or Ni(II))
In the proposed structures, the coordination
geometry about each metal-ion center, Ni(II) or Cu(II),
is square planar composed of four secondary amine
[1] Firdaus, F., Fatma, K., Azam, M., Khan, S.N., Khan,
A.U. and Shakir, M., 2008, Transition. Met. Chem., 33,
467-473.
[2] Salavati-Niasari, M., 2004, J. Mol. Catal. A: Chem.,
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963-966.
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Hazard. Mater., 213-214, 19-27.
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2004, Inorg. Chem., 43, 3271-3276.
[6] Husain, A., Nami, S.A.A. and Siddiqi, K.S., 2011, Appl.
Organometal. Chem., 25, 761-768.
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Pritzkow, H., 2010, Russ. Chem. Bull., 59, 1572-1581.
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Li, Y., 2006, Inorg. Chem. Commun., 6, 38-42.
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Chingsubam, P. and Siddiqi, M.Y., 2006, J. Braz.
Chem. Soc., 17, 272–278.
[10] Raman, N., Raja, J.D. and Sakthivel, A., 2008, J. Chill.
Chem. Soc., 53, 1568–1571.
[11] Sujatha, S., Balasubramanian, S. and Varghese, B.,
2009, Polyhedron., 28, 3723-3730.
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Jayaprakashvel, M. and Mathivanan, N., 2012, Inorg.
Chim. Acta., 386, 109-115.
[13] El-Sherif, A. A., 2009, Inorg. Chim. Acta., 362, 49915000.
[14] Patel, M.N., Patel, C.B and Patel, R.P., 1974, J. Inorg.
Nucl. Chem. 36, 3868-3870.
[15] Firdaus, F., Fatma, K., Azam, M., Khan, S.N., Khan,
A.U., and Shakir, M., 2008, Transition. Met. Chem., 33,
467-473.
[16] Husain, A., Moheman, A., Nami, S. A.A. and Siddiqi,
K.S., 2012, Inorganica Chimica Acta., 384, 309-317.
[17] Min, K.S., Park, M.J., and Ryoo, J.J., 2013, Chirality,
25, 54-58.
177
[18] Han, S., Lough, A.J., and Kim, J.C., 2012, Bull. Korean
Chem. Soc., 33, 2381-2384.
178
Cu(II) AND Zn(II) COMPLEXES OF POLYDENTATE SCHIFF BASE
LIGANDS: SYNTHESIS, CHARACTERIZATION, PROPERTIES AND
BIOLOGICAL ACTIVITY
Abdulaziz M. Ajlouni1∗, Ahmed. K. Hijazi1, Ziyad A. Taha1 and Waleed Al Momani2
1Department
of Applied Chemical Sciences, Jordan University of Science and Technology, Irbid 22110, Jordan
2 Department of Allied Medical Sciences, Al Balqa’ Applied University, Jordan
*E-mail:amajlouni@just.edu.jo Tel. : + 962 (0) 2 7201000, Fax : + 962 (0) 2 7095123
Abstract: Four Schiff base ligands bearing a 9fluorenylidene unit, L1-L4 where (L1 = N'-(9H-fluoren-9ylidene)-2,4-dihydroxybenzohydrazide,
L2
=N'-(9Hfluoren-9-ylidene)thiophene-2-carbohydrazide, L3 =N'(9H-fluoren-9-ylidene)furan-2-carbohydrazide, and L4 =2(9H-fluoren-9-ylidene)hydrazinecarbothioamide,
and
their [Zn(L)Cl2] and [Cu(L)Cl2] complexes have been
synthesized. The characterization and nature of bonding
of these complexes were elucidated by elemental analyses,
spectral analyses (1H NMR, FTIR), molar conductivity
measurements and thermo-gravimetric studies. Analytical
and spectral data revealed that L1 coordinates to metal
ions by its imine nitrogen atom and the phenolic oxygen
atom with a 1:1 stoichiometry. The L2-L4 coordinates to
metal ions by their imine nitrogen atom and the carbonyl
oxygen atom with the same stoichiometry. Most of the free
ligands L1-L4 and their complexes exhibit antibacterial
activities against a number of pathogenic bacteria. The
activities of metal complexes are found to be higher than
those of the free ligands.
1. Introduction
Schiff bases are some of the most widely used
organic compounds. They have been shown to exhibit
a broad range of biological activities, including,
antifungal, antibacterial, antimalarial, antiproliferative,
anti-inflammatory, antiviral, and antipyretic properties
[1]. Imine or azomethine groups are present in various
natural, natural-derived, and non-natural compounds.
The imine group present in such compounds has been
shown to be critical to their biological activities [2].
Fluorenone Schiff bases have a potential application
and biological activity in many therapeutic areas such
as antifungal and antitumor activity [3]. The
hydrazones metal complexes such as copper, zinc,
lanathanum and silvers complexes derived from (9Hfluorene-9-ylidine)-thiosemicarbazide,
have
also
shown many therapeutic activities [4].
In this work, different hydrazones containing
fluorenone Schiff bases L1-L4, and their Cu(II) and
Zn(II) complexes have been synthesized and
characterized by many physical and spectroscopic
techniques including elemental analyses, spectral
analyses (1H NMR, FT-IR), molar conductivity, and
thermogravimetric analysis. The biological activities
of these compounds were investigated by evaluating
the antibacterial behaviors against various pathogenic
bacterial strains using agar diffusion method.
H
N
O
N
H
N N
HO
O
S
HO
O
L2
L1
H
N
H
N
S
N
O
N
H2N
L3
L4
Figure 1. Structures of the Schiff base ligands L1-L4
Experimental
All solvents used were of analytical grade
purchased from Aldrich Chemical Company and were
used without further purification. Copper (II) chloride
dihydrate CuCl2·2H2O and anhydrous zinc (II)
chloride ZnCl2 were purchased from Sigma Aldrich
Chemical Company and used as received. Acid
hydrazides and 9H-fluoren-9-one were purchased from
Merck Schuchardt. The metal ions were determined by
EDTA titration using xylenol orange as an indicator
[5]. Carbon, nitrogen and hydrogen analyses were
performed using a Vario EL elemental analyzer.
Infrared spectra (4000–400 cm−1) were obtained with
KBr discs on a JASCO FT-IR model 470
spectrophotometer. 13C NMR and 1H NMR spectra of
the complexes were recorded on a Bruker AVANCE400 MHz NMR spectrometer. Spectra were taken in
DMSO-d6 using TMS as an internal reference. The
molar conductance measurements were carried out in
DMF using a WTW LF 318 model conductivity meter
equipped with a WTW Tetracon 325 conductivity cell.
Thermal analyses were performed on a PCT-2A
thermo balance analyzer operating at a heating rate of
10 ºC /min in the range of ambient temperature up to
700 ºC under N2.
General procedure for synthesis of hydrazones
A mixture of the respective acid hydrazides (1
mmol) and fluoren-9-one (1 mmol) in ethanol (30 ml)
in the presence of two drops of acetic acid was
refluxed for 4 h. Upon cooling L1-L4 were obtained
as crude products. The products were collected by
179
filtration, washed with cold ethanol, and air-dried. The
microcrystalline material obtained was recrystallized
from hot ethanol Table 1.
3. Results and discussion
Elemental analysis and molar conductivity
L1:N'-(9H-fluoren-9-ylidene)-2,4dihydroxybenzohydrazide, m.p. 214-216⁰C, 1H-NMR
(DMSO-d6, δ, ppm): 11.93 (s, 2H, OH); 11.35 (s, 1H,
NH), 8.41–6.18 (m,11H, C–H Aromatic). 13C NMR
(100 MHz, (DMSO-d6, δ, ppm)): 165.3 (C=O). 153.4
(C=N), 162.0 (2C-OH), 133,4, 132.4, 130.6, 128.9,
127.6, 126.5, 125.8, 125.3, 124.9, 124.8, 123.9, 122.4,
118.2, 117.8. 112.8.
L2:N'-(9H-fluoren-9-ylidene)thiophene-2carbohydrazide. m.p. 178-182⁰C, 1H-NMR (DMSO-d6,
δ, ppm): 10.85 (s, 1H, NH), 8.47–7.28 (m,11H, C–H
Aromatic).
13
C NMR (100 MHz, (DMSO-d6, δ, ppm)): 170.6
(C=O),155.2 (C=N), 133,4, 132.4, 130.6, 128.6,
127.6,126.5, 125.8, 125.3, 124.9, 124.8, 123.9, 122.4,
118.2, 117.8. 112.2
L3: N'-(9H-fluoren-9-ylidene)furan-2-carbohydrazide,
173-177⁰C, 1H-NMR (DMSO- d6, δ, ppm): 10.85 (s,
1H, NH), 8.47–7.28 (m,11H, C–H Aromatic).
13
(C=O),155.2 (C=N), 133,4, 132.4, 130.6, 128.6,
127.6, 126.5, 125.8, 125.3, 124.9, 124.8, 123.9, 122.4,
118.2, 117.8. 112.2
L4:2-(9H-fluoren-9-ylidene)hydrazinecarbothioamide,
m.p.155-157⁰C, 1H-NMR (DMSO-d6, δ, ppm): 11.24
(s, 2H, NH2), 10.78 (s, 1H, NH2), 8.57–7.48 (m,11H,
C–H Aromatic).
13
(C=S). 155.8 (C=N), 147.3, 134,4, 131.4, 130.6, 128.6,
127.6, 125.8, 124.9, 124.3, 123.9, 122.4, 119.5.
Synthesis of the complexes
A 1.0 mmol of a ligand was dissolved in 25 mL
methanol. To this solution, a 25 mL methanol solution
of 1.0 mmol CuCl2 was added dropwise. The reaction
mixture was stirred for 4 hours at room temperature.
The precipitated complex was separated from the
solution by filtration, purified by washing several
times with cold methanol, and then dried for 24 hours
under vacuum at room temperature. The other
complexes were prepared following the same
procedure.
Table 1 lists the elemental analysis data, and
molar conductivities of L1-L4 and their metal
complexes. All of metal complexes are air stable nonhygroscopic powder, partially soluble in water and
most
organic
solvents.
The elemental compositions (C, H, N and metals) of
the L1-L4 and the corresponding metal complexes are
relatively close to those calculated based on molecular
formulae proposed. The molar conductivity data for all
complexes in DMF solution at room temperature are in
the range of "18–50" S cm2 mol-1. This range of
conductivity is very common for non-electrolyte
solutions [6], and indicates that the anions are directly
bonded to the metal ions rather than exist as free ions
in the solution or counter anion in the solid lattice.
Infrared spectral analysis.
The most diagnostic infrared spectral bands
of L1-L4 and their metal complexes are listed in table
2. The IR spectrum of L1 reveals bands at 3473, 1664,
1627 and 1279 cm-1, which are assigned to ν(OH),
ν(C=O), ν(C=N), and ν(Ar–O) respectively. Upon
complexation with Zn(II) and Cu(II), the C=N bands
shift to 1604 and 1611 cm−1, respectively, which
indicates that the metal is coordinated to the schiff
base via the nitrogen atom of the azomethine group
[7]. This was confirmed by the appearance of new
bands at 491 and 492 cm-1 related to υ (Zn–N) and υ
(Cu–N) [8], respectively. The IR spectrum of the free
ligand L1 exhibits a broad band between 3600 and
3200 cm−1 with a maximum at 3473 cm−1 assigned to
the stretching frequency of the phenolic hydroxyl
substituent υ(O–H) which probably involving an
intramolecular hydrogen bonding. Upon complexation
with Zn(II) and Cu(II) to form, presumably,
[Zn(L1)Cl2] and [Cu(L1)Cl2] complexes, the intensity
of the υ (O–H) band increases and the maximum bands
(appear at 3473 cm-1 in the free ligand) are shifted to
3491 and 3492 cm−1, respectively. The remain of these
bands in the complexes spectra with few shifts show
that the hydroxyl oxygen atom is coordinated to the
metal center, Zn(II) or Cu(II), without proton
displacement. The coordination via the oxygen atom
was further supported by the appearance of new bands
at 615 and 617 cm−1, which may be assigned for υ
(Zn–O) and υ (Cu–O) [9], respectively. Furthermore,
the 1H NMR spectrum of the [Zn(L1)Cl2] complex
shows the presence of the OH signal at δ 11.93
confirming the IR data. Other IR bands related to υ
(NH), υ (C=O), and υ (Ar–O) have been appeared in
both free ligand and complex spectra with some shifts
due to the change in the environment after
complexation [10]. The IR spectra of the Zn(II) and
Cu(II) complexes with L2 and L3, display that the
Scheme 1. Synthetic Pathway for Compounds L1-L4
180
Table 1. Analytical data for the prepared compounds and molar conductance values for metal complexes.
C (%) found (calc.)
H (%)found
N (%)found
Metal (%)found
S (%)found (calc.)
Yield aΛ m
72.08 (72.71)
4.33 (4.27)
8.56 (8.49)
87
50.81 (51.47)
3.10 (3.02)
6.19 (5.99)
14.32 (14.06)
82
18.18
51.78(51.68)
3.01 (3.05)
5.57 (6.02)
13.75 (13.64)
86
19.28
71.48 (71.03)
4.18 (3.97)
9.25 (9.20)
10.32 (10.54)
90
49.33 (49.06)
2.84 (2.74)
6.69 (6.63)
14.61 (14.88)
7.32 (7.28)
85
33.28
48.78 (49.27)
2.71 (2.76)
6.12 (6.38)
14.56 (14.48)
7.38 (7.31)
84
39.75
74.58 (74.99)
4.29 (4.20)
9.80 (9.74)
90
51.54(51.12)
3.01(2.85)
6.68(6.60)
15.11(15.41)
79
34.88
52.69 (52.61)
3.10 (2.90)
6.76 (6.63)
14.20 (15.05)
82
37.87
66.20(66.38)
4.42(4.38)
16.38(16.54)
12.32 (12.66)
93
43.03(43.16)
3.09(2.89)
10.63(10.85)
16.60(16.71)
7.30 (7.23)
75
49.55
43.83(43.36)
3.09(2.90)
10.77(10.79)
16.74(16.35)
8.39 (8.27)
79
48.85
a
Λ m: Molar conductance (Ω-1 cm-1 mol-1) of 1 x 10-3 M solution in DMF at room temperature.
and the decomposition starts around 300°C and finished around 500°C with
υ(C=O) and υ(C=N) bands are shifted to lower
one decomposition step,
frequencies compared to the free ligands indicating
that the carbonyl oxygen atom and the azomethine
whereby the complexes decomposed in many stages.
nitrogen atoms are involved in the coordination Table
The first stage of the decomposition of Zn(L1)Cl2
2. This was further confirmed by the appearance of
complex is in the range of 218-333 °C may be to loss
new absorption bands between 595-600 and 489-495
of
two HCl molecules with a mass loss of 15.09 %
cm-1 assigned to υ(M-O) and υ(M-N), respectively
which is consistent with the theoretical value (15.24
[11]. The characteristic bands of the aromatic rings in
%). The second stage occurs between 333-500 °C with
the spectra of respective complexes remain almost
a mass loss of 71.13 % may be due to the loss of the
unshifted. The above arguments indicate that L2 and
organic moiety and is consistent with the theoretical
Compound
L1
[Zn(L1)Cl2]
[Cu(L1)Cl2]
L2
[Zn(L2)Cl2]
[Cu(L2)Cl2]
L3
[Zn(L3)Cl2]
[Cu(L3)Cl2]
L4
[Zn(L4)Cl2]
[Cu(L4)Cl2]
Table 2: Major infrared spectral data for the free ligands L1-L4 and their metal complexes (cm-1).
Compound
L1
[Zn(L1)Cl2]
[Cu(L1)Cl2]
L2
[Zn(L2)Cl2]
[Cu(L2)Cl2]
L3
[Zn(L3)Cl2]
[Cu(L3)Cl2]
L4
[Zn(L4)Cl2]
[Cu(L4)Cl2]
υ (OH)
3473
3489
3491
-
υ (NH)
3206
3341
3353
3200
3222
3227
3220
3219
3220
3200
3215
3216
υ (C=O)
1664
1664
1642
1648
1632
1638
1642
1626
1622
-
υ (C=N)
1627
1604
1611
1601
1584
1589
1594
1572
1574
1587
1578
1574
L3 behave as neutral bidentate ligands and the
coordination occurs via the carbonyl oxygen and the
azomethine nitrogen atom. The IR spectra of the Zn(II)
and Cu(II) of L4 complexes show the υ (C=S) and υ
(C=N) bands are shifted to lower frequencies
compared to the free ligands. Suggesting that (C=S)
and (C=N) coordinate with the metal by the sulfur
atom and azomethine nitrogen atom Table 2.
Thermal studies
Thermogravimetric (TGA) and differential
thermogravimetric (DrTGA) analyses were carried out
for L1-L4. The TGA-DrTGA curves show that ligands
L1-L4 are thermally stable in the range of 50-300 °C
υ (C-O)
υ (C-S)
υ (C=S)
υ (M-O) υ (M-N)
1279
1256
615
491
1261
617
492
1358
1318
598
489
1320
600
495
592
483
591
481
1409
1385
603
483
value (70.81 %). The last step is the oxidation of metal
- give metal- oxide [12].
1389
603
480
(II) to
Antibacterial activity
The antibacterial screening data show that the
complexes exhibit antimicrobial properties, and the
metal chelates exhibit more inhibitory effects than the
parent ligands Table 3. All synthesized compounds
showed high to moderate antimicrobial activities
against the Gram-negative bacteria tested. The highest
activities were found against Klebsiella pneumonia.
On the other hand, Pseudomonas aeruginosa was
found to be resistant to all free ligands L1-L4 and to
their complexes. L2 and its metal complexes inhibit
most of the tested microorganisms. All synthesized
compounds showed moderate, poor, and even non-
181
Table 3. Antibacterial activities of the free ligands L1-L4 and their metal complexes against test bacteria using
agar well diffusion.
Gram (− ) bacteria
Pm
++
++
++
++
+++
++
+
+
+
+++
Gram (+) bacteria
Sp
+
+
+
+
+
+++
Tested compounds
Ec
Kp
Se
Pa
Sa
En
+
+
+
+
L1
[Cu(L1)Cl2]
++
+++
+
+
[Zn(L1)Cl2]
++
+++
+
+
+
++
++
+
+
L2
[Cu(L2)Cl2]
++
+++
+++
++
+
[Zn(L2)Cl2]
++
++
++
+
++
++
++
L3
[Cu(L3)Cl2]
++
++
[Zn(L3)Cl2]
++
++
++
++
++
L4
[Cu(L4)Cl2]
++
+++
++
[Zn(L4)Cl2]
+++
+++
++
DMSO (-ve control)
Oxytetracycline
+++
+++
+++
++
+++
++
(+ve control)
Ec: Escherichia coli; Kp: Klebsiella pneumonia; Pm: Proteus mirabilis; Se: Salmonella enteritidis; Pa: Pseudomonas aeruginosa; Sa: Staphylococcus aureus; Sp:
detectible antimicrobial activities against the Gramproviding financial support for this Project (No.2011
positive bacteria tested.
/202).
The higher activities of the complexes compared to the
free ligands may be attributed to chelation, which
reduces the polarity of the metal ion by partial sharing
of the positive charge with donor atoms of the ligand
[13]. This increases the lipophilic character, favouring
the permeation through lipid layers of the bacterial
membrane. Higher activities observed against the gram
negative bacteria can be explained by considering the
effect on lipo–polysaccharide (LPS), a major
component of the surface of gram negative bacteria
[14]. LPS is an important entity in determining the
outer membrane barrier function and the virulence of
Gram negative pathogens. The free ligands L1-L4 can
penetrate the bacterial cell membrane by coordination
of the metal ion through oxygen or nitrogen donor
atoms to LPS which leads to the damage of the outer
cell membrane and consequently inhibits the growth of
the bacteria [15].
4. Conclusions
Four
hydrazone
compounds,
L1-L4,
containing a fluorenylidene unit and their Zn(II) and
Cu(II) complexes were synthesized and characterized
by different techniques. The compounds L1-L4 can
coordinate to a metal center in a bidentate fashion.
Most of the free ligands and the synthesized
complexes exhibit antibacterial activities against a
number of pathogenic bacteria. The metal complexes
show higher activities compared to those of the free
ligands.
References
[1] Fraga, C. and Barreiro, E., 2006, Curr. Med. Chem.
13 167-198.
[2] Rollas, S. and Küçükgüzel S¸, 2007, Molecules 12
1910-1939.
[3] Narasimhan, B., Kumar, P. and Sharma, D., 2010,
Acta Pharm. Sci. 52 169-180
[4] Ajlouni, A., Mhaidat, I., Al Momani, W., Taha, Z,.
Al Zouby, M,.; , 2013, Jordan Journal of
Chemistry, 8 (4) 225-236.
[5] Welcher,F. J. The Analytical Uses of EDTA,
Van Nostrand, New York, 1995, p.50.
[6] Geary. W., Coord. Chem. Rev., 1971, 81-122.
[7] Raman N,; Kulandaisamy A,; Shunmugasundaram
A,; Jeyasubramanian K, 2001, Transition Metal
Chemistry., , 26 131-135.
[8] Sumanta K P, Rojalin S and Vadivelu M 2008
Polyhedron, 27 805
[9] Chakraborty D and Chen E Y-X, 2003,
Organometallics, 22 769
[10] Paolucci, G.; Stelluto, S.; Sitran, S., 1985, Inorg. Chim.
Acta., , 110, 19–23
[11] Canpolat, E.; Kaya, M., J. 2002, Coord. Chem., , 55,
961-968.
[12] Wang, W., Huang, Y., and Tang, N., 2007
Spectrochim. Acta A, 66 1058.
[13] Kantouch, A .; El-Sayed A.,2008, Int. J. Biol.
Macromol., 43, 451-459.
[14] Taha, Z. A.; Ajlouni, A. M.; Al Momani, W.; 2012,." J.
Luminescence, 132, 2832-2841.
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Shaqra,Q. M.;. 2012, Asian Pacific Journal of Tropical
Biomedicine, 1-4.
Acknowledgements
The authors are very grateful to the Jordan University
of Science and Technology Research fund for
182
SOME FIRST ROW TRANSITION COMPLEXES WITH
ACETYLACETONATE AND TETRAAZAMACROCYCLIC LIGANDS FOR
ANTIBACTERIAL ACTIVITY
Tossapon Phromsatit, Supakorn Boonyuen*, Natthakorn Phadugsak and Pornsan Luangsriprech
Department of Chemistry, Faculty of Science and Technology, Thammasat University, Pathumthani 12120, Thailand
*E-mail: chemistrytu@gmail.com
Abstract: The complexes with two types of ligands, metal
acetylacetonate complexes (M(acac)2 where M = Cu2+
and M(acac)3 where M =Al3+, Mn3+, Fe3+ and Co3+) and
metal tetraazamacrocyclic complexes (ML[1] and ML[2],
where M = Ni2+, Cu2+ and Zn2+ and L[1] = 5,7,7,12,14,-14
hexamethyl-1 ,4 ,8 ,-1 1 tetraazacyclotetradeca4 ,-1 1 diene
perchlorate and L[2] = 7,14-diethyl-5,6,7 ,1 2 ,1 3,-1 4
hexamethyl-1 ,4 ,8 ,1 1 -tetraazacyclotetradeca4 ,-1 1 diene
perchlorate) have been synthesized and characterized.
The structures of synthesized complexes were confirmed
by IR, 1H-NMR, 13C-NMR, UV-Vis spectroscopy. All
compounds have been screened for their antibacterial
activityusing
disc
diffusion
technique.
The
microorganism used for antibacterial investigation
included Escherichia coli (E. coli) and staphylococcus
aureus (S. aureus).All complexes exhibited appreciable
activity especially CuL[1] and NiL[1], suggesting a
potential to develop for medical applications.
1. Introduction
The synthesis and study of macrocyclic complexes,
including chelating complexes have undergone
tremendous growth in recent years. Their
complexation chemistry with a wide variety of metal
ions has been extensively studied. For various
applications, tetraaza macrocyclic ligands are of
special interest, and coordinating side chain may
increase the stability of the metal complexes and the
selectivity between various metal ions [1 - 3]. The
coordination chemistry of square planar metal
complexes, involving nitrogen donor ligands, has
excited great interest among chemists in recent years
due to the catalyst application and relevance to
bioinorganic system. The metal complexes with
tetraaza macrocyclic ligands and acetyl acetonate
ligands are studied. Various biological applications
such as antifungal, antibacterial and anticancer activity
of synthesized transition metal complexes have been
carried out [4 - 6]. The ligands and complexes
described in this article have been synthesized and
characterized
with
various
physicochemical
techniques. Furthermore, antibacterial activities of the
ligands and their transition metal complexes have been
determined by screening of the compounds against
various bacterial strains. The results were compared
with standard drugs [7].
2.1 Measurement
Elemental analysis of C and H were performed on
Perkin Elmer (series II) CHNS/O Analyzer.
The electronic spectra were recorded on Shimadzu
UV-vis spectrophotometer (solution) and Shimadzu
UV- spectrophotometer(UV-2600 Series) (solid state).
Samples were prepared in quartz cells of 10 mm path
length in water (tetraaza macrocyclic complexes),
methanol and DMSO (acetyl acetonate complexes),
and spectra were recorded at room temperature.
The FT-IR spectra were recorded on a Perkin
Elmer infrared spectrophotometer (spectrum GX)
using the Nujol, NaCl(tetraaza macrocyclic
complexes)and KBr pellet technique (acetyl acetonate
complexes).
1
H-NMR and 13C-NMR spectra were recorded with
a Bruker (FT-NMR advance 400 MHz) spectrometer
in chloroform-d using TMS as the internal standard.
2.2 Synthesis of tetraaza macrocycilc ligands and their
complexes.
The ligands (L[1] and L[2]) were prepared by
mixing ethylene diamine (C2H8N2, 6.6 ml, 1 mol.) and
methanol (CH3OH, 5 ml) in a beaker and kept in an ice
bath (5°C). Then, perchloric acid (HClO4, 12.02 ml,1
mol.) was added (pH=7). Then, a proper ketone was
added (acetone, C3H2O for synthesis of ligand L[1],
C16H32N4Cl2O8, and ethyl methyl ketone, C4H8O for
synthesis of ligand L[2], C22H44N4Cl2O8), and the
mixture was kept in the freezer overnight. The mixture
was filtered and washed with acetone and dried under
vacuum, the white crystals are obtained. (Ligand L[1],
10.3304g, 21.57%, L[2], 9.0251g, 16.03%)
Each of methanolic solution of metal-ligands(M=
Ni2+, Cu2+, and Zn2+L[1], C16H32N4Cl2O8, 0.4790 g,
L[2], C22H44N4Cl2O8, 0.5630 g, 0.001 mol.) was
prepared in a round bottom flask, by mixing the solid
ligand with methanol (CH3OH, 30 ml). Each ligand
solution was reacted with various metal acetate
(Ni(OAc)2•4H2O, 0.2487 g, Cu(OAc)2•4H2O, 0.2536
g, and Zn(OAc)2•2H2O, 0.2195 g, 0.001 mol.). Then
the mixture was refluxed for 1 hr. The solution was
evaporated to concentrate before crystallization. Each
metal complex was separately filtered, washed with
cool methanol and dried in vacuum. (NiL[1], 0.2693 g,
50.08%, CuL[1], 0.3022 g, 55.09%, ZnL[1], 0.2246 g,
40.21%, NiL[2], 0.2481 g, 39.84%, CuL[2], 0.2590 g,
40.72% and ZnL[2], 0.1312 g, 20.7%).
183
Ligand L[1]: FT-IR (Nujol, NaCl): 3154.06 (N-H
Vibration), 1543.07 (NH2+ str.), 1667.85 (C=N str.).
1
H-NMR (DMSO): δ,ppm. 3.2 (N-H), 2.5(-CH2), 2.1(CH3). 13C-NMR (DMSO): δ, ppm. 44.45 (-CH2), 35.84
(-CH3).
Ligand L[2]: FT-IR (Nujol, NaCl): 3147.57 (N-H
Vibration), 1541.82 (NH2+ str.), 1667.77 (C=N str.).
1
H-NMR (DMSO): δ,ppm. 3.2 (N-H), 2.5(-CH2), 2.1(CH3). 13C-NMR (DMSO): δ,ppm. 40.07(-CH2), 31.10
(-CH3).
a
a
b
Figure 2 structure of metal ligandL[1](a) and metal
ligandL[2](b) where M = Ni, Cu and Zn
b
Figure 1 structure of ligand L[1](a) and ligand L[2](b)
NiL[1]: FT-IR (Nujol, NaCl): 3169.79 (N-H
1
H-NMR
Vibration),
1662.11
(C=N
str.).
(DMSO):δ,ppm. 3.2 (N-H), 2.6 (-CH2), 1.9 (-CH3).
13
C-NMR (DMSO): δ,ppm. 39.70 (-CH2) 24.59 (CH3).
CuL[1]: FT-IR (Nujol, NaCl): 3169.25 (N-H
Vibration), 1653.74 (C=N str.). 1H-NMR (DMSO):
δ,ppm. 3.4 (N-H), 2.5 (-CH2). 13C-NMR
(DMSO):δ,ppm. 40.09 (-CH2).
ZnL[1]: FT-IR (Nujol, NaCl): 3212.35 (N-H
δ,ppm. 3.4 (N-H), 2.5 (-CH2), 2.1 (-CH3). 13C-NMR
(DMSO): δ,ppm. 40.09 (-CH2) 31.12 (-CH3).
NiL[2]: FT-IR (Nujol, NaCl): 3212.05 (N-H
δ,ppm. 3.3 (N-H), 2.5 (-CH2), 1.9 (-CH3). 13C-NMR
(DMSO): δ,ppm. 40.07 (-CH2) 25.04 (-CH3).
CuL[2]: FT-IR (Nujol, NaCl): 3124.85 (N-H
δ,ppm. 3.3 (N-H), 2.5 (-CH2). 13C-NMR (DMSO):
δ,ppm. 40.01 (-CH2).
ZnL[2]: FT-IR (Nujol, NaCl): 3149.44 (N-H
δ,ppm. 2.8 (N-H), 2.5 (-CH2), 2.0 (-CH3). 13C-NMR
(DMSO): δ,ppm. 40.06 (-CH2) 31.11 (-CH3).
2.3 Synthesis acetylacetonate complexes
Synthesis of Al(acac)3
The Al(acac)3 complex was synthesized by mixing
acetylacetone(3.00 ml,0.03 mol.) and distilled
water(40.00 ml) in a flask and followed by ammonia
solution(8.00 ml,5.0M). Then aluminum sulphate
solution(3.00 g,0.005 mol) in 30.00 ml of cold distilled
water was added and shaked, the mixture was adjusted
to pH ≈ 7. The mixture was filtered and washed with
cold distilled water before dryingin vacuum. The
product was further purified by recrystallization from
cyclohexane. Finally, needle crystals were collected
(69.10%).
Synthesis of Mn(acac)3
The Mn(acac)3 complex was synthesized by mixing
manganese(II)chloride
tetrahydrate
(2.60
g,
0.013mol.), sodium acetate (6.80 g, 0.05 mol. in 100
ml of distilled water) and
acetylacetone(10.00
ml,0.100 mol.) Then potassium permanganate solution
(0.52 g, 0.003 mol. in 5.00 ml of distilled water), was
added and stirred. Then, sodium acetate (6.30 g,0.046
mol. in 25.00 ml of distilled water) was added, while
stirring and heating the mixtureto 70°C for 30 minutes
and then cool to room temperature. The mixture was
filtered and washed with cold distilled water and dried
under vacuum. The brown black needle products were
obtained from the crystallization with hot cyclohexane
and diethyl ether (68.20%).
Synthesis of Fe(acac)3
The Fe(acac)3 complex was synthesized by mixing
iron(III)chloride hexahydrate (3.30 g ,0.012 mol. in
25.00 ml of distilled water) and acetyl acetone (3.80
ml,0.038 mol. in 10.00 ml of ethanol). Then sodium
acetate (5.10 g in 15.00 ml of distilled water) was
added and stirred. The mixture was heated at 80°C for
15 minutes and then cooled to room temperature. The
mixture was filtered and washed with cold distilled
184
water and dried under vacuum. Recrystallization of the
product was performed in hot distilled water by adding
methanol dropwise to obtain the product (75.30%).
Synthesis of Co(acac)3
The Co(acac)3 complex was synthesized by refluxing
cobalt(II)carbonate(2.50 g,0.021 mol.) with acetyl
acetone(20.00 ml,0.200 mol.) The reaction was stirred
90°C, and 30.00 cm3 of a 10% hydrogen peroxide
solution was added dropwise using a dropping pipette.
Stirring should be maintained throughout the addition
and further 15 minutes after the addition. The mixture
was cooled in an ice bath for 30 minutes. The mixture
was filtered and dried under vacuum. Dark green
crystals were obtained. The products were
recrystallized from hot toluene by adding diethyl ether
to obtain dark green needles. (78.70%)
Synthesis of Cu(acac)2
The Cu(acac)2 complex was synthesized by mixing
copper(II)chloride dehydrate(4.00 g,0.025 mol. in
25.00 ml of distilled water) and acetyl acetone(5.00
ml,0.05 mol. in 10.00 ml methanol) in a flask. Then
sodium acetate(6.80 g in 15.00 ml of distilled water)
was added and the mixture was heated to 80°C on a
hot plate for 15 minutes. The mixture was cooled to
room temperature and then in an ice water bath. The
mixture was filtered and washed with cold distilled
water and dried under vacuum. The product was
recrystallized from hot methanol as blue-gray needles.
(73.50%)
Al(acac)3: FT-IR (KBr disk,): 2925 (-CH3str.),1594.4
((C=O str.) 1H-NMR (CDCl3): δ,ppm. 2.0
CH3), 5.5 (-CH).
Mn(acac)3: FT-IR (KBr disk): 2922.72 (-CH3
str.),1588.06 (C=O str.) 1H-NMR (CDCl3): δ,ppm.
2.05 (-CH3), 5.5 (-CH).
Fe(acac)3: FT-IR (KBr disk): 2920.30 (CH3 str.),
1570.81 (C=O str.) 1H-NMR (CDCl3): δ,ppm.2.2 (CH3), 5.3 (-CH).
Cu(acac)3: FT-IR (KBr disk): 2922.22 (CH3 str.),
1577.81 (C=O str.). 1H-NMR (CDCl3): δ,ppm. 2.2 (CH3), 5.3 (-CH)
a
b
Figure 3 structure of Cu(acac)2 (a) and M(acac)3(b)
where M = Al, Mn, Fe and Co
2.4 Biological activity
The antibacterial activities were evaluated against
E. coli and S. aureus, by Disc diffusion method [12].
The compounds were dissolved in methanol (solvent
control) to obtain concentration of 10 mg/L. Nutrient
agar medium was prepared by using nutrient broth
4.00 g and agar 7.50 g in water. The disc of Whatmann
No.1 filter paper having the diameter 5 mm was used.
The compound solution (50μL, 10 mg/L) are applied
on disc then placed over the media. The methanol was
served as control solvent, while penicillin (10 mg/L)
was selected for standard drug (inhibition zone of
penicilin; E. coli = 1.1500 ± 0.0531 mm and S. aureus
= 1.7820 ± 0.1940 mm). The samples were incubated
for 24 h at 37 ± 2 °C. The inhibition zone was
carefully measured in mm.
3.1 Elemental CHN analysis
The ligands and complexes were characterized by
elemental CHN analysis to confirm the success in the
synthesized process. The elemental CHN analysis of
all compounds is in agreement with theoretical value
as show in Table 1.
Table 1 Elemental CHN analysis data
Compounds
Ligand L[1]
NiL[1]
CuL[1]
ZnL[1]
Ligand L[2]
NiL[2]
CuL[2]
ZnL[2]
Al(acac)3
Mn(acac)3
Fe(acac)3
Co(acac)3
Cu(acac)2
Theoretical value (%)
C
H
N
40.08 6.68 11.69
35.58 6.35 10.37
35.27 6.29 10.28
35.15 6.27 10.25
47.06 7.54
9.98
42.61 6.83
9.03
42.27 6.77
8.96
42.15 6.75
8.94
55.55 6.54
51.00 6.02
50.55 5.94
45.88 5.39
-
Analyze value (%)
C
H
N
38.51 7.09 12.31
35.32 5.95 10.22
34.56 6.41 10.18
34.44 6.39 10.55
46.59 7.69
9.78
43.46 6.89
9.12
41.43 6.91
8.87
41.73 6.96
8.76
55.55 6.53
51.01 5.99
50.57 5.94
45.88 5.39
-
3.2 UV-Vis spectroscopy
Tetraaza macrocyclic complexes
According to UV-Visible spectroscopy data of ligand
L[1] and their complexes (NiL[1] and CuL[1]), when
each metal ion (Ni2+ or Cu2+) was added in to ligand
L[1], the soret band move to a longer wavelength. The
energy band gap (HOMO and LUMO) of NiL[1] and
CuL[1] from UV-Vis spectroscopy are less than ligand
L[1]. However, in the complex ZnL[1], the soret band
was moved to a shorter wavelength, compared with
NiL[1] and CuL[1]. The zinc ion in ZnL[1] was
Zn2+(d10).The higher energy may require to excite the
ground state electron to excited state. The UV-Visible
spectra of ligand L[2] and complexes (NiL[2], CuL[2],
and ZnL[2]) are shown the same trends as that of
ligand L[1] and complexes ML[1] the data are
summarized in Table 2
The UV-vis spectra of complexes M(acac)3
(M=Mn3+,Fe3+and Co3+) and Cu(acac)2 were recorded
in MeOH as a solvent. The spectra show a broad band,
at 568, 429, 593 and 635 nm, for Mn(acac)3, Fe(acac)3,
Co(acac)3 and Cu(acac)2 respectively. These bands
correspond to the d-d transitions in each complexes,
similarly to the results reported by Sertphon et.al [8].
Table 2 UV-Visible spectroscopy data
185
UV-Visible spectroscopy
λmax (nm.)
243
243
436
436
505
511
243
241
Compounds
Ligand L[1]
Ligand L[2]
NiL[1]
NiL[2]
CuL[1]
CuL[2]
ZnL[1]
ZnL[2]
Acetyl acetonate complexes
Varying metal complexes from Fe(acac)3 to
Mn(acac)3,Co(acac)3 and Cu(acac)2illustrated the red
shift in the spectra of complexes. Similarly, replacing
the solvent for these complexes [Fe(acac)3,Cu(acac)2]
from MeOH to DMSO also shown small red shifts.
This result might be because of weak attraction
between the complexes and the solvent which atom
known as solvatochromic effect [9]. In contrast, the
red shift was not observed for Co(acac)3.
Table3 UV-Visible spectroscopy data
Compounds
Mn(acac)3
Fe(acac)3
Co(acac)3
Cu(acac)2
UV-vis
(solution) λmax
MeOH
DMSO
568
429
438
593
598
635
647
UV-vis
(solid
state)λmax
560
438
593
563
and S. aureus, respectively. The result of CuL[1] and
Co(acac)3 showed greater inhibition than penicillin
drug standard especially for E. coli. Therefore, the
chelation between ligand and metal acetate make
complex more powerful and potentially bacterial
inhibiter agents E. coli andS. aureus. In complexes, the
positively charge of metal ion was partially shared
with the donor atom presented in ligands and may
allow the π-electron delocalized over the whole
complex, increasing the lipophilic character of
complex. The complex may permeate through the lipid
layer of the bacterial membranes and caused the
bacteria die. Similar result was found in complex of
PdC32H28N4Cl2 [10].
4. Conclusions
The tetraaza macrocycilc complexes and acetyl
acetonate complexes have been synthesized and
characterized by IR spectroscopy, 1H NMR, 13C NMR
spectroscopy and CHN elemental analysis. The UVVisible spectroscopy showed that metal has been
effected by on the energy gap of HOMO and LUMO
of complexes. The antibacterial activity indicated the
complexes and ligands were sensitive against both E.
coli and S. aureus. The complexes CuL[1] and
Co(acac)3 exhibited more inhibitory than other
compounds for both of bacteria and greater inhibition
capacity than penicillin drug.
Acknowledgements
3.3 Biological activity
In this study, the pure ligands, metal acetate
andthe metal complexes were evaluated for their
antibacterial activity against E. coli and S. aureus. The
antibacterial screening data (Table 4) for all ligands,
metal acetate and the metal complexes were found to
be sensitive against both E. coli and S. aureus,inwhich
each the inhibition zone was greater than control
solvent (methanol). The complex CuL[1] exhibited the
greatest inhibitory with clear zone = 1.350 ± 0.070 mm
and 1.100 ± 0.072 mm for E. coli and S. aureus,
respectively. Acetyl acetonate complexes Co(acac)3
exhibited the greatest inhibitory with clear zone =
1.825 ± 0.035 mm and 1.875 ± 0.247 mm for E. coli
We are grateful to the Department of Chemistry,
Faculty of Science and Technology, Thammasat
University and Science Achievement Scholarship of
Thailand (SAST), for financial and all experiments
support.
References
[1] Kong, D. and Xie, Y., 2002, Inorganic
ChimicaActa, 338, 142 – 148.
[2] Keypour, H., Aezhangi, P., Rehpeyma, N.,
Rezaeivala, M., Elerman, Y. and Khavasi, H. R.,
2011, Inorganic ChimicaActa, 367, 9 – 14.
Table 4 Antibacterial screening data for ligands and their complexes
Complex
Ligand L[1]
Ligand L[2]
NiL[1]
NiL[2]
CuL[1]
CuL[2]
ZnL[1]
Al(acac)3
Mn(acac)3
Fe(acac)3
Co(acac)3
Cu(acac)2
Escherichia coli
Inhibition zone (mm)
1.100±0.070
0.980±0.040
1.230±0.113
1.050±0.075
1.352±0.072
0.943±0.000
0.941
1.209±0.496
1.675 ±0.106
1.750±0.212
1.650±0.071
1.825±0.035
1.400±0.212
Control
Staphylococcus aureus
Inhibition zone (mm)
0.812±0.002
0.880±0.045
0.889±0.040
1.084±0.047
1.100±0.078
1.039±0.116
0.810
0.989±0.040
1.650±0.000
1.575±0.106
2.025±0.200
1.875±0.247
1.150±0.000
Control
186
[3] Chen, L. and Cotton, F. A., 1998, Journal of
Molecular Structure, 470, 161 – 166.
[4] El-Boraey, H. A., 2012, SpectrochemicalActa
Part A: Molecular and Biomolecular
spectroscopy, 97, 255-262.
[5] Kong, D., Meny, L., Ding, J., Xie, Y. and Huang,
X., 2000, Polyhedron 19, 217 – 223.
[6] Tyagi, M. and Chabdra, S., 2014, Journal of
Saudi Chemical Society, 18, 53-58.
[7] Masih, I. and Fahmi, N., 2011,
SpectrochemicaActa Part A, 79, 940 – 947.
[8] Patrique, N., Nora, V. N., Elisabete, C.B.A.A.,
Armando, J.L.P. and Isabel, C., 2014, Journal of
Molecular Structure, 1060, 142–149.
[9] Yogesh, S.W. and Bhalchandra, M.B., 2012,
Tetrahedron Letters, 53, 6500-6503
[10] Chandra, S., Tyagi, M. and Agrawal, S., 2011,
Journal of Saudi Chemical Society, 15, 49 – 54
187
ONE POT SYNTHESIS OF FREE BASE MESO-TETRA
(SUBSTITUTED PHENYL) PORPHYRINS
Jantima Sukjan, Supakorn Boonyuen*, Wootthiphan Jantayot
Department of Chemistry, Faculty of Science and Technology, Thammasat University, Pathumthani, 12120, Thailand
* E-mail: chemistrytu@gmail.com
Abstract: In this work, a series of meso-tetra (substituted
phenyl) porphyrins was synthesized and characterized. A
modified Adler method was used for the synthesis of
symmetrical porphyrins by condensation reaction
between pyrrole and different substituted benzaldehydes
in propionic acid. The synthesized porphyrins were
characterized by using proton nuclear magnetic
resonance spectroscopy, ultraviolet–visible spectroscopy,
fluorescence spectroscopy and mass spectrometry. In this
study, the trend of free base porphyrins when the
aldehyde precursors were different in the ability to
provide electron density to the π system was studied. The
aldehyde
precursors
were
benzaldehyde,
4hydroxybenzaldehyde, 4-methoxybenzaldehyde and 4carboxybenzaldehyde. The product yield of TPP,
TOMPP, TMPP, THPP and TCPP are 36.0%, 25.7%,
36.2%, 12.3 and 36.2%, respectively. The spectroscopic
information of synthesized compounds confirmed the
expected structures. The results showed that one pot
synthesis reaction was successful.
1. Introduction
3
2
1
20
Methine br idge
4
5
N
H
19
6
7
18
N
N
8
17
16
15
9
H
N
Porphyrins are found in many natural systems,
where they play an essential role as photoactive, redox,
guest-binding, and catalytic entities. They are of
immense biological importance and have fascinating
physical, chemical, and spectroscopic properties.
Because of their special properties, porphyrins have
wide applications in many fields such as biomimetic
catalysis, electro catalysis, biological sensors, solar
energy conversion, and so on. They are also important
in biomimetic models, and in fact they are widely used
as models to study oxygen transport4. Photophysical
properties of porphyrin derivatives have been the
target of a huge amount of investigations during the
past few decades, motivated by the possibilities of
their use in a large variety of applications including
light harvesting systems5, photodynamic therapy6,
chemical sensors7-8 and others.
The aims of this research mainly focus on two
different topics: a) the synthesis of symmetrical
porphyrin and b) characterization and study the
chemical properties of synthesized porphyrins. The
first objective of this work is to synthesize
symmetrical phenylporphyrins containing hydroxyl or
alkoxy or alkyl or carboxyl functional group on the
para position of the phenyl rings. The second objective
is to characterize all synthesized porphyrins and to
study their properties such as electronic absorption and
electronic emission for further applications.
10
14
11
Meso position
13
12
Figure1. The structure of porphyrins
Porphyrins are one of the important chemical parts
essential for several life processes in nature. Moreover,
porphyrin is the name given to a family of intensely
colored molecules all sharing a macrocycle of twenty
carbon atoms and four nitrogen atoms. The porphyrins
are aromatic molecules where four pyrrole rings
forming a square, are connected by unsaturated
methine bridges to complete a macrocycle (Figure 1)1.
They are aromatic macrocycles containing a total of 22
conjugated π electrons, 18 of which are incorporated
into the delocalized pathway in agreement with
Huckel’s [4n + 2] rule for aromaticity (n = 4). The
porphyrin macrocycles are quite flexible and easy for
being π-delocalized system by introducing substituents
at β- or meso-positions, adding the central metal or
extending the macrocycle.1-3
2.1 Reagents
The reagents were purchased and used without
further purification. Liquid reactants and solvents were
distilled prior to use. The distilled water was used.
Flash column chromatography was performed on
Silica gel 60.
2.2 Materials
Electronic absorption spectra were carried out on a
SHIMADSU UV-Vis spectrophotometer using a pair
of quartz cells of 10 mm path length at room
temperature. Emission spectra of porphyrins were
measured by a Jasco FP-6200 spectrofluorometer at
room temperature. Nuclear magnetic resonance spectra
were recorded at 400 MHz for 1H NMR using a
BRUKER-NMR 400MHz spectrometer. Infrared
spectroscopy spectra (4000-600 cm-1) were performed
using a spectrum GX FT-IR spectrometer (Perkin
188
Elmer). Mass spectra of the porphyrins were recorded
on a Thermo Finnigan mass spectrometer.
2.3 Methods
Scheme1. The synthesis of free base porphyrins
The free-based porphyrins that containing hydroxyl
or alkoxy or alkyl or carboxyl functional group on the
para position of the phenyl rings were synthesized by a
condensation reaction between pyrrole and aldehyde in
propionic acid according to the development of AdlerLongo method (scheme1)9. Pyrrole (1.0 ml, 14.3
mmol) was taken in a round bottomed flask, to which
propionic acid (100 ml) was added. To the above
stirred solution, aldehyde (benzaldehyde: 1.5 ml, 14.7
mmol, p-tolubenzaldehyde: 1.5 ml, 12.7 mmol, panisaldehyde:
1.5
ml,
12.4
mmol,
4hydroxybenzaldehyde: 1.75 g, 14.3 mmol,
or 4carboxybenzaldehyde: 2.15, 14.3 mmol) was added
dropwise. The reaction mixture was refluxed and
stirred for 60 minutes at 90˚C. Reaction was monitored
by TLC (hexane: dichloromethane) when reaction
completed. Then the dark brown mixture after cooling
was filtered that the solvent was remove under reduce
pressure. The deep-purple crystals are the resulting
residues. Moreover, the compound was purified by
using silica gel column chromatography and
recrystallization.
In column chromatography part, the wet method
was used to prepare a column. The free base porphyrin
was prepared of within the small of silica gel powder
which is a stationary phase. The sample to be purified
was dissolved in a small amount of appropriate
solvent, and then loaded onto the top of column. The
eluting solvent changed to a more polarity solvent
during the elution process and the composition of each
fraction is analysed by TLC-silica.
After purification, the UV-Vis absorption spectra
of these compounds were studied by recording
between 200 and 800 nm, the fluorescence spectra
were measured in range 530-700 nm. 1H NMR, the
infrared spectroscopy and mass spectrometry were
measured for study chemical properties to confirm the
structure.
5,10,15,20-Tetraphenylporphyrin (TPP): FT-IR
(Nujol, NaCl): 3435 (N-H str., porphyrin), 3054, 2987
(C-H str., phenyl), 1605, 1158 (C=C str., phenyl),
1558 (C-C str., porphyrin), 1269 (C-N str., porphyrin),
1018 (N-H bend, porphyrin), 896 (C-H bend,
porphyrin) cm-1. 1H NMR (400 MHz, CDCl3): δ 8.85
(Pyrrole, β-H), 8.21 (Phenyl, o-H), 7.73 (Phenyl, m-
H), 7.75 (Phenyl, p-H), -2.71 (Pyrrole, N-H). Mass
spectrum (m/z): 615.3 (cal., 615.78).
5,10,15,20-Tetrakis(4-methylphenyl)porphyrin
(TMPP): FT-IR (Nujol, NaCl): 3436 (N-H str.,
porphyrin), 3054, 2986 (C-H str., phenyl), 1606, 1158
(C=C str., phenyl), 1558 (C-C str., porphyrin), 1263
(C-N str., porphyrin), 1018 (N-H bend, porphyrin),
896 (C-H bend, porphyrin) cm-1. 1H-NMR (400 MHz,
CDCl3): δ 8.85 (Pyrrole, β-H), 8.18 (Phenyl, o-H),
7.56 (Phenyl, m-H), 2.70 (-CH3), -2.77 (Pyrrole, N-H).
Mass spectrum (m/z): 671.4 (cal., 671.84).
5,10,15,20-Tetrakis(4-methoxylphenyl)porphyrin
(TOMPP): FT-IR (Nujol, NaCl): 3435 (N-H str.,
porphyrin), 3053, 2987 (C-H str., phenyl), 1606, 1153
(C=C str., phenyl), 1553 (C-C str., porphyrin), 1265
(C-N str., porphyrin), 1017 (N-H bend, porphyrin),
895 (C-H bend, porphyrin) cm-1. 1H-NMR (400 MHz,
CDCl3): δ 8.88 (Pyrrole, β-H), 8.13 (Phenyl,o-H), 7.35
(Phenyl, m-H), 4.22 (-OCH3), -2.82 (Pyrrole, N-H).
Mass spectrometry (m/z): 735.3 (cal., 735.84).
5,10,15,20-Tetrakis(4-hydroxyphenyl)porphyrin
(THPP): FT-IR (Nujol, NaCl): ~3200-3400 broad band
(O-H str., phenyl), 3314 (N-H str., porphyrin), 2937,
2869 (C-H str., phenyl), 1604, 1170 (C=C str.,
phenyl), 1479 (C-C str., porphyrin), 1232 (C-N str.,
porphyrin), 967 (N-H bend, porphyrin), 802 (C-H
bend, porphyrin) cm-1. 1H-NMR (400 MHz, CDCl3): δ
9.80 (Phenyl, -OH), 8.90 (Pyrrole, β-H), 8.15
(Phenyl,o-H), 7.30 (Phenyl, m-H), -2.82 (Pyrrole, NH). Mass spectrometry (m/z): 678.2 (cal., 677.74).
5,10,15,20-Tetrakis(4-carboxyphenyl)porphyrin
(TCMPP): FT-IR (Nujol, NaCl): 3407 (N-H str.,
porphyrin), 2924, 2862 (C-H str., phenyl), 1686 (C=O,
carboxylic acid), 1604 (C=C str., phenyl), 1386 (C-N
str., porphyrin), 962 (N-H bend, porphyrin), 798 (C-H
bend, porphyrin) cm-1. 1H-NMR (400 MHz, CDCl3): δ
8.85 (Pyrrole, β-H), 8.32 (Phenyl,o-H), 8.25 (Phenyl,
m-H), -2.82 (Pyrrole, N-H). Mass spectrometry (m/z):
790.1 (cal., 789.77).
R
R
N
H
N
R = H; TPP
R = CH3; TMPP
R = OCH3; TOMPP
R = OH; THPP
R = CO2H; TCPP
N
H
N
R
R
Figure2. The structure of free base porphyrins
The free base porphyrins, including TPP, TMPP,
TOMPP, THPP and TCPP were prepared using a
modification of Adler-Longo method, i.e. by the
heating of pyrrole in propionic acid solvent followed
by addition of the same amount of aldehyde, further
189
heated for one hour, resulting in the dark solution with
deep purple microcrystals. The absorption spectra of
all synthesized was shown in Figure 3. They exhibited
an extreme intense band as a Soret band (S-band
ranged from 405.0 – 413.5 nm). At lower energy, the
spectra contain a set of weaker four absorption bands
(Q-band as shown in Table 1). The intensity and color
of porphyrins were derived from the highly conjugated
π-electron systems and the most attraction feature of
porphyrins was their characteristic UV-visible spectra
that consist of two distinct regions, in the near
ultraviolet (Soret band) and in the visible regions (Q
bands). The absorption bands in porphyrin systems
arise from transitions between two HOMOs and two
LUMOs.
The fluorescence spectra of free base porphyrins
show only one electron transition occurs at 649-656
nm, when excited at 513-518 nm. TMPP, TOMPP and
THPP were little shift to a longer wavelength when
comparing with TPP. It can conclude that the shifting
of emission spectra was depended on the ability to
donate electron to the benzene ring of the substituents.
The structure of each complex was confirmed by
FT-IR, 1H NMR, and mass spectrometry. Structural
studies by IR Spectroscopy found that the spectra of
each compound were quite similar. Each position has
shifted slightly because of the influence of
substituents. This result was expected as the ring core
part of porphyrins was the same. From mass
spectrometry, all free base porphyrins were consistent
with the expected structures.
4. Conclusions
Tetraphenylporphyrin with different in mesosubstituted position were successfully synthesized. The
colors of all synthesized compounds are in the purple
with micro crystals. The structure of each free base
porphyrins were confirmed by FT-IR, 1H NMR, and
mass spectrometer, which in agreement with the
expected values. The absorption spectroscopy showed
the intense S-band (405.0 – 413.5 nm) and weak Qbands, ranging from 513 to 650.5 nm. The
fluorescence spectra (excitation at 513-518 nm)
showed emission bands at 649 - 656 nm.
The financial and all experiments equipment were
Figure3. UV-Vis absorption spectra of free base
porphyrins
supported by the Thailand Research Fund (TRF),
Department of Chemistry, Faculty of Science and
Technology, Thammasat University and the Navamin
project of National Research Council of Thailand.
References
[1] Gouterman, M., 1961, J. Mol. Spectrosc., 6, 138–163.
[2] Gouterman, M., Wagnire, G.H. and Snyder, L.C., 1963,
J. Mol. Spectrosc., 11, 108–127.
[3] Kalyanasundaram, K., 1992, Academic Press, San Diego,
1992.
[4] Pavinatto, F.J., Gameiro Jr, A.F., Hidalgo, A.A., Dinelli,
L.R., Romualdo, L.L., Batista, A.A., Barbosa Neto,
N.M., Ferreira, M. and Oliveira Jr., O.N., 2008, Appl.
Surf. Sci. 254, 5946–5952.
[5] Gust, D., Moore, T.A. and Moore, A.L., 2001, Acc.
Chem. Res., 34, 40–48.
[6]Ochsner, M., 1997, J. Photochem. Photobiol. B, 39, 1–18.
[7] Chou, J.H., Kosal, M.E., Nalwa, H.S., Rakow, N.A. and
Suslick, K.S., 2000, Applications of porphyrins and
metalloporphyrins to materials chemistry, in: K. Kadish,
K. Smith, R. Guillard (Eds.), The Porphyrin Handbook,
Academic Press, New York.
[8] Pavinatto, F.J., Gameiro Jr., A.F., Hidalgo, A.A., Dinelli,
L.R., Romualdo, L.L., Batista, A.A., Barbosa Neto,
N.M., Ferreira, M. and Oliveira Jr., O.N., 2008, Appl.
Surf. Sci., 254, 5946–5952.
[9] Kilian, K. and Pyrzyńska, K., 2003, Talanta., 60(4), 669678.
Acknowledgements
Table 1: Percentage yield, mass spectrometric, UV-Visible spectroscopy data and fluorescence spectroscopy data of
meso-substituted porphyrins
Compounds
(Molecular Mass)
Yield
(%)
Major
product
ion(m/z)
TPP (614.78)
TMPP (670.84)
TOMPP (734.84)
THPP (678.74)
TCPP (790.77)
36.0
36.2
25.7
12.3
36.2
615.3
671.4
735.3
678.2
790.1
UV-Vis absorption (nm)
S-band
(ε x 103 )
405.0 (28.5)
408.0 (29.8)
413.5 (22.0)
407.0 (25.7)
405.0 (28.6)
Q-band
1
514.0
516.0
518.0
517.0
513.0
2
549.0
551.5
555.5
554.0
547.0
3
590.0
591.5
594.0
592.0
589.0
4
646.0
648.0
650.5
650.0
644.0
Fluorescence
(nm)
Excita- Emistion
Sion
514.0
649.0
516.0
652.0
518.0
655.0
517.0
656.0
513.0
648.0
190
SYNTHESIS AND CHARACTERIZATION OF LONG CHAINED
PORPHYRIN DERIVATIVES AND COBALT COMPLEXES
Wootthiphan Jantayot, Supakorn Boonyuen*, Jantima Sukjan, Kamolnate Jansaeng
Department of Chemistry, Faculty of Science and Technology, Thammasat University, Pathumthani 12120, Thailand
*E-mail: chemistrytu@gmail.com
Abstract: In the present work, the synthesis and
properties of long chained porphyrin and their cobalt
complexes were examined. The compounds were
synthesized by Adler-Longo method, refluxing aldehyde
and pyrrole in propionic acid. The modified porphyrins
are tetrakis(4-methoxyphenyl)porphyrin (TOMPP),
tetrakis(4-butyloxyphenyl)porphyrin (TOBPP), tetrakis
(4-octyloxyphenyl)porphyrin (TOOPP) and tetrakis(4decyloxyphenyl)porphyrin (TODPP). The products were
obtained in 26%, 5%, 13 and 14% yields, respectively.
Further refluxing the ligands with cobalt acetate in DMF
gave CoTOMPP, CoTOBPP, CoTOOPP and CoTODPP,
respectively with yields ranging from 75 to 92% yields.
All ligands and complexes were characterized by 1HNMR, MS, IR, UV-Vis and fluorescence spectroscopy,
and the results were in agreement with the expected
structures.
1. Introduction
Porphyrins are planar aromatic macrocycles and
biochemically important in nature. They are ubiquitous
classes of compounds with many important biological
representatives including heme, chlorophyll, coenzyme
F430 and several others [1].
The nature of bonding between a central metal and
the porphyrin ligand is found to be originating
essentially from the following two types of primary
interactions: σ-coordination of nitrogen lone pairs
directed towards the central metal atoms and πinteractions of metal pπ or dπ orbitals with nitrogenbased π orbitals [2]. Ability to exhibit variable
oxidation states of metals in their metalloporphyrins
are another important feature in this class of
compounds.
Porphyrins and their metal complexes have
received much attention. This has been mainly due to
the use of these compounds in catalysis, as materials
with novel electrical properties and as biomimetic
model systems of primary processes of natural
photosynthesis [3-5]. They can be used as
photosensitizing drugs in photodynamic therapy
(PDT). An extra stabilization of the porphyrin occurs
by complexation with transition metal ions and which
has been explained by the macrocyclic effect [6].
Porphyrins and their derivatives have well-known
technological applications. Concerning the field in
which the stability is one of the essential parameters to
be considered, aspects such as the use as dyes in solar
cells to improve efficiency [7]. Porphyrins can be used
as biodiesel fluorescent markers [8-9].
In the present work, the application of Adler Longo
synthesis method was selected to apply for the
porphyrin derivatives due to the most convenient
process. Porphyrin derivatives and cobalt porphyrins
were prepared and purified. Then, their properties
were characterized by IR spectroscopy, 1H NMR
spectroscopy and mass spectrometry (MS).To study
the properties of porphyrin derivatives and cobalt
porphyrins, the absorption spectra and emission
spectra were analyzed by using UV-Vis
spectrophotometry
and
spectrofluorometer
in
dichloromethane.
2. Methodology
2.1Apparatus
Nuclear magnetic resonance spectra were recorded
at 400MHz on a Bruker (FT-NMR advance 400
MHz) spectrometer. FT-IR (4000-400cm-1) spectra
were recorded on Perkin Elmer infrared
spectrophotometer (spectrum GX). Mass spectra were
obtained from Thermo Finnigan mass spectrometer
(LCQ Advantage). UV-Vis
absorption
and
fluorescence measurements were carried out on a
Shimadzu UV-spectrometer (UV-1700) and a Jasco
spectrofluorometer (FP-6200), respectively.
2.2 Method
2.2.1 Synthesis of aldehyde
H
O
O
+
n
K2CO3
n Br
H
DMF, 353 K
2 hr.
OH
4-Hydroxybenzaldehyde Alkyl bromide
O
Alkyloxybenzaldehyde
n=3, 1-Bromobutane
n=7, 1-Bromooctane
n=9, 1-Bromodecane
Figure 1.Synthesis of butyloxybenzaldehyde,
octyloxybenzaldehyde and decyloxybenzaldehyde.
A mixture of 4-hydroxybenzaldehyde (17.5 mmol)
and K2CO3 (18 mmol) was stirred in DMF. Various
alkyl bromide (18 mmol) was added dropwise and the
mixture was heated at 353 K for 2 hour. After cooling,
the salts were filtered. DMF was evaporated to
dryness, and the reaction mixture was re-dissolved in
CH2Cl2 and washed with distilled water. Magnesium
sulfate anhydrous was used for drying. Alkyloxybenzaldehyde as yellow oil was afforded by filtration
191
Porphyrin was used to reflux (0.04mmol) with
and evaporation. The reaction products were used
Table 2: 1H NMR spectroscopic data and FT-IR data for porphyrins long chain and cobalt porphyrins.
without any further purification [10].
cobalt acetate [(Co(II)(CH3COO)2)] (0.40mmol) in
DMF for 4 hours. The reactions mixture was diluted
with water and extracted with dichloromethane, and
the solvent was removed by evaporator. Cobalt
complexes were recrystallized. The title compounds
were isolated by column chromatography as purple
solid [13].
2.2.2 Synthesis of porphyrin with long chain
R
R
O
Propionic acid
H
Reflux , 383 K
4R
4
N
H
N
N H N
H
N
R
R
R= OCH3
R= O(CH2)3CH3
R= O(CH2)7CH3
R= O(CH2)9CH3
The porphyrin derivatives, including TOMPP,
TOBPP, TOOPP and TODPP were synthesized by a
modification Adler-Longo method. Porphyrins were
obtained from 5 to 26% yields. Adding cobalt ion into
the central position of ligands (CoTOMPP, CoTOBPP,
CoTOOPP, CoTODPP) by refluxing in DMF gave the
yields of the products ranging from 75 to 92% yields.
The characterization data of purified porphyrin
derivatives and cobalt complexes are shown in Table
1. The mass spectra of porphyrins long chain and
cobalt porphyrins could also confirm that the expected
structures as shown in Table 1.
Figure 2.Synthesis of TOMPP, TOBPP, TOOPP and
TODPP.
Porphyrins were synthesized by following the
development of Adler-Longo method [11-12]. A
round-bottomed flask equipped with a magnetic
stirring bar and a reflux condenser was charged with
various alkyloxybenzaldehyde (14 mmol), and
propionic acid and stirred for 15 min at 383 K. Pyrrole
(14 mmol) was added slowly, and the mixture was
refluxed for 2 hour. After refluxing, the reaction
mixture was cooled to room temperature and added 40
mL ethanol, kept in ice bath overnight. The purple
crystals were filtered, washed, and dried by vacuum
filtration with cold ethanol to remove traces of
propionic acid. The crude products were purified by
column chromatography to yield a purple crystal
product.
Table 1: Characteristic data for porphyrins long chain
and cobalt porphyrins.
Compounds
Empirical
formula
Yield
(%)
Formula
weight
Msm/z
(ESI)
TOMPP
TOBPP
TOOPP
TODPP
CoTOMPP
CoTOBPP
CoTOOPP
CoTODPP
C48H38N4O4
C60H62N4O4
C76H92N4O4
C84H108N4O4
CoC48H36N4O4
CoC60H60N4O4
CoC76H90N4O4
CoC84H106N4O4
26
5
13
14
75
92
81
88
734.84
903.16
1125.57
1237.78
791.76
960.08
1182.49
1294.70
735.32
902.19
1126.41
1238.46
793.01
959.95
1184.33
1294.29
2.2.3 Synthesis of cobalt (II) porphyrins
R
R
N
N H N
H
N
N
+
Co(CH3COO)2
DMF
Reflux
R
R
R
R
N Co N
N
Porphyrins long chain were dissolved in
chloroform-d (CDCl3) and the 1H NMR data for the
corresponding compounds are shown in Table 2.
Cobalt complexes were unable to identify by 1H NMR
spectroscopy due to a paramagnetic character. The
shielding effect of the proton signals of -NH groups in
porphyrin ring was observed at very high fields.
R
R
R= OH
R= OCH3
R= O(CH2)3CH3
R= O(CH2)7CH3
R= O(CH2)9CH3
Figure 3.Synthesis of CoTOMPP, CoTOBPP,
CoTOOPP and CoTODPP.
1
Porphyrins
Pyrrole
β-H
TOMPP
8.9
TOBPP
TOOPP
TODPP
CoTOMPP
CoTOBPP
CoTOOPP
CoTODPP
Phenyl
, o-H
Phenyl,
m-H
IR (cm-1)
H NMR (ppm)
O
CH3
O
CH2
OCH2
CH2
CH2
CH3
CH2
CH2
CH3
N-H
str.
C-H
str.
C=C
str.
2928,
1606,
2832
1509
2929,
1605,
8.9
8.1
7.3
4.3
2.17
1.6
1.26
3318
2868
1507
2926,
1606,
8.9
8.1
7.3
4.3
2.0
1.65
1.55
0.95
3316
2850
1508
2923,
1606,
8.9
8.1
7.3
4.2
2.0
1.65
1.55
0.95
3310
2852
1509
2929,
1602,
2829
1504
2935,
1605,
2857
1507
Unable to identify due to paramagnetic character in 1H NMR data
2924,
1607,
2845
1509
2924,
1606,
2853
1505
8.1
7.3
4.2
-
-
-
-
-
3317
C-N
str.
C-O
str.
N-H
bend
C-H
bend
1247
1175
965
802
1244
1173
965
800
1242
1174
965
803
1243
1175
967
804
1248
1174
-
800
1245
1174
-
794
1244
1174
-
797
1241
1173
-
795
192
Table 3: The absorption and emission data of porphyrins long chain and cobalt complexes in dichloromethane
Dichloromethane
Porphyrins
TOMPP
TOBPP
TOOPP
TODPP
CoTOMPP
CoTOBPP
CoTOOPP
CoTODPP
Soret band (nm),
Ɛ (103M-1cm-1)
422, 115.4
422, 112.5
412, 120.4
415, 122.5
407, 133.3
414, 130.4
407, 131.7
415, 125.4
Q1
517, 24.0
519, 21.4
519, 20.0
519, 16.7
530, 17.3
531, 17.8
531, 16.8
531, 12.9
Q band (nm), Ɛ (103M-1cm-1)
Q2
Q3
556, 16.6
556, 16.2
556, 14.9
556, 12.5
611, 1.5
613, 4.6
613, 3.1
614, 2.7
594, 7.6
595, 7.3
595, 6.7
595, 5.5
-
Q4
651, 10.2
651, 13.6
651, 10.1
651, 9.2
-
Excitation
wavelength
(nm)
530
530
530
530
540
540
540
540
Emission
wavelength
(nm)
655
655
655
655
-
*All solution were prepared in the concentration of 3X10-5mol/L, (n =3, %RSD ≤ 1.6).
(-2.71ppm). The results are in agreement with the
previous reported by A.Zabardasti [14].
FT-IR spectra of porphyrins long chain and cobalt
porphyrins were recorded using KBr pellets, ranging
from 4000-400 cm-1. The IR data are showed in Table
1. The most significant difference of free porphyrins
and cobalt porphyrins were N-H stretching and N-H
bending in the porphyrin ring. The signal at around
3310cm-1 (N-H stretching) and 965 cm-1 (N-H
bending) were disappeared because nitrogen atom in
cobalt porphyrin was bound to the metal ion.
(a.)
(b.)
Figure 4.UV-Vis spectra of porphyrin derivatives (a)
and cobalt complexes(b) in CH2Cl2
The intensity absorption and color of porphyrins
were derived from the highly conjugated π-electron
systems. The most attraction feature of porphyrins was
their characteristic UV-Visible spectra that consist of
two distinct regions: the near ultraviolet called the
Soret band (380-450 nm) and the visible region called
Q-band (500-700 nm). The absorption spectra of
porphyrin
derivatives
showed
significant
characteristics of one soret band and four Q-bands, as
shown in Figure 4. The electronic spectra of the
TOMPP and derivatives in dichloromethane were
investigated and the λ max values were given in Table
3. In metalloporphyrin, the proton on NH group of
porphyrin was deprotonated and then the nitrogen
atom binds with metal ion to give the metal-porphyrin.
The cobalt ions acting as Lewis acids interact with the
lone-pair electrons of porphyrin ligand. These
observed intense absorption bands were due to
absorption(s) in the porphyrin ligands, involving the
excitation of electrons from π to π* prophyrin ring
orbital [15], as shown in Figure 4. The absorption band
of cobalt complexes display two Q-bands. The results
are shown in Table 3.
Figure 5. Excitation spectrum and emission spectrum
of TOMPP in CH2Cl2
The term of band gap refers to the energy
difference between the top of the valence band to the
bottom of the conduction band, electrons are able to
jump from one band to another. The process requires a
specific minimum amount of energy for the transition,
the band gap energy [16]. The estimated energy gap
determined from an intersection of UV-Vis absorption
(Q4-band) and fluorescence emission spectrum was
calculated as described previously [17]. The energy
gap of TOBPP was 1.90 eV. The absorption and
emission spectra of TOBPP are showed in Figure 5.
Fluorescence spectroscopy of porphyrin derivatives
was characterized in dichloromethane and the results
are provided in Table 3. The published information,
exhibited the enlargement of the π-conjugation
yielding the emission characteristics at the emission
from 655 nm when excited at 530 nm. However, the
current work selects the first Q-band as the excitation
wavelength, the spectra also showed strong
fluorescence intensity. The results indicated that these
free base porphyrins can potentially be used in
fluorescent sensors and fuel marker applications.
4. Conclusions
The novel porphyrins with long chain and cobalt
porphyrins have been synthesized and their identities
were confirmed by mass spectrometry (MS), 1H NMR,
FT-IR
spectra,
UV-Vis
and
fluorescence
spectroscopy.The free porphyrin ligand at optimal
condition (refluxing in propionic acid) was obtained
from 5 to 26% yields. Reactions of ligands with metal
ions gave CoTOMPP, CoTOBPP, CoTOOPP and
CoTODPP in 75%, 92%, 81%and 88% yields,
respectively. The pure ligand gave the lower product
yield than metal complexes.
193
The UV-Vis absorption spectra for porphyrins long
chain exhibited a single S-band with four Q-bands,
which the cobalt complexes showed a single S-band
couple with only two Q-band. Exciting the synthesized
long chain porphyrin, the product showed the
fluorescence spectra at 655 nm. All porphyrin
derivatives can potentially be used as fluorescence
probe in sensors and marker applications.
[7]
[8]
[9]
[10]
Acknowledgements
The financial and all experiments equipment were
supported by the Thailand Research Fund (TRF),
Department of Chemistry, Faculty of Science and
Technology, Thammasat University and the Navamin
project of National Research Council of
Thailand.Theauthorsgratefullyacknowledgethefinancia
lsupportprovidedbyThammasatUniversityResearchFun
dundertheTUresearchScholar, Contractno27/2557
[11]
[12]
[13]
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porphyrin derivative from cardanol as a diesel
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2012, Covalent-bound conjugates of fullerene C60 and
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substituents, Mendeleev Commun., 22, 257-259.
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free base porphyrins with σ- and π-acceptor molecules,
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194
SYNTHESES OF MAGNETIC NANOCOMPOSITE SIZE SERIES
Wishulada Injumpa, Numpon Insin*
Materials and Catalysis Research Unit, Department of Chemistry, Faculty of Science,
Chulalongkorn University, Thailand, Bangkok
*
E-mail for Corresponding Author; E-mail:Numpon.I@chula.ac.th, Tel. +66 22187581, Fax. +66 22187598
Abstract: Different sizes of composites of magnetic
nanoparticles (MNPs) with narrow size distribution were
synthesized by two pathways. In the first method,
magnetites (Fe3O4) MNPs were synthesized using thermal
decomposition of iron oleate complex at above 290oC.
The resulting Fe3O4MNPs were then coated by silica via
a reverse microemulsion method, producing the coreshell nanostructures of Fe3O4 MNP@SiO2. For the
second pathway, silica nanoparticles (SiO2 NPs) with
diameters of 50–100 nm were prepared using a reverse
microemulsion method. Combining the Fe3O4MNP
solution with SiO2 NPs afforded silica-Fe3O4 (SiO2-Fe3O4)
magnetic nanocomposites (MNCPs). Sizes of MNCPs can
becontrolled within narrow size distribution of 20 to 150
nm in diameter. Small sizes MNCPs (20-40 nm)can be
controlled by adjusting the ratio of TEOS:MNPsfrom
first pathways. The second method gave lager sizes
ofMNCPs with ~120 nm in diameter.
1. Introduction
Nanomaterials are well known for their
applications in biological field such as drug delivery
system (Doxorubicin drug for tumour cells) [1] and
labelled-cell system (Magnetic resonance imaging or
MRI) [2]. One of the most important factors to be
considered for both systems is the size of
nanomaterials because different sizes of nanomaterials
will affect the cellular uptake and cell viability
differently. In this work, we focus on the syntheses of
magnetic nanocomposites in size range of 20–150 nm
which was claimed to be the best size range of
nanomaterial for biological applications [3]. These size
series of MNCPs in this work can be useful tools for
understanding the effect of sizes, surfaces, and
magnetization in these applications as well as in
magnetic separation and magnetically-guided drug
delivery systems.
2.1 Materials
Oleic acid, octadecene, sodium hydroxide (NaOH),
polyoxyethylene (5) nonylphenylether (Igepal co-520),
1-hexanol, triton x-100, 12-hydroxydodecanoicacid,
hydroxyl cellulose (HCP), 5-Amino-1-pentanol (AP)
and (3-aminopropyl)triethoxysilane (APS) were
purchased form Sigma-aldrich. 2-bomobytyl bromide,
ammonium hydroxide and tetraethyl orthosilicate
(TEOS) were purchased form Merck.Iron(III) chloride
and triethylamine were purchased form Riedel de
haën.
2.2 Characterization Methods
X-ray powder diffraction (XRD) analyse were
performed using Rigaku D/MaX-2200 Ultima-plus
instrument with Cu K radiation (1.5418 Aͦ) source
(40kV, 30mA). The powdered samples were placed on
glass holder. The scans were performed at 25 °C in
steps of 0.03° over 2-theta range from 20° to 70°. The
size and shape of MNPs and MNCPs in this wok were
monitored by JEM-2010 transmission electron
microscopy (TEM). The dispersed sample of MNCPs
was dispersed on carbon film on 300 mesh copper
grids. Fourier transform infrared spectra were recorded
on Nicolet 6700 FT-IR spectrometer. The powdered
samples were mixed with KBr (ratio 1:1000).
2.3 Synthesis of core-shell MNP@SiO2
Magnetic nanoparticles (MNPs) were prepared
using a thermal decomposition technique [4]. Iron
oleate was heated above 290 oC.
A micelle solution [5] was prepared by mixing
Igepalco-520 (20.0 mL) with cyclohexane (100 mL),
followed by an addition of the synthesized-MNPs (110
mg in 1 mL of cyclohexane) and 25% ammonium
hydroxide (2.00 mL) sequentially. Then, TEOS (0.500
or 3.20 mL) was added in the micelle solution. The
reaction mixture was stirred for 24 hours. Finally, it
was centrifuged and the resulting solid was washed
with ethanol (3 x 40.0mL) to afford the MNP@SiO2
nanoparticles (2.13g). The schematic diagram of this
process is shown in Figure 1A.
2.4 Synthesis of silica-MNPs (SiO2-MNP) MNCPs
Synthesis of silica NPs was done by reverse
emulsion method. For the formation of emulsion, a
mixture of 1-hexanol (12.0 mL), triton x-100 (25.0
mL) and cyclohexane (75.0 mL) was sonicated for 20
minutes followed by an addition of DI water (6 mL).
Then, the mixture was stirred for an hour, after which
ammonium hydroxide (1.25 mL) was added. After an
hour of stirring, TEOS (3.20 mL) was added and the
solution was stirred for 24 hours. After that it was
centrifuged. The resulting solid was washed with
ethanol (3 x 40.0 mL). At the end of this process, pure
silica NPs was obtained.
To prepare the MNP solution [6], MNPs were
first washed with ethanol several times. To a 0.500mL
ethanol dispersion of MNPs was added 12hydroxydodecanoic acid (100 mg). The mixture was
sonicated for an hour, after which AP (400 mg) and
195
APS (0.823 g) were added. After 4 hours of stirring,
the MNP solution was obtained.
To an ethanol solution (20.0 mL) of dispersed silica
(SiO2) NPs (100 mg) was added hydroxyl cellulose
(HCP) (20.0 mg).Then, after an hour of sonication, the
MNP solution (50.0–300 µL) was added. The mixture
was then stirred for 30 minutes at room temperature.
After that, water (50.0 µL), NH4OH (50.0 µL) and
TEOS (50.0 µL) were added, respectively. After 8
hours of stirring, SiO2-Fe3O4MNCPs were washed
with ethanol (5 x 40.0mL) and kept as an ethanol
solution. This process was illustrated in Figure 1B.
Fe3O4 MNCPs were compared with both of standard
patternJCPDS 19-0629 and JCPDS 29-0085
(amorphous silica). All of MNP@SiO2 and SiO2Fe3O4MNCPs show peak at 2-theta 35.42°, 43.06° and
62.12°. These peaks indicate that these MNCPs
contain magnetite. Moreover, Peak at 2-theta
22.48°can be observed and implies that these MNCPs
contain amorphous silica as well. The compared result
shows all of MNCPs contain both of magnetite and
amorphous silica.
The
IR
spectrum
of
MNP@SiO2(Figure3a)contains an absorption band
corresponding to a Si-O-Si stretching at 1070cm-1,
which indicates that MNPs were successfully coated
with silica. Transmission electron microscopy (TEM)
was used to characterize the size of all magnetic
nanoparticles (MNPs, MNP@SiO2MNCPs, and SiO2Fe3O4MNCPs).TEM image of MNPs (Figure 4a)shows
particle sizes with diameters of about 10 nm, while the
MNPs coated with silica exhibit larger particle sizes of
around 20 and 40 nm, as shown in Figure 4b and 4c,
respectively. The difference in MNP@SiO2 sizes was
based on the amount of TEOS used during the
synthesis. In particular, 0.500and 3.20 mL of TEOS
produced 20 and40 nm MNPs@SiO2, respectively.
Figure 1. Synthesis of core-shell
MNP@SiO2MNCPs(A), Synthesis of SiO2Fe3O4MNCPs (B)
Thesynthesizedmagnetite(MNPs)
was
characterized by X-ray diffraction (XRD) analysis,and
the resulted XRD pattern was shown in Figure 2.
Figure 3.The IR spectrum of MNPs@SiO2
Figure 2.The XRD pattern of the synthesized magnetic
nanoparticles (MNPs)(black), M@SiO2 (M@S-20
(blue), M@S-40 (orange) for the sizes of 20 and 40 nm
in diameter, respectively.) and SiO2-M MNCPs (SMS;
pink)compared with the standard patternfile JCPDS
19-0629(red)and JCPDS 29-0085 (green)
Compared with the standard pattern JCPDS 19-0629,
the XRD pattern of the MNPs indicates a crystalline
structure of Fe3O4 or magnetite. In addition, the XRD
pattern of both different size of MNP@SiO2and SiO2-
On the other hand, the TEM image of SiO2Fe3O4MNCPs (Figure 4e) reveals the particle size of
approximately 120±18 nm in diameter. In addition, all
magnetic nanoparticles have narrow size distribution
or monodispersity. Monodispersity of these
nanoparticles allows usto further apply such magnetic
nanocomposites for the study of size effect in
biological systems. Moreover, well-dispersity of the
MNCPs is claimed to have advantage in preventing
agglomeration that could impede activities in
biological applications.[7]
196
c
b
a
d
e
Figure4.TEM images of MNPs (a), MNP@SiO2 (b)
and (c), pure silica (d) and SiO2-Fe3O4MNCPs(e)
4. Conclusions
From this work, magnetic nanocomposite size
series in the range of 20–150 nm were synthesized
successfully via two synthetic pathways, core-shell
synthesis and attachment on silica. These size series of
magnetic nanocomposites in this work can be useful
tools to understand the effects of sizes, surfaces, and
magnetization in biological applications in our future
study.
Acknowledgements
This work was funded in part though the Thailand
Research Fund (MRG5680091) and partly by the
Grants for Development of New Faculty Staff,
Ratchadaphiseksomphot
Endowment
Fund,
Chulalongkorn University, and the Science
Achievement Scholarship of Thailand (SAST) and we
would like to thank Department of Chemistry, Faculty
of Science, Chulalongkorn University for laboratory
facilities and instruments.
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197
PREPARATION OF PERCHLORTE ANION SELECTIVE MEMBRANE
ELECTRODES FROM DONNAN EXCLUSION FAILURE PHENOMENON
INDUCED BY METAL IONS
Sutida Jansod1, Praput Thavoryutikarn2, Wanwisa Janrungroatsakul3, Wanlapa Aeungmaitrepirom1,
Thawatchai Tuntulani1*
1
2
Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50002, Thailand
3 Department of Chemistry, Faculty of Science, Naresuan University, Phitsanulok 65000, Thailand
*
E-mail for Corresponding Author; E-mail: Thawatchai.T@chula.ac.th
Abstract: A calix[4]arene derivative, tripodal amine
crown ether calix[4]arene, L1, was synthesized and used
as ionophore or ion carrier which incorporated in the onitrophenyl octyl ether (o-NPOE) plasticized PVC
membrane ion selective electrodes (ISE). The prepared
ion selective membrane also contained potassium
tetrakis(p-chlorophenyl)borate (KTpClPB) as anionic
additive. The membrane containing L1 showed Donnan
exclusion failure because the ionophore bound tightly to
metal ions such as Cu2+ and Zn2+ ions. The influence of
positive charges of metals could induce the co-extraction
of anions into the membranes that changed the
permselectivity of the membrane to the negative
direction. The fabricated electrodes containing L1 with
KTpClPB as anionic additive preconditioning in CuCl2
and ZnCl2 illustrated the highest selectivity toward
perchlorate with slopes of -56.11 and -56.58 mV decade-1,
respectively over a wide concentration range of ClO4(10-5 to 10-2 M) with detection limits as low as 2.88 x 10-6
and 2.78 x 10-6 M, respectively. In addition, the
fabricated membrane electrodes could be used in a wide
pH range with good ISE characteristics.
often bound metal ions very strongly. Polymeric
membrane containing L1 possessing only one tripodal
amine receptor was prepared to study the complex
stability and selectivity toward anions. When the
ionophore bound very tightly and stably with metal
ions, the polymeric membrane stored many positive
charges from metal ions. To balance the positive
charges, the membrane induced the co-extraction of
anions entirely into the membrane (Figure 1). This
phenomenon is called Donnan exclusion failure [1114]. The permselectivity of the membrane was then
changed to the opposite direction.
1. Introduction
Figure 1. Concept of Donnan exclusion failure
Ion selective electrodes (ISEs), a potentiometric
sensor, have been widely used as analytical devices for
the determination of an extensive range of ions in
environmental and clinical analysis as well as in the
process control [1-5]. In order to achieve highly
selective ISEs on the basis of PVC membrane, suitable
ionophores must be doped into the membrane. Thus
far, derivatives of calix[4]arene have been used as
ionophores in ISEs [6-10] due to their high
lipophilicity and robust structures.
In this work, we have fabricated new perchlorate
anion detectors by using calix[4]arene derivative,
mono-tripodal amine crown ether calix[4]arene (L1),
in a conventional ISE platform. The topology of the
receptor is of importance in determining the overall
receptor-ion interactions. Tripodal amine receptor is a
class of acyclic ionophore, which consists of multiarmed ligands with each arm bearing a functional
group that can coordinate with the target ion.
Currently, the tripodal amine-based receptor has been
used as a recognition motif successfully in ionselective electrode membranes [8,11]. According to
the enhanced chelating effects, the tripodal receptor
2.1 Synthesis
Calix[4]arene derivative, mono-tripodal amine
crown ether calix[4]arene (L1) was synthesized
according to the procedures described previously [15].
2.2 Reagents
High molecular weight poly(vinyl chloride) (PVC),
o-nitrophenyl octyl ether (o-NPOE), Potassium
tetrakis(p-chlorophenyl)borate (KTpClPB), Tetrahydro
furan (THF) and dichloromethane (CH2Cl2) were all
purchased from Fluka. Analytical grade of sodium and
potassium salts of the anions were from BHD, Fluka,
Carlo Erba, and Merck. All solutions were also
prepared with ultrapure water from Milli-Q.
2.3 Membrane preparation
The membrane was mixed and stirred with a total
amount of 220 mg consisted of ionophore (10 mmol
kg-1), various amount of the ion exchanger, KTpClPB,
(25, 50, and 75 mol% relative to the ionophore) and
PVC: o-NPOE plasticizer (1:2 w/w). The membrane
198
containing L1 was dissolved in the minimum amount
of dichloromethane. After that, the components were
dissolved totally into 2.5 mL of THF. The mixtures
were dispensed as a thin film on a glass slide.
2.4 The EMF measurement
The preconditioned membrane was attached to an
electrode body as working electrode that conditioned
in 10-2 M of metal chloride solution overnight before
measuring with anions. The electrode was also filled
with primary anion (10-2 M) and NaCl (10-3 M) as an
inner filling solution. A double junction Ag/AgCl/KCl
3M electrode containing 1 M LiAcO electrolyte bridge
was used as reference electrode. The EMF values and
the activity coefficients were recorded and calculated.
2.5 Selectivity measurement: The potentiometric
selectivity coefficients of the electrodes were
examined by using the separate solution method
(SSM) as recommended by the IUPAC [12]. The SSM
was the measurement of two separate solutions, both
containing calibration curves of interfering and
primary anions at the concentration range from 10-7 to
10-2 M. The selectivity coefficients were calculated
from the observed EMF values.
Polymeric membrane containing calix[4]arene
derivative, mono-tripodal amine crown ether
calix[4]arene (L1), was used to fabricate conventional
ISE, the structures of L1 was shown in Figure 2. The
properties of L1 as ion carrier based on PVC
membrane were first determined by investigating the
potentiometric responses toward cations. The
membranes containing L1 which possessing only one
unit of the receptor gave negative EMF responses to
most cations, the results were shown in Table 1. This
is a consequence of the formation of too strong
complexes inducing the co-extraction of anions into
the membranes. In addition, the permselectivity of the
membranes was changed from cations to anions, so
called Donnan exclusion failure. Considering the
membranes which nearest to the theoretical Nernstian
slopes, Cu(II) and Zn(II) were chosen for the
following experiments using membrane compositions
shown in Table 2.
Table 1: Potentiometric cation responses of the
membrane containing L1
IFS
Linear range
(10-2 M)
(M)
Cu(NO3)2 CuCl2
10-3 – 10-2
Zn(NO3)2 ZnCl2
10-3 – 10-2
Ni(NO3)2
NiCl2
10-3 – 10-2
Co(NO3)2 CoCl2
10-4 – 10-2
Cd(NO3)2 CdCl2
10-3 – 10-2
NaNO3
NaCl
10-3 – 10-2
KNO3
KCl
10-3 – 10-2
AgNO3
AgNO3
10-4 – 10-3
Mg(NO3)2 MgCl2
10-3 – 10-2
Ca(NO3)2 CaCl2
10-4 – 10-3
Hg(NO3)2 HgCl2
10-5 – 10-4
Pb(NO3)2
PbCl2
10-4 – 10-3
IFS: The inner filling solution
Samples
Slope
(mV decade-1)
-59.77 ±1.22
-61.52 ±0.86
-54.01 ±1.41
-20.92 ±0.45
-31.26 ±2.21
-41.79 ±1.58
-35.64 ±1.59
-53.64 ±2.86
-45.68 ±3.14
-6.73 ±0.54
-22.83 ±0.58
-51.47 ±0.77
In addition, we compared the selectivity
coefficients of anions using the separate solution
method (SSM). The results demonstrated in Figure 3
that both membranes were the most selective to
perchlorate, which followed lipophilicity of anions. As
we have known that, the membrane composition used
can influence the response performance such as the
selectivity, linear concentration range, a detection limit
and a response time of polymeric ion-selective
electrode. The further fabricated electrodes containing
L1 with KTpClPB as anionic additive preconditioning
in CuCl2 (electrode1) and ZnCl2 (electrode2) showed
the highest selectivity toward perchlorate with slopes
of -56.11 and -56.58 mV decade-1, respectively over a
wide concentration range of ClO4- from 10-5 – 10-2 M
with detection limits as low as 2.88 x 10-6 and 2.78 x
10-6 M, respectively. Moreover, the time trace line of
the optimize electrode1 toward perchlorate was shown
in Figure 4.
Figure 3. A comparison of the selectivity coeffcients
of the membranes of L1 preconditioning in CuCl2 (a)
and ZnCl2 (b)
Figure 2. Structure of mono-tripodal amine crown
ether calix[4]arene (L1)
199
Table 2: Membrane compositions and electrode
properties of the conventional ISE of L1 toward
perchlorate
KTpClPB
(mol%)
24.7
50.0
75.1
Linear
Range(M)
10-5 – 10-2
10-5 – 10-2
10-5 – 10-2
Slope
(mVdecade-1)
-56.19 ±0.40
-55.06 ±1.05
-48.10 ±0.82
DL
(µM)
3.09
3.70
5.38
CuCl2
24.7
50.0
75.1
10-5 – 10-2
10-5 – 10-2
10-5 – 10-2
-55.80 ±0.36
-56.11 ±0.36
-51.19 ±0.38
2.84
2.88
3.35
Cu(NO3)2
24.7
50.0
75.1
10-5 – 10-2
10-5 – 10-2
10-5 – 10-2
-55.12 ±0.31
-53.76 ±0.66
-50.40 ±1.73
2.86
3.33
4.14
Zn(ClO4)2
25.7
50.0
75.1
10-5 – 10-2
10-5 – 10-2
10-5 – 10-2
-55.69 ±0.33
-55.90 ±0.48
-52.95 ±1.10
3.45
3.26
3.64
ZnCl2
25.7
50.0
75.1
10-5 – 10-2
10-5 – 10-2
10-5 – 10-2
-56.58 ±0.52
-55.90 ±0.33
-51.39 ±0.74
2.78
2.80
3.47
Zn(NO3)2
25.7
50.0
75.1
10-5 – 10-2
10-5 – 10-2
10-5 – 10-2
-55.39 ±0.37
-56.27 ±0.16
-50.84 ±0.57
3.29
3.24
3.31
Condition
Cu(ClO4)2
Figure 6. pH effect on potentiometric responses of the
optimized electrode1 toward 10-3 to 10-2 M of
perchlorate
The performance of the new electrodes also
showed good reversibility of the optimized
perchlorate-ISEs by switching the concentrations of
perchlorate from 10-3 to 10-2 M (Figure 5). The
membranes can be further used in a wide pH range
(Figure 6).
4. Conclusions
Figure 4. Time-dependent response of the optimized
electrode1 toward perchlorate
Mono-tripodal amine crown ether calix[4]arene,
L1, was successfully synthesized and used as ion
carrier in polymeric membrane electrodes. The
membrane containing L1 demonstrated the Donnan
exclusion failure upon binding metal ions tightly and
induced anions into the membranes that changed the
permselectivity of the membrane into the negative
direction. The fabricated new perchlorate-selective
electrodes using Cu(II) and Zn(II) as effectors
illustrated the Nernstian slopes of -56.11 and -56.58
mV decade-1, detection limits as low as 2.88 x 10-6 and
2.78 x 10-6 M with good ISE characterictics.
Acknowledgements
The authors would like to thank Development and
Promotion of Science and Technology talents project
(DPST) and the Thailand Research Fund
(RTA5380003) for financial support.
References
Figure 5. Reversibility of the optimized electrode1 for
10-3 to 10-2 M of perchlorate
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201
BIMETALLIC ALUMINUM COMPLEXES SUPPORTED BY METHYLENE
BRIDGED BIS(PHENOXY-IMINE) LIGANDS FOR THE ROP OF
RAC-LACTIDE
Nattawut Yuntawattana, Pimpa Hormnirun*
Department of Chemistry, Faculty of Science, Kasetsart University, Bangkok, 10900, Thailand
*
E-mail fscipph@ku.ac.th, Tel. +66 2562 5555 ext. 2168
Abstract: A series of bimetallic aluminum complexes
bearing methylene bridged bis(phenoxy-imine) ligands
(1-3) have been successfully synthesized and
characterized by NMR spectroscopy. The complexes
were obtained in good yields by the reaction between the
corresponding ligand and 2 equivalents of trimethyl
aluminum (TMA) in toluene at 90 oC. All bimetallic
aluminum complexes were efficient initiators for the
ring-opening polymerization of rac-lactide and the
polymerizations proceeded in a controlled manner.
Kinetic studies revealed that all polymerizations were
first-order kinetics in monomer. The plots between
molecular weight versus conversion exhibited a good
linear relationship suggesting the living polymerizations.
In addition, the imino substituents on the ligand
framework and the ortho phenoxy substituents have
significant impacts on the catalytic activities and the
stereoselectivity of catalysts.
1. Introduction
Polylactides (PLA), aliphatic polyesters
derived from lactide (LA) monomers, have received
great attention over the past two decades. Owing to
their biocompatible and biodegradable properties, PLA
can be applied to use in many applications, for
instance, suture and fixing bone in biomedical
applications and drug delivery in pharmaceutical
applications. [1] Generally, high-molecular weight
PLA with narrow polydispersity index can be
produced by the ring-opening polymerization (ROP)
using single-site catalysts as initiators. [2] The general
formula of catalysts is LnMOR where Ln is an ancillary
ligand, OR is an initiating group and M is a metal
center. So far, many complexes of metals such as Zn,
[3] Fe, [4] Sn, [5] Ca, [6] Li [7] and Al [2a, 8] have
been reported to promote the ROP of lactide.
However, the most promising candidate for industrial
features is an aluminum metal because of no toxicity.
In the last two decades, there have been many
examples of the application of aluminum complexes as
initiators for the ROP of rac-lactide (rac-LA).
However, only a limited example of bimetallic
aluminum complexes has been published. For
example, Wang et al. reported that dinuclear
aluminum complexes suppoted by amino or iminophenolate ligands are efficient catalysts for the ROP of
rac-LA. [9] Haiyan Ma et al. proved that dinuclear
salan aluminum complexes are active initiators for the
ROP of rac-LA and ε-caprolactone (ε-CL) to give
copolymers between rac-LA and ε-CL with different
microstructures. [10]
Herein, we reported the synthesis and
characterization of a new series of bimetallic
aluminum complexes supported by methylene-bridged
bis(phenoxy-imine) ligands and their application as
initiators in the ROP of rac-LA
Ligand syntheses
Synthesis of [4-OH-3-{CH=N(C6H5)}-C6H3]2CH2 (a)
To a stirred solution of 5,5´-methylene bis(2hydroxy benzaldehyde) (2.00 g, 7.80 mmol) in ethanol
(25 mL) was slowly added aniline (1.45 g, 15.61
mmol) at room temperature. A catalytic amount of
formic acid was then added. The reaction mixture was
stirred at room temperature for 24 hours during which
time an orange solid precipitated. The product was
filtered and dried in vacuo. Yield: 2.49 g, 79%
1
H NMR (500.13 MHz, CDCl3): δ 13.14 (2H, s, OH),
8.53 (2H, s, NCH), 7.38 (4H, t, 3JHH = 7.8 Hz, ArH),
7.29.7.17 (8H, m, ArH), 7.14 (2H, d, 4JHH = 2.1 Hz,
ArH), 6.96 (2H, d, 3JHH = 8.4 Hz, ArH), 3.90 (2H, s,
CH2).
13
C NMR (125.77 MHz, CDCl3): δ 162.6 (NCH),
159.6 (ArCOH), 148.4 (ArC), 133.7 (ArCH), 132.1
(ArCH), 131.6 (ArC), 129.3 (ArCH), 126.9 (ArCH),
121.1 (ArCH), 119.0 (ArC), 117.3 (ArCH), 39.6
(CH2).
Synthesis
of
[4-OH-3-{CH=N(2,6-iPr2C6H3)}C6H3]2CH2 (b)
The synthesis of b was carried out by the same
procedure as that of a, except 2,6-diisopropyl aniline
(2.77 g, 15.61 mmol) was used. The product was
obtained as a pale yellow solid. Yield: 1.95 g, 87%
1
H NMR (500.13 MHz, CDCl3): δ 12.98 (2H, s, OH),
8.26 (2H, s, NCH), 7.30-7.23 (2H, m, ArH), 7.22-7.12
(8H, m, ArH), 7.02 (2H, d, 3JHH = 8.5 Hz, ArH), 3.95
(2H, s, CH2), 2.98 (2H, sept, 3JHH = 6.8 Hz,
CH(CH3)2), 1.17 (24H, d, 3JHH = 6.8 Hz, CH(CH3)2).
13
159.6 (ArCOH), 146.2 (ArC), 138.7 (ArC), 133.8
(ArCH), 132.0 (ArCH), 131.6 (ArC), 125.4 (ArCH),
123.2 (ArCH), 118.5 (ArC), 117.4 (ArCH), 39.9
(CH2), 28.1 (CH(CH3)2), 23.4 (CH(CH3)2).
202
Synthesis
of
[4-OH-5-tert-butyl-3-{CH=(N2,6i
Pr2C6H3)}-C6H3]2CH2 (c)
The synthesis of c was carried out by the same
procedure as that of a, except 5,5´-methylene bis(3tert-butyl-2-hydroxy benzaldehyde) (2.00 g, 5.43
mmol) and 2,6-diisopropyl aniline (1.94 g, 10.91
mmol) was used. The product was obtained as a pale
yellow solid. Yield: 2.98 g, 80%
1
H NMR (500.13 MHz, CDCl3): 13.45 (2H, s, OH),
8.25 (2H, s, NCH), 7.33 (2H, d, 4JHH = 2.2 Hz, ArH),
7.20-7.15 (6H, m, ArH), 6.99 (2H, d, 4JHH =2.2 Hz,
ArH), 3.93 (2H, s, CH2), 2.99 (2H, sept, 3JHH = 6.9 Hz,
CH(CH3)2), 1.48 (18H, s, CH(CH3)3), 1.17 (24H, d,
3
JHH = 6.9 Hz, CH(CH3)2).
13
C NMR (125.77 MHz, CDCl3): 167.2 (NCH), 159.0
(ArC), 146.3 (ArC), 138.8 (ArC), 137.9 (ArC), 131.2
(ArCH), 130.5 (ArC), 130.1 (ArCH), 125.3 (ArCH),
123.2 (ArCH), 118.3 (ArC), 40.4 (CH2), 35.0
(C(CH3)3), 26.4 (CH3), 29.4 (CH3), 28.0 (CH), 23.6
(CH3).
Complex syntheses
Synthesis
of
[4-(OAlMe2)-3-{CH=N(C6H5)}C6H3]2CH2 (1)
To a stirred solution of 5,5´-methylene bis(2hydroxy benzaldehyde) (1.00 g, 2.46 mmol) in toluene
(15mL) was slowly added TMA (2.46 mL of a 2.0 M
solution in toluene, 4.92 mmol) at 0 oC. The reaction
was stirred at 90 oC for 24 hours during which time an
orange precipitate formed. The orang solid was then
filtered and dried in vacuo. Yield: 0.51 g, 40%
1
H NMR (500.13 MHz, CDCl3): δ 8.25 (2H, s, NCH),
7.51-7.42 (4H, m, ArH), 7.42-7.31 (4H, m, ArH),
7.31-7.21 (2H, m, ArH), 7.21-7.13 (2H, m, ArH), 7.04
(2H, s, ArH), 6.90 (2H, d, 3JHH = 8.6 Hz, ArH), 3.85
(2H, s, CH2), -0.74 (12H, s, Al(CH3)2).
13
138.9 (ArC), 134.6 (ArC), 129.8 (ArCH), 128.7 (ArC),
128.2 (ArCH), 128.1 (ArCH), 128.0 (ArCH), 125.3
(ArC), 123.6 (ArCH), 122.2 (ArCH), 39.3 (CH2), -9.4
(Al(CH3)2).
Synthesis of [4-(OAlMe2)-3-{CH=N(2,6-iPr2C6H3)}C6H3]2CH2 (2)
Complex 2 was prepared according to the
same procedure as that of 1. The product was obtained
as a pale yellow solid. Yield: 0.50 g, 41%
1
7.37 (2H, dd, 4JHH = 2.3 Hz, 3JHH = 8.6 Hz, ArH), 7.33
(2H, d, 4JHH = 7.5 Hz, ArH), 7.25 (4H, d, 3JHH = 7.8
Hz, ArH), 6.99 (2H, d, 4JHH = 2.1 Hz, ArH), 6.96 (2H,
d, 3JHH = 8.6 Hz, ArH), 3.87 (2H, s, CH2), 3.06 (4H,
sept, 3JHH = 6.8 Hz, CH(CH3)2), 1.28 (6H, d , 3JHH =6.8
Hz, CH(CH3)2), 1.07 (6H, d, 3JHH = 6.8 Hz,
CH(CH3)2), -0.78 (12H, s, Al(CH3)2).
13
163.7 (ArC), 142.3 (ArCH), 141.8 (ArC), 138.9
(ArCH), 134.2 (ArC), 129.9 (ArC), 128.2 (ArCH),
124.2 (ArCH), 122.4 (ArCH), 118.4 (ArC), 39.2
(CH2), 28.2 (CH(CH3)2), 26.0 (CH(CH3)2), 22.6
(CH(CH3)2), -10.0 (Al(CH3)2).
Synthesis of [4-(OAlMe2)-5-tert-butyl-3-{CH=N2,6i
Pr2C6H3)}-C6H3]2CH2 ( 3)
Complex 3 was prepared according to the same
procedure as that of 1. The product was obtained as a
pale yellow solid. Yield: 0.50 g, 41%
1
7.32 (2H, s, ArH), 7.26-7.20 (2H, m, ArH), 7.19-7.12
(4H, m, ArH), 6.69 (2H, s, ArH), 3.75 (2H, s, CH2),
2.98 (4H, sept, 3JHH = 6.8 HZ, CH(CH3)2), 1.34 (18H,
s, C(CH3)3), 1.18 (6H, d, 3JHH = 6.8 Hz, CH(CH3)2),
0.96 (6H, d, 3JHH = 6.8 Hz, CH(CH3)2), -0.88 (12H, s,
Al(CH3)3)
13
163.1 (ArC), 142.5 (ArCH), 142.1 (ArC), 141.7 (ArC),
135.8 (ArCH), 132.3 (ArC), 128.8 (ArC), 128.0
(ArCH), 124.2 (ArCH), 118.5 (ArC), 39.9 (CH2), 29.3
(C(CH3)3), 28.1 (CH(CH3)2), 26.1 (CH(CH3)2), 22.7
(CH(CH3)2), -9.8 (Al(CH3)2).
Synthesis and Characterization of aluminum
methyl complexes 1-3
The methylene bridged bis(phenoxy-imine)
ligands (a-c) were successfully synthesized by a
Schiff-base condensation between one equivalent of
5,5´-methylenebis(2-hydroxy benzaldehyde) or 5,5´methylenebis(3-tert-butyl-2-hydroxy
benzaldehyde)
and two equivalents of the primary amine derivative in
ethanol at room temperature, as shown in Scheme 1.
All ligands were obtained in high yields (79-87%).
Treatment of the ligand with two equivalents of
trimethyl aluminum (TMA) in anhydrous toluene at 90
o
C afforded the corresponding bimetallic aluminum
complexes (1-3) in quantitative yields (40-41%). The
complexes were formulated on the basis of 1H and 13C
NMR spectroscopy.
Solution 1H NMR studies revealed that the
formation of aluminum complexes 1-3 from the
disappearance of the OH signal of the free ligands and
the appearance of methyl protons attached to the
aluminum center in the high field region of the 1H
NMR spectra, which is characteristic of an aluminummethyl group. In all cases, an integral ratio of
methylene protons to aluminum methyl protons is
1:12, indicating the formation of bimetallic aluminum
complexes.
R2
R2
O
N
O
CH2
HO
R1
OH + R2NH2
N
Ethanol
CH2
HO
R1
R1
OH
R1
a: R1 = H; R2 = C6H6
b: R1 = H; R2 = 2,6-iPr2C6H4
c: R1 = tBu; R2 = 2,6-iPr2C6H4
2AlMe3
Me
Toluene
R2
R2
N
N
Me
Me
Al
Al
CH2
O
1
R
O
Me
1: R1 = H; R2 = C6H6
2: R1 = H; R2 = 2,6-iPr2C6H4
3: R1 = tBu; R2 = 2,6-iPr2C6H4
1
R
Scheme 1. Synthetic pathway of complex 1-3.
203
8000
3.0
6000
2.5
4000
2.0
Aliquots periodically withdrawn from the
polymerization reactions of rac-LA with 1-3 were
used to construct plots of molecular weight versus
percent conversion of monomer. A linear correlation
between molecular weight and percent conversion, in
conjunction with a narrow PDI was observed in all
cases (Figure 1), which is indicative of a well–
controlled living polymerization and a single-site
reaction. In addition, the observation of relatively
narrow and constant PDI values throughout the course
of polymerization suggests that no significant degree
of tranesterifications operates in this initiating system
3.5
(a)
3.0
2.5
Ln[LA]0/[LA]t
Ring-opening polymerization of rac-lactide
The ROP of rac-LA using complexes 1-3
were carried out in toluene at 70 oC in the presence of
two equivalents of benzyl alcohol to form an in situ
aluminum alkoxide species. The results are
summarized in Table 1. All complexes were effective
for the polymerization of rac-LA. The molecular
weights and the PDI values were determined by gel
permeation chromatography (GPC) using the MarkHouwink correction factor of 0.58. [2a] The corrected
Mn values (entries 1-3) closed to the theoretical values
and narrow PDIs on indicative of living characteristic.
The polymerization using 1 and 2 proceeded to 98 and
99% conversion, respectively, in 24 h (entries 1 and 2)
whereas 3 polymerized rac-LA to 87% conversion
after 96 h (entry 3).
(a)
2.0
1.5
1.0
PDI
Mn
.5
0.0
0
2000
1.5
0
1.0
100
10000
20000
30000
40000
50000
60000
Time (s)
2.0
0
20
40
60
80
(b)
1.8
1.6
Conversion (%)
8000
Ln[LA]0/[LA]t
3.0
(b)
6000
2.5
4000
2.0
1.4
1.2
1.0
.8
.4
PDI
Mn
.6
.2
0.0
2000
0
1.5
5000
10000
15000
20000
25000
30000
35000
Time (s)
0
0
20
40
60
1.8
1.0
100
80
(c)
Conversion (%)
1.4
Ln[LA]0/[LA]t
(c)
2.0
4000
PDI
2.5
6000
Mn
1.6
3.0
8000
1.2
1.0
.8
.6
.4
.2
2000
1.5
0
1.0
100
0.0
0
50000
100000
150000
200000
250000
300000
Time (s)
0
20
40
60
80
Figure 2. Semilogarithmic plots of rac-lactide
conversion versus time in toluene at 70 ºC with (a)
complex 1a and (b) complex 2a (c) complex 3a
([LA]0/[Al] = 100, [Al]/[PhCH2OH] = 1, [LA]0 = 0.42
M, [Al] = 8.33 mM).
Table1. Polymerization results of rac-lactide by complexes 1-3a
Conversion (%)
Figure 1. Plots of PLA Mn (●) and PDI (○) as a
function of monomr conversion for a rac-LA
polymerization using (a) 1a/BnOH, (b) 2a/BnOH and
(c) 3a/BnOH ([Al]:[BnOH]:[LA]0 = 1:2:100, 70 oC).
Entry
complex
Time
(h)
Conv.
(%)b
Mn
(GPC)c
Mn
(Theory)d
PDI
Pme
kapp (s-1)
1
2
1
2
24
24
98
99
7,091
8,467
7,063
7,135
1.33
1.27
0.45
0.34
5.89 × 10-5
6.30 × 10 -5
3
3
96
87
6,024
6,270
1.18
0.55
6.31 × 10-6
a[LA] /[Al]
0
= 100, [Al]/[PhCH2OH] = 0.5, [LA]0 = 0.83 M, toluene, 70 ºC. bAs determined via integration of the methine
resonances (1H NMR) of LA and PLA (CDCl3, 400 MHz). cCalculated by ([LA]0/[Al]) × 144.13 × conversion. dDetermined
by gel permeation-chromatography (GPC) calibrated with polystyrene standards in THF and corrected by a factor of 0.58 for
PLA. ePm is the probability of meso linkage between monomer unit
204
Kinetic studies of the polymerizations with 1-3
were monitored by 1H NMR spectroscopy. In all cases,
kinetics of first-order in monomers were observed, as
evidenced from the linear relationship between
ln([LA]0/[LA]t) and time, as shown in Figure 2. The
apparent rate constant (kapp) were obtained from the
gradient of semilogarithmic plots of the rac-LA
conversion ln([LA]0/[LA]t) versus time. The
polymerization with 1 exhibits a kapp of 5.89 × 10-5 s-1
which is slightly slower than the rate of 2 (6.30 × 10-5
s-1). Complex 3 shows the lowest the polymerization
rate (kapp = 6.31 × 10-6 s-1). This may be attributed to
the steric protection at the aluminum center be the tertbuthyl at the ortho-position of the phenoxy ring.
The microstructure of the PLA samples
produced by 1-3 were determined by homonuclear
decoupled 1H NMR spectroscopy. It was found that
the imino substituent and the ortho phenoxy
substituent have some impacts on the stereoselectivity
of catalysts. PLA produced by 1 is slightly heterotactic
with a Pm value of 0.55 while the use of 2 resulted in a
higher heteroselectivity with a Pr value of 0.66. In the
case of 3, the slightly isotactic-biased PLA was
produced (Pm = 0.55).
(b) O'Keefe, B. J., Monnier, S. M., Hillmyer, M. A. and
Tolman, W. B., 2000, J. Am. Chem. Soc., 123, 339-340.
[5] Kowalski, A., Libiszowski, J., Duda, A. and Penczek, S.,
200, Macromolecules, 33, 1964-1971.
[6] (a) Zhong, Z., Ankoné, M. J. K., Dijkstra, P. J., Birg, C.,
Westerhausen, M. and Feijen, J., 2001, Polym. Bull., 46,
51-57
(b) Zhong, Z., Dijkstra, P. J., Birg, C., Westerhausen, M.
and Feijen, J., 2001, Macromolecules, 34, 3863-3868.
[7] Kricheldorf, H. R. and Boettcher, C., 1993, Die
Makromolekulare Chemie, 194, 1665-1669.
[8] Hormnirun, P., Marshall, E. L., Gibson, V. C., Pugh, R. I.
and White, A. J. P., 2006, Proc. Natl. Acad. Sci. U.S.A.,
103, 15343-15348.
[9] Yu, X.-F. and Wang, Z.-X., 2013, Dalton Trans., 42,
3860-3868.
[10] Wang, Y. and Ma, H., 2012, Chem. Commun., 48, 67296731.
4. Conclusions
A new series of bimetallic aluminum complexes
bearing methylene bridged bis(phenoxy-imine) ligands
were successfully synthesized and characterized by
NMR spectroscopy. All complexes were effective
initiators for the polymerization of rac-LA and the
polymerizations proceeded efficiently in a living
manner. Kinetic studies using complexes 1-3 revealed
a first-order in monomer in all cases. The rate of
polymerization decrease in the order 2 > 1 > 3.
Complexes 1 and 2 afforded slightly heterotactic PLAs
with the Pr values of 0.55 and 0.66, respectively. A
slightly isotactic PLA was produced by 3.
Acknowledgements
Department of chemistry, the Faculty of Science,
Kasetsart University and Development and Promotion
of Science and Technology Talents Project are thanked
for financial support of this work
References
[1] (a) Uhrich, K. E., Cannizzaro, S. M., Langer, R. S. and
Shakesheff, K. M., 1999, Chem. Rev., 99, 3181-3198
(b) Ikada, Y. and Tsuji, H., 2000, Macromol. Rapid
Commun., 21, 117-132.
[2] (a) Kowalski, A., Duda, A. and Penczek, S., 1998,
Macromolecules, 31, 2114-2122
(b) Löfgren, A., Albertsson, A.-C., Dubois, P. and
Jérôme, R., 1995, J. Macromol. Sci. Polymer Rev., 35,
379-418.
[3] Schwach, G., Coudane, J.. Engel, R. and Vert, M., 1998,
Polymer International, 46, 177-182.
[4] (a) O'Keefe, B. J., Breyfogle, L. E., Hillmyer, M. A. and
Tolman, W. B., 2002, J. Am. Chem. Soc., 124, 43844393
205
GOLD NANOPARTICLES WITH POLYANILINE FOR SELECTIVE
COUPLING AND OXIDATION REACTIONS OF ARYL BORONIC
AND ITS SUBSTITUTES
Vithawas Tungjitgusongun and Ekasith Somsook*
NANOCAST Laboratory and Center for Catalysis, Department of Chemistry and Center for Innovation in Chemistry, Faculty of
Science, Mahidol University, 272 Rama VI Rd., Thung Phaya Thai, Rachathewi, Bangkok 10400, Thailand
* E-mail: ekasith.som@mahidol.ac.th
Abstract: Gold catalysts were investigated for the
selective transformation of aryl boronic acids in
different pathways: (I) Coupling reaction and (II)
Oxidation reaction. Polyaniline and its derivatives
were considered as stabilizing ligands of gold
nanocatalysts to transform the reaction selectively.
In coupling reaction(I), aryl boronic A and B were
used as starting materials to study the effect of
selective coupling products, homocoupling and
cross coupling, resulted from different polyanilines.
For (II) oxidation reaction, phenol products were
considered as byproducts of the coupling reaction.
This research suggested how to tune the catalytic
activity of gold nanocatalysts selectively by
polyanilines.
its derivatives for example poly-(m-aminophenol), in
order to obtain more selective products.
1. Introduction
2.2 Catalyst preparation
Polymerization of polyanilines, poly-(maminophenol) and poly-(m-aminoaniline), were
prepared by using a simple oxidant, ammonium
persulfate, dissolved in 1 M sulfuric acid to gain the
polymer. HAuCl4·3H2O was stabilized by polyaniline
in water intermediate. The mixing solution of
HAuCl4·3H2O and polyaniline should be used freshly
after prepared.Gold nanocatalysts were observed by
transmission electron microscopy (TEM) technique.
Gold nanocatalysts have been used for several
years because of their surface activation on
nanoscale[1,2]. This metal was abundantly used in many
reactions especially coupling reactions and oxidation
reactions[3-8]. However the way to keep them in a
particle form is significant for each reaction. Reaction
of boronic acid and gold catalysts was recently
studied[9], not only homocoupling product was found
in this reaction but also oxidation of boronic into
phenol was occurred too. To study more information
of this reaction, cross coupling reaction of boronic acid
is considered as studying reaction model because of
many kinds of products that can be occurred in the
reaction such as cross coupling product: two products
from homocoupling and two products from oxidation
of boronic acid.
Polyaniline plays an important role not only
to stabilize this catalysts into the nanoparticle form[10],
in which aggregation of catalysts was not observed,
but also to be a reducing agent in the reaction.
Furthermore, it still can make reaction selective
between coupling and oxidation reactions resulting
from its steric and electronic effects. Mole ratio
between gold and polyaniline and optimization of the
ratio has been studied. Besides, type of polyaniline is
also significant. Variation of polyaniline has been
studied to reveal steric and electronic effects by using
2.1 Materials
HAuCl4·3H2O
(99.99%
purity),2aminophenol (98% purity), m-phenylenediamine (98%
purity), phenylboronic acid (98% purity), 2tolylboronic acid (98% purity), 3-tolylboronic acid
(98% purity) and 4-tolylboronic acid (98% purity)
were purchased from Aldrich. Ammonium persulfate
(98% purity) was from Univar. Potassium hydroxide
(99.99% purity) and tetrahydrofuran (99.9% purity)
were obtained from Merck. Sulfuric acid (>95%
purity) was from Fluka. Deionized water was used in
all experiments.
NH2
(NH 4) 2S2 O8
R
H2 SO4
rt, 24 h
N
H
R
H
N
N
H
R
R
2.3 Reaction of boronic acid with gold nanocatalysts
Reaction was carried out at room temperature
and under atmospheric pressure. 2 mmol of boronic
acid A and B and 2% mol of gold nanocatalysts were
mixed in tetrahydrofuran solvent, and the ratio
between tetrahydrofuran and water was 1:1, with
300% mol of potassium hydroxide as base for 24 h.
After finishing the process, the reaction was quenched
by 1 M hydrochloric acid until the solution become
neutral, pH = 7. Products were obtained by extraction
with ethyl acetate. The extracted product was analysed
by GC–MS and GC (Agilent Technologies 7890A GC
System with a 30 m HP-5 capillary column).
H
N
R
206
The product consisted of cross coupling
product of A and B, homocoupling product of A,
homocoupling product of B, oxidation product of A
and oxidation product of B depending on the type and
the amount of polyaniline.
functions: (i) polyaniline interrupts boronic acids in
coupling reaction and (ii) transforms boronic acid into
phenol.
Table 2: Reaction of boronic acid and gold
nanocatalysts with poly-(m-aminophenol)
Entry Reactions were carried out at room
temperature, 30 °C, under atmospheric pleasure and
basic condition. The reaction without polymer (Table
1), ligandless catalysts, gives products that can be
freely occurred depending on only steric and electronic
effects from starting materials. However, aggregation
of gold was found in every reaction.
1 Starting material phenylboronic (A) Product(% conversion) 1 2 3 4 5 4.4 27.7 31.4 8.2
28.0
23.8 30.8 15.0 8.7
21.3
20.2 33.2 30.3 5.6
10.5
23.2 26.1 3.4 36.0
11.2
12.8 30.3 5.3 30.6
14.5
o‐tolylboronic(B) 2 phenylboronic (A) m‐tolylboronic(B) 3 phenylboronic (A) p‐tolylboronic(B) Table 1: Reaction of boronic acid and gold
nanocatalysts without polyaniline
4 o‐tolylboronic(A) m‐tolylboronic(B) 5 o‐tolylboronic(A) p‐tolylboronic(B) (1) Homocoupling of A, (2) Cross Coupling of A and B, (3) Homocouping of
B, (4) Oxidation of A and (5) Oxidation of B The amount of poly-(m-aminophenol) is 5 mg
Entry Starting material 1 phenylboronic (A) Products (% conversion) 4 5 28.3 1 18.7 37.4 2 3 6.3 9.1 18.7 39.4 26.4 6.5 8.9 Table 3: Reaction of boronic acid and gold
nanocatalysts with poly-(m-aminoaniline)
Entry Starting material Product (% conversion) o‐tolylboronic(B) 2 phenylboronic (A) 1 m‐tolylboronic(B) 3 phenylboronic (A) 10.3 32.6 50.3 2.7 o‐tolylboronic(A) 2 24.6 25.3 28.1 10.4 o‐tolylboronic(A) 3 15.8 42.6 20.0 10.9 4 5 2.3
55.2
phenylboronic (A) 10.6 8.5 1.6 28.9
50.3
phenylboronic (A) 13.0 13.6 4.7 21.9
46.8
17.5 11.4 1.4 49.9
19.8
26.0 19.2 1.3 50.2
3.4
p‐tolylboronic(B) 10.5 4 p‐tolylboronic(B) 3 15.0 m‐tolylboronic(B) 11.4 m‐tolylboronic(B) 5 2 20.1 o‐tolylboronic(B) 4.0 p‐tolylboronic(B) 4 phenylboronic (A) 1 4.4 o‐tolylboronic(A) m‐tolylboronic(B) (1) Homocoupling of A, (2) Cross Coupling of A and B, (3) Homocouping of
B, (4) Oxidation of A and (5) Oxidation of B 5 o‐tolylboronic(A) p‐tolylboronic(B) For poly-(m-aminophenol) (Table 2) and poly-(maminoaniline) (Table 3), products were obtained by the
effect not only from starting materials themselves but
also from the stabilizer. Poly-(m-aminophenol)
motivates reaction to oxidation more than coupling
compared with ligandless catalysts (Table 1). Total
amount of homocoupling products is decreasing,
especially boronic acids with high steric effects.
Similarly, boronic acids with high steric become more
phenol in oxidation part. In the case of poly-(maminoaniline), this polyaniline gives more oxidation
products while most coupling products are decreasing.
The result shows that poly-(m-aminoaniline) can lead
reaction selectively to oxidation. When increasing the
amount of poly-(m-aminoaniline) to 40 mg, oxidation
products are found as major product (99 percentage
conversion). In the case of poly-(m-aminophenol) and
poly-(m-aminoaniline), both have significant two
(1) Homocoupling of A, (2) Cross Coupling of A and B, (3) Homocouping of
B, (4) Oxidation of A and (5) Oxidation of B The amount of poly-(m-aminoaniline) is 5 mg
207
Figure 1 : TEM images of a) poly-(m-aminophenol),
b) poly -(m-aminophenol) with gold, c) poly-(maminoaniline) and d) poly-(m-aminoaniline) with gold
4. Conclusions
Gold nanocatalysts can be stabilized by
polyaniline to prevent aggregation problem. Coupling
products decreased when poly-(m-aminophenol) is
used, and the reaction prefers oxidation when poly-(maminoaniline) is used as stabilizer.
Acknowledgements
We acknowledge PERCH-CIC and for Development
of Pharmaceuticals from Bioresources and Its
Management (NRU) financial support.
References
[1] Astruc, D.; Lu, F., Aranzaes, J. R., 2005, Angew. Chem,
Int. Ed., 44, 7852.
[2] Daniel, M. C.; Astruc, D., 2004, Chem. Rev, 104, 293.
[3] Gonzalez-Arellano, C.; Abad, A.; Corma, A.; Garcia, H.;
Iglesias, M. and Sanchez, F., 2007, Angew. Chem., Int.
Ed., 46, 1536.
[4]Corma, A.; Gonzalez-Arellano, C.; Iglesias, M. and
Sanchez, F., Angew. Chem., Int. Ed.
[5] Manea, F.; Houillon, F. B.; Pasquato, L. and Scrimin, P.,
2004, Angew. Chem., Int. Ed.
[6] Carrettin, S.; Guzman, J. and Corma, A., 2005, Angew.
Chem., Int. Ed., 44, 2242.
[7] Tsunoyama, H.; Sakurai, H.; Ichikuni, N.; Negishi, Y.
and Tsukuda, T., 2004, Langmuir, 20, 11293
[8] Gonzalez-Arellano, C.; Corma, A.; Iglesias, M. and
Sanchez, F., 2005, Chem. Commun., 1990.
[9] Chairoenwimolkul, L. and Somsook, E., 2008,
Tetrahedron Letters, 49, 7299-7302.
[10] Li, W. G.; Jia, Q. X. and Wang, H. L., 2006, Polymer,
47, 23.
208
CRYSTAL STRUCTURE OF SILVER(I) CHLORIDE COMPLEX WITH
N-ALLYLTHIOUREA AND TRIPHENYLPHOSPHINE
Mareeya Hemman1*, Chaveng Pakawatchai1, Saowanit Saithong1, Jaursup Boonmark2 and
Sujittra Youngme2
1Department
of Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90110, Thailand
2Department
of Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand
*E-Mail: mareeya.hemman@gmail.com, Tel. +66 83 1946463
Abstract: The complex of [Ag(Altu)(PPh3)2Cl]∙CH3CN
was synthesized by the reaction of silver(I) chloride with
N-allylthiourea (Altu) and triphenylphosphine (PPh3).
The structure has been characterized by single crystal
X-ray diffraction, Fourier transform infrared
spectroscopy and nuclear magnetic resonance
spectroscopy. The complex crystallizes in Pī with cell
parameters a = 11.0537(4) Å, b = 13.1661(5) Å, c =
14.6392(5) Å, α = 99.2140(10)°, β = 99.1030(10)°, γ =
92.5920(10)°, V = 2071.08(13) Å3 and Z = 2. The Ag(I)
ion is four-coordinated by one Altu molecule, two PPh3
molecules and one chloride ion, forming a distorted
tetrahedral geometry.
1. Introduction
The coordination chemistry of silver(I) complexes
with phosphorus and sulfur donor ligands has become
of wide interest in recent years because of several
potential; such as biological relevance of metal–
sulfur interactions in the living systems and the
potential applications of silver–phosphine complexes
as antitumor/antibacterial agents [1–4]. Nallylthiourea is a substituted thiourea which is the
sulfur donor ligands which can bind to a metal or a
group metals via a variety of bonding modes.
Furthermore, the reaction of inorganic silver(I) salts
with organophosphorus, such as triphenylphosphine,
lead to a design of different formation, depending on
the nature of the ligand, stoichiometric ratio between
the reactances and experimental conditions [5]. In this
work, we report the synthesis and structural
characterization of silver(I) complex containing Nallyltiourea and triphenylphosphine as ligands;
[Ag(Altu)(PPh3)2Cl]·CH3CN.
2.1 Material and instruments
All chemicals and solvents for synthesis were of
reagent grade and used without purification.
The complex was characterized by FT-IR
spectrum (KBr disk, 4000–400 cm−1) recorded on a
BX Perkin-Elmer FT-IR spectrophotometer, 1H NMR
and 13C NMR were recorded on a Bruker FT-NMR
Ultra Shield™ spectrometer, operating at a frequency
of 300 MHz and using CDCl3 or DMSO as solvent
with reference to an internal standard of
tetramethylsilane (TMS). The melting point was
determined with a capillary melting point apparatus.
The crystal structure was studied by single crystal Xray diffraction using the Bruker D8 Quest
diffractometer [6]. The structure was solved by direct
methods and refined using SHELXTL NT (version
6.14) and WinGX (version 2013) crystallographic
program [7-8].
2.2 Preparation of [Ag(Altu)(PPh3)2Cl]·CH3CN
Triphenylphosphine (0.26 g, 1.0 mmol) was first
dissolved in 30 mL of acetonitrile. AgCl (0.07g, 0.50
mmol) was then added into the solution. The mixture
was heated with stirring until a white precipitate was
formed, and N-allylthiourea (0.06g, 0.50 mmol) was
added. The reaction mixture was refluxed for 4 hours
where upon the precipitate gradually disappeared.
The resulting clear solution was filtered off and left
to evaporate at room temperature. The colorless
microcrystals were obtained after few days. The
melting point of complex is 174-176°C. Main IR
peaks (KBr disc)/cm−1: 3280(s), 3077(s), 1570(s),
1480(m), 1437(m), 1325(m), 1097(s), 1027(m),
752(s), 700(s), 667(m). 1H NMR (CDCl3, δ ppm):
8.30 s (-NH-), 7.39-7.22 m (HPh). 13C NMR data
(CDCl3, δ ppm): 180.91s (C=S), 134.03-128.63 m
(Cph). The structure was further confirmed by X-ray
diffraction.
3.1 Infrared Spectroscopy
The characteristic peaks of vibrational spectrum
at 3077 and 1480 cm-1 are assigned to ν(=C-H) and
ν(C=C) of phenyl rings respectively and the peaks at
700-752 cm-1 exhibit δ(C-H) out of plane of aromatic
ring, indicating the presence of triphenylphosphine in
the complex structure. The N-allylthiourea ligand
contains –NH–C(=S)– group which may apply either
the thione –NH–C(=S)– or thiol –N=C(–SH)– form.
In this case, the ligand adopts the thione form which
observed by the absence of the -SH band in the
region ca. 2400-2600 cm-l [9], but there is the sharp
band at 3280 cm-l, presenting ν(NH). In addition, the
spectra at 1570 1325, 1027 and 667 cm-1 are
attributed to ν(C-N) + δ (NH), ν(C-N) + δ(NH) +
δ(C-H), ν(C-N) + ν(C=S) and ν(C=S) respectively,
209
suggesting that N-allylthiourea is coordinated to
Ag(I) through S atom of thione group according to
Singh et al. (2008) [10].
3.2 1H NMR and 13C NMR Spectroscopy
The 1H NMR spectrum of triphenylphosphine
shows signals at 7.24 to 7.38 ppm due to equivalent
ring protons (aromatic protons), while the complex
shows there signals at 7.22-7.39 ppm. The complex
shows signal due to N–H proton at 8.30 ppm, while
free ligand N-allylthiourea shows a single resonance
at 7.65 ppm. The downfield shifting from free ligand
displays the ligand is coordinating to silver(I) via the
thione group. The deshielding of the N–H proton is
related to an increase of the π electron density in the
C–N bond upon complexation [11-12].
The 13C NMR spectra supply more convincing
information about the monodentate behaviour of
thiourea moiety in the complex. The signals of the
triphenylphosphine ring carbon (δ CPh) of the
complex were observed in the region 128.63-134.03
ppm, and the free ligand shows the signals about
128.43-137.16 ppm. It shows the aromatic rings in
the structure. Moreover, the important peak at 180.91
ppm is assigned the C=S signals appearing upfield
from the free ligand (183.76 ppm). The upfield shift
is attributed to lowering of C=S bond order upon
coordination, indicating the presence of sulfur to
metal bonds in the complex and a shift of N→C
electron density producing partial double bond
character in the C–N bond [12-13].
1
H NMR and 13C NMR spectra support that the
complex was synthesized to be the mixed ligand
Ag(I) complex.
3.3 X-ray structural investigation
The complex crystallizes in triclinic system space
group Pī with the crystallographic data are shown in
Table 1. The structure forms a distorted tetrahedral
silver(I) center with two phosphorus atoms of
triphenylphosphine molecules, one sulfur atom of Nallylthiourea molecule and one chloride ion. In
addition, an acetronitrile solvent molecule is found in
asymmetric unit. The structure is shown in Figure 1
and selected bond distances and angles are listed in
Table 2. Distorted tetrahedral geometries are also
found in similar silver(I) halide complexes which
contain phosphine and thiourea ligands [14-15]. There
are two notable hydrogen bonds. N(1)–H(1)...Cl(1)
(3.265(3) Å) is the hydrogen bond between N(1)–
H(1) of N-allylthiourea and chloride ion of the
adjacent molecule, and another is N(2)–H(2)...S(1)
(3.279(2) Å) formed between N(2)–H(2) of Nallylthiourea and sulfur atom of the adjoining sphere
as shown in Figure 2. Furthermore, the adjacent
molecules are connected together through N–H···Cl
and N-H···S hydrogen bonds to form a onedimension chain structure running along a axis as
shown in Figure 3.
Table 1: Crystal data and structure refinements of
[Ag(Altu)(PPh3)2Cl]∙CH3CN
Crystals parameters
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
α (°)
β (°)
γ (°)
V (Å3)
Z
F(000)
R indices [I > 2σ(I)]
R indices (all data)
Goodness-of-fit on F2
C42H41AgClN3P2S
825.10
Triclinic
Pī
11.0537(4)
13.1661(5)
14.6392(5)
99.214(1)
99.103(1)
92.592(1)
2071.08(13)
2
848
R1 = 0.0339, wR2 = 0.0678
R1 = 0.0522, wR2 = 0.0745
1.042
Table 2: Selected bond distances and angles of
Bond distances) (A๐)
Ag1-S1
2.5885(8)
Ag1-P1
2.4848(7)
S1-C37
1.710(3)
N1-C37
1.314(3)
N2-C37
1.332(3)
N2-C38
1.456(4)
P1-C1
1.822(3)
P1-C7
1.823(3)
P1-C13
1.823(3)
P2-C19
1.817(3)
P2-C25
1.827(3)
P2-C31
1.830(3)
Bond angles (๐)
P2-Ag1-P1
123.06(3)
P1-Ag1-S1
110.53(3)
P2-Ag1-S1
109.46(3)
P1-Ag1-Cl1 103.82(3)
P2-Ag1-Cl1 104.61(3)
S1-Ag1-Cl1 103.16(3)
Figure1. The [Ag(Altu)(PPh3)2Cl]∙CH3CN structure
and hydrogen atoms are omitted for clarity.
210
References
Figure2. Hydrogen bonding
[Ag(Altu)(PPh3)2Cl]∙CH3CN.
interactions
in
Figure3.
One-dimension
hydrogen
bonding
interactions of [Ag(Altu)(PPh3)2Cl]∙CH3CN run along
a axis.
4. Conclusions
[1] Ahmad, S., Isab, A. A., Ali, S. and Al-Arfaj, A. R.,
2006, Polyhedron, 25, 1633-1645.
[2] Lobana, T. S., Sharma, R. and Butcher, R. J., 2008,
Polyhedron, 27, 1375-1380.
[3] Meijboom, R., Bowen, R. J., Berners-Price, S. J.,
2009, Coord. Chem. Rev., 253, 325-342.
[4] Nomiya, K. Yoshizawa, A., Tsukagoshi, K., Kasuga,
N.C., Hirakawa, S. and Watanabe, J., 2004, J. Inorg.
Biochem., 98, 46-60.
[5] Ferrari, M. B., Bisceglie, F., Cavalli, E., Pelosi, G.,
Tarasconi, P. and Verdolino, V., 2007, Inorg. Chim.
Acta., 360, 3233-3240.
[6] Bruker, 2007, SMART, SAINT and SADABS, Bruker
AXS Inc., Madison, Wisconsin, USA.
[7] Sheldrick, G. M., 2008, Acta Cryst., A64, 112–122.
[8] Farrugia, L. J., 2012, J. Appl. Cryst., 45, 849-854.
[9] Bharti, A., Bharati, P., Bharty, M. K., Dani, R. K.,
Singh, S. and Singh, N. K., 2013, Polyhedron, 54,
131-139.
[10] Singh, N. K., Singh, M., Tripathi, P., Srivastava, A. K.
and Butcher, R. J., 2008, Polyhedron, 27, 375–382.
[11] Isab, A. A., Ahmad, S., and Arab, M., 2002,
Polyhedron, 21, 1267-1271.
[12] Isab, A. A., Nawaz, S., Saleem, M., Altaf, M.,
Monim-ul-Mehboob, M., Ahmad, S. and Evans,
H. S., 2010, Polyhedron, 29, 1251–1256.
[13] Isab, A. A., Fettouhi, M., Ahmad, S. and Ouahab,
L., 2003, Polyhedron, 22, 1349-1354.
[14] Jantaramas, P., 2011, Silver(I) complexes with
acetylthiourea and triphenylphosphine, Master's
Thesis, Prince of Songkla University.
[15] Lobana, T. S., Khanna, S., Sharma, R., Hundal, G.,
Sultana, R., Chaudhary, M., Butcher, R. J. and
Castineiras, A., 2008, Cryst.Growth Des., 8, 12031212.
The N-allylthiourea and triphenylphosphine react
with
AgCl
to
form
complex
of
[Ag(Altu)(PPh3)2Cl]∙CH3CN. Results from infrared
spectroscopy and 1H and 13C NMR spectroscopy
support the structure is the mixed ligands complex.
The crystal structure of a novel mononuclear silver(I)
complex is also presented, in which the thione and
phosphine ligands coordinate through the sulfur and
phosphorus atoms repectively, suggesting distorted
tetrahedral geometry around silver ion. In addition,
hydrogen bonding interactions are found in crystal
packing which link adjacent molecules, forming onedimention down a axis.
Acknowledgements
The authors thank the financial supports from the
Faculty of Science for the Research Assistant
scholarship to Miss Mareeya Hemman, the
Department of Chemistry and Graduate School,
Prince of Songkla University.
211
SYNTHESIS AND CHARACTERIZATION OF CADMIUM(II) COMPLEX
WITH 4,4′-BIPYRIDINE AND CINNAMIC ACID
Sirinart Chooset1, Anob Kantacha2, Arunpatcha Nimthong3, and Sumpun Wongnawa1*
1Department
of Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand
2Department
3Department
of Chemistry, Faculty of Science, Thaksin University, Patthalung, 93110, Thailand
of Chemistry, Youngstown State University, One University Plaza, Youngstown, OH 44555, USA
*E-mail: sumpun.w@psu.ac.th, Tel. +66 74 288443, Fax. +66 74558841
Abstract: [Cd3(4,4′-bipyridine)2(cinnamate)6(H2O)2]n was
synthesized
using
hydrothermal
method
with
Cd(CH3COO)2⋅2H2O , 4,4′-bipyridine, and cinnamic acid
as starting materials. The obtained complex was
investigated
by
Fourier-transformed
infrared
spectroscopy (FT-IR), single crystal x-ray diffraction
(SCXRD), and thermogravimetric analysis (TGA). Single
crystal x-ray diffraction study revealed that the complex
crystallized in triclinic space group P ī. The octahedral
geometry Cd(1) was coordinated by four oxygen atoms
from cinnamate ligand and two oxygen atoms from
water molecules, while Cd(2) and Cd(3) were coordinated
by five oxygen atoms from cinnamate ligand in the
equatorial position and the axial position by two nitrogen
atoms from 4,4′-bipyridine ligand, forming a pentagonal
bipyramidal geometry.
1. Introduction
Metal–organic coordination polymer is of great
current interest due to their potential applications as
functional materials such as catalysis, gas storage, ionexchange magnetism and molecular sensing [1].
Coordination chemistry of cadmium with carboxylic
acid ligands is interesting because of its possible
applications in catalysis, biologically active
compounds, molecular electrochemistry, etc [2].
Cinnamic acid is a carboxylate ligand which is an
important class of ligands in the formation of
coordination polymers. Cinnamate ligand is capable of
binding to a metal in a monodentate, bidentate or
bridging mode lead to mono- and polynuclear
molecular and polymeric structures [3]. 4,4′Bipyridine (4,4′-bipy) is a bidentate bridging ligand
with coordination sites at two ends of the rigid
molecule, which has been widely used in crystal
engineering of coordination polymers [4]. In this work,
we report the synthesis and structural characterization
of the cadmium(II) complex with 4,4′-bipyridine and
cinnamic acid as ligands.
mL Teflon-lined Parr autoclave at 120 °C for 3 days.
The resulting crystals were isolated by filtration,
washed with water, and dried in air. Crystals of this
complex were obtained and characterized by SCXRD,
FT-IR, and TGA analysis. The Cd(II) complex was
found to be air stable and insoluble in organic
solvents. Determination of cell parameters and data
collection was carried out with APEX2, cell
refinement with SAINT, and data reduction with
SAINT and SHELXTL. SHELXS97 was used in
solving the structure, while SHELXL2013 and
SHELXLE were used in the structure refining. All the
graphic manipulations were carried out with
MERCURY. IR spectra were obtained using KBr
pellet on Perkin-Elmer Spectrum One Fouriertransformed infrared spectrophotometer between 4000
– 400 cm-1. Thermogravimetric analyses (TGA) were
carried out on a Perkin Elmer TGA 7 over the
temperature range of 50 – 1000 ◦C and at a heating rate
of 10 ◦C/ min.
Figure 1. The infrared spectra of [Cd3(4,4′-bipyridine)2
(cinnamate)6(H2O)2]n (red line), 4,4′-bipyridine(blue
line) and cinnamic acid (green line).
Cd(CH3COO)2⋅2H2O, 4,4′-bipyridine, and cinnamic
acid were purchased from commercial sources and
used as received. [Cd3(4,4′-bipyridine)2(cinnamate)6
(H2O)2]n was prepared by a mixture of 1 mmol
Cd(CH3COO)2⋅2H2O, 2 mmol cinnamic acid, 1 mmol
4,4’-bipyridine, and 20 mL H2O was heated in a 23
212
Table 1. Selected bond distances and angles of
[Cd3(4,4′-bipyridine)2(cinnamate)6(H2O)2]n
Bond angles (๐)
Bond distances (Å)
Cd1—O5
2.2942 (18)
N2—Cd2—N1
174.13 (4)
Cd1—O4
2.3590 (11)
N2—Cd2—O2
98.22 (5)
Cd1—O7
2.2879 (13)
N1—Cd2—O2
87.42 (4)
Cd2—N2
2.2683 (13)
N2—Cd2—O1
96.42 (5)
Cd2—N1
2.3082 (12)
N1—Cd2—O1
85.48 (5)
Cd2—O2
2.3214 (11)
O2—Cd2—O1
54.95 (4)
Cd2—O3i
2.3554 (10)
O7—Cd1—O5
87.34 (6)
Cd2—O1
2.4222 (12)
O7—Cd1—O4
89.36 (4)
Cd2—O4
2.4336 (12)
O5—Cd1—O4
85.91 (5)
Cd2—O3
2.5016 (11)
Figure 2. Structure of [Cd3(4,4′-bipyridine)2
(cinnamate)6(H2O)2]n (H atoms and the disordered C
atoms omitted for clarity).
Figure 3. Crystal packing of [Cd3(4,4′-bipyridine)2
(cinnamate)6(H2O)2]n viewed along a axis (H atoms
and the disordered C atoms omitted for clarity).
Figure 4. The TGA curve of [Cd3(4,4′-bipyridine)2
(cinnamate)6(H2O)2]n
Infrared Spectroscopy
The preliminary identification of [Cd3(4,4′bipyridine)2(cinnamate)6(H2O)2]n complex was based
on the IR spectra in Figure 1. The bands at 3438 and
1611 cm-1 were assigned to the symmetric OH
stretching and the OH bending vibration of water
molecules, respectively. The unsaturated ν(=CH)
stretching vibrations appeared at 3114 and 3076 cm−1.
Three C=O stretches of this complex appeared at
(1594, 1442) , (1552, 1394), and (1574, 1354) cm−1
which were assigned to νas (COO) and νs(COO) vibrations
of three types of cinnamate ligands. The C=O
stretching vibrations of cinnamate ligand in the
complex compared with the same mode in free
cinnamatic acid molecule show a significant blue-shift
due to the coordination interactions. The ΔνCOO =
νas(COO) − νsym(COO) are 152, 202 and 220 cm−1 in the
complex corresponding to the presence of bidentate,
monodentate, and bridging carboxylate group,
respectively, of cinnamic acid [5-7]. The C–N
stretching vibration was approximately 1243 cm-1,
indicating that the bpy group was included in the
complex. The FT-IR information is consistent with the
results from the X-ray single crystal analysis of the
complex.
Thermogravimetric analysis
Thermogravimetric analysis (TGA) of 2-D
structure of a cadmium coordination polymer is shown
in Figure 4. The first weight loss of 3.12 % in the
temperature range of 100 – 130 oC which was assigned
to the release of two molecules of H2O (compared to
the calculated value of 2.27%). The second weight loss
of 56.88 % occurred in the temperature range of 140 –
380 oC corresponding to five cinnamate ligands and a
4,4′-bipyridine ligand, compared to the calculated
54.41 %. The third weight loss was 19.42% in the
temperature range of 400 – 680 oC corresponding to
one each of cinnamate and 4,4′-bipyridine ligand,
compared with the calculated value of 18.34 %. On
further heating the residue started to decompose
completely to CdO [1].
213
X-ray structural investigation
The X-ray crystallography revealed that the
complex crystallized in triclinic system space group P
ī with cell parameters a = 10.8357 (15), b = 11.6010
(16), c = 13.9036 (19) Å, α =74.388 (2) °, β = 80.131
(2) °, γ = 88.310 (2) °, V = 1658.1 (4) Å3 and Z = 1.
The size of the colorless crystal was 0.20 × 0.09 × 0.05
mm. The selected bond lengths and bond angles are
given in Table 1. Molecular structure of the title
complex is shown in Figure 2. The Cd(1) is
coordinated by four oxygen atoms from four
cinnamate units and two oxygen atoms from two water
molecules forming a distorted octahedral geometry.
The carboxylate group of cinnamate containing O5
and O5a is monodentate ligand and the other
carboxylate group containing O4 and O4a is bidentate
and bridging ligand. Cd(2) and Cd(3) are coordinated
by five oxygen atoms from carboxylic of three
cinnamic acid around Cd(2) and Cd(3). All five
oxygen atoms, O(1), O(2) O(3), O(3i) and O(4), are
located at the equatorial plane while N(1) and N(2)
occupy the axial position with bond angle N(1)-Cd(2)N(2) 174.13(4)o to give a pentagonal bipyramidal
geometry [8]. Furthermore, in the complex, each
cinnamate ligand adopts two coordination modes, the
O,O-bidentate chelate mode and the tridentate bridging
mode. The crystal packing of [Cd3(4,4′bipyridine)2(cinnamate)6(H2O)2]n is shown in Figure
3.
References
[1] Seung, P. J., Jung, I. P., Soo, H. K., Tae, G. L.,
Jin, Y. N., Cheal, K., Youngmee, K. and Sung, J.
K., 2012, Polyhedron., 33, 194–202.
[2] Tang, S. P. 2008., Chinese journal of inorganic
chemistry., 24, 977-980.
[3] Han, K., Sun, H. L., Soo, H. K., Young, M. L.,
Byeong, K. P., Eun, Y. L., Yu, J. L., Cheal, K.,
Sung, J. K. and Youngmee, K., 2008,
Polyhedron., 27,3484–3492.
[4] Rüdiger, W. S., Richard, G., Bodo, Z., and Iris,
M.O., 2011, Polymers., 3, 1458-1474.
[5] Kalinowska, M., S´wisłocka, R., and Lewandowski,
W. 2011, Journal of Molecular Structure.,
993, 404–409.
[6] Raj, P. S., Anju, S., Paloth, V., Julia, J. and
Valeria, F., 2012, Inorganic Chemistry
Communications., 20, 209–213.
[7] Glen, B. D., Maria, F., Peter, C. J., Stuart, G. L.
and Winnie, W. L., 2009., Journal for Inorganic
and General Chemistry., 635, 833-839.
[8] Xian,W.W., Jing, Z. C. and Jian, H. L., 2007, A
Journal of Chemical Sciences., 62, 1139 – 1142.
4. Conclusions
The complex [Cd3(4,4′-bipyridine)2(cinnamate)6
(H2O)2]n was prepared via the reaction of Cd(II)salt ,
4,4′-bipyridine, and cinnamic acid using hydrothermal
method. The complex structure was obtained from
single crystal x-ray diffraction technique combined
with spectroscopic and thermogravimetric techniques.
Within the crystal structure, Cd(1) coordinated to
oxygen atoms from cinnamic acid and water molecule
to form an octahedral geometry whereas Cd(2) and
Cd(3) coordinated to oxygen atoms from cinnamic
acid and nitrogen atoms from 4,4′-bipyridine forming
a pentagonal bipyramidal geometry. The 2-D structure
was formed via the bridging 4,4′-bipyridine and
cinnamate ligand.
Acknowledgements
This work was supported by the Songklanagarind
Scholarship for Graduate Studies from Prince of
Songkla University. We would like to thank
Dr. Matthias Zeller for valuable suggestions and
assistance with X-ray structure determination and use
of structure refinement programs. We would like to
thank the Department of Chemistry and the Graduate
School, Prince of Songkla University.
214
SYNTHESIS OF CALCIUM SILICATE FROM SHELL OF POMACEA
CANALICULATA AND RICE HUSK ASH BY MECHANOCHEMICAL
METHOD
Phatthareeya Suriya1, Ratchadaporn Puntharod1,2*
1Department
2Nanoscience
of Chemistry, Faculty of Science, Mae jo University Chiang Mai, 50290, Thailand
and Nanotechnology Laboratory, Mae Jo University, Chiang Mai, 50290, Thailand
*E-mail: ratchadaporn_p@mju.ac.th, Tel. +66 5387 3530, Fax. +66 5387 3548
Abstract:Calcium silicate was synthesized using silica
from rice husk ash and calcium oxide from shell of snail
namely Pomacea canaliculata calcined at 800 oC for 2
hours. The rice husk ash and calcined shell in molar ratio
of 1:1 were ground by alumina ball with high speed
milling. The solid powder was calcined at 800 and 1000
oC for 2 hours. The formation of calcium silicate was
firstly investigated by Fourier transform infrared
spectroscopy. The temperature for calcination could
affect the occurring of calcium silicate with appearance
the band of Ca−O−Si at 935 cm-1. Calcium silicate was
starting occurred while mixed oxide was ground for 1
hour and calcined at 1000 oC. The phase of calcium
silicate was confirmed by X-ray diffractometry.
1. Introduction
Calcium silicate or wollastonite is mineral from
nature. It has been applied in industry such as ceramic,
plastics, construction materials [1] and a substitute for
asbestos [2] including biodiesel reaction as catalyst in
transesterification reaction [3].
Mechanochemical method is a kind of solid state
reaction. This method in high energy milling has been
found widely spread applications for the synthesis of
many solid inorganic compounds[4].Anew approach to
the mechanochemical synthesis of inorganic
compounds is based on the mechanical activation of
mixtures of solid acids, bases and compounds with
reactive hydroxyl groups or coordinated water. This
process involved high-energy collisions of the grinding
media and reactant, resulting in chemical reactions
called mechanochemistry without any external heating.
The main advantage of the mechanochemical method
is carried out at room temperature instead of high
temperature. The high speed milling process involves
repeated mixing, deformation, comminuting, welding
and rewelding of the reactant powder particles in a
closed jar of a planetary ball mill. Also this method is
environmental friendly and free of organic-inorganic
solvents [5,6].
The purposed of this work was to synthesize of
calcium silicate from shell of snail namely Pomacea
canaliculata and rice husk ash by mechanochemical
method with high speed milling and to study the
temperature of calcination for occurrence of calcium
silicate.
2.1 Materials
The raw shells of snail namely Pomacea
canaliculata and rice husk were collected from rice
field in Chiangmai province. The shells were washed
with tap water, dried at room temperature, and
manually crushed by a porcelain mortar. The small
pieces of solids were calcined in muffle furnace at 800
ο
C for 2 hr. Rice husk ash was prepared by burned rice
husk in biomass gasifier stove.
2.2 Experimental
The staring raw materials were calcium oxide and
rice husk ash. The mixtures of these raw materials
equvivalent in molar ratio of 1:1were ground by
alumina ball with high speed milling at 380 rpm
(Foshan Shenglong Cermaics Equipment).The mixed
power-to-ball weight ratio was 1:4. The milling time
was varied in range of 1, 2, and 3 hr. The solid
powders werecalcined at 800 and 1000 οC for 2 hr to
remove carbonate.
Fourier transform infrared spectra were recorded
on a spectrometer (Perkin Elmer). The solid sample
was mixed with the single crystal potassium bromide
to obtain pellet.
X-ray diffraction was taken and analyzed using an
X-ray analyzer (Bruker). Scanning2θwasmeasured
from 10-90ο. The peak positions were consistent with
those of the international center for diffraction data
standards to identify the crystalline phases.
Scanning Electron Microscope ( Jeol) was used to
observe microstructures. The samples were mounted
on a stub using a carbon paste and were sputter-coated
with gold to improve electrical conductivity. The
magnification of 10,000× was used.
215
471
805
(b)
1429
3641
816
710
1104
(a)
4000
3500
3000
2500
2000
Wavenumber (cm-1)
1500
1000
500
Figure 1. FTIR spectra of (a)CaO from shell of snail
namely Pomacea canaliculata calcined at 800οC for 2
hr and (b)SiO2 from rice husk ash.
516
1470
(c)
band at 1429, 816 and 471 were assigned to CO32- of
shell of snail [7].The broad band at 1104 cm-1of the
rice husk ash was indicated the –OH vibration of
surface hydroxyl groups. The bands at 805 and 471
cm-1were assigned to O−Si−O stretching and bending,
respectively [8]. Figure 2 was the FTIR result of
mixture between CaO and SiO2 at milling time of1,2
and 3 hr with calcined at 800 oC for 2 hr. The band of
carbonate still appeared. It could not be removed
completely while the solid product was calcined at 800
°C. The formation of Ca−O−Si of calcium silicate was
disappeared. The result suggested that those conditions
were not appropriate to synthesize calcium silicate.
Figure 3 was the FTIR result of mixture between CaO
and SiO2 at the milling time of1,2 and3 hr with
calcined at 1000 oC for 2 hr. The band of Ca−O−Si of
calcium silicate was appeared at 923-926 cm-1, while
the band of CO32-was disappeared [9]. The calcination
at 1000 oC was suitable temperature to synthesize
calcium silicate.
1001
923
(b)
CaSiO3
518
1469
5000
4000
517
Arbitary unit
999
926
(d)
1000
924
1469
(a)
4000
3500
3000
2500
2000
Wavenumber (cm-1)
1500
1000
500
Figure 2. FTIR spectra of mixture between CaO and
SiO2 at milling time of(a) 1, (b) 2,and (c) 3 hr and
calcined 800 °C for 2 hr.
517
461
2000
(c)
1000
(b)
0
(a)
0
20
40
60
80
100
2θ
Figure 4. XRD pattern (a) wollastonite-1A (JCPDS
No. 00-019-0249) and mixture between CaO and SiO2
at milling time of (b) 1, (c) 2, and (d) 3 hr and calcined
1000 °C for 2 hr.
432
717
566
(b)
997
923
517
455
(a)
717
1096
990
938
1070
1009
935
718
796
646
566
(c)
3000
4000
3500
3000
2500
2000
Wavenumber (cm-1)
1500
1000
500
Figure 3. FTIR spectra of mixture between CaO and
SiO2 at milling time of (a) 1, (b) 2, and (c) 3 hr and
calcined 1000 °C for 2 hr.
3. Resultsand Discussion
The FTIR spectra of the silica from rice husk ash
and calcium oxide from shell of snail namely Pomacea
canaliculata calcined at 800 oC for 2 hr were shown in
Figure 1.The band at 3641 cm-1was assigned to the
Ca−O bonding of Ca(OH)2. The dominant peak around
2400 cm-1 was assigned to CO2 in atmosphere. The
Figure 5. SEM micrograph of mixture between CaO
and SiO2 at milling time of 1hr and calcined at 1000
o
C for 2 hr.
216
of calcium silicate was confirmed by XRD. The
milling time and calcined temperature were influence
the formation of calcium silicate, morphology and size
of particle. The mechanochemical method with high
speed milling is high potential tool and solvent free
synthesis.
Acknowledgements
This research was financial supported by National
Research Thailand.
References
and SiO2 at milling time of 2 hr and calcined at 1000
o
C for 2 hr.
[1] Tangboriboon, N.,Khongnakhon, T.,Kittikul, S.
Kunanuruksapong, and Sirivat, R.A., 2011,J. Sol-Gel
Sci. Technol., 58, 33-41.
[2] Demidenko, N.I., and Tel'nova, G.B., 2004, Glass
Ceram., 61, 183-186.
[3] Hsin, T., Chen, S., Guo, E., Tsai, C., Pruski, M., and
Lin, V.S.Y., 2010, Top. Catal., 53, 746-754.
[4] Billik, P. andCaplovicova, M., 2009, Powder Technol.,
191, 235-239.
[5] Zhou, C.F.,Du, X.S.,Liu, Z.,Ringer, S.P.,and Mai, Y.W.,
2009, Synth. Met., 159, 1302-1307.
[6] Huot, J., Ravnsbaek, D.B., Zhang, J., Cuevas, F.,
Latroche, M., and Jensen, T.R., 2013, Prog. Mater. Sci.,
58, 30-72.
[7] Engin, B., Demirtas, H., and Eken, M., 2006, Radiat.
Phys. Chem., 75, 268-277.
[8] Chandrasekhar, S., and Pramada, P.N., 2006,
Adsorption, 12, 27-43.
[9] Meiszterics, A., Rosta, L., Peterlik, H., Rohonczy, J.,
Kubuki, S., Henits, P., and Sinkó, K., 2010, J. Phys.
Chem. A, 114, 10403-10411.
and SiO2 at milling time of 3 hr and calcined at 1000
o
C for 2 hr.
Calcium silicate was starting occurred while mixed
oxide was ground for 1 hrand calcined at 1000 oC
corresponded with FTIR results. The crystallinity of
calcium silicate was increased as milling time
increased. The phase of product was wollastonite-1A
(JCPDS No. 00-019-0249) in Figure 4.
The SEM micrographs of mixture between CaO
and SiO2 at milling time of 1, 2 and 3 hr and calcined
at 1000 oC for 2 hr were shown in Fig 5, 6, and 7,
respectively. The size of particle was smaller as the
milling time increased. The average size was less than
1 µm with irregular shape. This observation shows the
influence of milling time on the morphology and the
size of the particles. The longer milling time could
provide the smaller particle size.
4. Conclusions
Calcium silicate was successfully synthesized by
mechanochemical method with calcination at 1000 οC
using shell of Pomacea canalicalata and rice husk ash
as starting materials. The temperature for calcination
could affect the occurring of calcium silicate with
appearance the band of Ca−O−Si by FTIR. The phase
217
EQUILIBRIUM EXTRACTION OF URANIUM AND THORIUM MIXTURES
IN 4 M HNO3 WITH 5 AND 10% TBP/KEROSENE
Uthaiwan Injarean1, Pipat Pichestapong1*, Yoreeta Marnchareon2, Sarin Cheephat2,
Nattawadee Wisitruangsakul2, Boonnak Sukhummek2
1 Research
and Development Division, Thailand Institute of Nuclear Technology, Bangkok 10900, Thailand
of Chemistry, Faculty of Science, King Mongkut’s University of Technology Thonburi,
Thung Khru, Bangkok 10140, Thailand
2 Department
*
E-mail: pipat55@gmail.com, Tel. +66 2562 0120, Fax. +66 2562 0120
Abstract: Solvent extraction technique has been used
extensively for the separation and purification of
uranium and thorium from other associated elements in
the nuclear materials processing. In this work, the
equilibrium extraction of uranium and thorium from 4
M HNO3 with 5 and 10% tributyl phosphate (TBP) in
kerosene was investigated. The distribution coefficients
of each element were studied at various concentrations of
the individual solution and of the mixed solution. The
element concentration was determined by ICP-AES. The
distribution coefficients of both uranium and thorium
were found to be varied with their concentration and the
distribution coefficient of uranium is much higher than
that of thorium. The extraction efficiency increased with
higher TBP concentration but decreased with the
increasing feed concentration. The uranium-thorium
separation factor in the mixed solution was seen to
depend on the mixture concentration and 10%
TBP/kerosene extractant provided higher uraniumthorium separation factor than 5% TBP/kerosene. These
equilibrium data are further developed according to the
McCabe-Thiele approach to simulate the multistage
counter-current extraction and separation of uranium
and thorium mixtures.
1. Introduction
Uranium fuel used in nuclear power plants is
normally extracted from uranium ores with relatively
high uranium content. However, some ores such as
monazite, phosphate rock, and titanium ore, which
contain a small amount of uranium, can be reserved for
uranium mining. In the South of Thailand, monazite
ore, found in the tailings of tin mines, contains about
0.24-0.79% of uranium, 4.5-10.6% of thorium and
other rare earth elements in the form of phosphate
compounds [1]. This monazite can be chemically
processed to extract and separate nuclear elements
from other components. In the alkaline process,
monazite is usually digested with 50% NaOH at about
140 °C to convert phosphate compounds to hydroxides
which later are dissolved by HCl and selectively
precipitated at pH 4.5 to separate uranium and thorium
from other rare earth elements. Mixed uranium and
thorium cake is then dissolved into a nitrate solution.
Solvent extraction process with a proper extractant is
widely used to separate uranium from thorium as well
as to purify each element.
Separation and purification of uranium using tributyl
phosphate (TBP) process has been employed in several
countries. Other processes using organophosphoric
compounds such as alkyl phosphine oxide and
phosphonate, phosphinate, and ketones or ethers were
also reported. However, the TBP process was seen to
have more advantages and was widely chosen [2-6].
The extraction of uranium nitrate and thorium nitrate
by TBP is shown in the following reactions:
UO22+ + 2 NO3− + 2 TBP = UO2(NO3)2 · 2 TBP
Th4+ + 4 NO3− + 4 TBP = Th(NO3)4 · 4 TBP
The typical separation and purification processes
usually include the scrubbing step using appropriate
solution to scrub some impurities, which may be
extracted into the extractant along with the uranium, to
ensure the purity of uranium before being stripped and
precipitated.
In this work, the equilibrium extraction of uranium
and thorium in 4 M HNO3 as individual and mixed
solutions has been investigated using 5 and 10%
TBP/kerosene extractants. Batch simulation of the
multistage extraction and separation of uranium in the
mixture with both extractants were also studied.
Feed solutions were prepared by dissolving
and
uranium(VI)
nitrate
(UO2(NO3)2•6H2O)
thorium(IV) nitrate (Th(NO3)4•5H2O), obtained from
Merck, in 4 M HNO3. TBP used in the extraction
solvent was from Fluka and kerosene was from PTT.
The solutions of 5 and 10% TBP in kerosene were
used as the extractants. Equilibrium extraction was
carried out using separatory funnels on a shaker at
room temperature (32 ± 2 °C) with a speed of 200 rpm
and contact time of 10 min to ensure an equilibrium
state [2-3]. Equilibrium distribution coefficient (D) of
U and Th between aqueous feed and organic extractant
at various feed concentrations was determined as the
ratio of element concentration in organic phase to
element concentration in aqueous phase. The
concentrations of elements in the samples were
determined using ICP-AES spectrometer (Optima
5300 DV, Perkin Elmer).
218
2.1 Equilibrium extraction of individual solution
The initial feed was prepared at high uranium or
thorium concentration and other feeds were prepared
by dilution of this initial feed with 4 M HNO3. The
concentrations of uranium feed and thorium feed
employed in this work were in the range of 500–
30,000 mg/L.
2.2 Equilibrium extraction of mixture solution
The feed of uranium and thorium mixtures were
prepared by mixing uranium feed and thorium feed.
Two series of mixture solutions were prepared. The
first series has a constant concentration ratio of
uranium to thorium at 1:1 and the total concentration
was in the range of 500–25,000 mg/L. The other series
has a fixed concentration at 15,000 mg/L and the
concentration ratio of uranium to thorium was varied.
2.3 Batch simulation of multistage extraction
The extraction of uranium from the mixture was
carried out in batchwise laboratory scale to simulate
the multistage counter-current extraction as shown in
Figure 1. The left figure illustrates the extraction
pattern that was followed for batch simulation of the 3stage continuous counter-current extraction process
shown on the right figure. The procedure consists of
repeated introductions of fresh feed solution (F) and
fresh extractant (S) into a series of batch extractions,
plus withdrawal of extract (E) and raffinate (R) phases.
Each circle represents a batch extraction in a
separatory funnel. After a number of extraction cycles,
the system should approached steady state and the
liquids in the funnels resemble the streams that would
exist in an actual continuous countercurrent extraction
[7-8]. The cycles of batch extraction were carried out
to simulate 2, 3 and 4 stages in counter-current
extraction using feed to extractant ratio of 1:1.
shown in Figure 3 and Table 2. It is seen that
extraction of both uranium and thorium with 10%
TBP/kerosene is higher than that with 5%
TBP/kerosene and their distribution coefficients
increase with decreasing concentrations which is
similar to other reports [5-6]. However, the
distribution coefficient of uranium, 1.12–7.50 with 5%
TBP/kerosene
and
4.11–18.00
with
10%
TBP/kerosene, is much higher than that of thorium,
0.05–0.20 with 5% TBP/kerosene and 0.20–1.05 with
10% TBP/kerosene. It is noted that distribution
coefficients of uranium and thorium increases about 4
times as the concentration of TBP increases from 5 to
10%. This distribution coefficient can be used to
calculate the extraction efficiency of the solvent and to
analyze the number of extractions required for the
desired process efficiency.
Table 1: Distribution coefficients of uranium in the
equilibrium extraction with 5 and 10% TBP/kerosene
U conc.
(mg/L)
29933
24180
20947
14633
11177
7992
3482
1540
852
596
Distribution coeff., DU
5% TBP
10% TBP
1.12
4.11
1.67
5.28
2.02
6.96
1.97
6.79
2.38
9.11
3.29
9.81
4.04
11.90
3.39
8.36
6.93
16.53
7.50
18.00
Figure 2. Equilibrium distribution of uranium in 4 M
HNO3 and 5 and 10% TBP/Kerosene
Figure 1. Batch simulation of 3-stage continuous
counter-current extraction
3.1 Equilibrium extraction of individual solution
The feed compositions and their equilibrium
distribution of uranium are shown in Table 1 and their
equilibrium concentrations are plotted in Figure 2. The
similar equilibrium extraction data for thorium are also
Figure 3. Equilibrium distribution of thorium in 4 M
HNO3 and 5 and 10% TBP/Kerosene
219
Table 2: Distribution coefficients of thorium in the
equilibrium extraction with 5 and 10% TBP/kerosene
Distribution coeff., DTh
5% TBP
10% TBP
Th conc.
(mg/L)
25633
18953
16037
12790
9516
6336
3074
1513
888
571
0.09
0.13
0.10
0.20
0.06
0.13
0.17
0.16
0.12
0.05
0.24
0.20
0.29
0.25
0.37
0.52
0.58
1.05
0.77
0.27
3.2 Equilibrium extraction of mixture solution
The mixture compositions and the separation factor
of uranium and thorium (SFU/Th) are shown in Table 3
and 4 and their equilibrium concentrations are plotted
in Figure 4 and 5. The uranium/thorium separation
factor was determined from the distribution coefficient
of uranium divided by that of thorium. The separation
factor from first extraction series with constant 1:1
mixing ratio (Table 3) indicates that 10%
TBP/kerosene extractant provides the separation
factor, 4.11–18.00, higher than 5% TBP/kerosene,
1.12–7.50. The larger separation between 10%
TBP/kerosene equilibrium lines of Th and U in Figure
4 also supports this data. However, the separation
factors from the second extraction series with various
mixing ratios (Table 4) show a different trend. The
equilibrium extraction with 5% TBP/kerosene has
separation factors of 19.5–67.7 corresponding to the
average of 41.4 and the extraction with 10%
TBP/kerosene has separation factors of 23.9–54.9
corresponding to the average of 31.7. This is hardly
determined from Figure 5 as the distances between
each pair of equilibrium lines are closely similar.
It is quite obvious that the separation of uranium
and thorium with TBP process can be affected by
many factors such as the concentration of TBP, the
concentration of feed and the concentration ratio
between U and Th in the feed. There are also related
factors involved in this separation process which are
the recovery of uranium and the purity of uranium
product.
Table 3: Separation factors of uranium- thorium in the
equilibrium extraction of feed with uranium and
thorium mixture at constant 1:1 ratio
U conc.
(mg/L)
Th conc.
(mg/L)
9021
7755
6054
4588
3019
1436
761
444
297
151
8995
7755
6054
4592
3003
1484
751
444
295
151
Separation factor, SFU/Th
5% TBP
10% TBP
1.12
4.11
1.67
5.28
2.02
6.96
1.97
6.79
2.38
9.11
3.29
9.81
4.04
11.90
3.39
8.36
6.93
16.53
7.50
18.00
Table 4: Separation factors of uranium-thorium in the
equilibrium extraction of feed with uranium and
thorium mixture at various ratios
U conc.
(mg/L)
Th conc.
(mg/L)
13710
11850
10550
9148
7789
5917
4579
3087
1587
1541
2843
4445
5894
7345
9026
10270
11570
12620
Separation factor, SFU/Th
5% TBP
10% TBP
19.5
54.9
50.9
34.7
20.4
24.6
63.4
25.5
44.6
25.0
67.7
28.9
28.5
23.9
27.2
30.4
50.7
37.3
Figure 4. Equilibrium distribution of uranium and
thorium mixtures at constant 1:1 ratio
Figure 5. Equilibrium distribution of uranium and
thorium mixtures at total constant concentration
3.3 Batch simulation of multistage extraction
To evaluate U recovery and purity, a feed mixture
of uranium and thorium, each with the concentration
of 15,000 mg/L, was used for batch simulation in
multistage extraction of uranium with 5 and 10%
TBP/kerosene solvent. Based on the feed mixture, the
initial purity of uranium is 50%. A suitable number of
stages required for this separation process was
predicted using McCabe-Thiele approach [7] with their
equlibrium distribution curves. The purity and the
recovery of uranium after simulation of 2, 3 and 4
stages counter-current extraction with feed to
extractant ratio at 1:1 were shown in Figure 6 and 7 for
the extraction with 5 and 10% TBP/kerosene,
respectively. It was found that the recovery of uranium
220
increased with an increasing number of extraction
stages as the uranium recovery with 5% TBP/kerosene
extractant in 2, 3 and 4 extraction stages were 80.52,
90.79 and 96.74%, respectively while the purity of
recovered uranium were around 94%. The extraction
with 10% TBP/kerosene revealed higher uranium
recovery at 97.91–99.85%, but the purity of recovered
uranium were lower at 88%. The selection of
extractant for the separation of uranium and thorium
then also relies on both recovery and purity factors. In
case of the 5% TBP/kerosene extractant, the U
recovery curve indicates that recovery of uranium can
be improved by increasing number of extraction stage.
Also, in a practical process, a scrubbing step with
proper solution or a re-extraction step can be used to
achieve higher uranium purity.
Figure 6. Uranium recovery and its purity obtained
from multistage extraction with 5%TBP/kerosene
5% TBP/kerosene. Separation of U and Th with the
TBP process was shown to be affected by many
factors such as concentrations of TBP, concentrations
of the feed and concentration ratios between U and Th
in the feed. Batch simulation of multistage extraction
of uranium in the mixture revealed that the recovery of
uranium increased with number of extraction stage and
higher TBP concentrations. However, the purity of
extracted uranium decreased as its recovery increased.
References
[1] Rare Earth Research and Development Center, Office of
Atomic Energy for Peace, 1996.
[2] Stas, J., Dahdouh, A. and Shlewit, H., 2005, Periodica
Polytechnica Ser. Chem. Eng., 49.
[3] Kraikaew, J and Srinuttrakul, W. , 2006, Journal of the
Nuclear Society of Thailand, 7.
[4] Schulz, W.W., Navratil, J.D. and Bess, T. 1987, Science
and Technology of Tributyl Phosphate, Volume II, CRC
Press, Florida.
[5] Ashbrook, A.W. and Lakshmanan, V. I., 1986, Uranium
Purification, Eldorado Nuclear Ltd., Canada.
[6] Huang, L., Zhuang, H., Niu Y. and Zhou, M., 1996,
Technical Improvement of Uranium Purification, The
International Conference on Uranium Extraction Conf.
Proc., Beijing, China.
[7] Treybal, R.E., 1963, Liquid Extraction, 2nd ed.,
McGraw Hill, New York.
[8] Thornton, J.D., 1992, Science and Practice of LiquidLiquid Extraction, Vol. 1, Oxford University Press,
New York.
Figure 7. Uranium recovery and its purity obtained
from multistage extraction with 10%TBP/kerosene
4. Conclusions
The equilibrium extraction of uranium and thorium
in 4 M HNO3 as individual and mixed solutions has
been studied using 5 and 10% TBP/kerosene
extractants. The distribution coefficients of each
element were determined at various concentrations of
the individual solution and of the mixed solution. The
distribution coefficients of both uranium and thorium
were found to be decreased with increasing
concentrations and the distribution coefficient of
uranium is much higher than that of thorium. 10%
TBP/kerosene provided higher extraction capacity than
221
PREPARATION OF BaZr1-xYxO3-BASED PROTON CONDUCTING
ELECTROLYTE USING TEA-METAL PRECURSOR BY
THE SOL-GEL METHOD
Suttiruk Salaluk 1, Apirat Laobuthee2, Chatchai Veranitisagul3, Panitat Hasin1, Nattamon
Koonsaeng1*
2
1 Department of Chemistry, Faculty of Science, Kasetsart University, Chatuchak, Bangkok, Thailand 10900
Department of Materials Engineering, Faculty of Engineering, Kasetsart University, Chatuchak, Bangkok, Thailand 10900
3 Department of Material and Metallurgical Engineering, Faculty of Engineering, Rajamangala University of Technology
Thanyaburi, Klong 6, Thanyaburi, Pathumthani 12110
*
E-mail: fscinmk@ku.ac.th*, Tel. +66 2562 4444
A simple and rapid method, triethanolamine (TEA) solgel, for preparing barium zirconate (BaZrO3, BZ) and
yttrium-doped barium zirconate (BaZr1-xYxO3, BZY,
with x = 0, 0.15 and 0.20) is reported. Appropriate
amount of Y(NO3)3 was introduced to 1:1 mole ratio of
Ba(NO3)2 and ZrO(NO3)2 in excess TEA. The asprepared ceramic powders were characterized by X-ray
diffraction (XRD). The evolution of the crystalline phase
is studied as a function of the calcination temperature
(1000 oC, 1200 oC, and 1300 oC in static air). As
increasing calcination temperature, the impurity phase,
BaCO3, decreases. The XRD pattern of the powder
calcined at 1300 oC displayed pure cubic perovskite
phase of barium zirconate. In addition, the total
conductivity in different doping concentration of yttrium
in BaZrO3 has been systematically studied and the
highest total conductivity (1.63x10-3 S∙cm-1) was obtained
for 15% Y-doped BaZrO3. The electrical properties of
the as-prepared BZY showed potential application for
electrolyte membrane in solid oxide fuel cell.
preparation method. The BZY powder prepared by
conventional solid state reaction needs to ball-mill all
of the reaction mixture for many hours in zirconia
containing with zirconia balls. The mixture was
subsequently fired at high temperature. However,
repeated milling and post firing may be needed in
order to reduce phase contamination of the resulting
BZY powder [18-20]. According to time consuming
and high energy consumption in solid state process, in
recent years, a number of chemistry-based processing
routes, such as sol-gel, co-precipitation, freeze drying
method combined with vacuum heating, base-hotwater treatment have been developed for preparing
BZY powder [2,21,22]. In this research, we present a
simple and low cost preparation method for BZY via
TEA sol-gel, using metal salts as starting materials
instead of expensive and high sensitive metal
alkoxides which are difficult to handle in atmospheric
moisture.
1. Introduction
Barium zirconate-based perovskites have been
extensively received much attention and studied for
utilization in various applications, such as proton
conducting materials, thermal barrier coating material
for aerospace industries, hydrogen sensor and
photocatalyst [1-4]. Because barium zirconate
(BaZrO3, BZ) has distinctive physical and chemical
properties such as high thermal stability, excellent
chemical durability, low thermal expansion coefficient
and good structural compatibility [5-7]. Currently, a
number of reports have been focused on yttrium-doped
barium zirconate (BaZr1-xYxO3-δ, BZY) for application
in intermediate temperature solid oxide fuel cells (ITSOFCs) due to its extraordinarily high proton in the
temperature range 200-500 oC [8-10] and high
chemical stability in fuel cell atmosphere [11-16].
Therefore, BZY has a great potential to use as a high
efficiency proton conducting electrolyte in protonic
ceramic fuel cell [17].
As the differences in physical morphology and
chemical composition of BZY play an important role
to proton conducting ability of BZY depending on the
Barium zirconate precursor was prepared by
dissolving Ba(NO3)2 (Acros Organics, 99.9%) and
ZrO(NO3)2.H2O (Acros Organics, 99.9%) with the
mole ratio of 1:1 in deionized water and heated up to
100 oC, then excess triethanolamine (TEA, Carlo Erba
Reagents) was added. The mixture solution was
continued heating and stirring for 20 minutes to
promote polymerization of the TEA sol-gel. Then
water was slowly evaporated to from white sticky gel.
The gel precursor was calcined at 1000 oC, 1200 oC
and 1300 oC to obtain un-doped BaZrO3 (BZ) powder.
The precursor of Y-doped barium zirconate was
also prepared by TEA sol gel method, using the same
procedure as described. The stoichiometric molar
and
dopant
quantities
of
ZrO(NO3)2.H2O
Y(NO3).6H2O (Acros Organics, 99.9%) were varied
with the molar ratio of Ba(NO3)2 : ZrO(NO3)2.H2O :
Y(NO3).6H2O as 1 : 0.85 : 0.15, and 1 : 0.80 : 0.20.
The gel formed was converted to Y-doped barium
zirconate powder by calcination at 1300 oC for 15 h.
The calcined products are expressed as BaZr1-xYxO3
222
(BZY) where x = 0.15 and 0.20, although the actual
composition may be non-stoichiometric with relation
to the oxygen.
The as-prepared un-doped and Y-doped barium
zirconate powders were characterized by X-ray
diffraction (XRD) using BRUKER diffractometer (D8
Advance A25) with Cu Kα radiation (0.154 Å), tube
voltage 40 kV, and tube current 40 mA. Intensities
were collected in the 2θ range between 20o and 90o
with step size of 0.02 and a measuring time of 0.5 s at
each step. The surface morphology were carried out by
Scanning Electron Microscope (SEM, FEI Quanta
450).
BZY powders were uniaxial pressed (150 MPa) to
bar samples and sintered at 1700 oC for 24 h. Silver
paste was painted to each end of the bar and contacted
with silver wire. The DC conductivity were measured
on bar samples by four-point DC technique under 5%
H2/95%He saturated with H2O atmosphere.
Fig. 2 comparatively shows XRD patterns of the
un-doped and Y-doped BaZrO3 calcined at 1300 °C
for 15 h. With increasing the amount of Y(III) dopant,
the diffraction peaks of cubic perovskite are broaden,
gradually shifted to lower 2-theta angles and the
intensities strongly reduced, especially the main 110
hkl diffraction peak. Furthermore, the unit cell
parameter increases with increasing Y content as
illustrated in Table 1, agreeing well with the fact that
the ionic radius of Y(III), 0.9 Å is significantly larger
than Zr(IV), 0.72 Å. These implied that the B site,
Zr(IV) ion of BaZrO3 perovskite was partly substituted
by Y(III) ion to form solid solution of BaZr1-xYxO3
(x = 0.15 and 0.20) so no phase change in XRD was
observed. In addition, no separated phase of ZrO2 or
Y2O3 was detected.
Table 1 The lattice parameter of BaZr1-xYxO3 powders
calcined at 1300 oC for 15 h
Fig. 1 shows the XRD diffraction patterns of the
un-doped ceramic powders with different calcination
conditions. It was found that the samples calcined at
lower temperature (1000 oC and 1200 oC) exhibit
mixed phases of the cubic BaZrO3 perovskite and
BaCO3, agreeing well with standard JCPDS file No.
The phase of the bar samples confirmed by XRD
showed identical diffraction pattern as that of pure
BaZrO3 (Figure 3). The relative densities of all bars,
determined by using Archimedes’s principle, were
higher than 90% of the theoretical value as presented
in Table 2. Selected SEM images of BZ and BZY15
are shown in Fig. 4. For Y-doped sample, smaller
grains with approximate size of 1.5 μm was observed,
corresponding to lower density of the bar sample
Sample
composition
Abbreviation
Lattice
parameter (Å)
BaZrO3
BaZr0.85Y0.15O3
BaZr0.80Y0.20O3
BZ
BZY15
BZY20
4.1923
4.1985
4.2007
Figure 1. XRD patterns of BZ powder calcined at
(a) 1000 oC for 5 h, (b) 1200 oC for 4 h, and
(c) 1300 oC for 15 h.
06-0399 and 05-0378, respectively. However, as
increasing temperature and heating period up to
1300 oC for 15 h, single phase BaZrO3 was obtained.
Therefore, this calcinations condition was performed
for further experiment.
Figure 2. XRD patterns of un-doped and Y-doped
BaZrO3 calcined at 1300 oC for 15 h (a) BZ,
(b) BZY15, and (c) BZY20.
(Table 2).
223
Table 2 Activation energy and total conductivity of
BZY samples at 600 oC
Sample
Density
(% theoretical)
BZ
BZY15
BZY20
96
94
90
(a)
Total
conductivity
(S∙cm-1)
2.75x10-5
1.63x10-3
0.98x10-3
Ea
(eV)
0.59
0.58
0.49
(b)
4. Conclusions
BaZr1-xYxO3 (x = 0, 0.15, and 0.20) based
perovskites was successfully prepared by a cost
effective simple TEA sol gel method. The XRD results
clearly showed pure phase of cubic BaZrO3 perovskite
for the samples calcined at 1300 oC, 15 h. The highest
total conductivity, 1.63x10-3 S∙cm-1 at 600 oC, was
obtained for BZY15. We believe that the prepared
samples could have potential to be applied for proton
conducting in SOFC or in some new application as
electronic material for nanodevices.
Acknowledgements
Figure 4. Cross-section SEM image of the bar
sample sintering at 1700 oC for 24 (a) BZ and (b)
BZY15.
Fig. 5 shows the total conductivity of BZY samples
measured as a function of inverse temperature in
humidified atmosphere (5%H2/95%He). The total
conductivity of the BZ is lower than those of Y-doped
sample for about two order of magnitude as presented
in Table 2. For BZY15 and BZY20, the total
conductivity is ̴ 10-3 S∙cm-1 at 600 oC. The activation
energy of all samples is in the range 0.49-0.59 eV.
These values are typically observed for proton
transport in BZY ceramics [23]. The slightly lower in
activation energy of the Y-doped samples compared to
that of BZ leads to an increase in mobility of proton,
consequently the conductivity increases as presented in
Table 2. Therefore, the TEA sol-gel method for
preparing yttrium doped barium zirconate has a
potential to use as proton conducting electrolyte in
solid oxide fuel cell.
Figure 5. Total conductivity of the prepared
samples measured under wet condition as a
function of the inverse temperature (a) BZ, (b)
BZY15, and (c) BZY20.
Figure 3. XRD patterns of (a) BZ, (b) BZY15, and
(c) BZY20 bar sintering at 1700 oC 24 h.
This work is supported by Faculty of Science,
Kasetsart University, Chemistry Department, Faculty
of Science, Kasetsart University and Department of
Materials Engineering, Faculty of Engineering,
Kasetsart University. A part of this study was also
financially support by Development and Promotion of
Science and Technology Talents Project (DPST).
Thank Prof. Jose Manuel Serra and Dr. Sonia
Escolastico, The Instituto de Tecnología Química
(ITQ), Spain, for the DC conductivity measurement.
References
[1] Zajac, W., Rusinek, D., Zheng, K., Molenda, J., 2012,
Cent. Eur. J. Chem., 11(4) 2013 471-484.
[2] Prastomo, N., Zakaria, N.H., Kawamura, G., Muto, H.,
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225
DEVELOPMENT OF IMPROVED IRON CHELATORS
Filip Kielar1,2*
1
*
Department of Chemistry, Faculty of Science, Naresuan University, Phitsanulok, Thailand
2 Centre of Excellence in Biomaterials, Naresuan University, Phitsanulok, Thailand
E-mail for Corresponding Author; E-mail: filipkielar@nu.ac.th, Tel. +66 5596 3460, Fax. +66 5596 3401
Abstract: Iron chelation is an important therapeutic tool,
for example in the treatment of thalassemia.
Development of new iron chelators is still an important
task, despite the availability of three iron chelators for
clinical practice. Aroyl hydrazone chelators such as
salicyl aldehyde isonicotinoyl hydrazone (SIH) possess
interesting properties for iron chelation, however, they
are susceptible to hydrolytic cleavage. To address this
issue a novel hydrazine analogue of SIH, N’-(2hydroxybenzyl)isonicotinohydrazide
(BIH)
was
developed. The binding of BIH to iron was investigated
using UV-Vis spectroscopy and through competitive
binding assays using nitrilotriacetic acid (NTA) and
calcein. Furthermore the ability of BIH to protect against
reactive oxygen species damage was evaluated using
deoxyribose assay. The results indicate that BIH
maintains significant iron binding capability. However,
the strength of the binding is weaker than that of SIH, as
indicated by the results of the calcein assay test.
Furthermore the ability of BIH to protect against
oxidative damage has also been diminished in
comparison to SIH. On their own these results do not
rule out BIH as a potential iron chelator and warrant
further investigation
1. Introduction
Iron is the most abundant transition element found
in the human body [1]. It is indispensable for the
proper physiological function taking part in vital and
varied processes such as oxygen transport, oxidative
phosphorylation, and neurotransmitter synthesis [1,2].
However, iron also has the potential to cause toxic
effects, for example through the catalysis of Fenton
reaction leading to more damaging reactive oxygen
species [1,3]. Therefore the uptake, distribution,
storage, and excretion of iron need to be regulated [4].
Failures in iron homeostasis can results in pathologies
such
as
anemia,
hemochromatosis,
and
neurodegenerative
diseases
[1,5]. Therapeutic
interventions can also affect iron status, as is the case
of iron overload in Thalassemia patients receiving
blood transfusions [6].
Some of the issues relating to iron mediated
pathologies can be addressed using iron chelation
[1,6,7]. Three chelators (desferrioxamine, desferasirox,
and deferiprone) have been approved for clinical
practice [6,7]. However, these compounds do possess
unwanted side effects [7]. Furthermore, the variation
in scenarios where iron chelation might be used
therapeutically requires a broader range of chelators to
be available. Hydrazone based chelators (e.g.
salicylaldehyde isonicotinoyl hydrazone, SIH) are an
interesting class of such compounds [8,9]. However,
these chelators suffer from relative instability of the
hydrazone bond [9]. We have assumed that this
property could be improved by changing the link to a
hydrazine, which should not suffer from this problem.
Herein we report the synthesis and initial
characterization of such a hydrazine chelator derived
from SIH, N’-(2-hdroxybenzyl)isonicotinohydrazide
(BIH).
2.1 Chemicals and Instruments
All chemicals were used as purchased. Salicyl
aldehyde, isonicotinoic acid hydrazide, and
nitrilotriacetic acid were purchased from Acros.
Thiobarbituric acid, sodium borohydride, and 2deoxyribose were purchased from Sigma Aldrich. Iron
chloride, ascorbic acid, and trichloroacetic acid were
purchased from POCH chemicals. Ferric ammonium
and trisodium ortho phosphate were purchased form
Ajax Fine Chemicals. Concentrated hydrochloric acid
and glacial acetic acid were purchased from Carlo
Erba. Hydrogen peroxide (30%) was purchased from
Merck. Organic solvents were purchased from Lab
Scan and deuterated solvents for NMR were purchased
from Cambridge Laboratories. Salicyl aldehyde
isonicotinoic hydrazone (SIH) was prepared according
to a published procedure [9].
UV-Vis spectra were recorded on an Analytik Jena
Specord
S100
spectrometer
a
298K.
Photoluminescence spectra were recorded on a Perkin
Elmer LS 55 fluorometer at 298K. NMR spectra were
recorded on a Bruker Avance spectrometer operating
at 400 MHz (1H). NMR spectra are referenced to the
residual solvent peaks. The MS spectra were collected
using an Agilent Technologies LC-MS QTOF 6540
UHD Accurate Mass spectrometer.
2.2
Synthesis
of
N’-(2-hydroxybenzul)
isonicotinohydrazide (BIH)
A suspension of SIH (1.5 g, 6.2 mmol) and sodium
borohydride (470 mg, 12.4 mmol) in MeOH (40 ml)
was stirred at room temperature for 1 hour. The
solvent was removed under reduced pressure. The
residue was dissolved in dichloromethane (100 ml)
and washed with a 5% aqueous solution of ammonium
chloride (3 x 50 ml). The organic layer was dried over
sodium sulphate, filtered, and the solvent was removed
under reduced pressure to yield the product as an off
white solid (1.1g, 73%). 1H NMR (400 MHz, DMSOd6) δ 3.96 (2H, d, J = 6.0, CH2), 5.64 (1H, m, NH
226
amine), 6.74 (1H, dd, J = 7.4, J = 7.4, CH-Ph), 6.79
(1H, d, J = 8.0, CH-Ph), 7.08 (1H, dd, J = 7.8, J = 7.8,
CH-Ph), 7.40 (1H, d, J = 7.4, CH-Ph), 7.70 (2H, d, J =
5.8, CH-Py), 8.70 (2H, d, J = 5.8, CH-Py), 9.61 (1H, s,
OH), 10.43 (1H, d, J = 6.0, NH amide). HR-MS (ES+)
C13H14N3O2 requires 244.1086 [M+H]+; found
244.1080.
2.3 UV-Vis titration with ferric ammonium citrate
(FAC)
Stock solutions of SIH and BIH (100 mM) were
prepared in DMSO. Stock solution of FAC (10 mM)
was prepared in 50 mM sodium phosphate buffer (pH
7.4). A 100 µM solution of the ligands was prepared
by diluting the stock solution in the phosphate buffer.
The titration was carried out by adding aliquots of the
FAC stock solution to the solution of the ligands. Each
addition was followed by a 10-minute equilibration
period.
BIH (100 mM) were prepared in DMSO and then
diluted to 100 µM in phosphate buffer. Sodium
phosphate buffer containing 0.1% (v/v) DMSO was
prepared. The reaction mixtures were prepared by
mixing adding the reagents in the following order:
chelator (0-90 µM), FeCl3 (10 µM), 2-deoxyribose (15
mM), hydrogen peroxide (200 µM) and ascorbic acid
(2 mM). The reaction mixture volume was adjusted to
a total volume of 1 ml using phosphate buffer
containing 0.1% DMSO. The reaction mixtures were
incubated at 37oC for 1 h and then quenched with
trichloroacetic and thiobarbituric acid solutions (1 ml
each). The quenching reaction was carried out at
100oC for 20 minutes. Absorbances of the mixtures
were recorded at 532 nm after cooling to room
temperature. The results are displayed as ratio with
absorbance of the sample containing no chelator. The
experiment was carried out in triplicate.
2.5 Iron binding competition with calcein
Stock solution of SIH and BIH (4 mM) were
prepared in DMSO. Stock solution of calcein (400
µM) was prepared in DMSO. Stock solution of FAC
(1 mM) was prepared in phosphate buffer. Calcein and
FAC were mixed and diluted in the phosphate buffer
to final concentrations of 2 and 4 µM respectively. The
solutions were left to equilibrate for 1 h in darkness.
Aliquots of the SIH and BIH solutions were added to
the prepared calcein iron mixtures (final concentration
8 µM) and the solutions were left to equilibrate for 1 h
in darkness. Appropriate volumes of DMSO were
added to the samples so that final DMSO
concentration in all samples was 1%. A positive
control was prepared containing calcein only. A
negative control was prepared containing calcein and
FAC but no added iron chelator. Fluorescence spectra
were collected after diluting the mixtures 10x with
phosphate buffer. The fluorescence spectra were
collected between 470 and 650 nm with excitation at
460 nm. The experiment was performed in duplicate.
2.6 Deoxyribose assay
Stock solutions of dexoyribose (300 mM),
hydrogen peroxide (10 mM), ascorbic acid (100 mM),
and trichloroacetic acid (2.8% w/v) were prepared in
deionized water. Stock solution of FeCl3 (1 mM) was
prepared in 10 mM HCl. Stock solution of
thiobarbituric acid (1% w/v) was prepared in 50 mM
sodium hydroxide solution. Stock solutions of SIH and
3.1 BIH synthesis
BIH has been synthesized by a reduction of SIH
with sodium borohydride in methanol (Figure1.). It
was observed that the use of bigger excess of sodium
borohydride and shorter reaction times lead to a
cleaner product. BIH was characterized using NMR
and MS spectroscopies
Figure 1. Synthesis of BIH
3.2 Investigation of iron binding using UV-Vis
spectroscopy
2
1.5
Abs.
2.4 Iron binding competition with nitrilotriacetic acid
(NTA)
A solution of 100 µM SIH or BIH and 50 µM
FAC in phosphate buffer was prepared and left to
equilibrate for 1 h. A stock solution of NTA (10 mM)
was prepared in the phosphate buffer. An aliquot of the
NTA stock solution was added to the equilibrated
solution of the ligands and FAC. The solution was left
to equilibrate for 1 h before recording the UV-Vis
spectra.
1
100 µM SIH
SIH + 10 µM FAC
SIH + 20 µM FAC
SIH + 30 µM FAC
SIH + 40 µM FAC
FAC + 50 µM FAC
0.5
0
200 250 300 350 400 450 500 550 600
Wavelngth (nm)
Figure2. UV-Vis spectra of titration of SIH (100 µM)
with ferric ammonium citrate (pH 7.4, 298K)
The UV-Vis spectra of both SIH and BIH (100
µM) were recorded in phosphate buffer (50 mM, pH
7.4). The UV-Vis spectra of SIH and BIH are shown
227
in Figure 2 and Figure 3 respectively. Figures 2 and 3
also show the changes in the UV-Vis spectra of SIH
and BIH resulting from the addition of ferric
ammonium citrate (FAC). These spectra indicate the
formation of the iron complexes of these ligands.
1
0.8
100 µM BIH
BIH + 10 µM FAC
BIH + 20 µM FAC
BIH + 30 µM FAC
BIH + 40 µM FAC
BIH + 50 µM FAC
1.2
1
0.8
0.4
I/I
0
Abs.
0.6
Iron in biological setting is capable of promoting
the effects of oxidative stress through the Fenton
reaction. Evaluation of the effect of iron chelation on
Fenton reaction can be performed using the
deoxyribose assay. Effects of 10 to 90 µM SIH and
BIH on the results of the deoxyribose assay are shown
in Figure 6.
0.2
0.6
0
200 250 300 350 400 450 500 550 600
Wavelength (nm)
Figure 3. UV-Vis spectra of titration of BIH (100 µM)
with ferric ammonium citrate (pH 7.4, 298K)
The binding interaction between SIH and BIH was
further investigated using a competition experiment
with nitrilotriacetic acid (NTA). Complexes of SIH
and BIH with Fe3+ (50 µM) were prepared and their
UV-Vis spectra were recorded (Figure 4). NTA (100
µM) was added to these complexes and the UV-Vis
was recorded after an equilibration period (Figure 4).
0.4
0.2
Calcein
Fe
SIH
BIH
Abs.
1
+
+
+
-
SIH
BIH
1
0.8
0.8
0
50 µM FeSIH
50 µM FeBIH
FeSIH + 100 µM NTA
FeBIH + 100 µM NTA
100 µM NTA
+
+
+
1.2
A/A
1.2
+
+
-
Figure 5. Graph of normalized calcein fluorescence
intensity showing the effect of quenching by iron and
the recovery of luminescence upon the addition of
iron chelators (SIH, BIH)
1.6
1.4
+
-
0.6
0.4
0.6
0.2
0.4
0
0.2
0
200 250 300 350 400 450 500 550 600
Wavelength (nm)
Figure 4. UV-Vis spectra of iron complexes with SIH
and BIH before and after the addition of NTA (pH 7.4,
298K).
3.3 Investigation of iron binding using calcein
Further insight into the binding of Fe3+ with SIH
and BIH was obtained using the fluorescent metal
indicator calcein (Figure 5). This experiment evaluates
the ability of the chelators to restore the fluorescence
of calcein after its quenching with Fe3+ ions. The
results comparing the properties of SIH and BIH are
shown in Figure 5.
0
20
40
60
80
Concentration (µM)
100
Figure 6. Graph of normalized absorbance showing the
results of deoxyribose assay carried out in the presence
of SIH and BIH (0-90 µM).
BIH has been synthesized using a simple reduction
reaction of SIH (Figure 1). The main issue with this
reaction is the decomposition of the product under the
reaction conditions with extended reaction times.
Therefore a fast reaction using excess of NaBH4 was
deemed preferable and could yield clean product
without a formal purification step.
UV-Vis spectra of SIH and BIH (100 µM) were
recorded in phosphate buffer (50 mM, pH 7.4) and can
be seen as the solid red traces in Figures 2 and 3
respectively. SIH exhibits major peaks at 225 nm, 288
228
nm, and 328 nm as well as a broad shoulder at 410 nm.
In comparison BIH exhibits significantly blue shifted
UV-Vis spectrum with peaks at 225 nm and 270 nm.
The spectrum also contains a broad shoulder 330 nm.
The absorbances of the peaks of BIH are also
significantly smaller than in the case of SIH. These
differences are consistent with the change of the
carbon nitrogen hydrazone double bond in SIH to a
single hydrazine bond in BIH. Figures 2 and 3 also
show the changes in the UV-Vis spectra when titrated
with Fe3+ ions in the form of FAC (10 to 50 µM). The
changes in the spectra, especially the formation of the
broad features at 450 and 365 nm for SIH and BIH
respectively, are indicative of the formation of Fe3+
complexes of these ligands [10].
The interactions of the ligands SIH and BIH with
Fe3+ were further investigated through competitive
binding assays using nitrilotriacetic acid (NTA) and
calcein. The results of the experiment with NTA are
shown in Figure 4. In this case the complexes of SIH
and BIH with Fe3+ (50 µM) were formed first followed
by the addition of NTA (100 µM). NTA is a metal
chelator with modest affinity for Fe3+ ions. The
minimal changes in the spectra of the SIH and BIH
iron complexes upon NTA addition indicate that NTA
was unable to remove iron from these complexes to
any significant extent. This result has been previously
observed for SIH. Therefore, both SIH and BIH can be
regarded as having binding affinity for Fe3+ at least as
strong as that of NTA. The final test employed in the
investigation of iron binding properties of the ligands
SIH and BIH was the investigation of their interaction
with the iron complex of the metal sensitive
fluorophore calcein (Figure 5) [10]. The fluorescence
of calcein is quenched upon its complexation with Fe3+
ions, as shown in the first two bars of Figure 5. The
strength of a chelator can be deduced from its ability to
restore calcein fluorescence by competitively
removing iron from its calcein complex. The third and
fourth bars in Figure 5 show that 8 µM SIH was able
to completely restore calcein fluorescence whereas
BIH was only able to restore it to 75 % of the original
value. It should be noted that BIH was able to restore
calcein fluorescence fully at higher concentrations and
that SIH actually lead to the full recovery even at
lower concentrations (results not shown). These results
indicate that BIH is a weaker iron binder than SIH.
Iron can be toxic in biological systems given its
ability to promote oxidative stress through the Fenton
reaction. Ability of iron to take part in this reaction
and the extent of damage it can do depends on its
coordination environment and its redox properties
[10]. Deoxyribose assay is a method of testing the
ability of chelators to protect against iron mediated
oxidative damage [10]. The results of this assay in the
presence of SIH and BIH are shown in Figure 6. The
data is reported as ration with the absorbance in the
absence of the chelators, which means that values
below 1 indicate protection against oxidative stress,
whereas values above 1 mean the added compound
promotes oxidative stress. As can be seen from Figure
6, both SIH and BIH give A/A0 values below 1.
However, the protection offered by BIH seems to be
significantly lower than that offered by SIH as the
final A/A0 values for these compounds are 0.8 and 0.4
respectively. These results indicate that even though
BIH is not very effective in protecting against iron
mediated oxidative stress it does not exacerbate it and
thus could be used for iron chelation in situations
where prevention of oxidative stress is not the main
goal.
4. Conclusions
A novel aroyl hydrazine compound BIH has been
synthesized and its ability to bind iron has been
evaluated and compared to its parent hydrazone iron
chelator SIH. It has been found that BIH maintains
significant iron binding affinity, however, it is reduced
when compared to SIH. Furthermore, the ability of
BIH to protect against iron mediated oxidative stress is
also reduced when compared to SIH. Despite this BIH
is an interesting compound that should be further
tested as very high binding strength and great efficacy
in protecting against oxidative stress are not the only
parameters important for biological iron chelators.
Acknowledgements
This research was financially supported by Naresuan
Univesity DRA grant No. R2556C110.
References
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Chemistry, Wiley-VCH Verlag GmbH, Weinheim, 307350.
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Neural. Transm., 118, 301-314.
[3] Theil, E.C., Goss, D.J., 2009, Chem. Rev., 109, 45684579.
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Physiol., 69, 69-85.
[5] Crichton, R., Dexter, D., Ward, R., 2011, Monatshefte
Fur Chemie, 142, 341.
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Berndahrd, P.V. 2011, Curr. Top. Med. Chem., 5, 591607.
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Jirkovsky, E., Sterba, M., Popelova, O., Kalinowski,
D.S., Kovarikova, P., Vavrova, K., Richardson, D.R.,
Simunek, T., 2010, Chem. Res. Toxicol., 23, 1105-1114.
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P., Mackova, E., Stariat, J., Vavrova, A., Vavrova, K.,
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Metallomics, 4, 899-909.
229
ONE-POT SYNTHESIS OF CuO/ZnO NANOSTRUCTURE WITH
DISCRETE CuO NANOPARTICLES ON ZnO HEXAGONAL PLATE
Karnrat Hongpo1, Karaked Tedsree2*
1,2Nanocatalysis
*
laboratory, Department of Chemistry, Faculty or Science, Burapha University, 20131, Thailand
1,2Center of Excellent on Environmental Health and Toxicology (ETH)
E-mail for Corresponding Author; E-mail: karaked@buu.ac.th, Tel. +66 80565 9915
Abstract:
A
new
surface-modified
CuO/ZnO
nanostructure was sucessfully synthesized by one-pot
hydrothermal method. Heating an aqueous solution of
zinc acetate and copper nitrate in the presence of
hexamethylenetetramine )HMT( at 97°C and calcination
at 350°C gave discrete CuO nanoparticles with
seggregrated ZnO hexagonal plate. The particle size and
thickness of ZnO nanoplate can be tuned by varying
mole percent of Cu2+ added. The particle sizes and shape
of the obtained products were investigated by
transmission electron microscopy (TEM) and scanning
electron microscopy (SEM). Crystal structure was
identified by X-Ray diffraction (XRD). Chemical
composition was confirmed by EDX analysis. Surface
composition and oxidation states of metals were studied
by
X-Ray
photoelectron
spectroscopy
(XPS).
Photoluminescence was used to further characterize
their optical properties.
1. Introduction
ZnO nanostructures have been studied extensively
over the last decade due to their interesting size- and
shape-dependent properties. It can be prepared on a
large scale at low cost by simple solution route, such
as chemical precipitation, sol-gel and solvothermal/
hydrothermal process, etc. [1-2]. Efforts have been
focused on the preparation of ZnO nanostructures with
various morphologies including the nanorod,
nanoplate, nanobelt and flower-like [3-4]. It has been
reported that the hexagonal platelike particles of ZnO
show superiority to rod-shaped particles as
photocatalysts due to their large specific surface area
and high population of polar (0001) faces [5].
Therefore, much attention has been paid on the
synthesis of its plate like nanostructure. In addition,
considerable attention has been paid to surface
modification of ZnO nanostructure by doping with
selective elements such as Ag Au and Cu metal [6].
These can induce dramatic changes in the electrical,
optical and magnetic properties.
Different methods for the preparation of Cu-doped
ZnO nanostructure (Cu/ZnO) can be found in literature
such as impregnation, co-precipitation, sol–gel,
microemulsions, hydrothermal and polyol process [710]. Of all these methods, hydrothermal is gaining
increasing popularity owing to simple operation and
the possibility to large-scale synthesis. Different sizes,
shapes and morphologies can be systematically
obtained by optimising appropriate experimental
parameters such as type and concentration of zinc and
Cu precursor, pH, reaction temperature and capping
agent, etc.
It has been known that particle size, composition,
dispersion of Cu species on ZnO was found to
influence on its activity and selectivity in catalytic
hydrogenation of CO2 to methanol. Currently, shape
control selectivity in nanocatalysts has clearly been
demonstrated with the type of surface sites expressed
at the catalyst surface. Tsang and co-workers [11]
prepared Cu/ZnO by physical mixing of ZnO
nanoplates with Cu nanoparticles. Their results clearly
showed that surface modified ZnO nanostructures with
(002) polar facet of platelike ZnO nanoparticles gives
a much stronger electronic interaction with Cu
nanoparticles than other facets and they also showed
high selectivity of this reaction by this mixture.
Herein, we report the synthesis method of a novel
surface-modified CuO/ZnO nanostructure by simple
one-pot single-step hydrothermal method. Initimate
mixture of discrete CuO nanoparticles seggregrated
from ZnO nanoplates was obtained. The structure was
confirmed by various techniques. In addition, for the
potential application in photocatalysis, the optical
properties of the samples were also explored.
2.1 Materials
Zinc acetate dihydrate (Zn(CH3COO)2•2H2O) and
hexamethylenetetramine (C6H12N4) were purchased
from Sigma Aldrich. Cupper nitrate trihydrate
(Cu(NO3)2.3H2O) was purchased from )Qrec, New
Zealand(
2.2 Synthesis of Surface-modified CuO/ZnO
Nanostructures
CuO/ZnO nanostructures were synthesized by
hydrothermal method. Typically 3.00 g of zinc acetate
dihydrate, 1.92 g of hexamethylenetetramine and
0.0997 g of cupper nitrate (3 mol %) were dissolved in
24 mL of deionized water. After stirring for 10 min,
the solution was transferred into a 50 ml Teflon-lined
autoclave and maintained at 97°C for 5 h. The white
precipitate was collected by centrifugation and washed
several times with deionized water and followed by
ethanol. The products were dried at 100°C for 2h and
calcination at 350°C for 3 h. The percentage of Cu
loading was studied between 0.25, 0.5, 1.0, 3.0, 5.0
and 10 mol %.
230
ZnO hexagonal plate was synthesized by following
the literature [12]. Typically, the preparation method
was performed the same method of surface-modified
CuO/ZnO nanostructures (section 2.2), but the reaction
was carried out in the absence of Cu(NO3) precursor.
The crystal structure of the synthesized CuO/ZnO
hexagonal plate was characterized by X-ray powder
diffraction (XRD). The XRD-patterns were acquired
on a Bruker AXS D8 Advance diffractometer using Cu
Kα radiation as an X-Ray source. Transmission
electron microscope (TEM) and scanning electron
microscopy )SEM( were used to indentified size, shape
and distribution of the particles. TEM observations
were conducted on a JEOL JEM 2011 microscope
operated at 200 kV. The SEM images were recorded
on a LEO 1450 VP electron microscope (LEO,
England). Energy-dispersive X-ray spectrometer
(INCA-OXFORD, England) was connected to SEM
used for element analysis and elemental distribution.
Photoluminesence spectroscopy was used to study the
optical property of samples. The photoemission of
colloidal CuO/ZnO hexagonal plate in water was
recorded at room temperature using a model FP-6200
)Jasco, Japan) with an excitation wavelength of 370
nm. Surface composition of the particles was analyzed
by Scienta ESCA-300 high-resolution X-ray
photoelectron spectrometer.
ZnO hexagonal plate was prepared by
hydrothermal method. Zinc acetate dihydrate was used
as a precursor in the presence of HMT. HMT plays an
important role to supply hydroxyl ions which react
with Zn2+ ions to form Zn(OH)42- [13]. Acetate anion
was widely accepted to control the formation of plate
structure. It could be adsorbed on the (0001) surface of
ZnO and block the contact between the growth units
and the (0001) surface [14]. In addition, HMT was
accepted to control the particle shape of ZnO. Mixing
of Cu2+ ion in the preparation reaction, the chemical
reaction processes for the generation of the CuO on
ZnO hexagonal plate was proposed in equation 1-3.
Zn2+ + Cu2+ + xOH -
(1)
Cu(OH)2/ZnO
(2)
97°C
Zn(OH)42- + Cu(OH)2
Cu(OH)2/ZnO
Zn(OH)42- + Cu(OH)2
Hydrothermal
Calcination
350°C
CuO/ZnO
(3)
SEM and TEM images of surface-modified CuO/ZnO
nanostructures with different % Cu2+ loading after
annealing at 350°C are shown in Figure 1 and 2. The
particle size and chemical compositions of the samples
are also shown in Table 1.
Figure 1. SEM images of a) ZnO hexagonal plate and
surface-modified CuO/ZnO nanostructures b) 1 mole
% c) 3 mole % and d) 5 mole % of Cu2+loading
Figure 2. TEM images of surface-modified CuO/ZnO
nanostructures a) 3 mole % of Cu2+ loading b) high
magnification of the image, average particle size
diameter of CuO is about 9.54 ± 1.85 nm.
Table 1: Particle size and chemical compositions of
the synthesized ZnO and surface-modified Cu/ZnO
nanostructures
Mole % Cu loading
Calculation
EDX
0
1.0
3.0
5.0
10.0
2.5
2.9
4.5
7.8
Particle size of ZnO
Diameter
Thickness
(nm)
(nm)
1427 ±216
873 ±149
1357 ±363
554 ±96
1311 ±160
200 ± 48
1386 ±198
189 ±67
1227 ±500
107 ± 23
SEM coupled with EDX measurements can be
confirmed the incorporation of Cu species into the
ZnO matrix. The atomic ratio between Cu and Zn
(analysis by EDX) was found close to the theoretical
calculation. It can be noticed that increasing mole % of
Cu2+ loading, the thickness of ZnO hexagonal plate
decreased significantly while the particle sizes tend to
slightly decrease.
Decreasing of the thickness of hexagonal plate when
doping with Cu2+ may affect to growth rate of ZnO.
Generally, ZnO grows preferentially along [001] direction in aqueous solution because of the lowest surface
energy of (001) facet. And the growth velocity along
[010] directions is slower than that of [001] direction,
231
resulting in rod-like structure. However, in the
presence of HMT, it might be adsorbed on the (001)
facets of ZnO crystals and significantly decrease the
growth rate of these facets, resulting in platelike
structure. [15] In case of adding Cu2+, it may serve as a
surface-passivating agent in the reaction system the
same as HMT. A schematic diagram of the proposed
growth mechanisms of CuO/ZnO hexagonal plate is
shown in Figure 3. It is possible that the growth
process took place at the interface of the Zn terminated
facets by combination of Cu(OH)42- species and the
growth unit Zn(OH)42-. The enhanced passivation
effects become stronger as the content of Cu2+ ions
increased, which can be confirmed by the decrease in
thickness of the hexagonal plate from 554 nm to 90
nm. These results were in accordance with the studied
of Liu et al. [16].
the CuO peak in the low contents (3 mole %) is due to
the high dispersion of the small clusters. In addition,
there is no significant shift of all diffraction peaks,
implying that no Zn1-xCuxO solid solution is formed.
This indicates the segregation of CuO particles in the
grain boundaries of ZnO crystallites rather than going
into the lattice of ZnO although the ionic radius of Cu
(Cu2+ = 0.057 nm) is almost same as zinc site in ZnO
(Zn2+= 0.060 nm [17]. In addition, as Cu2+ ions prefer
octahedral environment with Jahn Teller elongation in
z axis while Zn2+ cannot support this. Thus,
structurally mismatch hence no evidence of cross
substitution from XRD.
The surface composition and chemical state of the
samples have been investigated by XPS. Figure 5
displays the XPS spectrum of Zn2p O1s and Cu2p of the
ZnO sample with 3 mole % of Cu2+ loading.
Figure 3. Schematic diagram of the proposed
formation mechanisms of surface-modified CuO/ZnO
nanostructure
The crystal phase and phase purity of the synthesized
ZnO and surface-modified CuO/ZnO samples prepared
with different Cu2+ loading were examined by XRD.
The results are shown in Figure 4.
Figure 4 XRD patterns of a) ZnO and Cu-modified
ZnO with b) 3 and c) 10% mole of Cu loading.
The appearance of the characteristic ZnO peaks at
31.74, 34.40, 36.24, 47.48, and 56.62 corresponding to
the (100), (002), (101), (102), and (110) crystal plane,
which is comparative with the XRD pattern of ZnO
with hexagonal wurtzite structure (JCPDS file no. 361451). The crystalline form of ZnO has not been
changed by loading Cu. The small Cu diffraction
peaks appeared at 2θ = 35.52 and 38.98 on only on the
high loading samples (10 mole %) can be indexed to
face-centered–cubic (fcc) of Cu. The disappearance of
Figure 5. XPS spectrum of a) O1s b) Zn2p c) Cu2p of
surface- modified CuO/ZnO nanostructure
The asymmetric peak observed in the O1s region
was resolved into two peaks. The peak with low
binding energy (530.3 eV) corresponds to O2- ions in a
normal ZnO wurtzite structure, while the second one
centered at 531.8 eV may be attributed to different
kinds of species, such as adsorbed hydroxyl group or
O2- ions in the oxygen deficient regions within the
ZnO matrix [18]. The Zn2p core level located at 1021.2
and 1044.2 eV attributed to Zn2p1/2 and Zn2p3/2 eV
respectively, typicaly ZnO. The binding energies at
933.4 and 953.8 eV were Cu2p3/2 and Cu2p1/2,
respectively. Broadening of the peaks were observed.
The strong sattlelite peaks observed at 942.4 eV was
clearly showed the presence of Cu2+ species. This
result suggested the presence of CuO. Surface
compositions of the sample determined by XPS
analysis were 44.20 % atom for Zn2+, 51.15 % atom
for all species of oxygen and 4.65 % A for all Cu and
Cu ion species. It can be seen that Zn:Cu ratios was
higher than that the compositions from theoretical
calculation and EDX analysis (Table 1). This is an
indication of segregation of the Cu doping on the
surface of ZnO. This results was in accordance with
the studied of Bellini, J. et al. [9]
Surface defect plays an important role in the
photocatalytic activity. This work, photoluminesence
spectroscopy was used to investigate defects.
Photoluminescence (PL) spectra of the synthesized
232
ZnO hexagonal plate and surface-modified CuO/ZnO
at different mole % Cu2+ loading are shown in Figure 6
Figure 6. Room temperature PL spectra of surfacemodified CuO/ZnO nanostructure at excitation 370 nm
In visible region, a strong violet emission centered
at 412 nm and a broad band of blue and green
emission was observed at 465 nm and 530 nm,
respectively. These visible emissions are due to
various transitions of defects such as Zn interstitial and
oxygen vacancies, etc [20]. Increasing Cu contents of
CuO/ZnO samples, the photoluminescence intensity
decreased considerably in this region. Therefore, the
incorporation of Cu impurities during the growth will
contribute to the decreasing of defective levels .
Q. 2007, 61, 703–707.
[10] Tincekic, T.G. and Boz, I., 2008, Bull. Mater.
Sci., 31, 619–624
[11] Liao, F., Huang Y., Ge J, Zheng W, Tedsree K.,
Collier P., Hong X. and Tsang S. C., 2011,
Angew. Chem. Int. Ed., 50, 2162–2165.
[12] Hu, J., Fan, Y., Pei, Y., Qiao, M., Fan, K., Zhang,
X. and Zong, B. 2013, ACS Catalysis, 3, 22802287.
[13] Li, B. and Wang, Y. 2009, J. Phys Chem C, 114,
890-896.
[14] Ashford, S., 2007, J. Phys Chem B, 127-154.
[15] Chu, D. and Li, S., 2012, New journal of glass
and Ceramics, 2, 13-16.
[16] Liu, J., Xu L., Wei, B., Wei, L., Gao, H. and
Zhang, X, 2011, Cryst Eng Comm, 13, 1283–
1286.
[17] Li, J. C., Cao Q., Yan, X., Hou, Wang, B. F. and
Ba, D. C., 2013, Superlattices and
Microstructures, 59, 169–177.
[18] Atanasova1, G., Dikovska A. O., Stankova, M.,
Stefanov, P. and Atanasov, P. A., 2012, Journal
of Physics: Conference Series, 356, 012036.
[19] Bellini, J., Morelli, M. and Kiminami, K., 2002,
J. Mater. Sci. Mater. Electron, 8, 485-489.
[20] Ischenko, V., Polarz, S., Grote, D., Atavarache,
V., Fink, K. and Driess, M. 2005, Funct. Mate, 15,
1945-1954.
4. Conclusions
We have successfully synthesized a novel CuOmodified ZnO nanostructure by a single step
hydrothermal method. Their structure contains discrete
CuO segregation on the surface of ZnO hexagonal
plate. Moreover, the particle size and thickness of ZnO
can be tuned by varying mole % of Cu2+ incorporation.
Acknowledgements
We gratefully center of excellence on
Environmental Health and Toxicology for the financial
support.
References
[1] Baruah, S. and Dutta J., 2009, Sci. Technol. Adv.
Mater, 10, 013001- 013018.
[2] Liu, J., Huang, X., Li, Y., Zhong, Q. and Ren, L.,
2006, 60, 1354–1359.
[3] Li, B. and Wang, Y., 2010, J. Phys. Chem. C, 114,
890–896.
[4] Xu, F., Yuan, Z. Y., Du, H. G., Halasa, M., and Su,
B. L. 2007, Appl. Phys. A, 86, 181–185.
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Chemistry, 216, 149–155.
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Chem., 639, 15, 2683–2695.
[8] Rahmati, A, Sirgani A. B., Molaei, M. and
Karimipour, 2014, Eur. Phys. J. Plus, 129, 250
[9] Zhao, Y. M., Li, Y, H., Jin, Y. Z., Zhang, X, P.,
Hu, W. B., Ahmad, I., McCartney, G. and Zhu, Y.
233
OPTICAL SENSING PROPERTIES OF PLASTICIZED POLYMERIC
MEMBRANE INCORPORATING N,N'-ETHYLENEBIS(SALICYLIMINE)
AS TRANSITION METAL ION-SELECTIVE IONOPHORE
Jiraporn Pandoidan1, Phetlada Kunthadee1*
1
Department of Chemistry, Faculty of Science, Maejo University, San Sai, Chiang Mai, 50290, Thailand
*
E-mail: phetlada@mju.ac.th, phetk19@hotmail.com Tel. +66 5387 3530-1, Fax. +66 53873548
Abstract: Novel polymeric membrane optical sensors for
the highly selective detection of transition metal ions
using N,N'-Ethylenebis(salicylimine) (salen) as ionophore
have been developed. The salen ligand was incorporated
into plasticized PVC polymer matrix along with the
presence of cation exchanger to enhance ion-ligand
interaction. Optical sensing properties of prepared
sensors were then comparatively examined towards
cations such as Al3+, Fe2+, Cr3+, Co2+, Ni2+, Cu2+, and
Zn2+, in terms of membrane sensitivity, selectivity,
response time, and linear concentration range, using UVVis spectrophotometric technique. Preliminary results
showed that the proposed membranes tended to be
selective to Fe2+ over other cations with the working
concentration range of 10-4 to 10-2 M.
ions [3-7]. In this work, we aim to immobilize the
ionophore in the membrane while the cation analyte
are presented in aqueous solutions. Salen is soluble in
polar organic solvents and therefore suitable being
chosen as ionophore in polymeric membrane for the
detection of metal cations such as Al3+, Fe2+, Cr3+,
Co2+, Ni2+, Cu2+, and Zn2+ via the reversible metal
chelation at the membrane-aqueous interphase. Optical
sensing properties and important characteristics of the
fabricated sensors will be investigated in order to find
the most selective metal ions and then the high
performance ion-selective optical sensor is expected to
be applied in real samples.
1. Introduction
Optical sensor, or optode, is one type of chemical
sensors in which electromagnetic (EM) radiation is
used to generate the analytical signal relating to the
interaction of this radiation with the sample and the
concentration of the analyte. Typically, an optical
chemical sensor consists of a chemical recognition
phase (sensing element or receptor) coupled with a
transduction element [1]. Optical sensor is recently one
of analytical devices employing for the measurement
of ions due to its several benefits such as simplicity,
high sensitivity and selectivity, good reversibility, and
fast response. It is well-known that the selectivity of
poly(vinyl chloride) or PVC membranes correlates
with their transport selectivity and also the extraction
selectivity. The most important component in a
polymeric membrane sensor is the ionophore which
contains the sensing unit that can bind and transfer the
most selective ion across the membrane. Another
important component is the ion exchanger which
functions as a balance charge, enhancing the metal ion
transfer and limits the co-anions entering the
membrane [2].
N,N'-Ethylenebis(salicylimine) or ‘salen’ is one of
the chelating ligands widely used in coordination
chemistry. The structure of this compound is depicted
in Figure 1. Metal-salen complexes and their
derivatives are commonly prepared and studied using
several techniques including spectrophotometric
methods. However, most studies have been carried out
in the same media/phase and might not be able to reuse
due to the non-reversible interaction. There are also a
few reports on electrochemical and optical sensing
properties of salen and its derivatives towards typical
2.1 Reagents and solutions
N,N'-Ethylenebis(salicylimine) or salen ligand was
prepared by the condensation of ethylenediamine and
salicylaldehyde according to the previous report [8].
Potassium tetrakis(p-chlorophenyl)borate (KTpClPB),
Tetrahydrofuran (THF), high molecular weight
poly(vinyl chloride) (PVC), and o-nitrophenyl octyl
ether (o-NPOE) were purchased from Fluka and
Merck. Analytical reagent grade of metal salts:
Co(NO3)2·6H2O,
FeSO4·7H2O,
Al(NO3)3·9H2O,
Cu(NO3)2·2.5H2O, Cr(NO3)3·9H2O, NiSO4·6H2O,
ZnSO4·7H2O were obtained from Unilab, Ajax
Finechem, and Volchem. All solutions of metal salts
were prepared with ultrapure water.
2.2 Instrumentation
The UV-Vis absorption spectra were recorded on a
double beam Hitachi (U-2900) spectrophotometer with
1.0-cm quartz cells, in the wavelength range between
200 and 1000 nm.
N
OH
N
HO
Figure 1. Chemical structure of salen ligand: N,N'Ethylenebis(salicylimine).
2.3 Membrane preparation
234
Polymeric membranes prepared for UV-Vis
measurements consisted of salen as ionophore (1%
w/w), KTpClPB as cation exchanger (75% relative to
the ionophore), and PVC: o-NPOE plasticizer (1 : 2
w/w), with a total amount of 100 mg. All components
were dissolved and stirred in 1.5 mL of THF for 30
minutes, giving a transparent homogeneous paleyellow cocktail solution. A cover glass with 22 mm ×
22 mm dimensions was cut to fit into standard
spectrophotometer cell. The membrane slide was
prepared by pipetting 20 μL of the casting membrane
solution onto a glass slide and the sovent was then
completely removed before the measurements (see
Figure 2).
2.4 Analytical procedure
Spectrophotometric measurements were carried out
to investigate the response of optical membrane
towards metal cations. The membrane slide was placed
vertically inside the quartz cell containing 2 mL of
metal ion aqueous solution for 5, 10, 20, and 30
minutes. The absorption spectra were recorded against
the blank membrane in ultrapure water as a reference
over the wavelength range of 200-1000 nm. The
concentration of cations was varied from 10-7 to 10-2 M
to examine the linear working range.
salen ligand
salen + Al(III)
salen + Co(II)
salen + Fe(II)
0.15
423
0.1
Abs
413
0.05
0
350
450
550
650
wavelength (nm)
Figure 3. Spectral changes of salen ligand with
different metal ions (10-3 M) (the spectra for Cr3+,
Co2+, Ni2+, Cu2+, and Zn2+ are not shown here).
A series of UV-Vis titrations was carried out to
confirm the recognition mechanism of salen towards
Fe(II) ion. As illustrated in Figure 4, the absorption
spectrum increases gradually with increasing Fe(II)
concentration, suggesting the complexation between
this ion and salen via N and O donor atoms. Moreover,
the cationic size effect probably played a role in
discriminating Fe2+ from other cations.
Series1
salen
ligand
Fe(II)
Series3
10-6 M Fe(II)
Series4
10-5 M Fe(II)
Series5
10-4 M Fe(II)
Series6
10-3 M Fe(II)
Series7
10-2 M Fe(II)
Series2
10-7 M
0.2
0.15
Abs
0.1
0.05
0
350
Figure 2. Preparation of a membrane slide and UV-Vis
absorbance measurement.
400
450
500 550 600 650
Wavelength (nm)
700
750
800
Figure 4. Absorption spectra of a membrane slide in
the presence of different concentrations of Fe(II).
N,N'-Ethylenebis(salicylimine) contains a nitrogen
and oxygen donor atom which could form internal
bonds with hard metal ions. UV-Vis absorbance
measurements were made to review the complexation
properties between salen ligand and various metal
cations in solutions (10-3 M) such as Al3+, Fe2+, Cr3+,
Co2+, Ni2+, Cu2+, and Zn2+ spectrophotometrically. The
preliminary results showed the characteristic band of
salen ionophore in the absence of metal ions at 413 nm
in Figure 3. Upon addition of 10-3 M of Al3+ and Co2+
solutions and the reaction was then left to reach
equilibrium, it was found that the absorption spectra
remain practically unchanged, indicating that salen did
not complex these cations, while the addition of Fe2+
led to a slight shift to 423 nm with higher absorbance.
As a result, there was expected the interaction between
ionophore and Fe2+.
The linear working concentration range determined
by plotting the absorbance against the logarithm of
Fe(II) concentration was found in the range of 10-4 to
10-2 M as presented in Figure 5 with the limit of
detection of 1.19 × 10-4 M. However, the membrane
compositions must be further varied to obtain the
better linear range and also detection limit. In addition,
other membrane characteristics, for example, working
pH range, reversibility, lifetime of optical sensor, as
well as the optimized membrane composition will be
further studied in order to find the best performance
sensor which could be reusably applied for the
determination of target ion in real samples.
235
Abs (423 nm)
0.2
y = 0.0317x + 0.1908
R² = 0.9936
0.15
0.1
0.05
0
-8
-7
-6
-5
-4
-3
-2
-1
log [Fe(II)]
Figure 5. Response of a polymeric optical film in
various concentrations of Fe(II) at 423 nm.
4. Conclusions
N,N'-Ethylenebis(salicylimine) or Salen ligand
showed good sensitivity and selectivity as ionselective ionophore due to its stability in polymeric
optical membrane. This compound tended to be
selective to Fe(II) ion, considering from the
preliminary results. The absorption spectra increased
gradually with increasing Fe(II) concentration,
suggesting that salen could bind this ion using N and O
donor atoms along with the suitable cavity size. The
presence of cation exchanger could also enhance the
sensing property of proposed optical film. Moreover,
the response time of prepared membrane slides was 5
minutes to reach the equilibrium of complexation
between our ionophore and target ion with the working
concentration range of 10-4 to 10-2 M of Fe(II) ion and
the limit of detection of 1.19 × 10-4 M. The membrane
composition, especially the amounts of salen
ionophore and cation exchanger should be optimized
to improve the membrane performance. Other
important characteristics of the proposed optodes must
also be monitored in order to find the best performance
sensor for further applications.
[4] Badr, I.H.A. and Meyerhoff, M.E., 2005, Highly
selective single-use fluoride ion optical sensor based on
aluminum(III)-salen complex in thin polymeric film,
Analytica Chimica Acta, 553, 169-176.
[5] Badr, I.H.A., 2006, Potentiometric anion selectivity of
polymer-membrane electrodes based on cobalt,
chromium, and aluminum salens, Analytica Chimica
Acta, 570, 176-185.
[6] Gorski, Ł., Matusevich, A., Parzuchowski, P., Łuciukb,
I. and Malinowska, E., 2010, Fluoride-selective
polymeric membrane electrodes based on Zr(IV)- and
Al(III)-salen ionophores of various structures, Analytica
Chimica Acta, 665, 39-46.
[7] Rezayi, M., Ahmadzadeh, S., Kassim, A. and Heng,
L.Y., 2011, Thermodynamic Studies of Complex
Formation Between Co(SALEN) Ionophore with
Chromate (II) Ions in AN-H2O Binary Solutions by The
Conductometric Method, International Journal of
Electrochemical Science, 6, 6350-6359.
[8] Diehl, H. and Hach, C.C., 1950, Bis(N,N'Disalicylalethylenediamine)-μ-Aquodicobalt(II),
Inorganic Syntheses, 3, 196-201.
Acknowledgements
This work was supported in part from Faculty of
Science, Maejo University, and National Science and
Technology
Development
Agency
(NSTDA),
Thailand.
.
References
[1] Lobnik, A., Turel, M. and Urek, Š.K., 2012, Optical
Chemical Sensors:Design and Applications, Advances
in Chemical Sensors, InTech, Rijeka, Croatia.
[2] Bakker, E., Bühlmann, P. and Pretsch, E., 1997,
Carrier-Based Ion-Selective Electrodes and Bulk
Optodes. 1. General Characteristics, Chemical
Reviews, 97, 3083-3132.
[3] Górski, Ł. , Saniewska, A., Parzuchowski, P.,
Meyerhoff, M.E. and Malinowska, E., 2005,
Zirconium(IV)-salophens
as
fluoride-selective
ionophores in polymeric membrane electrodes,
Analytica Chimica Acta , 551, 37-44.
236
PREPARATION OF PROTIC IONIC LIQUID/POLYVINYLPYRROLIDONE
COMPOSITES WITH ENHANCED HYDROPHOBICITY
Nuttakarn Moolthong, Natkritta Maipul and Phawit Putprasert*
Department of Chemistry, Faculty of Science and Technology, Thammasat University, Pathumthani, 12120, Thailand
*E-mail:
phawit@tu.ac.th, Tel. +66 2564 4440, Fax. +66 2564 4483
Abstract: Hydrophobic surfaces have recently gained
attentions from several industries due to various
potential applications. To overcome the static charge
accumulation, such surfaces with good electrical
conductivity are needed. The introduction of ionic liquids
with a certain degree of hydrophobicity into polymer
provides the desired conductivity. In this report, several
protic ionic liquids (PILs) have been prepared from
reactions between Brønsted acids and Brønsted bases.
Simple and low cost neutralization reactions between
these organic acids and bases produced PILs with high
conductivity (up to 3.36 mS cm-1) at room temperature.
The obtained PILs were characterized by 1H-NMR
spectroscopy and their thermal stabilities were studied
by thermogravimetric analysis. Several PILs including
triethylammonium benzoate with potentially high
hydrophobicity were then selected for the composite
fabrication. Polymer composites of polyvinylpyrrolidone
(PVP) with enhanced hydrophobicity have been prepared
with various amounts of the selected PILs. Water contact
angles of PVP/PIL composites were measured to evaluate
the enhanced hydrophobicity. The surface of PVP
without PIL shows poor hydrophobicity with the water
contact angle of 65.9°. Upon the addition of PILs, the
PVP composite with 20% of triethylammonium benzoate
exhibits the largest water contact angle of 117.4°.
1. Introduction
In recent years, a hydrophobic surface has become
a growing interest for many industries. Two major
factors that control such property are the chemical
composition and the geometrical microstructure. Its
potential applications include self-cleaning surface,
stain-resisting fabrics, and antifouling coatings, for
example [1]. However, such hydrophobic surface often
leads to static charge accumulation, which can cause
fire or explosion under dry conditions. It has been
known that conductive materials are used to dissipate
static charge. To prevent potential dangers of static
charge accumulation, the hydrophobic surface,
therefore, must be conductive.
Ionic liquids are a group of ionic compounds in a
liquid state around room temperature, unlike common
ionic compounds with high melting points [2-3]. Ionic
liquids have gained attention in past few decades with
many potential applications. Protic ionic liquids (PILs)
are a subset of ionic liquids. PILs can be easily
produced via a combination reaction between a
Brønsted acid and a Brønsted base, involving a proton
transfer from the acid to the base [4-5]. Similar to other
ionic liquids, PILs also show high conductivity and
high thermal stability. There are many reports which
ionic liquids, both protic and aprotic, have been used
to prepare conductive polymer composites for various
applications such as conductive membrane for dyesensitized solar cells (DSSCs) or proton exchange
membrane fuel cells (PEMFCs) [6-10].
In this report, PILs were utilized not only as
conducting agent, but also as hydrophobicity enhancer
for the polymer composites. Even though PILs are
composed of ions only, these ions are organic
compounds. Due to its organic nature, the PILs are
hydrophobic to some extent and can enhance the
hydrophobicity of the polymer composites which can
be evaluated using the water contact angle (WCA)
measurement [11].
2.1 General Setting
All chemicals and solvents were standard
analytical grade and used without further purification.
2.2 Synthesis and characterization of PILs
The synthesis PILs was adapted from literatures
[12-13]. In a typical synthesis of PIL, a Brønsted base
(0.2 mol) was added to a round bottom flask and was
cooled in an ice bath. A Brønsted acid (0.2 mol) was
added dropwise while stirring. The reaction was
allowed to warm up to room temperature and was
stirred for 12 hours to obtain the desired PIL. The
remaining starting materials were removed under
reduced pressure for one hour by using rotary
evaporator. When benzoic acid was used as a Brønsted
acid, it was dissolved in minimal amount of diethyl
ether before the solution was added to the Brønsted
base. Diethyl ether and any remaining starting
materials were then removed under reduced pressure
using a similar procedure described above.
1
H-NMR spectra were obtained using a Bruker
DPX-400, CDCl3 as a solvent and TMS as internal
standard. Ionic conductivities of PILs were measured
by conductometer (WTW, Cond 340i). Thermal
gravimetric analysis (TGA) was conducted on a Perkin
Elmer TGA7 under N2 flow with a heating rate of 10
°C/min.
2.3 Preparation and characterization of PVP/PIL
composites
The polymer composites were prepared with 5%,
10%, and 20% by weight of PIL. In a typical
preparation, 5 g of PVP and an appropriate amount of
237
PIL (0.25, 0.5, and 1.0 g) were dissolved in 20 mL
ethanol. After stirring for two hours, the mixture was
cast on a Teflon container. The solvent was allowed to
evaporate overnight and the composite polymer was
peeled off for characterization.
TGA was conducted on a Perkin Elmer TGA7
under N2 flow with a heating rate of 10 °C/min. Water
contact angles (WCAs) were measured on a ramé-hart
Model 220 Standard Contact Angle Goniometer.
PILs were obtained in good yields and were
characterized by 1H-NMR spectroscopy. Because the
structures of PILs are almost similar to their
corresponding starting materials, the chemical shifts of
PILs’ protons are also almost identical to those of the
starting acids and bases. The features from the NMR
spectra that can distinguish the PILs are the presence
of peaks of ammonium proton, which could be
observed as a broad singlet in the downfield region,
usually around 9–10 ppm. The NH chemical shifts of
the obtained PILs are listed in Table 1.
The conductivities of PILs were measured using a
conductometer. The results are shown in Table 1.
Triethylammonium formate shows the highest
conductivity of 3.36 mS cm-1 and N,Ndimethylanilinium benzoate shows the lowest
conductivity of 0.0001 mS cm-1. The size of the ions of
PILs probably affects the conductivity of PILs since
smaller size implies greater ion mobility and
consequently better conductivity. The small size of
ions in triethylammonium formate, therefore, results in
high conductivity. On the other hand, PILs containing
larger ions such as benzoate or p-toluenesulfonate
show lower conductivity.
From TGA analysis, the temperatures of
decomposition (Td) of PILs were presented in table 1.
From the result, PILs with formate and benzoate as
anions started to decompose at around 70 and 110 °C,
respectively. This can probably be attributed to the
molecular weight of PILs. Specifically, thermal
stability of PILs increases as the molecular weight
increases, making. PIL with p-toluenesulfonate anions
the most thermally stable (Td > 279 °C).
Table 1: Percent yields, ionic conductivities, and temperature of decomposition (Td) of obtained PILs
Yield (%)
Conductivity (mS cm-1)
Td (°C)
Triethylammonium formate
31.26
3.36
70
NH chemical
shift (ppm)
10.50
Triethylammonium benzoate
82.46
0.10
150
9.56
Triethylammonium p-toluenesulfonate
64.63
0.18
321
9.95
N,N-dimethylanilinium formate
27.53
0.15
70
10.00
N,N-dimethylanilinium benzoate
97.22
0.0001
110
8.85
N,N-dimethylanilinium p-toluenesulfonate
61.09
0.27
279
10.00
PIL
Two of the obtained PILs, triethylammonium benzoate
and N,N-dimethylanilinium formate, were selected to
prepare polymer composites with PVP. The benzene
ring in the benzoate anion and the benzene ring in
aniline were expected to increase the hydrophobicity
of the polymer composites. The resulting PVP/PIL
composites are transparent and uniform film with a
thickness of about 1 mm.
Figure 1 shows photographs taken during WCA
measurements of PVP and PVP/PIL composites with
various amounts of triethylammonium benzoate. PVP
exhibits WCA of 65.9° and is regarded as hydrophilic.
Addition of triethylammonium benzoate increases the
WCA of the PVP/PIL composites significantly as
clearly observed in Figure 1 (b-d). The higher loading
of triethylammonium benzoate also increases the
hydrophobicity of the PVP/PILs composite. In fact, the
PVP/PIL composite with 20% triethylammonium
benzoate exhibits the highest WCA of 117.4°.
However, N,N-dimethylanilinium formate showed
only slight improvement on the hydrophobicity of the
PVP composites. With 20% N,N-dimethylanilinium
formate, the PVP/PIL composites exhibit the WCA of
79.0°, only 9.6° greater than pure PVP film.
Figure 1. Photographs of WCA measurements of (a)
PVP and (b-d) PVP with 5%, 10% and 20%
triethylammonium benzoate, respectively.
238
WCAs of all PVP composites are presented in table 2.
In addition, PVP/PIL composites are thermally
stable. Table 2 shows the initial decomposition
temperatures (IDTs) of PVP/PIL composites.
Compared to pure PVP, the PVP/PIL composites
generally have lower IDT because PILs decompose at
lower temperatures than PVP. Thus higher loadings of
PILs slightly lower the IDT of PVP/PIL composites as
shown in table 2. However, even with 20% loading of
PILs, the PVP/PIL composites still exhibit high
thermal stability (>200 °C).
Table 2: Water contact angles (WCAs) and initial
decomposition temperatures (IDTs) of PVP/PIL
composites
PVP only
WCA
(°)
65.9
IDT
(°C)
350
5%
108.7
260
10%
111.4
250
20%
117.4
215
5%
69.4
270
10%
75.8
265
20%
79.0
231
PIL
% PIL
triethylammonium
benzoate
N,Ndimethylaniline
formate
[5] Angell, C. A., Byrne, N. and Belieres, J-P., 2007, Acc.
Chem. Res., 40, 1228
[6] Fuller, J., Breda, A. C. and Carlin, R.T., 1997, J.
Electrochem. Soc., 144, L67–69.
[7] Wang, P., Zakeeruddin, S. M., Exnar, I. and Gratzel,
M., 2002, Chem Commun., 2972–2973.
[8] Bansal, D., Cassel, F., Croce, F., Hendrickson, M,,
Plichta, E. and Salomon, M., 2005, J. Phys. Chem. B.,
109, 4492.
[9] Yeon, S. H., Kim, K. S., Choi, S., Cha, J. H. and Lee,
H., 2005, J. Phys. Chem. B., 109, 17928–17935.
[10] Fukushima, T., Asaka, K,, Kosaka, A. and Aida, T.,
2005, Angew. Chem. Int. Ed., 44, 2410–2413.
[11] Lu, X., Zhou, J., Zhou, Y., Qiu, Y. and Li, J., 2008,
Chem. Mater., 20, 3420.
[12] Anouti, M., Caillon-Caravanier, M., Dridi, Y., Galiano,
H. and Lemordant, D., 2008, J. Phys. Chem. B., 112,
13335-13343.
[13] Anouti, M., Caillon-Caravanier, M., Le Floch, C. and
Lemordant, D., 2008, J. Phys. Chem. B., 112, 94069411.
4. Conclusions
In summary, we have utilized simple neutralization
reactions between Brønsted acids and Brønsted bases
to produce several protic ionic liquids in good yields.
Some of the obtained PILs exhibit high conductivity
and high thermal stability. Triethylammonium
benzoate and N,N-dimethylanilinium formate were
selected to prepare composites with PVP. The results
showed that the PVP/PIL composites with 20%
triethylammonium benzoate demonstrated the largest
water contact angle of 117.4°. All PVP/PIL
composites also exhibited high thermal stability.
Acknowledgements
We would like to thank Thailand Research Fund
(MRG5480199) and Department of Chemistry, Faculty
of Science and Technology, Thammasat University for
financial support.
References
[1] Zhu, Y., Zhang, C., Zheng, M., Huang, B., Feng, L. and
Jiang, L., 2006, Adv. Funct. Mater., 16, 568-574.
[2] Welton, T., 1999, Chem. Rev., 99, 2071-2083.
[3] Wasserscheid, P. and Keim, W., 2000, Angew. Chem.
Int. Ed., 39, 3772-3789.
[4] Greaves, T. and Drummond, C. 2008, Chem. Rev., 108,
206-237.

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