Synthesis and complexing properties of 4-arylthiazolyl-substituted Schiff bases

Article abstract of DOI:10.1023/B:RUGC.0000025156.16373.17

Reactions of 2-amino-4-arylthiazoles with aromatic aldehydes afforded the corresponding Schiff bases. Complex formation of the latter with nickel, zinc, cobalt, manganese, and copper salts was studied.

Full text of DOI:10.1023/B:RUGC.0000025156.16373.17

Russian Journal of General Chemistry, Vol. 73, No. 12, 2003, pp. 1932 1935. Translated from Zhurnal Obshchei Khimii, Vol. 73, No. 12, 2003,
pp. 2043 2046.
Original Russian Text Copyright
2003 by Sadigova, Magerramov, Allakhverdiev, Alieva, Chyragov, Vekilova.
Synthesis and Complexing Properties
of 4-Arylthiazolyl-substituted Schiff Bases
S. E. Sadigova, A. M. Magerramov, M. A. Allakhverdiev, R. A. Alieva,
F. M. Chyragov, and T. M. Vekilova
Baku State University, Baku, Azerbaidjan
Received October 29, 2001
Abstract Reactions of 2-amino-4-arylthiazoles with aromatic aldehydes afforded the corresponding Schiff
bases. Complex formation of the latter with nickel, zinc, cobalt, manganese, and copper salts was studied.
Various thiazoles exhibit pharmacological activity,
e.g., antimicrobial, antihistaminic, antiparazitic, anti-
helminthic, antipyretic, and antiviral. Such medicines
as Sulfathiazole, Phthalylsulfathiazole, and related
compounds are widely used in medical practice.
Thiazole ring is a structural component of natural
compounds, e.g., Vitamin B1 (thiamine), penicillin,
and carboxylase [1]. Thiazole derivatives are widely
used as antioxidants for petrochemical products,
vulcanization accelerators, and photochromic sub-
stances [2, 3]. Taking the above into account, it
seemed important to synthesize a series of 2-amino-
4-arylthiazoles I III. Compounds I III were prepared
by reaction of substituted acetophenones with thiourea
in the presence of iodine.
R
R
I2
N
C CH3 + H2NCNH2
NH2
S
O
S
I III
I, R = H; II, R = 2,5-(MeO)2; III, R = Cl.
When the reactant ratio substituted acetophenone
Schiff bases are used in analytical chemistry as
ligands for determination of various transition metals.
They are also convenient synthons for preparation
of various heterocycles, as well as for cyclization of
terpenes. We were the first to examine the reaction
of 2-amino-4-arylthiazoles I III with aromatic
aldehydes. As a rule, the reaction required no external
heating. The products (compounds IV X) were yellow
crystalline substances which were recrystallized from
ethanol. Their yields, melting points, Rf values, and
elemental analyses are collected in Table 2.
thiourea iodine was 1:1:1 or 2:2:1, the yield of
the products was 20 50 or 43 70%, respectively.
2-Amino-4-arylthiazoles I III are colorless crystalline
substances, which are insoluble in benzene and
heptane but soluble in acetone and ethanol. Their
yields, melting points, and analytical data are given
in Table 1. The structure of I III was proved by the
1
IR and H and 13C NMR spectra, and the purity was
checked by elemental analysis and thin-layer chrom-
atography. The IR spectra of 2-amino-4-arylthiazoles
I III contained absorption bands at 1470, 1610,
1
1635 1680, 3375, and 3290 cm due to vibrations
The IR spectra of Schiff bases IV X resemble
those of thiazoles I III with the difference that
1
of the C C, C N, and N H bonds. In the H NMR
1
spectra of I III, protons of the aromatic fragment
give rise to a multiplet in the region 6.8 7.27 ppm.
A singlet at 3.45 ppm in the spectrum of II belongs
to protons of the two methoxy groups. The NH2 group
a broad absorption band at 3450 cm is observed in
the spectra of compounds VI X. This band was
assigned to stretching vibrations of the phenolic
hydroxy group involved in intramolecular hydrogen
bonding with the N CH fragment. No absorption
gives a doublet at
3.8 ppm.
1070-3632/03/7312-1932$25.00 2003 MAIK Nauka/Interperiodica

SYNTHESIS AND COMPLEXING PROPERTIES
1933
R
R
O
N
N
+
C R
H2O
NH2
N=CH R
H
S
S
IV X
IV, R = H, R = Ph; V, R = 2,5-(MeO)2; R = Ph; VI, R = H, R = 2-HOC6H4; VII, R = 2,5-(MeO)2, R = 2-HOC6H4;
VIII, R = H, R = 2-HO-4-BrC6H3; IX, R = 2,5-(MeO)2, R = 2-HO-4-BrC6H3; X, R = 4-Cl, R = 2-HO-4-BrC6H3.
typical of stretching vibrations of primary amino
multiplet at
7.2 7.5 belongs to nonequivalent
group was present. The phenolic proton in VI X gives
aromatic protons in the 2-hydroxyphenyl fragment.
1
a signal at 3.25 ppm in the H NMR spectra, while
the N CH proton appears at
7.85 7.90 ppm. A
We reacted of 2-(2-hydroxybenzylideneamino)-4-
N
N=CH
S
HO
O
N
M
+ M(CH3COO)2
N=CH
2CH3COOH
O
S
N
HC=N
S
M = Cu, Zn, Mn, Co, Ni.
Table 1. Yields, melting points, Rf values, and elemental analyses of 2-amino-4-arylthiazoles I III
Found, %
Cl
Calculated, %
Cl
Comp. Yield,
no.
mp,
C
Rf
Formula
%
C
H
N
S
C
H
N
S
I
II
70 148 150 0.75 61.09 4.62
65 178 179 0.34 55.55 5.43
15.48 18.31 C9H8N2S
11.58 13.73 C11H12N2O2S 55.91 5.12
61.34 4.58
15.89 18.19
11.86 13.57
III
43 165 167 0.46 51.03 3.64 16.71 13.07 14.93 C9H7N2ClS
51.31 3.35 16.83 13.30 15.22
Table 2. Yields, melting points, Rf values, and elemental analyses of Schiff bases IV X
Found, %
Calculated, %
Cl/Br
Comp. Yield,
no.
mp,
C
Rf
Formula
%
C
H
Cl/Br
N
S
C
H
N
S
IV
V
69 155 156 0.74 72.61 4.73
73 147 148 0.36 66.78 4.72
75 143 144 0.36 68.73 4.17
68 139 140 0.51 63.29 4.61
80 100 103 0.82 53.63 2.85 22.08
71 145 147 0.43 51.76 3.44 18.85
10.75 12.02 C16H12N2S
8.82 9.76 C18H16N2O2S
10.16 11.17 C16H12N2OS
8.42 9.08 C18H16N2O3S
7.39 8.49 C16H11BrN2OS 53.49 3.09 22.24 7.80 8.93
6.37 6.98 C18H15BrN2O3S 51.56 3.61 19.06 6.68 7.65
72.80 4.58
66.65 4.97
68.55 4.32
63.51 4.74
10.60 12.13
8.64 9.88
9.99 11.44
8.23 9.42
VI
VII
VIII
IX
X
68 120 123 0.44 48.72 2.19
8.79/ 7.26 8.33 C16H10BrClN2OS 48.81 2.56 9.01/ 7.12 8.14
20.11 20.30
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 12 2003

1934
SADIGOVA et al.
phenylthiazole (VI) with copper, zinc, manganese,
cobalt, and nickel acetates to synthesize new
coordination compounds.
its position. The (C N) frequency decreases on the
1
average by 10 15 cm on complex formation, and
1
new absorption bands appear at 1245 1250 cm due
to stretching vibrations of the C O bond. These data
suggest that the ligand coordinates to the central metal
ion through the oxygen and nitrogen atoms. The cop-
per(II), nickel(II), cobalt(II), and iron(III) complexes
are colored substances. Therefore, they can be used
in photometric determination of the corresponding
metals.
The composition of the resulting complexes was
determined by elemental and gravimetric analysis. We
found that the copper complex contains two water
molecules, one water molecule is present in the zinc
complex, and the other complexes contain no water:
Cu(C16H11N2OS)2 2H2O, Zn(C16H11N2OS)2 H2O,
Mn(C16H11N2OS)2,
Co(C16H11N2OS)2,
and
Ni(C16H11N2OS)2. The complexes are readily soluble
in pyridine, dimethylformamide, and dimethyl sul-
foxide. They were identified by the X-Ray powder
diffraction method using a DRON-2 diffractometer
(CuK radiation, Ni filter). The diffractograms
indicated that the complexes Mn(C16H11N2OS)2 and
Co(C16H11N2OS)2 are isostructural, presumably due
to similar ionic radii of the corresponding metals.
Thermographic and thermogravimetric studies were
performed using platinum crucibles in air; Paulik
Paulik Erdey Q-derivatograph, temperature range 20
to 1000 C, heating rate 10 deg/min. Thermal decom-
position of the complexes may be represented by the
following schemes.
EXPERIMENTAL
The IR spectra of compounds I X were recorded
on a Specord IR-75 spectrophotometer from samples
dispersed in mineral oil (spectral range 3700
1
700 cm ; KBr, NaCl, and LiF prisms). The IR
spectra of the complexes were measured in the range
1
from 4000 to 400 cm in KBr using a UR-20 instru-
1
ment. The H NMR spectra were recorded on a Varian
VXR-400S spectrometer (400 MHz) from solutions in
DMSO-d6 using TMS as internal reference. Silufol
UV-254 plates were used for TLC analysis; eluent
isopropyl alcohol heptane (1:1); development in
iodine vapor.
Cu(C16H11N2OS)2 2H2O 55 65 C Cu(C16H11N2OS)2
2-Amino-4-phenylthiazole (I). Iodine, 50.8 g,
was added to a mixture of 24 g of acetophenone and
30.4 g of thiourea. The mixture was heated on a water
bath in a closed vessel for 24 h, diluted with water,
and heated again until it became almost homogeneous.
The small amount of elemental sulfur was filtered off,
the filtrate was cooled and made alkaline by adding
aqueous ammonia, and the precipitate was filtered off
and recrystallized from ethanol. Yield 30.2 g (85%),
140 450 C
CuO,
Zn(C16H11N2OS)2 H2O50 65 C Zn(C16H11N2OS)2
135 460 C
ZnO,
145 480 C
Mn(C16H11N2OS)2
Co(C16H11N2OS)2
Ni(C16H11N2OS)2
Mn2O3,
Co2O3,
Ni2O3.
140 470 C
145 480 C
1
mp 148 150 C, Rf 0.75. IR spectrum, , cm : 1635
1
(C N); 3375, 3290 (NH2). H NMR spectrum,
,
ppm: 3.7 3.9 (2H, NH2), 6.92 7.25 (6H, CH, Harom).
Found, %: C 61.09; H 4.62; N 15.48; S 18.31.
C9H8N2S. Calculated, %: C 61.34; H 4.58; N 15.89;
S 18.19. Compounds II and III were synthesized in
a similar way (Table 1).
The low temperature corresponding to dehydration
of the Cu(II) and Zn(II) complexes suggests that water
is not incorporated into the coordination sphere of
these complexes. All complexes are characterized by
almost similar decomposition onset temperatures. This
process corresponds to endothermic effect on the DTA
curve. According to the X-ray powder diffraction data,
the final thermolysis products are the respective metal
oxides.
2-Benzylideneamino-4-phenylthiazole (IV).
A 500-ml three-neck flask was charged with 4.8 g of
benzaldehyde, and 8.2 g of 2-amino-4-phenylthiazole
(I) was added under vigorous stirring. The reaction
was accompanied by heat evolution and liberation of
water. After 30 min, the mixture was poured into
a 50-ml beaker containing 10 ml of 95% ethanol.
Crystallization began in a few minutes. The mixture
was cooled with ice, and the precipitate was filtered
off and dried in air. Yield 9 g (69%), mp 155 156 C,
The structure of the prepared complexes was
refined on the basis of their IR spectra. The IR
absorption bands were assigned with account taken of
the data given in [4]. Of particular interest was the
1
frequency range 1700 1500 cm , where bands
1
belonging to stretching vibrations of C OH, C N,
and C C bonds appear. In going from the free ligand
to the complexes, the (C C) band does not change
Rf 0.74. IR spectrum, , cm : 1643 (C N), 1350
(C N), 1460 (C C). Found, %: C 72.61; H 4.73;
N 10.75; S 12.02. C16H12N2S. Calculated, %:
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 12 2003

SYNTHESIS AND COMPLEXING PROPERTIES
C 72.80; H 4.58; N 10.60; S 12.13. Compounds V X
1935
REFERENCES
were synthesized in a similar way (Table 2).
1. Zbarskii, B.I., Ivanov, I.I., and Mardashev, S.R.,
Biologicheskaya khimiya (Biological Chemistry),
Leningrad: Meditsina, 1972, p. 171.
2. Comprehensive Organic Chemistry, Barton, D. and
Ollis, W.D., Eds., Oxford: Pergamon, 1979, vol. 5.
Translated under the title Obshchaya organicheskaya
khimiya, Moscow: Khimiya, 1985, vol. 9, p. 481.
3. Uchikawa, O., Fukatsu, K., and Suno, M., Chem.
Pharm. Bull., 1996, vol. 44, no. 11, p. 2070.
Bis[2-(2-hydroxybenzylideneamino)-4-phenyl-
thiazolato]copper(II). A solution of 0.95 g of cop-
per(II) acetate in 30 ml of water was heated to 60
70 C, and a solution of 2.7 g of compound VI in
20 ml of ethanol was added over a period of 30 min.
The mixture was stirred for 2 h at that temperature
and evaporated by 2/3 of the initial volume. The
residue was cooled to room temperature and was left
to stand for 2 days. The green precipitate of
Cu(C16H11N2OS)2 2H2O was filtered off. Yield 75%.
The other complexes were synthesized in a similar
way.
4. Cross, A.D., An Introduction to Practical Infra-red
Spectroscopy, London: Butterworths, 1960. Translated
under the title Vvedenie v prakticheskuyu infrakras-
nuyu spektroskopiyu, Moscow: Inostrannaya Litera-
tura, 1961, p. 110.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 12 2003