Monophenylantimony(III) derivatives of cyclic dithiocarbamates; Synthesis, spectroscopic characterization, and antimicrobial study

Article abstract of DOI:10.1080/10426507.2012.740695

Some new monophenylantimony(III) compounds having the formulas have been synthesized by reaction of phenylantimony(III) dichloride with the sodium salt of cyclic dithiocarbamates in 1:1 and 1:2 molar ratios. These newly synthesized compounds have been characterized by elemental analyses, molecular weight measurements, and their plausible structures have been proposed on the basis of IR, NMR (¹H and ¹³C), and ESI-mass studies. Sodium salts of cyclic dithiocarbamates and their corresponding organoantimony(III) derivatives (1-8) have been screened for antimicrobial activity against E. coli, P. aeruginosa (Bacteria) and A. niger and A. flavus (Fungi).

Full text of DOI:10.1080/10426507.2012.740695

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Monophenylantimony(III) Derivatives
of Cyclic Dithiocarbamates; Synthesis,
Spectroscopic Characterization, and
Antimicrobial Study
Deepak Kumar Sharma a , Yashpal Singh a & Jyoti Sharma a
a Department of Chemistry , University of Rajasthan , Jaipur , India
Accepted author version posted online: 01 Nov 2012.Published
online: 16 Aug 2013.
To cite this article: Deepak Kumar Sharma , Yashpal Singh & Jyoti Sharma (2013)
Monophenylantimony(III) Derivatives of Cyclic Dithiocarbamates; Synthesis, Spectroscopic
Characterization, and Antimicrobial Study, Phosphorus, Sulfur, and Silicon and the Related Elements,
188:9, 1194-1204, DOI: 10.1080/10426507.2012.740695
To link to this article: http://dx.doi.org/10.1080/10426507.2012.740695
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Phosphorus, Sulfur, and Silicon, 188:1194–1204, 2013
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2012.740695
MONOPHENYLANTIMONY(III) DERIVATIVES OF CYCLIC
DITHIOCARBAMATES; SYNTHESIS, SPECTROSCOPIC
CHARACTERIZATION, AND ANTIMICROBIAL STUDY
Deepak Kumar Sharma, Yashpal Singh, and Jyoti Sharma
Department of Chemistry, University of Rajasthan, Jaipur, India
GRAPHICAL ABSTRACT
Abstract Some new monophenylantimony(III) compounds having the formulas
have been synthesized by reaction of phenylantimony(III) dichloride with the sodium salt of
cyclic dithiocarbamates in 1:1 and 1:2 molar ratios. These newly synthesized compounds
have been characterized by elemental analyses, molecular weight measurements, and their
plausible structures have been proposed on the basis of IR, NMR (1H and 13C), and ESI-mass
studies. Sodium salts of cyclic dithiocarbamates and their corresponding organoantimony(III)
derivatives (1–8) have been screened for antimicrobial activity against E. coli, P. aeruginosa
(Bacteria) and A. niger and A. flavus (Fungi).
Received 28 June 2012; accepted 14 October 2012.
aWe are thankful to IIT, Chennai (SAIF Centre), for recording the ESI-mass spectra of the compounds and
also thankful to UGC, Bhopal, for financial support.
Address correspondence to Jyoti Sharma, Department of Chemistry, University of Rajasthan, Jaipur 302-004,
India. E-mail: dr jyoti sharma@yahoo.co.in
1194

DERIVATIVES OF CYCLIC DITHIOCARBAMATES
1195
Supplemental materials are available for this article. Go to the publisher’s online edition of
Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.
Keywords Monophenylantimony(III) derivatives; cyclic dithiocarbamates; anisobidentate;
trigonal bipyramidal; pseudo-octahedral geometry; antimicrobial activity
INTRODUCTION
In the past decades, the chemistry of dithiocarbamate derivatives has gained sub-
stantial importance due to their structural possibilities ranging from monomeric to poly-
meric1–10 monodentate, bidentate nature of ligands, and supra-molecular assemblies; and
these compounds are biologically important.11–13 Antimicrobial and antitumor activity of
dithiocarbamate derivatives of antimony(III) have been reported.14,15 Some of these are
used in gas chromatography16 and as precursor for superconducting materials in moCVd
process17 in recent years.
A survey of the literature reveals that although considerable amount of work on
organoantimony compounds with N,N-dialkyldithiocarbamates has been reported during
the past decades,18 the work on cyclic dithiocarbamate is limited to diphenylantimony(III)
compounds of cyclic dithiocarbamates as reported from our laboratory.19 In this article, we
describe the synthesis and characterization of monophenylantimony(III) compounds with
cyclic dithiocarbamate ligands. A comparative study of the antimicrobial activity of sodium
salts of cyclic dithiocarbamate ligands and the corresponding monophenylantimony(III)
derivatives 1–8 is also reported in this article.
RESULTS AND DISCUSSION
The reactions of phenylantimony(III) dichloride with the sodium salt of cyclic dithio-
carbamates in 1:1 and 1:2 molar ratios yield the corresponding monophenylantimony(III)
derivatives.

1196
D. K. SHARMA ET AL.
Chloro-monophenylantimony(III) dithiocarbamates are white colored solids, whereas
phenylantimony(III) bisdithiocarbamates are yellow colored solids. These derivatives are
soluble in common organic solvents and are purified by crystallization from benzene/n-
hexane mixtures.
Reactions of monophenylantimony(III) derivatives with the sodium salt of piperazine
dithiocarbamate in 1:1 and 1:2 molar ratios did not yield the desired product.
IR SPECTRA
IR spectra of these derivatives have been recorded in the region 4000–400 cm−1. All
monophenylantimony(III) derivatives exhibit strong bands in the region 1440–1450 cm−1
,
due to v(C N) stretching vibration and these bands show small shifts toward higher wave
numbers (∼20–30 cm−1) as compared to their position in the spectra of the corresponding
sodium dithiocarbamates. Split bands in the region ∼1130–970 cm−1 due to v(C S) stretch-
ing vibrations have been observed in the monophenylantimony(III) derivatives as well as
their corresponding sodium salt of ligands. The value of ꢀv [v(CS2)asym–v(CS2)sym] may
be used to determine the coordination pattern of the monophenylantimony(III) dithiocar-
bamates. The v(CS2)asym and v(CS2)sym stretching bands are observed at 1110–1130 cm−1
and 970–995 cm−1, respectively. The ꢀv values are in the range of 115–140 cm−1, which
are smaller than ꢀv values for bidentally coordinated derivatives, reported earlier, and
larger than the corresponding sodium dithiocarbamate values. The above-mentioned data
suggest that the dithiocarbamate ligands are coordinated to the Sb atom in an aniso-
bidentate manner. A sharp absorption band at 450 20 cm−1 may be attributed to v(Sb–S)
stretching, which also supports the bonding of central antimony with the sulfur atom,
and bands due to v(Sb–C) have also been observed in the range 470–455 cm−1 in these
spectra.
NMR SPECTRA
1H NMR
1
The H NMR spectra of the monophenylantimony(III) dithiocarbamate derivatives
are summarized in Table 1.
Characteristic proton signals due to –CH2–, –CH(CH3)–, –N(CH3), and –CH2OCH2–
have been observed at the expected positions (Table 1) and do not show any appreciable
shift in their positions as compared to the spectra of the corresponding sodium salts of the
dithiocarbamate ligands in both chloro- and bis-dithiocarbamate derivatives of phenylan-
timony(III). Phenyl ring protons attached to the antimony atom have been observed in the
region 6.46–8.50 ppm.
13C NMR Spectra
The 13C NMR spectra of the complexes are summarized in Table 2.
13C NMR spectra of the chloro-phenylantimony(III) dithiocarbamate derivatives 1–4
and phenylantimony(III) bis(dithiocarbamate) derivatives 5–8 provide useful information
about the mode of bonding in these compounds. The comparative study of 13C NMR
spectra of the monophenylantimony chloro- and bis(dithiocarbamate) complexes 1–8 with
the corresponding sodium salts of dithiocarbamate exhibits a remarkable upfield shift in the

1197

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DERIVATIVES OF CYCLIC DITHIOCARBAMATES
1199
position of the CS2 carbon atom (∼20 ppm) due to bidentate behavior of the dithiocarbamate
moiety. Other carbon signals of monophenylantimony(III) chloro- and bis(dithiocarbamate)
derivatives have been observed at the expected position (Table 2).
The corrected chemical shift value δꢁ 20 and Hammett-Taft constant σR◦ 21 for phenyl
group carbons attached to the antimony atom in these derivatives have been calculated by
the relation δꢁ = Cp–Cm, where δ Cp and δ Cm are the chemical shift value of para and
meta carbon atoms of the phenyl group attached to metal atom and by the equation δꢁ =
23.06 σR◦, respectively, the δꢁ and σR◦ values are found to be negative for 1–4 and 5–8 in
a range of δ(–) 5.64 to 1.83 and δ(–) 0.07 to (–)0.24 and δ(–) 6.95 to (−)3.54 and δ(–) 0.14
to (–) 0.27, respectively, which indicates the electron release from the metal toward the
phenyl group through dπ –pπ conjugation in these derivatives and poor donor capability
of the antimony atom.
ESI MASS SPECTRA
The ESI-mass spectra of two compounds, one each from chloro-phenylantimony(III)
dithiocarbamate derivatives and phenylantimony(III) bis-dithiocarbamate have been
recorded, which exhibit monomeric nature of these compounds and their fragmentation
patterns are summarized in Table 3 and 4. In view of the above mentioned spectroscopic
evidences, which indicate a monofunctional bidentate nature of the dithiocarbamate moiety,
the following structures in which the antimony atom acquires a trigonal bipyramidal
geometry for compounds 1–4 and pseudo-octahedral geometry for compounds 5–8 due to
the presence of lone pair electrons on the antimony atom have been proposed.

1200
D. K. SHARMA ET AL.
Table 3 ESI-mass fragmention mode of compound 1
Scan no.
1.
Assignment
Mass no.
Relative abundance (%)
60.52/46.05
394.12/395.46
2.
3.
379.12/
100
351.0/352.86
3.94/2.63
4.
5.
233.65/235.18
154.37/156.13
6.57/14.47
21.05/14.43
Moity containg Sb atom is observed in 3:2 ratio.
BIOLOGICAL ACTIVITY
Sodium salts of dithiocarbamates and the corresponding chloro-phenylantimony(III)
dithiocarbamate and phenylantimony(III) bis(dithiocarbamate) derivatives were screened
against A. niger, A. flavus (fungi) and E. coli, P. aeruginosa (bacteria) to examine their
growth inhibitory potential toward the microorganisms. The results indicate that the metal
derivatives were more inhibitory than the corresponding ligands and this can be explained
by Tweedy’s chelation theory.22 According to this theory “chelation reduces the polarity of
metal atom mainly because of the partial sharing of its positive charge with donor group
and possible electron delocalization over the whole ring.” This increases the lipophilic
character of the metal chelate that favors the permeation through the lipid layer of cell
membranes. Since, the compounds inhibit the growth of microorganism, it is assumed that
the protonation of ATP and enzyme is affected in bacteria as they are unable to utilize
food for themselves or intake of nutrient decreases and subsequently growth decreases. It
Table 4 ESI-mass fragmention mode of compound 5
Scan no.
Assignment
Mass no.
Relative abundance (%)
1.
2.
3.
4.
5.
6.
519.06/520.26
345.08/346.01
317.06/314.86
240.90/237.89
215.85
11.47/8.57
8.57/5.71
11.47/8.57
20.0/14.25
100/
154.37/155.37
34.28/22.85
Moity containg Sb atom is observed in 3:2 ratio.

DERIVATIVES OF CYCLIC DITHIOCARBAMATES
1201
is also observed that the concentration of compounds is an important factor too by which
the inhibition of growth is affected. Growth is slowed down at lower concentration, while
at higher concentration more enzymes become inhibited, leading to a quicker death of
the microorganism. The observed results seem to conclude that the phenylantimony(III)
bis(dithiocarbamate) possess more cytotoxicity than the phenyl chloro-antimony(III) dithio-
carbamate and the free dithiocarbamate ligand moiety. Figures S1 and S2 (Supplemental
Materials posted online only) show photographs of the results of the antibacterial tests.
EXPERIMENTAL
All reactions were carried out under moisture free environment. All glassware was
carefully dried prior to use. Benzene and n-hexane were dried by refluxing over sodium
immediately prior to use.
Phenylantimony(III) dichloride23 and sodium salt of cyclic dithiocarbamates24 have
been synthesized by the literature method. Antimony and sulfur were estimated by iodo-
metric and gravimetric25 methods, respectively.
IR spectra of 1–8 have been recorded as Nujol mull using KBr pallets in the range
4000–400 cm−1 on a FT-IR spectrophotometer (Shimadzu, 8400s). The 1H and 13C NMR
spectra have been recorded on a Jeol-FTAL 300 MHz spectrometer in CDCl3 solutions,
using TMS as an internal reference.
Chloro Phenylantimony(III) Complexes of Dithiocarbamate
The reaction mixture containing equimolar amount of sodium salt of piperidine
dithiocarbamate (0.92 g) and PhSbCl2 (1.36 g) in benzene (∼50 mL) was stirred for ∼6 h at
r.t. (∼25 ◦C). The NaCl thus formed was filtered off and the excess of solvent was removed
from the filtrate under reduced pressure to yield the title compound as a white solid in
quantitative yield. The product was recrystallized from benzene/n-hexane. Analysis found:
Sb, 30.97; S, 16.25%; calculated for C12H15SbS2NCl: Sb, 30.85; S, 17.05%. Compounds
2–4 have been synthesized by the same method. Their synthetic and analytical details are
summarized in Table 5.
Phenylantimony Bis(dithiocarbamates)
A benzene solution (∼50 mL) of PhSbCl2 (1.03 g) was added to piperidinium dithio-
carbamate (1.41 g) in a 1:2 molar ratio. The reaction mixture was stirred for ∼6 h at r.t.
(∼25 ◦C). The NaCl thus formed was filtered off and the excess of the solvent was removed
from the filtrate under reduced pressure to yield the title compound as a yellow colored solid
in quantitative yield. Analysis found: Sb, 24.17; S, 12.34 calculated for C18H25SbN2S4: Sb,
23.87; S, 13.95%. The compounds 6–8 were synthesized by the same method. Synthetic
and analytical details are summarized in Table 5.
Test for Antifungal Activity
For the antifungal bioassay, two fungi were used: A. flavus (MTCC-2456) and A. niger
(MTCC 282). The organisms were obtained from the Microbial Type Culture Collection
(MTCC) and Gene Bank, Institute of Microbial Technology (imtech), Chandigarh.

1202

DERIVATIVES OF CYCLIC DITHIOCARBAMATES
1203
Table 6 MIC of ligand and corresponding organoantimony(III) derivatives 1–8 against bacteria and fungi
Compound and Ligand
E. coli
P. aeruginosa
A. niger
A. flavus
1
2
3
4
5
6
7
8
45.9 0.09
41.2 0.01
44.9 0.06
53.2 0.19
39.3 0.02
37.7 0.09
43.1 0.05
46.3 0.19
60.7 0.2
29.1 0.02
31.1 0.04
31.9 0.08
58.6 0.19
24.5 0.06
21.4 0.12
30.6 0.08
51.2 0.29
62.3 0.06
40.2 0.08
36.8 0.18
53.3 0.21
53.6 0.90
49.6 1.12
51.6 0.79
59.2 1.0
33.7 0.90
34.7 1.39
41.5 0.94
47.1 1.0
35.1 1.10
41.5 1.09
47.1 0.66
54.5 0.98
27.9 0.88
33.8 0.82
31.1 1.0
42.1 0.98
57.2 0.10
44.1 1.2
Pipdtc
4-MePipdtc
Morphdtc
N-mepzdtc
65.08 0.08
53.6 0.90
57.7 1.9
52.4 1.5
50.2 0.18
40.8 0.20
45.2 0.24
40.6 0.19
45.1 0.20
Test for Antibacterial Activity
Two gram negative bacteria, Escherichia coli (MTCC 1652) and Pseudomonas aerug-
inosa (MTCC 2584) were used. The organisms were obtained from the Microbial Type
Culture Collection (MTCC) and Gene Bank, Institute of Microbial Technology (IMTECH),
Chandigarh.
Microdilution Test
The minimum inhibitory and bactericidal concentrations (MICs and MBCs; Table 6)
were determined using 96-well micro plates. The bacterial suspension was adjusted with
sterile saline and the compounds to be investigated were dissolved in LB growth medium
(100 μL) with bacterial inoculums (1.0 × 107 CFU per well) to achieve the wanted
concentrations (1 mg/mL). The microplates were incubated for 72 h at 24 ◦C.
The lowest concentrations without visible growth (at the binocular microscope) were
defined as concentrations that completely inhibited bacterial growth (MICs). The optical
density of each well was measured at a wave length of 655 nm by microplate reader
(perlong, ENM 8602) and compared with a blank and positive control. Streptomycin and
ampicillin were used as positive controls (1mg/mL DMSO).
All experiments were performed in duplicate and repeated three times.
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