Synthesis, spectral, and biological studies of some metal(II) complexes with benzil salicylaldehyde acyldihydrazones

Article abstract of DOI:10.1134/S1070328408040064

Complexes of the general formula [M(Bsodh)]Cl and [M(Bsmdh)]Cl, where M = Co(II), Ni(II), Cu(II), Zn(II,) and Cd(II) (HBsodh = benzil salicylaldehyde oxalic acid dihydrazone and HBsmdh = benzil salicylaldehyde malonic acid dihydrazone) were synthesized and characterized by elemental analyses, molar conductance, magnetic moments, electronic, ESR, infrared spectra, and X-ray diffraction studies. The complexes are stable solids insoluble in common organic solvents and 1: 1 electrolytes. The magnetic moments and electronic spectra reveal a square-planar geometry for [M(Bsodh)]Cl and a six-coordinate octahedral geometry for [M(Bsmdh)]Cl. The HBsodh ligand bonds to the metal ion via one >C=O, two >C=N-, and one deprotonated phenolate group, whereas HBsmdh bonds through three >C=O, two >C=N-, and one phenolate group. The lattice parameters for [Co(Bsodh)]Cl and [Ni(Bsmdh)]Cl correspond to tetragonal and orthorhombic crystal lattices, respectively. ESR spectral data indicate the presence of an unpaired electron in d_x₂ - y₂ of the Cu²⁺ ion. The ligands, as well as their metal complexes, show significant antibacterial activity against Bacillus subtilis and Pseudomonas fluorescens.

Full text of DOI:10.1134/S1070328408040064

ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2008, Vol. 34, No. 4, pp. 270–277. © Pleiades Publishing, Ltd., 2008.
Synthesis, Spectral, and Biological Studies of Some Metal(II)
Complexes with Benzil Salicylaldehyde Acyldihydrazones1
V. P. Singha, P. Guptaa, and N. Lalb
a Chemistry Department, Faculty of Science Banaras Hindu University,
Varanasi 221005, India
b Institute of Life Sciences, Chhatrapati Shahu Ji Maharaj University, Kanpur 208024, India
E-mail: singvp@yahoo.co.in
Received November 7, 2006
Abstract—Complexes of the general formula [M(Bsodh)]Cl and [M(Bsmdh)]Cl, where M = Co(II), Ni(II),
Cu(II), Zn(II,) and Cd(II) (HBsodh = benzil salicylaldehyde oxalic acid dihydrazone and HBsmdh = benzil sal-
icylaldehyde malonic acid dihydrazone) were synthesized and characterized by elemental analyses, molar con-
ductance, magnetic moments, electronic, ESR, infrared spectra, and X-ray diffraction studies. The complexes
are stable solids insoluble in common organic solvents and 1 : 1 electrolytes. The magnetic moments and elec-
tronic spectra reveal a square-planar geometry for [M(Bsodh)]Cl and a six-coordinate octahedral geometry for
[M(Bsmdh)]Cl. The HBsodh ligand bonds to the metal ion via one >C=O, two >C=N–, and one deprotonated
phenolate group, whereas HBsmdh bonds through three >C=O, two >C=N–, and one phenolate group. The lat-
tice parameters for [Co(Bsodh)]Cl and [Ni(Bsmdh)]Cl correspond to tetragonal and orthorhombic crystal lat-
tices, respectively. ESR spectral data indicate the presence of an unpaired electron in dx2 – y2 of the Cu2+ ion.
The ligands, as well as their metal complexes, show significant antibacterial activity against Bacillus subtilis
and Pseudomonas fluorescens.
DOI: 10.1134/S1070328408040064
1
INTRODUCTION
studies on such ligands, viz., benzyl salicylaldehyde
oxalic acid dihydrazone (HBsodh) and benzyl salicyla-
ldehyde malonic acid dihydrazone (HBsmdh), their
complexes with some bivalent transition metal ions
(Co2+, Ni2+, Cu2+, Zn2+, and Cd2+) were synthesized,
characterized and discussed in the present study:
Schiff base transition metal complexes have been
studied extensively and have applications in various
fields, viz., in radioimaging and radiotherapy [1], in
sweetening of hydrocarbon fractions [2], in the forma-
tion of electroluminescent devices [3], as heat stabiliz-
ers for polyamides, etc. [4]. Such complexes have been
implicated in the transport of active substances through
membranes [5]. Schiff base complexes containing
nitrogen and oxygen as donor atoms play an important
role in biological systems and represent models for
metalloproteins and metalloenzymes that catalyze the
reduction of nitrogen and oxygen [6]. These complexes
have been reported to show significant antifungal and
antibacterial activities [7, 8].
H
C
C C NNHC (CH ) CNHN
2 x
O
O
O
HO
where x = 0 for HBsodh and 1 for HBsmdh.
Acyldihydrazines (or organic acid dihydrazides),
such as oxalic acid dihydrazide, (CONHNH2)2, mal-
onic acid dihydrazide, CH2(CONHNH2)2, etc. having
two terminal amino groups can react either with two
molecules of monoketo group containing compounds
[9], one molecule of diketo compounds [10], or one
molecule each of two different keto group containing
compounds under suitable conditions. The acyldihy-
drazones thus obtained have two C = N groups in addi-
tion to several other potential donor sites for bonding
with metal ions [11–13]. In the absence of an adequate
EXPERIMENTAL
Material. All the chemicals used were of BDH
(AnalaR) or equivalent grade. The precursor acyldihy-
drazines, oxalic acid dihydrazide (Odh), (CONHNH2)2
and
malonic
acid
dihydrazide
(Mdh),
CH2(CONHNH2)2 were prepared as by the procedure
given in the literature [14] and were characterized by
their melting points, Odh m.p. 232°C (lit.: 232°C); Mdh
m.p. 150°C (lit.: 152°C).
Synthesis of the ligands. For the synthesis of HBsodh,
C6H5COC(C6H5)=NNHCOCONHN=CHC6H4OH, and
1
The text was submitted by the authors in English.
270

SYNTHESIS, SPECTRAL, AND BIOLOGICAL STUDIES
271
HBsmdh,
C6H5COC(C6H5)=NNHCOCH2CONHN=
The molar conductance of 10–3 M solutions of the
CHC6H4OH, benzil (10 mmol, 2.1 g) and salicylaldehyde complexes in DMF were measured at room temperature
(10 mmol, 1.22 ml) were taken in a beaker containing on a Systronic conductometer (model–306). Room
50 ml of ethanol. The above solution mixture was reacted temperature magnetic susceptibilities of the complexes
separately with an aqueous solution (50 ml) of oxalic acid were determined on a Faraday balance using
dihydrazide (10 mmol, 1.18 g) or malonic acid dihy- Hg[Co(SCN)4] as calibrant and corrected for diamag-
drazide (10 mmol, 1.32 g), respectively, and was continu- netism [16]. IR spectra of the ligands and their metal
ously stirred for ~2 h on a magnetic stirrer at room temper- complexes were recorded in a KBr medium in the
ature. The product was filtered off by suction and purified 4000–500 cm–1 range on a Vertex 70 (Bruker) spectro-
by washing several times with hot water and then with eth- photometer. Electronic spectra were recorded in DMF
anol. The pure ligands were dried in a desiccator over on a Cintra 10 spectrophotometer. The X-band ESR
anhydrous CaCl2.
The ligands were characterized by elemental analy-
ses (C, H, N), melting points, and infrared spectra.
spectra of the Cu(II) complexes were recorded on an
EMX 1444 EPR spectrometer at liquid-nitrogen tem-
perature in a DMF solution and at room temperature
(300 K) in the solid state. Powder X-ray diffraction pat-
terns were recorded on an Iso Debye Flex 2002 appara-
tus using CuKα radiations.
Synthesis of the complexes. Metal complexes of
HBsodh and HBsmdh were prepared by reacting of
50 ml aqueous solutions containing 5 mmol of CoCl2 ·
6H2O (1.19 g) (or NiCl2 · 6H2O (1.19 g), CuCl2 · 2H2O
(0.85 g), ZnCl2 (0.68 g), and CdCl2 · 2.5H2O (1.14 g)
with 50 ml of aqueous ethanolic solutions (v/v, 1 : 1),
5 mmol of HBsodh (2.07 g) or HBsmdh (2.14 g) in the
1 : 1 (M : L) molar ratio in a RB flask. The Co(II) and
Ni(II) complexes were formed by refluxing the reaction
mixture solutions for 3–4 h with shaking at regular
intervals. However, Cu(II), Zi(II), and Cd(II) com-
plexes were obtained by stirring their corresponding
solutions for 1, 2, and 3 h on a magnetic stirrer, respec-
tively. The products were filtered by suction and dried
in a desiccator over anhydrous CaCl2 at room tempera-
ture after washing. Since these complexes were insolu-
ble and non-crystallizable, and they were purified by
washing thoroughly with water and ethanol to remove
unreacted metal chlorides or ligands.
The analytical and physicochemical data are given
in Tables 1–5.
Antibacterial activity. The antibacterial activity of
the ligands and their complexes was studied against
Pseudomonas fluorescence (Gram −ve) and Bacillus
subtilis (Gram +ve) bacteria. Each of the compounds
was dissolved in DMSO and solutions with the concen-
tration 2.0 and 1.0 mg/ml were prepared separately.
Paper discs of whatman filter paper (no. 42) of uniform
diameter were cut and sterilized in an autoclave. The
paper disc soaked in the complex solution of the desired
concentration was placed aseptically in the Petri dishes
containing nutrient agar media (agar 15 g + beef extract
3 g + peptone 5 g) seeded with Bacillus and Pseudomo-
nas sp. bacteria separately. The Petri dishes were incu-
bated at 32°C and the inhibition zones were recorded
after 24 h of incubation. Each treatment was replicated
for 9 times.
Analyses and instrumentation. Metal contents
were determined gravimetrically by a literature proce-
dure [15] after digesting the organic matter with aqua
regia and evaporating the residue to dryness with con-
A common standard antibiotic Ampicillin was also
centrated sulfuric acid. The chloride content was ana- screened for antibacterial activity in the same solvent
lyzed gravimetrically as silver chloride. C, H, N data and at the same concentration. The percent activity
were determined on an Elementar Vario EL model ele- index data for the metal complexes were calculated as
mental analyzer.
follows:
Zone of inhibition by test compound (diameter)
-----------------------------------------------------------------------------------------------------------------
Zone of inhibition by standart (diameter)
%Activity index =
× 100.
RESULTS AND DISCUSSION
MCl · xH O + HBsodh
[M(Bsodh)]Cl + HCl + xH O,
2
2
2
or
or
It appears from the analytical data of the complexes
(Table 1) that both the ligands HBsodh and HBsmdh
undergo deprotonation of their phenolic proton during
complexation. The ligands react with metal ions in 1 : 1
(M : L) molar ratio to form the complexes of the general
compositions [M(Bsodh)]Cl and [M(Bsmdh)]Cl. The
reactions are shown below:
HBsmdh
[M(Bsmdh)]Cl
where M = Co(II), Ni(II), Cu(II), Zn(II), and Cd(II);
x = 0–6.
The metal complexes are air-stable solid powders,
insoluble in water and common organic solvents, such
as methanol, ethanol, chloroform, carbon tetrachloride,
diethyl ether, ethyl acetate, and benzene but are fairly
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SINGH et al.
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SYNTHESIS, SPECTRAL, AND BIOLOGICAL STUDIES
273
Table 2. Magnetic moments, electronic spectra and some ligand field parameters
Band maxima, cm–1
Compound
µeff
10 Dq, cm–1
B
β
β0
LFSE
v1
v2
v3
[Co(Bsodh)]Cl
[Ni(Bsodh)]Cl
[Cu(Bsodh)]Cl
[Co(Bsmdh)]Cl
[Ni(Bsmdh)]Cl
[Cu(Bsmdh)]Cl
2.32
Diamag.
1.78
25000
25125
29410
28900
12048
15430
9260
4.76
20410
27770
10370
10525
817
857
0.84
0.83
15.9
16.8
23.63
35.98
3.20
10525
15870
16660
25315
2.21
Table 3. ESR and bonding parameters for the Cu(II) complexes
β12
Complex
T, K
Medium
A||
A⊥
Aav
g||
g⊥
gav
α2
α'2
[Cu(Bsodh)]Cl
300 Solid state
120 DMF solution 120 70
[Cu(Bsmdh)]Cl 300 Solid state 83 50
120 DMF Solution 160 55
Aiso = 93
giso = 2.0822
2.1006
84
61
90
2.2257 2.0616
2.1800 2.0800
2.3270 2.0442
0.62
0.83
0.41
0.20
0.90
0.96
2.1133
2.1384
soluble in DMF and DMSO. The complexes either melt yellow, Cu(II) complexes are yellow-green and green,
whereas, Zn(II) and Cd(II) complexes are yellow to
light yellow in color. The molar conductance values of
10–3 M solution of the complexes in DMF at room tem-
perature fall in the range 69.4–81.5 Ohm–1 mol–1 cm2.
These values indicate that all the complexes are 1 : 1
or decompose in the temperature range 188–266°C
except [Cu(Bsodh)]Cl, which does not melt up to
300°C.
The Co(II) complexes are light orange and light
brown, Ni(II) complexes are light yellow and greenish electrolytes [17].
Table 4. IR spectral data (cm–1) and assignment of important bands
Compound ν(OH + NH) ν(C=O)
ν(C=N)
Amide II
1530 m
Amide III
1371 s
ν(N–N) ν(C–O) phenolic ν(M–O)
HBsodh
3327 b
3233 s
1673 b
1630 s
983 s
HBsmdh
3280 b
3204 s
1688 b
1615 s
1535 s
1370 s
992 w
[Co(Bsodh)]Cl
[Ni(Bsodh)]Cl
[Cu(Bsodh)]Cl
[Zn(Bsodh)]Cl
[Cd(Bsodh)]Cl
3233 b
3230 b
3239 s
3235 b
3230 b
1668 s,
1648 m
1605 s
1602 m
1605 m
1614 s
1600 m
1531 m
1529 s
1530s
1370 s
1372 s
1372 s
1369 s
1371 s
1020 w
1025 w
1020 m
1008 m
1028 m
1274 s
1261 s
1268 m
1270 s
1267 m
531 w
533 m
530 m
528 w
536 w
1669 s,
1652 m
1668 s,
1650 m
1672 s,
1656 m
1525 s
1523 m
1669 s,
1655m
[Co(Bsmdh)]Cl
[Ni(Bsmdh)]Cl
[Cu(Bsmdh)]Cl
[Zn(Bsmdh)]Cl
[Cd(Bsmdh)]Cl
3206 s
3205 b
3214 b
3210 s
3209 s
1670 b
1669 b
1665 b
1658 b
1663 b
1596 s
1595 s
1593 s
1598 m
1590 m
1520 m
1515 s
1512 s
1516 m
1520 m
1389 s
1389 m
1390 s
1390 m
1383 s
1030 w
1028 w
1012 w
1010 w
1003 s
1268 m
1265 w
1272 s
1260 s
1269 m
549 m
545 m
569 m
540 s
565 m
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274
SINGH et al.
Table 5. Antibacterial activity of the ligands and their complexes
Diameter of inhibition zone (in mm)
Pseudomonas
Activity Index, %
Pseudomonas
Compound
Bacillus subtilis, mg ml–1
Bacillus subtilis, mg ml–1
fluorescence, mg ml–1
fluorescence, mg ml–1
1.0
2.0
1.0
2.0
1.0
2.0
1.0
2.0
HBsodh
2.5
6.0
3.0
8.0
1.0
2.5
3.0
2.5
3.5
4.0
4.5
6.0
5.0
5.0
8.0
9.0
11.0
2.0
4.0
20
48
24
16
20
32
32
72
68
64
80
88
100
21
57
29
21
21
32
46
93
82
64
82
89
100
9
23
27
23
32
36
41
55
45
45
73
82
100
15
31
27
23
35
38
42
58
50
54
85
88
100
HBsmdh
[Co(Bsodh)]Cl
[Ni(Bsodh)]Cl
[Cu(Bsodh)]Cl
[Zn(Bsodh)]Cl
[Cd(Bsodh)]Cl
[Co(Bsmdh)]Cl
[Ni(Bsmdh)]Cl
[Cu(Bsmdh)]Cl
[Zn(Bsmdh)]Cl
[Cd(Bsmdh)]Cl
Ampicillin
3.0
4.0
3.5
2.0
3.0
3.0
2.5
3.0
4.5
4.0
4.5
5.0
4.0
6.5
5.5
9.0
13.0
11.5
9.0
7.5
8.5
6.5
8.0
7.0
10.0
11.0
12.5
11.5
12.5
14.0
11.0
11.5
13.0
The Co(II) octahedral complexes generally show
The Ni(II) complexes show three bands in an octa-
magnetic moments (meff) between 4.7–5.2 µB, because hedral environment corresponding to the transitions
3A2g (F)
3T2g (F) (ν1), 3A2g (F)
3T1g (F) (ν2), and
of the orbital contribution [18], while the tetrahedral
3A2g (F)
3T1g (P) (ν3) [22]. In the spectra of
complexes show these values between 4.0–4.6 µB. The
µeff value of 4.76 µB observed for [Co(Bsmdh)]Cl is
fairly close to those reported for three unpaired elec-
trons in an octahedral environment. However,
[Co(Bsodh)]Cl shows a low µeff value (2.32 µB) corre-
sponding to one unpaired electron [19] suggesting a
square-planar geometry for the complex.
[Ni(NH3)6]2+, these bands have been reported at 10700,
17540, and 28170 cm–1, respectively [16]. The
[Ni(Bsmdh)]Cl complex also shows the above three
transitions at 10525 (ν1), 16660 (ν2), and 27770 cm–1
(ν3), suggesting an octahedral geometry for the com-
plex. Various ligand field parameters (10 Dq, β, β0, and
LFSE) have also been calculated for Ni(II) and Co(II)
octahedral complexes by the procedure laid down by
Lever [20]. The significant low value of the Racah
parameter (B) compared to the free ion value indicates
appreciable covalent character in the metal–ligand
bond. The nephelauxetic ratio β and other parameters
also support some covalency in the complex. The elec-
tronic spectrum of [Ni(Bsodh)]Cl suggests a square-
planar geometry (Table 2) similar to that reported for
Ni(dithiooxamide)2Cl2 [23] and many other Ni(II) com-
plexes.
The effective magnetic moments reported for the
high-spin octahedral Ni(II) complexes are in the range
2.9–3.4 µB, while for the tetrahedral complexes the val-
ues range from 3.5–4.0 µB [20]. The [Ni(Bsmdh)]Cl
complex in this paper shows the µeff value 3.20 µB cor-
responding to two unpaired electrons in an octahedral
environment. The [Ni(Bsodh)]Cl complex is diamag-
netic, suggesting square-planar geometry for the com-
plex. The magnetic moments of the two Cu(II) com-
plexes (1.78 and 2.21 µB) correspond to µeff values for
one unpaired electron.
The Co(II) complexes generally give rise to three
absorption bands in the visible region under the influ-
ence of the octahedral field by the excitation of the elec-
tron from the ground state 4T1g (F) to the excited states
The [Cu(Bsodh)]Cl complex shows a broad band
centered at 15430 cm–1 indicating a square planar
geometry for the complex similar to [Cu(NH3)4]2+
(16600 cm–1) [20]. The other complex in this study,
4
4
4T2g (F), A2g (F) and T1g (P). In the [Co(Bsmdh)]Cl
complex, only two bands are observed at 9260 cm–1 (ν1)
and 20410 cm–1 (ν3) as reported in many octahedral
cobalt(II) complexes [21]. The ν2 transition was not
observed due to very weak intensity. The two bands
observed at 25000 and 29410 cm–1 for [Co(Bsodh)]Cl
are in good agreement with the bands reported for
cobalt(II) square planar complexes [19].
[Cu(Bsmdh)]Cl, shows two bands at 15870 and
2
25315 cm–1, which may be assigned to B1g
2B2g
(ν1) and 2B1g
2Eg (ν2) suggesting a tetragonally dis-
torted octahedral geometry [14] for the complex.
The ESR spectra of the powdered sample of
[Cu(Bsodh)]Cl exhibit are isotropic at room tempera-
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SYNTHESIS, SPECTRAL, AND BIOLOGICAL STUDIES
275
(a)
(b)
[Cu(Bsodh)]Cl
[Cu(Bsmdh)]Cl
[Cu(Bsodh)]Cl
[Cu(Bsmdh)]Cl
1500 2000 2500 3000 3500 4000 4500 1500 2000 2500 3000 3500 4000 4500
G
ESR spectra of Cu(II) complexes: (a) in solid state at 300 K and (b) in DMSO solution at 120 K.
plane σ-bond strength (α2) is 0.62 and 0.83, thereby
suggesting appreciable covalency of the in-plane
σ-bonding [28]. The α'2 parameter, the out-of-plane
σ-bond strength, increases with the corresponding
decrease in α2, indicating that the axial σ-bonding is
decreasing with the corresponding increase in the in-
ture with intense broad signals having no hyperfine
structure. This can be due to dipolar exchange and unre-
solved hyperfine interactions in the solid state [24]. The
giso value of 2.0822 suggests a geometry involving
grossly misaligned tetragonal axes [25]. The
[Cu(Bsmdh)]Cl complex shows an axial signal with
two g values at room temperature (figure). The axial
signals were analyzed using the procedure given by
Hathaway and Billing [26]. The g|| and g⊥ values are
>2.04 (Table 3) and consistent with copper(II) in axial
symmetry with all the principal axes aligned parallel.
plane σ-bonding. The β21 values also indicate signifi-
cant in-plane π-bonding in these complexes.
The bonding of the ligand to metal has been judged
by a careful comparision of the infrared spectra of the
complex with those of the free ligand. A few significant
bands have been selected to observe the effect on ligand
vibration in the complexes. The ligands HBsodh and
HBsmdh show two broad bands due to –OH and >NH
groups in the region 3200–3350 cm–1. In all the metal
complexes ν(NH) occurs either at the same wave num-
ber as in the parent ligand or at slightly shifted wave
numbers, indicating noninvolvement of >NH groups in
bonding. The ν(OH) band in the same region due to the
phenolic –OH group as observed in the ligands is not
observed in the complexes, suggesting the possibility of
deprotonation of the phenolic –OH group during com-
plexation.
Frozen DMF solution spectra of both the Cu(II)
complexes give more intense axial signals, and the cop-
per(II) hyperfine lines are well resolved. Both the com-
plexes show a well-defined hyperfine structure of four
lines due to coupling of the electron with the nuclear
spin (I = 3/2) of the copper atom. The g||, g⊥, A||, and A⊥
values were measured accurately from the frozen solu-
tion spectra. The gav and Aav values were calculated
using the equations gav = (g|| + 2g⊥)/3; Aav = (A|| + 2A⊥)/3.
Moreover, the observation that g|| > g⊥ >ge (2.0023)
shows that the unpaired electron is in the orbital of the
Cu2+ ion [27]. The g|| values of 2.2257 for
[Cu(Bsodh)]Cl and 2.3270 for [Cu(Bsmdh)]Cl suggest
square-planar and tetragonally distorted octahedral
geometries, respectively.
The amide I band, ν(C=O), in the ligands HBsodh
and HBsmdh appears as a broad band at 1673 and
1688 cm–1 respectively due to the presence of three
>C=O groups in the ligands. In the HBsodh complexes
The bonding parameters α2, α'2, and β12 were also
calculated for the Cu(II) complexes (Table 3). The in- the ν(C=O) bands appear at two positions: one nearly at
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 34 No. 4 2008

276
SINGH et al.
the same frequency as in the ligand and the other
ν(C=O) occurs at considerably lower wave number
(17–25 cm–1) indicating the coordination of the benzyl
>C=O group only with the metal ion. A negligible
change in the position of amide II and amide III bands
in all the HBsodh complexes than the ligand further
supporting the coordination of only the benzylic >C=O
group. In the HBsmdh complexes, however, ν(C=O)
shifts to lower frequency by 18–30 cm–1 as compared to
the parent ligand (Table 4), indicating coordination of
all the three >C=O groups to metal [29]. The amide II
bands appear to have shifted considerably to lower fre-
quency (15–23 cm–1) and amide III bands to higher fre-
quency (13–20 cm–1) in all the HBsmdh complexes than
the ligand supporting coordination through the >C=O
groups.
The ν(C=N) bands observed at 1630 cm–1 in the
spectra of HBsodh and at 1615 cm–1 in HBsmdh shifted
considerably to lower frequency by 16–30 cm–1 in their
metal complexes suggesting coordination through two
azomethine groups [10]. The shift to higher wave num-
ber in ν(N–N) from the free ligands to the complexes by
15–45 cm–1 suggests involvement of only one nitrogen
of the hydrazone (–NHN = C<) group [30]. A new band
assigned as ν(C–O) in the spectra of the metal com-
plexes suggests that the ligands are coordinated through
the deprotonated phenolate group [31]. A non-ligand
band appears in the region 528–569 cm–1 in all the com-
plexes has been assigned to ν(M–O).
On the basis of above discussion, general structures
for the metal complexes have been proposed below:
H
N
H
C
CH
H
N N
C
N
C
O
O
O
M
O
CH2
M
O
O
Cl
Cl
C
N
C
O
O C N N
H
N
H
C
C
C
[M(Bsodh]Cl
[M(Bsmdh)]Cl
where M = Co(II), Ni(II), Cu(II), Zn(II), and Cd(II)
The X-ray powder diffraction method provides a compared with the activity of a common standard anti-
way of investigating within limits: the crystallography
of a crystal in the powder form. The diffraction patterns
for the two complexes were recorded and indexed by
Ito’s method [32]. The following lattice constants were
obtained:
biotic Ampicillin and % Activity Index has been calcu-
lated.
The % activity index data indicate that the
[Co(Bsmdh)]Cl complex shows the highest activity
(93%) against Pseudomonas flourescens at a concen-
tration of 2.0 mg/ml among all the metal complexes.
The [Cd(Bsmdh)]Cl complex shows 88–89% activity
against both the bacteria. The activity increases with
increasing concentration of the complexes [33].
a, Å
5.47
7.24
b, Å
5.47
6.69
c, Å
12.50
6.40
[Co(Bsodh)]Cl
[Ni(Bsmdh)]Cl
These constants indicate a tetragonal crystal lattice
for the [Co(Bsodh)]Cl complex and an orthorhombic
crystal lattice for the [Ni(Bsmdh)]Cl complex.
Observed and calculated Qand hkl values can be
received at authors by e-mail: singvp@yahoo.co.in.
ACKNOWLEDGMENTS
The authors thank the Director of the University
Institute of Engineering and Technology (C.S.J.M.
University, Kanpur, India) for providing laboratory
facilities, Dr. J.K. Berra (Department of Chemistry,
Indian Institute of Technology, Kanpur) for recording
IR and ESR spectra, and Director of the RSIC Central
Drug Research Institute (Lucknow) for elemental anal-
The ligands (HBsodh) and (HBsmdh) and their
metal complexes are screened against Bacillus subtilis
(Gram + ve) and Pseudomonas flourescens (Gram – ve)
bacteria and generally show significant antibacterial
activity. From the experimental data (Table 5) it has
been observed that the complexes are more toxic than
the ligands. The HBsmdh ligand shows better activity
than HBsodh. The activity of the complexes has been yses.
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SYNTHESIS, SPECTRAL, AND BIOLOGICAL STUDIES
277
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