Synthesis, spectral studies of cobalt(II) tetrathiocyanoto dicuperate(I) complexes with some acylhydrazones and their antimicrobial activity

Article abstract of DOI:10.1134/S1070328408050102

Cobalt(II) complexes of the type Co[Cu(NCS)₂]₂ ? L, where L is acetophenonebenzoylhydrazone (Abh), acetophenoneisonicotinoylhydrazone (Ainh), acetophenonesalicyloylhydrazone (Ash), acetophenoneanthraniloylhydrazone (Aah), p- hydroxyacetophenonebenzoylhydrazone (Phabh), p- hydroxyacetophenoneisonicotinoylhydrazone (Phainh), p- hydroxyacetophenonesalicyloylhydrazone (Phash), and p- hydroxyacetophenoneanthraniloylhydrazone (Phaah) were synthesized and characterized by elemental analyses, molar conductance, magnetic moments, electronic and IR spectra, and X-ray diffraction studies. The complexes are insoluble in common organic solvents and are non-electrolytes. These complexes are coordinated through the >C=O and >C=N groups of the hydrazone ligands. The magnetic moments and electronic spectra suggest a spin-free octahedral geometry around Co(II). The X-ray diffraction parameters (a, b, c) for Co[Cu(SCN)₂]₂ ? Ainh and Co[Cu(SCN)₂] ₂ ? Phabh correspond to orthorhombic and tetragonal crystal lattices, respectively. The complexes show a fair antifungal and antibacterial activity against a number of fungi and bacteria. The activity increases with increasing concentration of the compounds.

Full text of DOI:10.1134/S1070328408050102

ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2008, Vol. 34, No. 5, pp. 374–381. © Pleiades Publishing, Ltd., 2008.
Synthesis, Spectral Studies of Cobalt(II) Tetrathiocyanoto
Dicuperate(I) Complexes with Some Acylhydrazones
and Their Antimicrobial Activity1
V. P. Singh and A. Singh
Department of Chemistry, Banaras Hindu University, Varanasi, 221005 India
e-mail: singvp@yahoo.co.in
Received March 1, 2007
Abstract—Cobalt(II) complexes of the type Co[Cu(NCS)2]2 · L, where L is acetophenonebenzoylhydrazone
(Abh), acetophenoneisonicotinoylhydrazone (Ainh), acetophenonesalicyloylhydrazone (Ash), acetophenon-
eanthraniloylhydrazone (Aah), p-hydroxyacetophenonebenzoylhydrazone (Phabh), p-hydroxyacetophenon-
eisonicotinoylhydrazone (Phainh), p-hydroxyacetophenonesalicyloylhydrazone (Phash), and p-hydroxyace-
tophenoneanthraniloylhydrazone (Phaah) were synthesized and characterized by elemental analyses, molar
conductance, magnetic moments, electronic and IR spectra, and X-ray diffraction studies. The complexes are
insoluble in common organic solvents and are non-electrolytes. These complexes are coordinated through the
>C=O and >C=N groups of the hydrazone ligands. The magnetic moments and electronic spectra suggest a
spin-free octahedral geometry around Co(II). The X-ray diffraction parameters (a, b, c) for Co[Cu(SCN)2]2 ·
Ainh and Co[Cu(SCN)2]2 · Phabh correspond to orthorhombic and tetragonal crystal lattices, respectively. The
complexes show a fair antifungal and antibacterial activity against a number of fungi and bacteria. The activity
increases with increasing concentration of the compounds.
DOI: 10.1134/S1070328408050102
1
INTRODUCTION
acylhydrazones. The antifungal and antibacterial prop-
erties of the ligands and their complexes were also
tested.
Schiff bases containing the RC=N– group constitute
an interesting class of chelating agents capable to coor-
dinate with one or more metal ions giving mononuclear
or polynuclear metal complexes, which serve as models
for metalloproteins [1]. It has been suggested that
monoamine oxidase enzyme inhibition occurs via
metal Schiff base complex formation [2]. Copper(II)
salicylaldehyde benzoylhydrazone [3] and 2-pyridine
carboxaldehyde–2-pyridylhydrazone [4] have been
reported to produce significant inhibition of tumor
growth.
EXPERIMENTAL
Materials. All chemicals were of AnalaR (BDH) or
equivalent grade. Isonicotinic acid hydrazide
(NC5H4NHNH2) was obtained from S.D. Fine Chemi-
cals (Mumbai) and used after recrystallization in etha-
nol. Benzoic acid hydrazide (C6H5CONHNH2), sali-
cylic acid hydrazide (HOC6H4CONHNH2), and anthra-
nilic acid hydrazide (H2NC6H4CONHNH2) were
synthesized by the reported methods [6].
Synthesis of acetophenone acylhydrazones (L).
Acetophenone benzoyl hydrazone (C6H5C(CH3)=NN
HCOC6H5, Abh), acetophenone isonicotinoyl hydra-
zone (C6H5C(CH3)=NNHCOC5H4N, Ainh), acetophe-
none salicyloyl hydrazone (C6H5C(CH3)=NNHCO
C6H4(OH), Ash), acetophenone anthraniloyl hydrazone
Cobalt(II) complexes, besides existing in several
stereochemical dispositions, interact with molecular
oxygen ultimately oxidizing complexed Co(II) to
Co(III). The best studied examples are cobalt(II) Schiff
base complexes that take up O2 in DMF or pyridine
solution [5]. Heterobimetallic complexes formed by the
combination of two metal thiocyanates, Co(NCS)2 and
CuSCN, with a potent acylhydrazone ligand should be
more biologically active than the metal thiocyanate or (C6H5C(CH3)=NNHCOC6H4(NH2), Aah) were synthe-
the hydrazone ligand. Therefore, we report here the
synthesis, characterization, electronic, and IR spectral
studies, and X-ray diffraction studies of cobalt(II)
tetrathiocyanatodicuperate(I) complexes with some
sized by reacting the corresponding acid hydrazides
with acetophenone in a 1 : 1 molar ratio in 50 ml of eth-
anol in a round-bottom flask. The reaction mixture was
refluxed at 60°C for 2–4 h and then allowed to cool in a
beaker, and the product was filtered off by suction on a
buckner funnel. The Abh and Aah ligands were recrys-
1
The text was submitted by the authors in English.
374

SYNTHESIS, SPECTRAL STUDIES OF COBALT(II) TETRATHIOCYANOTO
Table1. Analytical data of the ligands
375
Contents (found/calcd), %
Empirical formula
Ligand (color)
Abh (white)
Melting point, °C
Yield, %
(formula wt.)
C
H
N
C15H14N2O (238)
C14H13N3O (239)
C15H14N2O2 (254)
145
162
205
175
210
260
240
225
74.89/75.63
70.10/70.29
70.22/70.86
70.72/71.15
70.40/70.86
65.32/65.88
65.95/66.67
66.40/66.91
5.92/5.88
5.50/5.44
5.61/5.51
5.81/5.93
5.67/5.51
5.18/5.10
5.26/5.18
5.48/5.57
11.16/11.76
17.32/17.57
10.85/11.02
16.41/16.60
10.72/11.02
16.08/16.47
10.32/10.37
15.41/15.61
65
60
65
50
60
55
65
55
Ainh (white)
Ash (white)
Aah (cream yellow) C15H15N3O (253)
Phabh (light yellow) C15H14N2O2 (254)
Phainh (light yellow) C14H13N3O2 (255)
Phash (light yellow) C15H14N2O3 (270)
Phaah (light yellow) C15H15N3O2 (269)
tallized from hot benzene while Ash and Ainh were
recrystallized from hot ethanol and dried in a desiccator
over anhydrous CaCl2.
Synthesis of Co[Cu(SCN)2]2. The Lewis acid
Co[Cu(SCN)2]2 was prepared by reacting Co(NCS)2
(1.74 g, 10 mmol) and CuSCN (2.42 g, 20 mmol) in a
1 : 2 molar ratio in a round-bottom flask containing
50 ml of dioxane and fitted with anhydrous CaCl2 guard
tube. The reaction mixture was stirred continuously for
48 h on a magnetic stirrer at room temperature to com-
plete the reaction. Bright green Lewis acid thus formed
was filtered off through a closed assembly, washed with
dioxane, and dried in a desiccator at room temperature.
Synthesis of p-hydroxy acetophenone acylhydra-
zones (L). p-Hydroxy acetophenone benzoylhydrazone
(C6H4(OH)C(CH3)=NNHCOC6H5, Phabh); p-hydro-
xyacetophenone
isonicotinoylhydrazone
(C6H4
(OH)C(CH3)=NNHCOC5H4N, Phainh); p-hydroxyac-
etophenone salicyloylhydrazone (C6H4(OH)C(CH3)=N
NHCOC6H4(OH), Phash); p-hydroxyacetophenone
anthraniloylhydrazone (C6H4(OH)C(CH3)=NNHCO
C6H4(NH2), Phaah) were synthesized by reacting their
corresponding acid hydrazide with p-hydroxyacetophe-
none in a 1 : 1 molar ratio in 50 ml of ethanol. The reac-
tants were refluxed for 4–6 h in a round-bottom flask at
60°C. The crude product was filtered off after cooling,
recrystallized from hot ethanol, and dried in a desicca-
tor.
Syntheses of Co[Cu(SCN)2]2 · L were carried out by
reacting Lewis acid Co[Cu(SCN)2]2 (2.85 g, 5 mmol)
separately with 5 mmol each of the ligands Abh
(1.19 g), Ainh (1.20 g), Ash (1.27 g), Aah (1.26 g),
Phabh (1.27 g), Phainh (1.28 g), Phash (1.35 g), and
Phaah (1.35 g) dissolved in 50 ml of dioxane in a round-
bottom flask. The mixture was well stirred on a mag-
netic stirrer for 20–48 h at room temperature until a vis-
ible color change of the product occurred. The product
was filtered off, washed with dioxane followed by
diethyl ether and then dried in a desiccator at room tem-
perature.
The ligands were characterized by their melting
points, CHN analyses, and IR spectra (Table 1).
Synthesis of metal thiocyanates. (a) Cobalt(II)
thiocyanate was prepared by dissolving Co(NO3)2 ·
6H2O (2.90 g, 10 mmol) in 50 ml of absolute ethanol
and KSCN (1.94 g, 20 mmol) in 25 ml of absolute eth-
anol separately. Both solutions were mixed in a beaker
at room temperature. Potassium nitrate was thus
formed as white solid and removed by filtration. The fil-
trate containing Co(NCS)2 was slowly evaporated to
dryness to obtain a blue colored solid product, which
was redissolved and then purified from dry ethanol to
ensure removal of water soluble KNO3.
Analyses and physicochemical studies. For deter-
mination of the copper and cobalt contents were used
method described in [7]. Carbon, hydrogen, and nitro-
gen contents were determined by using an Elemental
Vario EL III Carlo Erba 1108 model microanalyzer.
The molar conductances of 10–3 M solutions of the
complexes in DMSO were measured at room tempera-
ture on a Systronic Conductivity meter model-306.
Room temperature magnetic susceptibilities were
determined on a Faraday balance using Hg[Co(SCN)4]
as calibrant and corrected for diamagnetism [8]. IR
spectra were recorded in a KBr medium on a Vector-22
spectrophotometer. Electronic spectra were recorded in
DMSO solution on a Perkin Elmer Lambada-2 spectro-
photometer. Powder X-ray diffraction patterns of a few
(b) Copper(I) thiocyanate was prepared according to
the method [7] by dissolving CuSO4 · 5H2O (2.49 g,
10 mmol) in 50 ml of dilute HCl (0.05 N). The solution
was treated with sulfurous acid (H2SO3) to reduce Cu2+
to Cu+ and then was treated with NH4SCN (0.77 g, complexes were recorded on an Iso Debye Flex 2002
apparatus using CuKα radiations. The elemental analy-
CuSCN was filtered off and washed with water fol- sis and physicochemical data of complexes are given in
lowed by ethanol and finally with diethyl ether. Tables 2−4.
10 mmol) dissolved in 25 ml of distilled water. White
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376
V. P. SINGH, A. SINGH
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 34 No. 5 2008

SYNTHESIS, SPECTRAL STUDIES OF COBALT(II) TETRATHIOCYANOTO
Table 3. Magnetic moments and electronic spectral bands of complexes
377
Band maxima, cm–1
LFSE,
Kcal/mol
Complexes
µeff, µB
10 Dq, cm–1 B, cm–1
β
B, %
ν1
ν3
Co[Cu(SCN)2]2
4.20
4.72
4.85
4.68
4.70
4.76
4.82
4.80
4.73
15150
20060
19935
20175
20380
20490
20350
20430
19980
Co[Cu(SCN)2]2 · Abh
Co[Cu(SCN)2]2 · Ainh
Co[Cu(SCN)2]2 · Ash
Co[Cu(SCN)2]2 · Aah
Co[Cu(SCN)2]2 · Phabh
Co[Cu(SCN)2]2 · Phainh
Co[Cu(SCN)2]2 · Phash
Co[Cu(SCN)2]2 · Phaah
9260
9355
9430
9380
9410
9295
9360
9250
10460
10525
10655
10600
10630
10500
10575
10405
800
783
798
815
820
817
819
792
0.824 17.60
0.806 19.40
0.822 17.80
0.839 16.10
0.844 15.60
0.841 15.90
0.843 15.70
0.815 18.50
23.84
23.99
24.28
24.16
24.23
23.93
24.10
23.71
Antifungal activity. The ligands, as well as their
complexes, were screened for antifungal activity
against various fungi, viz., Rizoctonia sp. and Penicil-
lium sp. These species were isolated from the infected
organs of the host plants on a potato dextrose agar
(potato 250 g + dextrose 20 g + agar 20 g) medium. The
cultures of the fungi were purified by the single spore
isolation technique.
The solutions with different concentrations 0.5, 1,
and 1.5 mg/ml of each compound in DMSO were pre-
pared for testing against spore germination. A drop of
the solution of each concentration was kept separately
on glass slides. The conidia, fungal reproducing spores
(~200) lifted with the help of an inoculating needle,
were mixed in each drop of each compound separately.
Each treatment was replicated thrice and a parallel
DMSO solvent control set was run concurrently on sep-
arate glass slides. All the slides were incubated in
humid chambers at 25 2°C for 24 h. Each slide was
observed under a microscope for spore germination,
and the percent germination was finally calculated.
Antibacterial activity of the ligands and their com-
plexes were studied against Clostridium sp. (Gram +ve)
and Pseudomonas sp. (Gram –ve) bacteria. Each of the
compounds was dissolved in DMSO, and solutions of
concentration 2 and 1 mg/ml were prepared separately.
Paper discs of Whatman filter paper (no. 42) of uniform
diameter (2 cm) were cut and sterilized in an autoclave.
The paper discs soaked in the desired concentration of
the complex solutions were placed aseptically in the
petridishes containing nutrient agar media (agar 20 g +
beef extract 3 g + peptone 5 g) seeded with Clostridium
and Pseudomonas sp. bacteria separately. The petri
dishes were incubated at 37°C and the inhibition zones
were recorded after 24 h of incubation. Each treatment
was replicated 9 times.
The antibacterial activity of a common standard
antibiotic Ampicillin was also recorded using the same
procedure as above at the same concentrations and sol-
vent. The % Activity Index for the complex was calcu-
lated by the formula as follows:
Zone of inhibition by test compound (diameter)
---------------------------------------------------------------------------------------------------------------------------------
%Activity Index =
× 100.
Zone of inhibition by standart (diameter)
RESULTS AND DISCUSSION
The complexes are light pink, orange-yellow to light
brown in color in contrast to the parent Lewis acid
Co[Cu(SCN)2]2, which was bright green in color. They
are generally insoluble in common organic solvents,
viz., ethanol, methanol, benzene, chloroform, carbon
tetrachloride, ethylene chloride, and diethyl ether, but
are soluble in DMF and DMSO. The complexes disso-
ciate in water, acetonitrile, and acetone. Free Lewis
acid is highly stable and decomposes at 347°C, while
the complexes decompose at lower temperature
between 185–240°C. The low molar conductance val-
ues (8.9–13.2 Ohm–1 cm2 mol–1) of 10–3 M solutions of
The analytical data of the complexes (Table 2) indi-
cate that Co(NCS)2 and CuSCN react in a 1 : 2 molar
ratio in dioxane to form a stable Co[Cu(SCN)2]2 com-
plex. The Lewis acid further reacts with the acylhydra-
zone (RCONHN=C<) ligands in a 1 : 1 (M : L) molar
ratio as follows:
Dioxane
Co(NCS)2 + 2CuSCN
Co[Cu(SCN)2]2,
Dioxane
Co[Cu(SCN)2]2 + L
Co[Cu(SCN)2]2 · L.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 34 No. 5 2008

378
V. P. SINGH, A. SINGH
Table 4. IR spectral data and assignment of important bands of complexes
SCN bands
ν(CN), ν(CS)
Amide I
ν(C=O)
Amide Amide
II III
Compound
ν(NH + OH)
ν(C=N)
ν(N–N)
Abh
3435 b, 3280 b, 3189 s 1650 s 1620 s 1540 s 1378 s
3380 w, 3260 b, 3180 b 1665 s 1630 s 1560 m 1376 s
975 m
980 s
Ainh
Ash
3410 w, 3275 m
1655 s 1633 m 1548 m 1386 s
990 w
Aah
3469 s, 3356 m, 3189 b 1648 m 1631 s 1575 s 1377 m 980 m
3526 s, 3248 b, 3399 w 1640 m 1610 m 1573 s 1370 m 988 m
Phabh
Phainh
Phash
Phaah
3550 w, 3285 s, 3436 b 1653 s 1615 s 1567 m 1384 s
3390 w, 3269 w 1660 w 1633 m 1539 s 1367 s
3468 s, 3355 m, 3136 b 1645 s 1625 s 1545 s 1371 s
3284 b, 3192 b
Co[Cu(SCN)2]2 · Ainh 3378 w, 3260 b, 3175 b 1648 s 1614 s 1549 s 1382 s 1003 w 2156 s, 2102 s 761 s
979 m
976 m
988 m
Co[Cu(SCN)2]2 · Abh
1631 s 1600 s 1529 s 1384 s 1000 w 2171 s, 2089 s 717 s
Co[Cu(SCN)2]2 · Ash
3415 w, 3277 b
3464 b, 3381 b, 3190 w 1629 s 1608 s 1552 s 1384 s 1002 w 2169 s, 2104 s 730 s
1630 s 1601 s 1555 s 1381 s 1012 w 2153 s, 2071 s 710 s
Co[Cu(SCN)2]2 · Phainh 3550 w, 3440 b, 3287 b 1632 s 1602 s 1547 m 1392 s 994 w 2160 s, 2080 s 742 s
1635 s 1610 s 1523 s 1398 s 1010 w 2154 s, 2065 s 756 s
Co[Cu(SCN)2]2 · Aah
Co[Cu(SCN)2]2 · Phabh 3416 b, 3248 b
Co[Cu(SCN)2]2 · Phash 3385 b, 3266 w
Co[Cu(SCN)2]2 · Phaah 3360 b, 3140 b
1638 m 1612 s 1522 s 1386 m 990 m 2162 s, 2090 s 750 s
1627 s 1605 s 1530 m 1388 s 1002 w 2150 s, 2086 s 745 s
4
the complexes in DMSO at room temperature suggest
that they are nonelectrolytes [9].
Co[Cu(SCN)2]2, which can be assigned to A2(F)
4T1(P) transition corresponding to the tetrahedral envi-
ronment around Co(II) [10]. The various ligand field
parameters (10 Dq, B, β, β0, and LFSEl (igand field sta-
bilization energy) were also calculated and indicate a
considerable covalent character of the M–L bonds
(Table 3).
For octahedral cobalt(II) complexes, the spin only
magnet moment is 3.87 µB but because of the orbital
contribution they usually show µeff values between
4.8−5.2 µB [8]. The µeff values observed for the present
complexes are reasonably close to that reported for
three unpaired electrons in octahedral Co(II). However,
the Lewis acid Co[Cu(SCN)2]2 shows magnetic
moment 4.20 µB only, indicating a tetrahedral structure
for the complex.
The bonding of the ligands Abh, Ainh, Ash, Aah,
Phabh, Phainh, Phash, and Phaah to cobalt(II) has been
judged by a careful comparison of the infrared spectra
of the complexes with those of the free ligands. A few
significant bands have been selected to observe the
effect on ligand vibration in the complexes.
The cobalt(II) complexes give rise to three absorp-
tion bands in the visible region under the influence of
the octahedral field by the excitation of the electron
The ligands show a broad band or a number of weak
bands in the region 3100–3500 cm–1 due to ν(NH). In
the complexes, these bands either occur at the same fre-
quency as in the parent ligands or are slightly shifted to
higher frequency suggesting no participation of the –
NH group in bonding. The ν(C=O) band observed in
the range 1640–1665 cm–1 in the ligands is shifted to
lower wave numbers by 10–22 cm–1 in their complexes
4
4
from ground state T1g(F) to the excited state T2g(F),
4A2g(F), and T1g(P). In the present study, only two
4
bands are observed between 9260–9430 (ν1) and
19935–20490 cm–1 (ν3) suggesting octahedral geome-
try for the complexes. The ν2 transition was not
observed due to very weak intensity [10]. A single band
at 15150 cm–1 was observed for the Lewis acid (Table 4) indicating coordination of the >C=O group to
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SYNTHESIS, SPECTRAL STUDIES OF COBALT(II) TETRATHIOCYANOTO
Table 5. Antifungal activity of ligands and their complexes
Inhibition of spore germination, %
379
Compound
Rizoctonia solani, mg/ml
Penicillium citrinum, mg/ml
0.5
1.0
1.5
0.5
1.0
1.5
Abh
46
60
62
39
44
76
67
33
86
94
90
81
89
88
56
68
64
94
69
77
45
92
71
61
88
95
92
86
91
96
72
72
80
95
79
84
78
95
82
65
91
96
95
90
94
99
88
80
55
49
52
65
49
61
50
64
56
51
57
72
68
65
52
65
60
58
57
70
53
68
56
69
68
59
65
80
72
72
58
70
61
62
65
71
59
70
68
72
72
68
67
84
73
78
79
81
Ainh
Ash
Aah
Phabh
Phainh
Phash
Phaah
Co[Cu(SCN)2]2 · Abh
Co[Cu(SCN)2]2· Ainh
Co[Cu(SCN)2]2 · Ash
Co[Cu(SCN)2]2 · Aah
Co[Cu(SCN)2]2 · Phabh
Co[Cu(SCN)2]2 · Phainh
Co[Cu(SCN)2]2 · Phash
Co[Cu(SCN)2]2 · Phaah
the metal ion in all the complexes [11]. In the com-
plexes, amide II bands appear to have shifted consider-
ably to lower frequency (11–25 cm–1) compared to the
parent ligand bands and a shift to higher frequency
(6−19 cm–1) in the amide III bands in the complexes,
further supporting the coordination through the >C=O
group.
S
S
S
S
L/2
Co
C
C
C
C
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
N
N
N
N
Co
N
N
N
N
C
C
C
C
L/2
S
S
S
S
a) Co[Cu(SCN)2]2.
b) Co[Cu(SCN)2]2 · L
The ν(C=N) frequency observed in the region
1610–1633 cm–1 in the spectra of ligands shifted to
lower frequency by 9–23 cm–1 in the metal complexes
suggesting coordination through the azomethine group
[12]. The ν(N–N) vibration observed between 975 and
990 cm–1 in the ligands shifts to higher frequency by
14–25 cm–1 in the complexes, indicating the coordina-
tion of one of the nitrogen atom of the N–N group [13].
The strong bands in the ranges 2150–2171 and 2065–
2104 cm–1 in all the complexes are assigned to ν(CN)
of the bidentate-bridged SCN group. The ν(CS) modes
appearing at 710–761 cm–1 also support the above type
of thiocyanate bonding [14].
CH
H
N
3
L = R C
N
C
1
R
O
where R = C6H5 for Abh and Phabh; NC5H4 for Ainh
and Phainh; C6H4 for Ash and Phash; H2NC6H4 for Aah
and Phaah; R' = C6H5 for Abh, Ainh, Ash and Aah;
HOC6H4 for Phabh, Phainh, Phash and Phaah.
Since the complexes are insoluble in common or-
ganic solvents suitable for single crystal growth for
On the basis of the above mentioned data these com- X-ray analysis, X-ray powder diffraction patterns for
plexes have the following structures: two of the complexes were recorded and the prominent
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 34 No. 5 2008

380
V. P. SINGH, A. SINGH
Table 6. Antibacterial activity of ligands and their complexes
Diameter of inhibition
Diameter of inhibition
zone, mm
Activity index, %
Activity index, %
zone, mm
Compound
Clostridium sp., mg/ml
Pseudomonas sp., mg/ml
2.0 1.0
11.1
1.0
2.0
1.0
2.0
1.0
2.0
Abh
2
4
4
6
14.3
28.6
14.3
28.6
21.4
14.3
14.3
21.4
42.9
50.0
50.0
64.3
42.9
64.3
50.0
42.9
100.0
25.0
37.5
18.8
31.2
25.0
25.0
12.5
18.8
43.8
56.3
56.3
62.5
50.0
75.0
56.3
50.0
100.0
2
3
3
16.7
33.3
22.2
33.3
11.1
11.1
16.7
22.2
55.6
50.0
44.4
44.4
50.0
44.4
50.0
44.4
100.0
Ainh
Ash
6
4
16.7
11.1
27.8
11.1
11.1
11.1
16.7
44.4
38.91
33.3
27.81
33.3
33.3
38.91
33.3
100.0
2
3
2
Aah
4
5
5
6
Phabh
Phainh
Phash
Phaah
3
4
2
2
2
4
2
2
2
2
2
3
3
3
3
4
Co[Cu(SCN)2]2 · Abh
Co[Cu(SCN)2]2 · Ainh
Co[Cu(SCN)2]2 · Ash
Co[Cu(SCN)2]2 · Aah
Co[Cu(SCN)2]2 · Phabh
Co[Cu(SCN)2]2 · Phainh
Co[Cu(SCN)2]2 · Phash
Co[Cu(SCN)2]2 · Phaah
Ampicillin (standard)
6
7
8
10
9
7
9
7
7
9
6
8
9
10
8
5
8
6
6
9
9
12
9
6
8
7
7
9
6
8
6
8
14
16
18
18
lines were indexed by Ito’s method [6]. The following Among the metal complexes, the Co[Cu(SCN)2]2 ·
lattice constants were calculated (Å):
Phainh complex shows the highest activity (99%)
against Rizoctonia sp. and Co[Cu(SCN)2]2 · Aah shows
highest activity (84%) against Penicillium sp., at a con-
centration of 1.5 mg/ml. From these data it has also
been observed that the complexes are more active than
their parent ligands against both fungi [15].
Co[Cu(SCN) ] · Ainh a = 5.48; b = 4.05; c = 3.63.
2 2
Co[Cu(SCN) ] · Phabh a = 5.83; b = 5.83; c = 4.59.
2 2
The above values of lattice constants indicate an
orthorhombic crystal lattice for the former and a tetrag-
onal crystal lattice for the latter complex.
The toxicity of the complexes can be related to the
strength of the metal-ligand bond in addition to other
factors such as size of the cation [16], receptor sites
[17], diffusion [18], and a combined effect of the metal
and ligand [19] for the inactivation of biomolecules.
The experimental antifungal activity data (Table 5)
indicate the ligands, as well as their complexes, show a
fair degree of activity against Rizoctonia sp. and Peni-
cillium sp. at 0.5, 1, and 1.5 mg/ml concentration. Their
The antibacterial data of the ligands and their com-
activity generally increases with increasing the concen- plexes (Table 6) show a moderate activity against
tration of the compounds. Ligand Phainh shows the Clostridium sp. (Gram +ve) and Pseudomonas sp.
highest activity (95%) among all ligands against Rizoc- (Gram –ve) at 1.0 and 2.0 mg/ml concentration. Their
tonia sp. at 1.5 mg/ml concentration, while Phaah activity is greatly enhanced at the higher concentration
shows the highest activity (72%) against Penicillium [20]. The activity of the complexes has been compared
sp. However, the ligands and their complexes are more with the activity of common standard antibiotic Ampi-
efficient against Rizoctonia sp. than Penicillium sp. cilline, and % Activity Index for the complexes has
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 34 No. 5 2008

SYNTHESIS, SPECTRAL STUDIES OF COBALT(II) TETRATHIOCYANOTO
381
6. Narang, K.K., Pandey, J.P., and Singh, V.P., Polyhe-
dron, 1994, vol. 13, p. 529.
7. Vogel, A.I., Vogel’s Text Book of Quantitative Chemical
Analysis, Amsterdam: Longman, 1989.
8. Dutta, R.L. and Syamal, A., Elements of Magnetochem-
istry, New Delhi: Affiliated East–West Press Pvt. Ltd.,
1993.
been calculated. The % Activity Index data show the
highest activity (75%) for Co[Cu(SCN)2]2 · Phainh
against Pseudomonas sp. at the concentration of 2 mg / ml.
Co[Cu(SCN)2]2 · Abh shows the highest activity
(55.6%) against Pseudomonas sp. The complexes show
a higher antibacterial activity than the parent ligands.
9. Geary, W.J., Coord. Chem. Rev., 1971, vol. 7, p. 81.
10. Lever, A.B.P., Inorganic Electronic Spectroscopy, New
York: Elsevier, 1984.
11. Shama, S.A. and Omara, H., Spectrosc. Lett., 2001,
vol. 34, p. 49.
12. Narang, K.K., and Singh, V.P., Transition Met. Chem.,
1993, vol. 18, p. 287.
13. Chohan, Z.H., Farooq, M.A., Scozzafava, A., and Supu-
ran, C.T., J. Enz. Inh. Med. Chem., 2002, vol. 17, p. 1.
14. Nakamoto, K., Infrared and Raman Spectra of Inorganic
and Coordination Compounds, New York: Wiley Inter-
science, 1986, p. 284.
15. Nagar, R., J. Inorg. Biochem., 1990, vol. 40, p. 349.
16. Thimmaiah, K.N., Chandrappa, G.T., Rangaswamy, and
Jayarama, Polyhedron, 1984, vol. 3, no. 11. p. 1237.
ACKNOWLEDGMENTS
The authors thank the Director (Institute of Engi-
neering and Technology, C.S.J.M. University, Kanpur)
for providing laboratory facilities, the Head (Chemistry
Department, Indian Institute of Technology, Kanpur)
for recording electronic, infrared spectra, and X-ray
diffraction data, and Dr. Nand Lal (Institute of Life Sci-
ences, C.S.J.M. University, Kanpur) for his help in anti-
microbial screening.
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