Synthesis, characterization, and antibacterial activities of organotin(IV) complexes with 2-acetylpyridine-N(4)-cyclohexylthiosemicarbazone (HAPCT)

Article abstract of DOI:10.1002/hc.21061

The reaction of 2-acetylpyridine-N(4)-cyclohexylthiosemicarbazone [(HAPCT), (1)] ligand with organotin(IV) chloride(s) afforded the five new organotin(IV) complexes: [MeSnCl₂(APCT)] (2), [BuSnCl₂(APCT)] (3), [PhSnCl₂(APCT)] (4), [Me₂SnCl(APCT)] (5), and [Ph ₂SnCl(APCT)] (6). The ligand (1) and its organotin(IV) complexes (2-6) have been synthesized and characterized by CHN analyses, molar conductivity, UV-vis, FT IR, ¹H, ¹³C, and ¹¹⁹Sn NMR spectral studies. The single crystal X-ray diffraction studies indicated that [PhSnCl₂(APCT)] (4) is six coordinated and strongly adopts a distorted octahedral configuration with the coordination through pyridine-N, azomethine-N, and thiolato-S atoms of the ligand. The compound crystallizes into a monoclinic lattice with the space group P21/n. The ligand (1) and its organotin(IV) complexes (2-6) were assayed for in vitro antibacterial activity against Staphylococcus aureus, Escherichia coli, Enterobacter aerogenes, and Salmonella typhi. The screening results have shown that the organotin(IV) complexes (2-6) have better antibacterial activity than the free ligand. Furthermore, it has been shown that the diphenyltin(IV) derivative (6) exhibits significantly better activities than the other organotin(IV) derivatives (2-5).

Full text of DOI:10.1002/hc.21061

Heteroatom Chemistry
Volume 24, Number 1, 2013
S
2
ynthesis, Characterization, and Antibacterial
Activities of Organotin(IV) Complexes with
-Acetylpyridine-N(4)-
cyclohexylthiosemicarbazone
(
HAPCT)
1
1
2
2
M. A. Salam, M. A. Affan, Md. Azharul Arafat, Ramkrishna Saha,
3
and Runia Nasrin
1
Faculty of Resource Science and Technology Universiti Malaysia Sarawak 94300, Kota
Samarahan, Sarawak, Malaysia
2Department of Chemistry Shahjalal, University of Science and Technology, Sylhet 3114,
Bangladesh
3Department of Chemistry, University of Chittagong, Chittagong 4331, Bangladesh
Received 16 May 2012; revised 11 October 2012
reus, Escherichia coli, Enterobacter aerogenes, and
Salmonella typhi. The screening results have shown
that the organotin(IV) complexes (2–6) have better an-
tibacterial activity than the free ligand. Furthermore,
it has been shown that the diphenyltin(IV) deriva-
tive (6) exhibits significantly better activities than the
other organotin(IV) derivatives (2–5). ꢀC 2012 Wiley
Periodicals, Inc. Heteroatom Chem. 24:43–52, 2013;
View this article online at wileyonlinelibrary.com.
DOI 10.1002/hc.21061
ABSTRACT: The reaction of 2-acetylpyridine-N(4)-
cyclohexylthiosemicarbazone [(HAPCT), (1)] ligand
with organotin(IV) chloride(s) afforded the five
new organotin(IV) complexes: [MeSnCl2(APCT)]
(
[
2), [BuSnCl2(APCT)] (3), [PhSnCl2(APCT)] (4),
Me2SnCl(APCT)] (5), and [Ph2SnCl(APCT)] (6). The
ligand (1) and its organotin(IV) complexes (2–6) have
been synthesized and characterized by CHN analyses,
1
13
119
molar conductivity, UV–vis, FT IR, H, C, and Sn
NMR spectral studies. The single crystal X-ray diffrac-
tion studies indicated that [PhSnCl2(APCT)] (4) is six
coordinated and strongly adopts a distorted octahedral
configuration with the coordination through pyridine-
N, azomethine-N, and thiolato-S atoms of the ligand.
The compound crystallizes into a monoclinic lattice
with the space group P21/n. The ligand (1) and its
organotin(IV) complexes (2–6) were assayed for in
vitro antibacterial activity against Staphylococcus au-
INTRODUCTION
Thiosemicarbazone derivatives have attracted con-
siderable attention in the past few decades,
because of their potential biological (viz., antibac-
terial and antitumor) activities [1–3]. The hetero-
cyclic NNS donor ligands play an important role
in the development of coordination chemistry as
they readily form complexes with most of metal ions
Correspondence to: M. A. Salam; e-mail: salambpx@yahoo.com.
Contract grant sponsor: Ministry of Science Technology and
Innovation.
[4–6]. Thiosemicarbazones and their organotin(IV)
Contract grant number: 06-01-09-SF0046.
ꢀ
2012 Wiley Periodicals, Inc.
C
complexes are of considerable interest due to their
43

44 Salam et al.
potential biological (namely, antiviral and an-
titumor) activities as well as their industrial
and agricultural applications [7–10]. Beraldo and
Gambino have investigated the pharmacological
profiles of 2-formyl, 2-acetyl, and 2-benzoylpyridine
thiosemicarbazones [11]. The organotin compound
has antiproliferative ability and antitumor activ-
ity on mammalian cells both in vitro and in vivo
TABLE 1 Crystal Data and Refinement Parameters for
PhSnCl (APCT)] (4)
[
2
Compound
[PhSnCl
2
(APCT)] (4)
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
C H24 Cl N SSn
542.10
150
Monoclinic
P21/n
20 2 4
[12, 13]. Roberto et al. have reported the syn-
Unit cell dimensions
˚
a (A)
11.52126(19)
13.37948(16)
15.2648(2)
90.00
109.6302(17)
90.00
thesis and the coordination mode of interaction
of the tin(IV) tetrahalide with 2-formylpyridine
thiosemicarbazone, in which the geometry about
tin(IV) is best described as roughly octahedral
˚
b (A)
˚
c (A)
◦
α ( )
◦
β ( )
◦
[14]. Among main-group organometallic com-
γ ( )
Volume (A )
3
˚
2216.29(6)
4
pounds, organotin has been receiving consider-
able attention in recent years [15], for some of
them are biologically active or have been used
as reagents or catalysts in organic reactions [16].
Our group recently reported the structural and bio-
logical properties of organotin(IV) complexes with
substituted thiosemicarbazones [17–19]. The re-
sults reveal that N(4)-cyclohexylthiosemicarbazones
derived from 2-benzoylpyridine and pyruvic acid
and their organotin(IV) complexes show signifi-
cant antibacterial activities. To fortify this idea
and keeping in view the biological potential
of organotins, we synthesized five new organ-
otin(IV) complexes (2–6) with 2-acetylpyridine-N(4)-
cyclohexylthiosemicarbazone [HAPCT, (1)]. Here
we report the synthesis, characterization, and an-
tibacterial activities of organotin(IV) complexes (2–
Z
Calculated density
1.625
3
(
mg/m )
Wavelength ( A˚ )
0.71073
Mo Kα
1088
˚
Radiation type λ(A)
F(000)
Crystal size (mm)
Crystal color
Scan range θ ( )
0..37 × 0.21 × 0.15
Orange
◦
2.417–28.986
1.502
Absorption coefficient
–
1
(μ) (mm )
Maximum and minimum
0.7983 and 0.7295
transmission
Goodness-of-fit on F
2
0.9906
5354/0/253
Data/restrains/
parameters
Final R indices
R
1
1
= 0.0207, wR
2
= 0.0456
= 0.0479
[
I > 2σ(I)]
R indices (all data)
R
= 0.0246, wR
2
6
4
). Single-crystal X-ray crystal structures of complex
also described here. These compounds proved to
ried out with a Jenway 4510 conductivity meter
using a DMSO solvent mode. The crystallographic
data and structure refinement parameters for com-
plex 4 are given in Table 1. An orange prismatic
crystal of compound 4 was measured at 150 K on a
CrysAlis CCD (Oxford diffraction, 2002) diffractome-
be effective antibacterial agents. This study will be
helpful in designing new organotins of pharmaceu-
tical value.
EXPERIMENTAL
General Procedure
ter with graphite monochromated Mo Kα radiation
˚
(
λ = 0.71073 A). CrysAlis RED; program(s) was used
to solve the structure, and SHELXS97 (Sheldrick,
008) program(s) was used to refine structure: Posi-
All reagents were purchased from Fluka, Aldrich,
and JT Baker. All solvents were purified accord-
ing to standard procedures [20]. UV–vis spectra
were recorded in DMSO solution with a Perkin
Elmer Lambda 25 UV–vis spectrophotometer. In-
frared spectra were recorded on KBr disks using a
Perkin Elmer Spectrum GX Fourier Transform spec-
2
tional and anisotropic atomic displacement param-
eters were refined for all non-hydrogen atoms. Hy-
drogen atoms were placed in calculated positions.
Synthesis of N(4)-Cyclohexylthiosemicarbazide
−1
trometer in the range of 4000–370 cm at room
temperature. H, C NMR, and 119Sn NMR spec-
tra were recorded on a Jeol 500 MHz NMR spec-
trophotometer relative to SiMe4 and Me4Sn using
CDCl3 as the solvent. CHN analyses were obtained
with a Flash EA 1112 series CHN elemental ana-
lyzer. Molar conductivity measurements were car-
1
13
N(4)-Cyclohexylthiosemicarbazide has been re-
ported earlier in the literature [17, 18]. N(4)-
Cyclohexylthiosemicarbazide was synthesized as fol-
lows: Cyclohexylisothiocyanate (1.41 g, 10 mmol) in
4 mL of ether was added dropwise into 4 mL of ether
solution of hydrazine hydrate (2 g, 40 mmol). The
Heteroatom Chemistry DOI 10.1002/hc

Synthesis, Characterization, and Antibacterial Activities of Organotin(IV) Complexes 45
SCHEME 1 Synthesis of 2-acetylpyridine-N(4)-cyclohexylthiosemicarbazone [HAPCT] (1).
mixture was stirred vigorously for 5 h. Then, 5 mL
of petroleum ether was added into the resulting so-
lution and stirred for another 1 h and white precip-
itate was formed. The white precipitate was filtered,
washed with a small amount of cool diethyl ether,
and dried in vacuo over silica gel. Yield: 2.12 g, 62%:
(NH C S), 160.03 (C N), 147.32–136.29 (pyridine
ring), 53.11–26.49 (cyclohexyl), 10.01 (CH3). Anal.
Calcd for C14H20N4S: C, 60.83; H, 7.29; N, 20.26%.
Found: C, 60.53; H, 7.11; N, 20.01%.
◦
−1
mp.: 146–148 C: FT-IR (KBr, cm ) νmax: 3334 (s,
NH2), 3297 (s, NH), 2929, 2853 (s, cyclohexyl), 1349,
Synthesis of [MeSnCl (APCT)] (2)
2
HAPCT (1) (0.28 g, 1.0 mmol) was dissolved in ab-
solute methanol (10 mL) under a nitrogen atmo-
sphere in an Schlenk round-bottomed flask. Then,
a methanolic solution of methyltin(IV) trichloride
849 (w, C S).
Synthesis of 2-Acetylpyridine-N(4)-
cyclohexylthiosemicarbazone [HAPCT]
(0.24 g, 1.0 mmol) was added dropwise and resulted
in a yellow solution. The resulting reaction mix-
ture was refluxed for 4 h (Scheme 2) and cooled to
room temperature. The yellow microcrystals were
obtained from slow evaporation of the resulting so-
lution at room temperature. The microcrystals were
filtered off, washed with a small amount of cold
methanol, and dried in vacuo over silica gel. Yield:
(
1)
N(4)-Cyclohexylthiosemicarbazide (0.51 g, 3 mmol)
was dissolved in 10 mL of dry methanol before
mixing it with 10 mL of dry methanolic solution
of 2-acetylpyridine (0.363 g, 3 mmol). The result-
ing mixture was refluxed for 4 h (Scheme 1) and
cooled to room temperature. White microcrystals
were formed and filtered off. The microcrystals were
washed several times with a small amount of cool
methanol subsequent with cool hexane. The micro-
crystals were recrystallized from methanol and dried
◦
0.447 g, 83%: mp.: 278–280 C: molar conductance
−1
2
−1
(DMSO) ꢀ cm mol : 9.28: UV–visible (DMSO)
−1
λmax/nm: 325, 327, 382, 465: FT-IR (KBr, cm ) νmax:
3256 (s, NH), 2928, 2854 (s, cyclohexyl), 1596 (m,
C N N C), 1025 (w, N N), 1347, 830 (m, C S),
649 (w, pyridine in plane), 567 (w, Sn C), 477 (w,
in vacuo over silica gel. Yield: 0.643 g, 72%: mp.:
◦
1
1
3
2
1
80–182 C: UV–visible (DMSO) λmax/nm: 325, 327,
Sn N). H NMR (CDCl3, ppm) δ: 10.29 (s, 1H, N4-
−1
82: FT-IR (KBr, cm ) νmax: 3335 (s, NH), 2938,
845 (s, cyclohexyl), 1583 (w, C N), 984 (m, N N),
358, 865 (w, C S), 608 (m, pyridine in plane). H
H), 8.86 (d, J = 5.18 Hz, 1H, pyridine ring C13-H),
8.80 (t, J = 5.22 Hz, 1H, pyridine ring C11-H ), 8.77
(d, J = 5.20 Hz, 1H, pyridine ring C10-H), 8.14 (t, J =
5.25 Hz, 1H, pyridine ring C12-H), 7.39 (s, 1H, CyC1-
H), 2.45 (s, 3H, CH3 C N), 2.19–1.71 (m, 10H, Cy-
1
NMR (CDCl3, ppm) δ: 10.30 (s, 1H, N4-H), 8.57
d, J = 5.20 Hz, 1H, pyridine ring C13-H), 8.25 (t,
J = 5.24 Hz, 1H, pyridine ring C11-H ), 8.13 (d, J =
(
2
119
1
H), 1.26 (s, 3H, Sn CH3), J[( Sn, H) = 93.4 Hz].
1
3
5
.19 Hz, 1H, pyridine ring C10-H), 7.81 (t, J = 5.27
C NMR (CDCl3, ppm,) δ: 180.88 (N C S), 172.619
(C N), 144.11–140.21 (pyridine ring), 53.35–26.33
(cyclohexyl), 14.28 (CH3), 17.88 (Sn-CH3), [J( C–
Hz, 1H, pyridine ring C12-H), 7.39 (s, 1H, CyC1-
H), 2.37 (s, 3H, CH3 C N), 2.24–1.71 (m, 10H,
Cy-H), 1.8 (SH). 13C NMR (CDCl3, ppm) δ: 190.07
1
3
119
119
Sn) = 812 Hz)]. Sn NMR (CDCl3, ppm) δ: –328,
Heteroatom Chemistry DOI 10.1002/hc

46 Salam et al.
3
6
13
10
1
4
5
2
12
11
S
N
SH
N
2
4
N
H
3
N
N
1
7
9
N
H
N
H
N
8
CH3
CH3
2
Refluxed, 4 h N atmosphere
Organotin(IV) chloride(s) Abs.MeOH
b
a
c
3
6
13
10
1
Sn
2
N
4
5
2
12
11
S
N
9
4
3
N
1
7
N
H
8
CH3
b = Me, c = Cl, a = Cl (2)
b = Bu, c = Cl, a = Cl (3)
b = Ph, c = Cl, a = Cl (4)
b = Cl, c = Me, a = Me (5)
b = Cl, c = Ph, a = Ph (6)
SCHEME 2 Reaction scheme for the synthesis of organotin(IV) complexes (2–6).
Anal. Calcd for C15H22N4SSnCl2: C, 37.53; H, 4.62;
N, 11.67. Found: C, 37.23; H, 4.39; N, 11.55.
The other complexes (3–6) were synthesized
using a similar procedure of organotin(IV) com-
plex (2) using appropriate organotin(IV) chloride(s)
141.25 (pyridine ring), 53.35–36.31 (cyclohexyl),
12.24 (CH3), 32.81, 28.15, 26.35, 17.77 (Sn-Bu).
Sn NMR (CDCl3, ppm) δ: –324. Anal. Calcd for
C18H28N4SSnCl2: C, 41.40; H, 5.40; N, 10.73. Found:
C, 41.24; H, 5.17; N, 10.59.
1
19
(Scheme 2).
Synthesis of [PhSnCl (APCT)] (4)
2
Synthesis of [BuSnCl (APCT)] (3)
2
◦
Yield: 0.45 g, 77%: mp.: 250–252 C: molar con-
◦
−1
2
−1
Yield: 0.438 g, 78%: mp.: 248–250 C: molar con-
ductance (DMSO) ꢀ cm mol : 8.70: UV–visible
(DMSO) λmax/nm: 318, 354, 382, 403: FT-IR (KBr,
cm ) νmax: 3414 (s, NH), 2931, 2854 (s, cyclohexyl),
1603 (m, C N N C), 1019 (w, N N), 1334, 829 (m,
C S), 695 (w, pyridine in plane), 574 (w, Sn C),
−1
2
−1
ductance (DMSO) ꢀ cm mol : 8.80: UV–visible
DMSO) λmax/nm: 320, 376, 385, 400: FT-IR (KBr,
cm ) νmax: 3308 (s, NH), 2931, 2855 (s, cyclo-
−1
(
−1
hexyl), 1602 (m, C N N C), 1020 (w, N N), 1345,
1
8
33 (m, C S), 652 (w, pyridine in plane), 570 (w,
472 (w, Sn N). H NMR (CDCl3, ppm) δ: 10.30 (s,
1
Sn C), 475 (w, Sn N). H NMR (CDCl3, ppm)
1H, N4-H), 8.84 (d, J = 5.17 Hz, 1H, pyridine ring
C13-H), 8.80 (t, J = 5.23 Hz, 1H, pyridine ring C11-
H ), 8.61 (d, J = 5.19 Hz, 1H, pyridine ring C10-
H), 8.35 (t, J = 5.26 Hz, 1H, pyridine ring C12-H),
8.11 (s, 1H, CyC1-H), 7.52–7.35 (m, 5H, phenyl ring),
2.73 (s, 3H, CH3 C N), 2.13–1.29 (m, 10H, Cy-H).
δ: 10.28 (s, 1H, N4-H), 8.81 (d, J = 5.19 Hz,
1H, pyridine ring C13-H), 8.79 (t, J = 5.21 Hz,
1H, pyridine ring C11-H ), 8.75 (d, J = 5.20 Hz,
1H, pyridine ring C10-H), 8.45 (t, J = 5.24 Hz,
1H, pyridine ring C12-H), 7.25 (s, 1H, CyC1-H),
2.58 (s, 3H, CH3 C N), 2.38–1.76 (m, 10H, Cy-H),
1.74–1.72 (t, 2H, Sn CH2 CH2 CH2 CH3), 1.53–
1.48 (m, 2H Sn CH2 CH2 CH2 CH3), 1.38–1.22
1
3
C NMR (CDCl3, ppm) δ: 180.80 (N C S), 172.28
(C N), 143.94–141.79 (pyridine ring), 135.97–128.80
(phenyl ring), 53.35–32.03 (cyclohexyl), 16.11 (CH3).
1
19
(
3
m, 2H, Sn CH2 CH2 CH2 CH3), 0.98–0.84 (t,
H, Sn CH2 CH2 CH2 CH3). 13C NMR (CDCl3,
ppm) δ: 182.23 (N C S), 173.61 (C N), 145.15–
Sn NMR (CDCl3, ppm) δ: –322. Anal. Calcd for
C20H24N4SSnCl2: C, 44.31; H, 4.46; N, 10.33. Found:
C, 44.11; H, 4.31; N, 10.16.
Heteroatom Chemistry DOI 10.1002/hc

Synthesis, Characterization, and Antibacterial Activities of Organotin(IV) Complexes 47
6
Synthesis of [Me SnCl(APCT)] (5)
an absorbance value of 2.0 × 10 colony-forming
2
units (CFU/mL) or 0.168 at wavelength of 550 nm
◦
Yield: 0.36 g, 72%: mp.: 215–217 C: molar conduc-
in the spectrophotometer. Sterile cotton swab was
dipped into the broth culture and inoculated on the
Mueller Hinton agar. Sterile paper disks with 6 mm
diameter were placed on the agar at equal distance.
The recommended concentration of the test sample
2 mg/mL in DMSO) was introduced individually to
each of the disks. The agar plates were incubated
immediately at 37 C for 20 h. For each plate, DMSO
mixture and reference antibacterial drug such as
doxycycline served as negative and positive controls,
respectively. The activity was determined by measur-
ing the diameter of zones showing complete inhibi-
tion (mm). Growth inhibition was calculated with
reference to the positive control.
−1
2
−1
tance (DMSO) ꢀ cm mol : 11.36: UV–visible
DMSO) λmax/nm: 322, 329, 381, 454: FT-IR (KBr,
(
−1
cm ) νmax: 3251 (s, NH), 2927, 2855 (s, cyclohexyl),
596 (m, C N N C), 1021 (w, N N), 1345, 829 (m,
C S), 649 (w, pyridine in plane), 587 (w, Sn C), 478
w, Sn N). H NMR (CDCl3, ppm) δ: 10.31 (s, 1H,
N4-H), 8.83 (d, J = 5.16 Hz, 1H, pyridine ring C13-H),
.79 (t, J = 5.20 Hz, 1H, pyridine ring C11-H ), 8.58
d, J = 5.18 Hz, 1H, pyridine ring C10-H), 8.32 (t, J =
.28 Hz, 1H, pyridine ring C12-H), 7.73 (s, 1H, CyC1-
H), 2.50 (s, 3H, CH3 C N), 2.33–1.71 (m, 10H, Cy-
1
(
1
(
◦
8
(
5
2
119
1
H), 1.17 (s, 6H, Sn-CH3), J[( Sn, H) = 112 Hz].
1
3
C NMR (CDCl3, ppm) δ: 181.11 (N C S), 173.32
C N), 144.25–141.61 (pyridine ring), 54.35–26.33
(
1
3
(
cyclohexyl), 15.39 (CH3), 18.46 (Sn CH3), [J( C–
Sn) = 865 Hz)]. Sn NMR (CDCl3, ppm) δ: –341.
1
19
119
RESULTS AND DISCUSSION
Synthesis
Anal. Calcd for C16H25N4SSnCl: C, 41.81; H, 5.48; N,
12.18. Found: C, 41.77; H, 5.44; N, 12.16.
2
-Acetylpyridine-N(4)-cyclohexylthiosemicarbazone
Synthesis of [Ph SnCl(APCT)] (6)
[HAPCT, (1)] was synthesized by the condensation
reaction of N(4)-cyclohexylthiosemicarbazide and
2
◦
Yield: 0.423 g, 68%; mp.: 190–192 C: molar con-
2
-actylpyridine in absolute methanol. It has two
−
1
2
−1
ductance (DMSO) ꢀ cm mol : 9.84; UV–visible
DMSO) λmax/nm: 325, 334, 393, 400; FT-IR (KBr,
tautomers within the structure, existing as either
a thione or a thiol tautomer (Scheme 1). Five new
organotin(IV) complexes (2–6) were obtained in
good yields by the equimolar reaction of organ-
otin(IV) chloride(s) with HAPCT (1) (Scheme 2). The
physical and analytical data of 1–6 are given in the
Experimental section. All organotin(IV) compounds
were stable under N2 atmosphere and soluble in
CH2Cl2, CHCl3, DMF, DMSO, and MeCN solvents.
The molar conductivity of the organotin(IV) com-
(
−1
cm ) νmax: 3357 (s, NH), 2929, 2851 (s, cyclohexyl),
604 (m, C N N C), 1020 (w, N N), 1299, 828 (m,
C S), 693 (w, pyridine in plane), 548 (w, Sn C),
1
1
4
55 (w, Sn N). H NMR (CDCl3, ppm) δ: 10.31 (s,
H, N4-H), 8.84 (d, J = 5.16 Hz, 1H, pyridine ring
1
C13-H), 8.80 (t, J = 5.21 Hz, 1H, pyridine ring C11-
H ), 8.63 (d, J = 5.24 Hz, 1H, pyridine ring C10-
H), 8.38 (t, J = 5.26 Hz, 1H, pyridine ring C12-H),
7
.52 (s, 1H, CyC1-H), 7.42–7.25 (m, 10H of phenyl
−1
2
−1
plexes (2–6) in DMSO is 11.36–8.70 ꢀ cm mol
showing that the complexes are nonelectrolytes
22].
ring), 2.53 (s, 3H, CH3 C N), 2.07–1.61 (m, Cy-H).
1
3
C NMR (CDCl3, ppm) δ: 182.36 (N C S), 172.19
[
(
(
C N), 143.87–141.05 (pyridine ring), 134.87–127.50
phenyl ring), 52.35–33.15 (cyclohexyl), 17.05 (Sn-
1
3
119
119
Ph), [J( C– Sn) = 986 Hz)].
ppm) δ: –335. Anal. Calcd for C26H29N4SSnCl: C,
3.49; H, 5.00; N, 9.59. Found: C, 53.31; H, 4.82;
Sn NMR (CDCl3,
UV–Visible Spectra
5
The UV–Vis spectra analyses of ligand (1) and its
organotin(IV) complexes (2–6) were carried out in
N, 9.43.
−4
DMSO (10 M) at room temperature. The electronic
spectrum of the ligand (1) showed three absorption
bands at 325, 327, and 382 nm correspond to the
Antibacterial Test
*
The antibacterial test of synthesized ligand (1) and
its organotin(IV) complexes (2–6) was carried out
using the agar well diffusion method [21]. Doxycy-
cline was used as the standard drug. The bacteria
from stock culture were lightly inoculated into the
Mueller Hinton broth (MHB) and allowed to grow
n–π transition of the pyridine ring, azomethine,
thiolate functions, and the benzene group, respec-
tively [23]. After complexation, the complexes (2–6)
showed four absorption bands at 318–325, 327–376,
381—393, and 400–465 nm, respectively. In the elec-
tronic spectra of complexes (2–6), the intraligand
transition is shifted to higher wavelength as a result
of coordination. The new absorption at 400–465 nm,
◦
overnight at 37 C in an ambient air incubator. The
culture was diluted with a new MHB to achieve
Heteroatom Chemistry DOI 10.1002/hc

48 Salam et al.
observed in the spectra of organotin(IV) complexes
2–6), is assigned to ligand → metal charge transfer
24]. The shift of the λmax band from the ligand to
the complexes is a clear indication that coordination
occurred between tin(IV) and ligand.
the resonance signal of N4-H. The resonance sig-
nal at 1.8 ppm is assigned to the SH proton. The
pyridine ring protons gave four resonance signals
at 8.57, 8.25, 8.13, and 7.81 ppm corresponded to
the C13-H, C11-H, C10-H, and C12-H, respectively.
A singlet at 7.39 ppm corresponded to CyC1-H. The
resonance signal at 2.37 ppm is due to CH3 C N.
After complexation, the resonance signal of SH is
absent in the spectra of the complexes (2–6), which
suggested the deprotonation of the SH proton and
confirming that the ligand coordinated to the tin(IV)
in the thiolate form. The resonance signals of the
C13-H in the organotin(IV) complexes (2–6) were
observed at 8.86–8.81 ppm shifted downfield com-
pared to the free ligand (1). The resonance signals
of the C11-H, C10-H, and C12-H were observed at
a range of between 8.80–8.79, 8.77–8.61, and 8.55–
8.14 ppm, which are shifted downfield compared
to the free ligand (1), respectively. This downfield
shift also supported the observation that the pyri-
dine ring nitrogen is coordinated to the Sn atom.
The azomethine proton (CH3 C N) signal appears
at 2.37 ppm in the free ligand (1), which is shifted
to downfield at 2.73–2.45 ppm in the complexes
(2–6). This downfield shift indicating the azome-
thine nitrogen atom is coordinated to the Sn(IV)
atom [30]. The proton resonance signals for N4-
H and CyC1-H are appeared at 10.31–10.27 and
8.11–7.25 ppm in the complexes (2–6). The multi-
plet signals of aromatic-H in the complexes 4 and 6
were observed at 7.52–7.25 ppm. In cyclohexyl, the
equatorial protons are observed at a slightly higher
chemical shift compared to that of the axial pro-
ton in the free ligand (1) and complexes (2–6). The
methyl group attached to the tin(IV) core in 2 and
5 gives a singlet at 1.26 and 1.17 ppm, respectively.
(
[
Infrared Spectra
The free ligand (1) showed absorption bands at
3
335, 2938, 2845, 1583, 984, 1358, 865, and 608
−1
cm due to ν(NH), ν(cyclohexyl), ν(C N), ν(N N),
ν(C S), and the pyridine ring in plane, respectively.
After complexation, there are significant changes
with respect to the free ligand (1) and its organ-
otin complexes (2–6). The newly formed C
N C
bond showed medium to strong absorption peaks
−1
within the range of 1596–1604 cm in the spec-
tra of the complexes (2–6), indicating the coordina-
tion of the azomethine nitrogen to the tin(IV) atom
[
25]. The ν(N N) band of the free ligand (1) at 984
−1
cm is shifted to higher frequencies at 1019–1028
−1
cm in the organotin(IV) complexes (2–6), again
supported the coordination of azomethine nitrogen
to the Sn(IV) ion [26]. The stretching and bend-
ing frequency of the ν(CS) bands observed at 1358
−1
and 865 cm in the spectrum of free ligand (1) are
shifted to lower frequencies at 1299–1347 and 828–
−1
8
33 cm in the spectra of the complexes (2–6), in-
dicating the coordination of the sulfur atom in the
−1
thiolate form [27]. A sharp band at 608 cm of the
pyridine ring in plane in the spectrum of the free
ligand (1) is shifted to higher frequencies at 649–
−
1
6
95 cm in the complexes (2–6), suggesting the co-
ordination of the pyridine ring nitrogen to tin(IV) ion
28]. Characteristically one new band was observed
[
−1
2
119
1
at 455–478 cm in the spectra of the complexes (2–
), suggesting the presence of Sn N bonding in their
structure [29]. There are IR bands observed at 548–
The J [ Sn, H] values of the tin(IV) complex (2),
93.4 Hz, and tin(IV) complex (5), 112 Hz, supported
the six-coordinated environments around the tin(IV)
atom [31]. The butyl groups attached to the tin(IV)
moiety in the organotin(IV) complex 3 gave four
resonance signals, namely 1.75–1.65 ppm (triplet,
Sn CH2 CH2 CH2 CH3), 1.53–1.47 ppm (mul-
tiplet, Sn CH2 CH2 CH2 CH3), 1.38–1.20 ppm
6
−
1
5
87 cm tentatively assigned to the ν(Sn C) mode
of the complexes (2–6). The IR observation indicated
the coordination of ligand (1) to the tin(IV) core of
the complexes (2–6) via pyridine-N, azomethine-N,
and thiolato-S atoms. These observations have also
been confirmed by X-ray single structures analyses
of complex 4.
(multiplet, Sn CH2 CH2 CH2 CH3), and 0.99–
1
0.84 ppm (triplet, Sn CH2 CH2 CH2 CH3).
H
NMR information also supported the IR data of the
complexes (2–6).
The 13C NMR signals of the free ligand (1) was
observed at 190.07, 160.03, 147.32–136.29, 53.11–
26.49, and 10.01 ppm are attributed to δ(NH C S),
δ(C N), δ(pyridine ring), δ(cyclohexyl ring), and
δ(CH3), respectively. After complexation, the car-
bon signals of the N C S group shifted to upfield
at 182.36–180.80 ppm in the complexes (2–6) in
1H, 13C, and 119Sn NMR Spectra
1
The H NMR spectral assignments of ligand (1) and
its organotin(IV) complexes (2–6) were carried out
and interpreted based on the atom labeling as shown
1
in Scheme 2. H NMR spectrum of free ligand (1)
showed a singlet at 10.30 ppm, corresponding to
Heteroatom Chemistry DOI 10.1002/hc

Synthesis, Characterization, and Antibacterial Activities of Organotin(IV) Complexes 49
compared to the free ligand, indicating coordina-
tion of the N C S group with the tin(IV) atom.
The chemical shifts of the C N and CH3 were ob-
served at 160.03 and 10.01 ppm, respectively, in the
free ligand (1), which were shifted to downfield at
174.60–172.19 and 17.05–12.24 ppm, respectively, in
all the complexes (2–6). This is also supported the
H3C C N coordinated to the tin(IV) moiety. The
resonance signals of the carbons assigned to the pyri-
dine ring was shifted to the approximately 3.45–1.77
ppm upfield region in the complexes (2–6) in com-
parison with the free ligand (1), suggesting partici-
pation of the pyridine ring nitrogen in coordination
1
119
to the tin(IV) atom. The coupling constant, J[ Sn,
1
3
C] is one of the key parameters in assessing the
possible coordination geometries of organotin(IV)
1
13
119
compounds in solution. The observed [ J( C– Sn]
coupling constant are 812.62, 865.20, and 986.5 Hz
for monomethyltin(IV) (2), dimethyltin(IV) (5), and
diphenyltin(IV) (6) compounds, respectively. These
values are in accordance with a hexa-coordinate en-
vironment about the tin atom in these compounds
[31–33].
The
1
19
Sn NMR chemical shift of the complexes
FIGURE 1 Molecular structure of [PhSnCl
2
(APCT)] (4).
1
19
(
2–6) was recorded in CDCl3 solution.
Sn NMR
spectroscopy gives significant information to deter-
mine the coordination number around the tin atom.
◦
TABLE 2 Selected Bond Lengths ( A˚ ) and Angles ( ) of
1
19
The
Sn NMR of all the complexes (2–6) shows
2
[PhSnCl (APCT)] (4)
only one resonance signal in the range of –322.18
to –341.42 ppm. The occurrence of 1 Sn chemical
shifts in these areas indicates six-coordinated en-
vironment in organotin(IV) derivatives around the
central tin atom [34].
˚
Bond Lengths (A)
19
Sn1–S4
Sn1–N7
Sn1–N10
N7–C8
N6–C5
C5–S4
2.4766(4)
Sn1–Cl2
Sn1–Cl3
C23–C24
C24–C25
C25–C26
C26–C27
C27–C28
2.4588(5)
2.5088(4)
1.3892(3)
1.393(2)
1.386(3)
1.384(3)
1.396(2)
2.2301(13)
2.2544(13)
1.298(2)
1.322(2)
Sn1–C23
2.1559(16)
X-Ray Crystallography Diffraction Analyses
◦
Suitable single crystals of phenyltin(IV) complex (4)
were grown from methanol at room temperature.
The molecular structure of the phenyltin(IV) com-
plex (4) with appropriate numbering is shown in
Bond Angles ( )
Cl2–Sn1–Cl3
C23–Sn1–Cl2
S4–Sn1–Cl2
N7–Sn1–N10
S4–Sn1–C23
163.986(15) C9–N10–C11 120.21(14)
95.97(5) N10–C11—C12 112.09(16)
94.162(18) C11–C12—C13 118.43(16)
151.03(4) C12–C13—C14 119.70(16)
◦
˚
Fig. 1. Selected bond length (A) and bond angle ( )
of the complex (4) are summarized in Table 1. The
summary of crystal data and refinement parameters
of the phenyltin(IV) complex (4) is listed in Table 2.
In the molecular structure of complex (4), the tin(IV)
atom adopts a distorted octahedral geometry with
the N(4)-cyclohexylthiosemicarbazone ligand coor-
dinated to it as a mononegative tridentate chelating
agent via pyridine-N, azomethine-N, and thiolato-
S atoms. The equatorial position is occupied by
S4, N7, and N10, and remaining sites are occupied
by the two chlorine atoms and one carbon atom
of the phenyl group. The Sn1–S4 bond distance is
107.95(4)
C23–Sn1–N10 101.01(5)
C13–C14—C9 119.39(16)
C14–C9–N10 120.16(15)
˚
lent radii of tin and sulfur 2.42 A [35], but much
smaller than the Van der Waals radii 4.0 A [36], in-
dicating the S atom is coordinated in the thiolate
form. The Sn1–N7 and Sn1–N10 bond lengths are
2.2301(13) A and 2.2544(13) A, respectively, which
is close to the sum of the covalent radii of Sn–
˚
˚
˚
˚
N (2.15 A), indicating significant bonding of the
Sn1 atom with N7 and N10, respectively [37]. In
˚
2
.4766(4) A, which is close to the sum of the cova-
Heteroatom Chemistry DOI 10.1002/hc

50 Salam et al.
a
general, the Sn–N bond distances reported here can
be considered within the usual range reported for
other related tin(IV)–thiosemicarbazone complexes
TABLE 3 Antibacterial Activity of the Free Ligand (1) and
Its Organotin(IV) Complexes (2–6) (Inhibition Zone in mm)
Bacterium
[
38]. The bond distances N7–C8 and N6–C5 are
˚ ˚
.298(2) A and 1.322(2) A, respectively, which is in
Samples S. aureus E. coli E. aerogenes Salmonella typhi
1
conformity with a formal C N double bond (1.28
A). Therefore, the C5–S4 bond changes from a dou-
1
2
3
4
5
6
R
–
10
–
8
˚
21.8
22.2
22.5
25.1
27.6
34.2
20.7
20.1
20.8
23.2
27.5
33.7
22.6
22.4
23.3
24.8
25.9
29.6
25.5
23.5
22.6
23.7
24.8
34.8
ble bond to a predominately single bond, whereas
C5–N6 acquires some double bond characteristics.
The remaining sites are occupied by the negative
˚
charged phenyl group [d(Sn1–C23) = 2.1559(16) A]
and by two chlorine atoms [d(Sn1–Cl2) = 2.4588(5)
a
Concentration used: 2 mg/mL of DMSO, R = standard drug: doxy-
˚
˚
A, d(Sn1–Cl3) = 2.5088(4) A]. The bond length
cycline, dash indicates inactivity.
˚
Sn1–C23 (2.1559(16) A is very much longer than
C23–C24 (1.3892(3) A, C24–C25 (1.393(2) A, C25–
C26 (1.386(3) A, C26–C27 (1.384(3) A, and C27–C28
˚
˚
˚
˚
˚
erence drug (doxycycline). Diphenyltin(IV) complex
6 showed the highest inhibition to growth of organ-
isms, i.e., 27.6, 27.5, 25.9, and 24.8 mm inhibition
zones against S. aureus, E. coli, E. aerogenes, and
Salmonella typhi, respectively. Dimethyltin(IV) com-
plex 5 was second in toxicity to all bacterial strains.
PhSn(IV)/BuSn(IV) complexes (3–4) show enhanced
activity compared to the corresponding MeSn(IV)
(2) complex. The activity might be due to the in-
creasing of lipophilic nature of these complexes re-
sulted from the metal chelation [40–42]. The elec-
tron delocalization in the chelate ring increases the
lipophilic character of the metals chelate. Therefore,
changing the organotin(IV) groups must play a sig-
nificant role in these compounds growth inhibitory
activity. In addition, the antimicrobial activity might
due to the presence of the NH group; this group is
believed to impart the transformation reaction in
the biological system. It is believed that the antimi-
crobial activity of the organotin(IV) complexes may
also be due to the inhibition of ATP production (en-
ergy production) such as inhibiting the respiration
or by uncoupling of oxidative phosphorylation [43].
Antibacterial activity of compounds is due to either
bactericide effects (killing the bacteria) or bacterio-
static effects (inhibiting multiplication of bacteria
by blocking their active sites) [44]. The present ob-
servations corroborates previously reported tin com-
pounds, wherein enhancement of activity has been
described due to coordination of ligand to metal and
efficient diffusion of the metal complexes into bac-
terial cell takes place [45,46].
(1.396(2) A in a phenyl ring; it may be due to steric
hindrance of the central Sn1 atom. The two chlo-
rines do not occupy the exact axial positions as
a result the (Cl2–Sn1–Cl3) angle is 163.98 , which
◦
showed the significant distortion from the linear an-
◦
gle 180 . The deviation of the axial plane from linear-
ity might be due to the steric hindrance by the phenyl
group. Owing to steric effects between the phenyl
group and chlorine atom, the tin(IV) atom may be
viewed as distorted octahedral geometry. The angle
◦
C23–Sn1–Cl2 (95.97(5) ) is larger than S4–Sn1–Cl2
◦
(
94.162(18) ). The sum of the equatorial angles S4–
Sn1–N7 (79.00(4) ), N7–Sn1–N10 (72.08(5) ), and
S4–Sn1–N10 (151.03(4) ) is 302.11 showing more
distortion from an ideal bond angle 360 . The sum
◦
◦
◦
◦
◦
◦
of the angle S4–Sn1–C23 (107.95(4) ), S4–Sn1–N7
◦
◦
(
79.00(4) ), N7–Sn1–N10 (72.08(5) ), and C23–Sn1–
◦
◦
N10 (101.01(5) ) is 360 . So that the atoms Sn1, S4,
C23, N10, and N7 are almost in the same plane.
◦
The angle C11–N10–C9 (120.24(14) ), N10–C11–
C12 (122.04(16) ), C11–C12–C13 (118.43(16) ), C12–
C13–C14 (119.70(16) ), C13–C14–C9 (119.39(16) ),
and C14–C9–N10 (120.16(15) ) are not 120 ; thus
all the atoms in the pyridine ring are not in the
same.
◦
◦
◦
◦
◦
◦
Antibacterial Activity
The synthesized ligand (1) and its organotin(IV)
complexes (2–6) were tested for their antibacterial
activity against Staphylococcus aureus, Escherichia
coli, Enterobacter aerogenes, and Salmonella typhi.
The results are presented in Table 3. Inhibition zone
diameter over 7 mm indicates that all test com-
pounds are active against the bacteria under inves-
tigation [39]. The free ligand (1) was found to be of
little activity against bacteria. The screening results
exhibited that complexes (2–6) showed high activity
against various bacteria but low activity than the ref-
CONCLUSIONS
2-Acetylpyridine-N(4)-cyclohexylthiosemicarbazone
(1) and its organotin(IV) complexes (2–6) were
synthesized and completely characterized. The
Heteroatom Chemistry DOI 10.1002/hc

Synthesis, Characterization, and Antibacterial Activities of Organotin(IV) Complexes 51
ligand (1) exists in a thione form in a solid state,
[14] Roberto, S. B.; Heloisa, O. B.; Carlos, A. L. F.; Abras,
A.; Nixon, J. F.; Hitchcock, P. B. Inorg Chim Acta
but it takes on a thiol form when it is in solution.
The results obtained from the spectroscopic char-
acterization support the proposed six-coordinated
structures of the complexes (2–6). The X-ray
crystallography diffraction has also revealed that
the complex 4 is rendered a distorted octahedral
geometry. Biological studies revealed that all the
organotin(IV) complexes (2–6) are more potent an-
tibacterial agent than their free ligand (1), whereas
the diphenyltin(IV) complex (6) is more active than
the other organotin(IV) derivatives (2–5).
1
993, 206, 169.
[
15] Chandrasekhar, V.; Gopal, K.; Sasikumar, P.;
Thirumoorthi, R. Coord Chem Rev 2005, 249,
1745.
[16] Li, D.; Hu, R.; Zhou, W.; Sun, P.; Kan, Y.; Tian, Y.;
Zhou, H.; Wu, J.; Tao, X.; Jiang, M. Eur J Inorg Chem
2
009, 2009(18), 2664.
[
17] Salam, M. A.; Affan, M. A.; Ahmad, F. B.; Hitam, R.
B.; Gal, Z.; Oliver, P. J Coord Chem 2011, 64, 2409.
[18] Affan, M. A.; Salam, M. A.; Ahmad, F. B.; Ismai, J.;
Shamsuddin, M. B.; Ali, H. M. Inorg Chim Acta 2011,
3
66, 227.
[
[
19] Affan, M. A.; Salam, M. A.; Ahmad, F. B.; Hitam, R.
B.; White, F. Polyhedron 2012, 33, 19.
20] Armarego W. L. F.; Perrin, D. D. 1996, Purification
of Laboratory Chemicals, 4th Edition Butterworth-
Heineman: London.
SUPPLEMENTARY DATA
CCDC reference number 795016 contains the supple-
mentary crystallographic data for [PhSnCl2(APCT)]
[
21] Rahman, A.; Choudry, M. I.; Thomsen, W. J. 2001,
Bioassay Techniques for Drug Development, Har-
wood Academic: Amsterdam,The Netherlands.
22] Sharaby, C. M. Spectrochim Acta A 2007, 66, 1271.
23] Rebolledo, A. P.; de Lima, G. M.; Gambi, L.
N.; Speziali, N. L.; Maia, D. F.; Pinheiro, C. B.;
Ardisson, J. D.; Cort e´ s, M. E.; Beraldo, H. Appl
Organomet Chem 2003, 17, 945.
(
4). This data can be obtained free of charge from
[
[
the Cambridge Crystallographic data center via
www.ccdc.ac.uk/data_request/cif or from the Cam-
bridge Crystallographic data center, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033;
or e-mail: deposit@ccdc.cam.ac.uk.
[24] Maurya, R. M.; Jayaswal, M. N.; Puranik, V. G.;
Chakrabarti, P.; Gopinathan, S.; Gopinathan, C. Poly-
hedron 1997, 16, 3977.
[
25] Costa, F. F.; Rebolledo, A. P.; Matencio, T.; Calado,
H. D. R.; Ardisson, J. D.; Cortes, M. E. Rodrigues, B.
L.; Beraldo, H. J Coord Chem 2005, 58, 1307.
26] Garg, B. S.; Kurup, M. R. P.; Jain, S. K.; Bhoon, Y. K.
Trans Met Chem 1988, 13, 309.
ACKNOWLEDGMENTS
The authors would like to thank Universiti Malaysia
Sarawak (UNIMAS) for providing the facilities to
carry out the research work.
[
[
27] Mendes, I. C.; Moreira, J. P.; Mangrich, A. S.; Balena,
S. P.; Rodrigues, B. L.; Beraldo, H. Polyhedron 2007,
2
6, 3263.
[
28] Mendes, I. C.; Moreira, J. P.; Speziali, L. N.;
Mangrich, A. S.; Takahashi, J. A.; Beraldo, H. J Braz
Chem Soc 2006, 17, 1571.
REFERENCES
[
1] Beraldo, H.; Gambino, D. Mini Rev Med Chem 2004,
, 159.
2] Liberta, A. E.; West, D. X. Biometals 1992, 5, 121.
3] Afrasiabi, Z.; Sinn, E.; Chen, J.; Ma, Y.; Padhye, S.
Toxicol Appl Pharmacol 2004, 197, 40.
4] Momeni, B. Z.; Shahbazi, S.; Khavasi, H. R. Polyhe-
dron 2010, 29, 1393.
5] Wiecek, J.; Dokorou, V.; Zbigniew, C.; Kovala-
Demertzi, D. Polyhedron 2009, 28, 3298.
6] Suni, V.; Prathapachandra, M. R.; Nethaji, M. Poly-
hedron 2007, 26, 5203.
7] Pellerito L.; Nagy, L. Coord Chim Rev 2002, 224, 111.
8] Hanif, M.; Hussain, M.; Ali, S.; Bhatti, M. H.; Ahmed,
M. S.; Mirza, B.; Stoeckli-Evans, H. Polyhedron 2010,
4
[29] Yin, H. D.; Chen, S. W.; Li, L. W.; Wang, D. Q. Inorg
Chim Acta 2007, 360, 2215.
[30] Salam, M. A.; Affan, M. A.; Ahmad, F. B.; Jusoh,
I.; Shamsuddin, M. B.; Yamin, B.; Farina, Y. J
Organomet Chem 2012, 696, 4202.
[31] Lockhart, T. P.; Manders, W. F. Inorg Chem 1986, 25,
892.
[32] Nadvornik, M.; Holecek, J.; Handlir, K.; Lycka, A. J
Organomet Chem 1984, 275, 43.
[
[
[
[
[
[33] Holecek, J.; Nadvornik, M.; Handlir, K.; Lycka, A. J
Organomet Chem 1986, 315, 299.
[
[
[34] Lycka,
A.;
Hole cˆ ek,
J.;
Nadvornik,
M.;
Handlir, K.
323.
J Organomet Chem 1985, 280,
2
9, 613.
[
9] Benetollo, F.; Lobbia, G. G.; Mancini, M.; Pellei, M.;
Santini, C. J Organomet Chem 2005, 690, 1994.
[35] Casas, J. S.; Castineiras, A.; Martinez, E. G.;
Gonzalez, A. S.; Sanchez, A.; Sordo, J. Polyhedron
1997, 16, 795.
[36] Ali, S.; Ahmad, S. U.; Saddiq-ur-Rehman, Shahzadi,
S.; Purvez, M.; Mazhar, M. Appl Organomet Chem
2005, 19, 200.
[37] Yin, H. D.; Chen, S. W. Inorg Chem Acta 2006, 359,
3330.
[38] Mendes, I. C.; Corta, F. B.; de Lima, G. M.;
Ardisson, J. D.; Santos, I. G.; Castineiras, A.; Beraldo,
H. Polyhedron 2009, 28, 1179.
[
10] Baul, T. S. B.; Masharing, C.; Basu, S.; Rivarola, E.;
Hol cˇ apek, M.; Jir a´ sko, R.; Ly cˇ ka, A.; Vos D.; Linden,
A. J Organomet Chem 2006, 691, 952.
[
[
[
11] Beraldo, H.; Gambino, D. Mini Rev Med Chem 2004,
4
, 31.
12] Koch, B.; Baul, T. S.; Chatterjee, A. J Appl Toxicol
008, 28, 430.
13] Syng, A. C; Basu, B. T. S.; Chatterjee, A. Mutat Res
002, 513, 49.
2
2
Heteroatom Chemistry DOI 10.1002/hc

52 Salam et al.
[
[
[
39] Refat, M. S.; Deen, I. M. E.; Anwer, Z. M.; Ghol, S. E.
J Mol Struct 2009, 920, 149.
40] Singh, R. V.; Chaudhary, P.; Chauhan, S.; Swami, M.
Spectrochim Acta, A 2009, 72, 260.
41] Kaczmarek, M. T.; Jastrzab, R.; Holderna-Kedzia, E.;
Radecka-Paryzek, W. Inorg Chim Acta 2009, 362,
[43] Chaudhary, A., Singh, A. K., Singh, R. V. J Inorg
Biochem 2006, 100, 1632.
[44] Nath, M.; Pokharia, S.; Song X.; Eng, G.; Gielen,
M.; Biesemans, M.; Willem, R.; De Vos, D. Appl
Organomet Chem 2003, 17, 305.
[45] Sedaghat, T.; Monajjemzadeh, M.; Motamedi, H., J
Coord Chem 2011, 64, 3169.
3
127.
[
42] Angelusiu, M.V.; Barbuceanu, S. F.; Draghici, C.;
Almajan, G. L. Eur J Med Chem 2010, 45, 2055.
[46] Sharma, N.; Sharma, S.; Kumar, V.; Sharma, R.;
Chaudhry, S. C. J Coord Chem 2011, 64, 351.
Heteroatom Chemistry DOI 10.1002/hc