Synthetic aspects, spectral, thermal studies and antimicrobial screening on bis(N,N-dimethyldithiocarbamato-S,S′)antimony(III) complexes with oxo or thio donor ligands

Article abstract of DOI:10.1016/j.saa.2014.03.054

The bis(N,N-dimethyldithiocarbamato-S,S′)antimony(III) complexes have been obtained by the reaction of chloro bis(N,N-dimethyldithiocarbamato-S, S′)antimony(III) with corresponding oxo or thio donor ligands such as sodium benzoate 1, sodium thioglycolate

Full text of DOI:10.1016/j.saa.2014.03.054

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 130 (2014) 230–237
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Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthetic aspects, spectral, thermal studies and antimicrobial screening
on bis(N,N-dimethyldithiocarbamato-S,S0)antimony(III) complexes with
oxo or thio donor ligands
⇑
H.P.S. Chauhan , Jaswant Carpenter, Sapana Joshi
School of Chemical Sciences, Devi Ahilya University, Takshashila Campus, Khandwa Road, Indore 452001, India
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Mixed bis(N,N-dimethyldithio-
carbamato-S,S0)antimony(III)
complexes.
The complexes adopted distorted
octahedral geometry with lone pair of
electrons.
These are crystalline in nature, nano-
ranged and having monoclinic crystal
system.
Antimony sulfide was a final
decomposition product upon thermal
decomposition.
These showed a greater or equal
antimicrobial activity than the
standard drugs.
a r t i c l e i n f o
a b s t r a c t
The bis(N,N-dimethyldithiocarbamato-S,S0)antimony(III) complexes have been obtained by the reaction of
chloro bis(N,N-dimethyldithiocarbamato-S,S0)antimony(III) with corresponding oxo or thio donor ligands
such as sodium benzoate 1, sodium thioglycolate 2, phenol 3, sodium 1-propanethiolate 4, potassium
thioacetate 5, sodium salicylate 6, ethane-1,2-dithiolate 7 and disodium oxalate 8. These complexes have
been characterized by the physicochemical [melting point, molecular weight determination and elemen-
tal analysis (C, H, N, S and Sb)], spectral [UV–Visible, FT-IR, far IR, NMR (1H and 13C)], thermogravimetric
(TG & DTA) analysis, ESI-Mass and powder X-ray diffraction studies. Thermogravimetric analysis of the
complexes confirmed the final decomposition product as highly pure antimony sulfide (Sb2S3) and
powder X-ray diffraction studies show that the complexes are in lower symmetry with monoclinic crystal
lattice and nano-ranged particle size (11.51–20.82 nm). The complexes have also been screened against
some bacterial and fungal strains for their antibacterial and antifungal activities and compared with
standard drugs. These show that the complexes have greater activities against some human pathogenic
bacteria and fungi than the activities of standard drugs.
Article history:
Received 29 December 2013
Received in revised form 10 March 2014
Accepted 20 March 2014
Available online 13 April 2014
Keywords:
Antimony(III)
Dithiocarbamate
Thermogravimetric
Powder XRD
Antimicrobial
Antimony sulfide
Ó 2014 Elsevier B.V. All rights reserved.
Introduction
Dithiocarbamates owe special significance due to their wide
spread applications such as vulcanization additives, stabilizers for
PVC, nitrogen–oxygen trapping agents, chelating agents of heavy
⇑
Corresponding author. Tel.: +91 731 2460208 (office), mobile: +91
9826219748; fax: +91 731 2365782.
E-mail address: hpsc@rediffmail.com (H.P.S. Chauhan).
http://dx.doi.org/10.1016/j.saa.2014.03.054
1386-1425/Ó 2014 Elsevier B.V. All rights reserved.

H.P.S. Chauhan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 130 (2014) 230–237
231
metals, lubricants and catalysts [1–4]. They have also been used as
biologically active molecules [4,5–9] such as fungicides, bacteri-
cides, anticancer agents [10–12] and as arrestors of human immu-
nodeficiency virus (HIV) infections such as AIDS [13–15]. The
antimicrobial effect of dithiocarbamates has been reported to arise
by the reaction of HS-groups with physiologically important
enzymes by transferring the alkyl group of the dithioester to the
HS-function of the enzyme [19,20].
[42]. Tris(N,N-dimethyldithiocarbamato-S,S0)antimony(III) and
chlorobis(N,N-dimethyldithiocarbamato-S,S0)antimony(III)
were
prepared by the method reported in the literature [40,43].
Synthesis of new complexes
Synthesis of compound 1–6 in 1:1 M ratios
Chlorobis(N,N-dimethyldithiocarbamato-S,S0)antimony(III)
These are versatile ligands with remarkable diversities in their
bonding and coordination pattern with main group metals [16–
21] and have been widely studied [1–4,5–9]. A number of metal
dithiocarbamate complexes have been used in analytical chemis-
try [22], as antioxidants [23,24], polymer photo stabilizers [25]
and precursor for creating sulfide film semiconductors [26]. Triva-
lent antimony compounds have also been used as drugs for the
treatment of laishmaniasis span more than 50 years [27,28]. Anti-
mony metal complexes containing SbAS bonds have been widely
used in industrial processes [29] as well as antimony derivatives
of carboxylic and phenolic ligands have also been used as anti-
wear agents or multifunctional additive to lubricants [30]. Ther-
mal degradation of such type of complexes yield highly pure
binary antimony sulfide (Sb2S3) as final degradation product,
which is a kind of semiconductor with its interesting high ther-
moelectric power. It is a layer-structured direct band gap semi-
conductor with orthorhombic crystal structure [31] and
considered a promising material for solar energy owing to its
band gap that covers the range of the solar spectrum [32]. It has
been extensively investigated for its special applications as a tar-
get material for microwave devices [33], television cameras,
switching devices [34], rechargeable storage cells [35] and various
optoelectronic devices [36].
In view of the wide range of applications and to keep forward
the our research on the design, characterization and development
of new biologically active agents containing group 15 metals [37–
41], we have synthesized new mixed antimony(III) dimethyldi-
thiocarbamato complexes with oxo or thio donor ligands and
characterized by a variety of analytical techniques: physicochem-
ical [melting point, molecular weight determination and elemen-
tal analysis (C, H, N, S and Sb)], spectral [UV–Visible, FTIR, far IR,
NMR (1H and 13C)], thermal (TGA, DTA and ESI-Mass) analysis and
powder X-ray diffraction studies. The free ligands and their anti-
mony complexes have also been screened for their bactericidal
and fungicidal effects. These exhibit higher bactericidal and fungi-
cidal effect in comparison to free ligands and some standard anti-
biotics used.
(1.9 g; 4.8 mmol) dissolved in hexane (ꢁ40 ml) was added to
sodium benzoate 1 (0.7 g; 4.8 mmol) drop-wise. The reaction mix-
ture was refluxed for ꢁ5 h. It was then cooled and precipitated
sodium salt was filtered off. The filtrate was reduced under vac-
uum to obtain the product (Scheme 1).
Compounds (2–6) were also synthesized by adopting the simi-
lar procedure.
Synthesis of compound 7 and 8 in 2:1 M ratios
The hexane solution (ꢁ40 ml) of chlorobis(N,N-dimethyldithio-
carbamato-S,S0)antimony(III) (2.6 g; 6.6 mmol) was added drop-
wise to hexane solution of ethane-1,2-dithiol 7 (0.3 g; 3.3 mmol).
The reaction mixture was refluxed for ꢁ5 h followed by filtration.
The product was obtained by reducing the solvent under vacuum.
The compound 8 have also been prepared by similar procedure. All
pertinent analytical and physicochemical data have been summa-
rized in Table 1.
Antimicrobial evaluation
Test micro-organism strains
The ligands used and their synthesized complexes were
screened in vitro for their antimicrobial activities against four
human pathogenic bacterial species [Staphylococcus aureus (ATCC
9144) (G+ve), Bacillus subtilis (ATCC 6051) (G+ve), Escherichia coli
(ATCC 9637) (Gꢂve) and Pseudomonas aeruguinosa (ATCC 25619)
(Gꢂve)] and two plant fungal species [Aspergillus niger (ATCC
9029) and Trichoderma ressie (ATCC 164)] by using the well diffu-
sion method [37,44]. Standard drugs such as chloramphenicol
and terbinafine were used as a reference for antibacterial and anti-
fungal screening respectively.
Method
The compound was dissolved in DMF, to get 200
tion. Further progressive double dilutions were performed to
obtain the required concentrations of 100 and 50
g mLꢂ1. A
l
g mLꢂ1 solu-
l
0.5 mL solution of the each investigated micro-organisms was
added to a sterile nutrient agar (for bacteria)/dextrose agar (for
fungi) medium just before solidification, then poured onto sterile
Petri dishes (9 cm in diameter) and left to solidify. Using sterile
cork borer (6 mm in diameter), three holes (wells) were made in
each dish and then 0.1 mL of tested compound dissolved in DMF
Experimental
Material and methods
The precursors and complexes form are highly moisture sensi-
tive; therefore, all the experimental manipulations have been car-
ried out under moisture free conditions. Antimony(III) chloride (E.
Merck) was purified by distillation before use. Sodium dim-
ethyldithiocarbamate (Aldrich) and ligands [sodium benzoate,
sodium thioglycolate, phenol, sodium 1-propanethiolate, potas-
sium thioacetate, sodium salicylate, ethane-1,2-dithiol and diso-
dium oxalate (all Aldrich and E. Merck)] were used as received
without further purification. Solvent (hexane, dichloromethane,
chloroform, acetonitrile, etc.) were purified by standard methods
(50, 100 and 200 l
g mLꢂ1) was poured into these holes. Finally
the dishes were incubated at 37 °C (24 h) for bacteria and at
30 °C (72 h) for fungi, where clear or inhibition zones were
detected around each hole (Fig. S1a and b). Inhibitory activities
were measured (in mm) as diameter of the inhibition zones.
A quantity of 0.1 ml DMF alone was used as a control under the
same conditions for each organism and by subtracting the diame-
ter of inhibition zone resulting with DMF from that obtained in
each case, both antibacterial and antifungal activities can be calcu-
lated as a mean of three replicates.
Scheme 1. Synthetic route of compound 1.

232
H.P.S. Chauhan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 130 (2014) 230–237
Table 1
Analytical and physicochemical data of bis(N,N-dimethyldithiocarbamato-S,S0)antimony(III) complexes.
Compound
Yield (%)
Empirical formula M.W.
g/mol found (calc.)
M.P. (°C)
Color and state
Elemental analysis (%) found (calc.)
C
H
N
S
Sb
1
2
3
4
5
6
7
8
91
47
45
68
86
78
82
59
C
13H17N2O2S4Sb
97
Yellow solid
32.22
(32.31)
3.45
(3.55)
5.71
(5.80)
26.35
(26.54)
25.01
(25.19)
481.13 (483.31)
C8H15N2O2S5Sb
448.51 (453.30)
120a
–
Whitish solid
21.08
(21.20)
3.25
(3.34)
6.11
(6.18)
35.28
(35.37)
26.59
(26.86)
C12H17N2OS4Sb
449.95 (455.30)
Yellow semi-solid
Light yellow solid
Yellow solid
31.48
(31.66)
3.56
(3.76)
6.08
(6.15)
28.01
(28.17)
26.61
(26.74)
C9H19N2S5Sb
434.49 (437.35)
205a
206
107a
137
–
24.58
(24.72)
4.29
(4.38)
6.38
(6.41)
36.48
(36.66)
27.67
(27.84)
C8H15N2OS5Sb
433.29 (437.30)
21.81
(21.97)
3.33
(3.46)
6.34
(6.41)
36.36
(36.66)
27.71
(27.84)
C
13H17N2O3S4Sb
Light yellow solid
Yellow solid
31.22
(31.27)
3.38
(3.43)
5.49
(5.61)
25.51
(25.69)
24.13
(24.39)
495.52 (499.31)
C
14H28N4S10Sb2
20.43
(20.59)
3.41
(3.46)
6.78
(6.86)
39.21
(39.27)
29.65
(29.82)
812.50 (816.57)
C14H24N4O4S8Sb2
809.22 (812.40)
White semi-solid
20.51
(20.70)
2.91
(2.98)
6.81
(6.90)
31.41
(31.58)
29.73
(29.98)
a
Decomposed.
Analytical methods and physical measurements
transition as a second band between 300 and 312 nm and third
one of low intensity band appeared at 340–360 nm probably due
to n–pꢃ or charge transfer transition involving the transition of
an electron of the lone pair of the sulfur atom to an antibonding
Antimony was estimated iodometrically and sulfur was esti-
mated gravimetrically as barium sulfate [45]. Melting points were
determined on a B10 Tech India melting point apparatus and are
uncorrected. Molecular weights were determined cryoscopically
in benzene solution. 1H (at 400 MHz) and 13C (at 100 MHz) NMR
spectra were obtained on a Brucker AVANCE-III FT-NMR spectrom-
eter in CDCl3 solution using TMS as an internal standard. Infrared
spectra (KBr) were recorded at BX series in the range 4000–
400 cmꢂ1 and far-IR spectra were recorded as a Nujol mull over
CsI disks using a Megna-IR Spectrophotometer-550 instrument in
the range 600–50 cmꢂ1. Powder X-ray diffraction studies were per-
p-orbital of dithiocarbamate group. In addition, the electronic
spectra of synthesized complexes also show medium to strong
intensity absorption bands owing to chromophoric group of the
oxo or thio donor ligands. The compound 1, 2, 5, 6 and 8 shows a
medium intensity band between 248 and 261 nm due to corre-
sponding carbonyl (C@O) group.
FTIR and far-IR
formed on diffractometer system XPERT-PRO using Cu Ka radiation
Three regions in IR spectra of the complexes are of particular
importance. The stretching frequency region 1523–1542 cmꢂ1
may be assigned to polar CN partial double bond of R2 NCS2
at a wavelength of 1.54 Å, ESI-Mass spectra were recorded with a
Waters Micromass Q-Tof Micro Mass Spectrometer and thermo-
gravimetric analysis were carried out on Mettler Toledo, model
TGA/SDTA 851e.
[47–49]. Due to asymmetric
t t
(COOꢂ) and symmetric (COOꢂ)
group appeared as medium to strong intensity bands at 1714–
1719 cmꢂ1 and 1251–1262 cmꢂ1 respectively, and another band
Results and discussion
at 1021–1027 cmꢂ1 due to
t
(CAS) determine the mode of binding
of the dithiocarbamate group in the complexes (Table 2). However,
the (CAS) band in the complexes has been splitted into two sig-
Synthesis
t
nals due to anisobidentate mode of binding [48]. In addition, the
Bis(N,N-dimethyldithiocarbamato-S,S0)antimony(III) complexes
have been synthesized by the replacement reactions of chloro-
bis(N,N-dimethyldithiocarbamato-S,S0)antimony(III) with oxo or
thio donor ligands in 1:1 or 2:1 M ratios in refluxing hexane solu-
tion for ꢁ5 h (Schemes 1 and 2).
bands appearing between 559–568 cmꢂ1 and 304–311 cmꢂ1 may
be assigned to t(SbAO) and t(SbAS) respectively [37–40,43].
NMR spectral studies
1H NMR
Electronic spectra
All the spectra of these complexes exhibit the expected pattern
without any appreciable shift from the reported data [37–40,43]
(Table 3). The CH3 protons of dimethyldithiocarbamate appeared
as a singlet at d 3.31–3.46. The complex 2 and 6 exhibits a singlet
at d 11.10 and d 10.93 due to AOH group bearing ligands. In addi-
tion, complexes also show expected proton resonance due to corre-
sponding ligand moieties. The 1H NMR spectra of the compounds 1
and 4 are shown in Figs. S2 and S3.
The electronic absorption spectral data of these mixed com-
plexes are listed in Table 2 and important characteristic bands
were tentatively assigned on the basis of earlier publication
[37,39,46]. Three characteristic absorption bands were obtained
in the UV spectra. An intense band around 248–261 nm was
observed due to the
of the dithiocarbamate group. The NCS group shows
p–
pꢃ intramolecular charge transfer transition
p–
pꢃ
Scheme 2. Synthetic route of compound 7.

H.P.S. Chauhan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 130 (2014) 230–237
233
Table 2
UV–Visible (nm) and IR (cmꢂ1) spectral data of bis(N,N-dimethyldithiocarbamato-S,S0)antimony(III) complexes.
Compound
I Band
II Band
III Band
m
(CAH)
m
(C@O)
m
Asy. (COOꢂ)
m
(CAN)
m
Sym. (COOꢂ)
m
(CAS)
m
(SbAO)
m(SbAS)
1
2
3
4
5
6
7
8
256
249
243
260
253
261
255
248
310
304
309
312
300
303
300
305
361
348
355
362
343
351
364
359
2963
2962
2960
2959
2963
2965
2960
2960
1714
1713
–
1714
1713
1535
1540
1530
1542
1523
1528
1540
1535
1256
1259
–
1025
1027
1024
1021
1027
1026
1023
1024
559
–
563
–
–
561
–
308
306
311
308
304
311
304
310
–
–
–
1719
–
–
–
1709
1719
–
1251
1255
–
1712
–
1262
568
Table 3
13
1H and C NMR spectral data of bis(N,N-dimethyldithiocarbamato-S,S0)antimony(III)
complexes.
Compound
1H NMR (ppm)
13C NMR (ppm)
1
3.42 (s, 12HACH3)
43.7 (ACH3)
7.38 (t, J = 7.2 Hz, 1H, p-CH)
7.57 (t, J = 7.2 Hz, 1H, m-CH)
8.10 (d, J = 7.2 Hz, 1H, o-CH)
128.4 (Ar C-3,5)
129.9 (Ar C-1)
130.2 (Ar C-2,6)
133.5 (Ar C-4)
170.1 (COO)
200.3 (NCS2)
2
3
3.41 (s, 12H, ACH3)
3.69 (s, 2H, ACH2 acetate)
11.10 (s, 1H, AOH)
24.1 (ASCH2)
43.9 (ACH3)
172.4 (ACOOH)
200.4 (ANCS2)
3.36 (s, 12H, ACH3)
43.1 (ACH3)
7.07 (t, J = 7 Hz, 1H, m-CH)
7.11 (t, J = 7 Hz, 1H, p-CH)
7.38 (d, J = 7.2 Hz, 1H, o-CH)
115.2 (Ar C-2,6)
120.3 (Ar C-4)
129.5 (Ar C-3,5)
156.3 (Ar C-1)
199.5 (ANCS2)
4
1.02 (t, J = 7.4 Hz, 3H, ACH3 ligand)
1.70 (m, 2H, ACH2CH3)
12.42 (ACH3 ligand)
21.15 (ACH2A)
Fig. 1. Powder X-ray diffraction pattern of compound 1.
2.65 (t, J = 7.2 Hz, 2H, ASCH2A)
3.40 (s, 12H, ACH3 of dtc)
27.38 (ASCH2A)
43.83 (ACH3 of dtc)
200.1 (ANCS2)
rized in Table 4, S1 and S2. The complexes have been identified as
a
monoclinic crystal lattice with unit cell volume
5
6
2.20 (ACH3 ligand)
3.31 (ACH3 of dtc)
32.7 (ACH3 ligand)
44.1 (–CH3 of dtc)
196.3 (ACO)
V = 400.06 ꢄ 10ꢂ8 cmꢂ3 (1), V = 1028.02 ꢄ 10ꢂ8 cmꢂ3 (2) and
V = 833.70 ꢄ 10ꢂ8 cmꢂ3 (4). The mean crystallite size can be
determined from the full width at half-maximum (FWHM) of the
diffraction peaks using Debye–Scherrer formula [50,51]:
199.8 (ANCS2)
3.40 (s, 12H, ACH3)
43.8 (ACH3)
6.85 (t, J = 7.4 Hz, 1H, Ar C-3)
6.93 (t, J = 8.4 Hz, 1H, Ar C-5)
7.39 (d, J = 7 Hz, 1H, Ar C-2)
7.88 (t, J = 8 Hz, 1H, Ar C-4)
10.93 (s, 1H, AOH)
114.1 (Ar C-1)
117.3 (Ar C-5)
119.0 (Ar C-3)
131.0 (Ar C-2)
161.6 (Ar C-4)
174.9 (Ar C-6)
199.1 (ANCS2)
Kk
D ¼
B cos h
where D is the particle size, K is a constant whose value is approx-
imately 0.9, k the wavelength of the X-ray, B the full width at half-
maximum and h is the Bragg angle. The particle size of the com-
plexes found between the range of 11.51–20.82 nm characteristic
of nanoparticles. We have synthesizes mixed ligand complexes with
characteristic of both type of ligands; therefore, some deviation
between the distances (d) may exceed up to 1.08 as observed in
Table 4, which shows that synthesized complexes are in multi-
phase. Interplanar d spacing and unit cell volume of the synthesized
complexes were calculated by the formulae [52]:
7
8
3.38 (s, 4H, ASCH2)
3.62 (s, 12H,ACH3)
40.8 (ASCH2)
44.1 (ACH3)
198.2 (ANCS2)
3.46 (s, 12H, ACH3)
43.2 (ACH3)
160.4 (ACO)
198.7 (NCS2)
dtc: Dimethyldithiocarbamate; Ar: aromatic.
!
13C NMR
1
1
h2 k2sinb l2 2hl cos b
¼
þ
þ
ꢂ
c2
The 13C NMR spectra of dimethyldithiocarbamate moieties
show signals at d 43.1–44.1 due to CH3 carbon. All these complexes
also exhibit a weak signal at d 198.2–200.4 due to NCS2 carbon
resonance as well as compound 1, 2, 4, 5 and 8 exhibits an
expected weak signal between d 169.83–172.60 due to COO carbon
resonance (Table 3).
d2 sin2b
b2
a2
ac
V ¼ abc sin b
We have obtained interplaner distances matched with com-
plexes, which are equal and in some cases nearly matches with
standard diffraction card JCPDS 72-0022, 43-1978, 01-0303, 36-
2000 and 04-0118. Complexes lies under lower symmetry (mono-
clinic), which is probably due to the complex nature and lone pair
of electron present on the metal center, which does not take part in
bonding and results in distorted geometry of complexes.
Powder X-ray diffraction studies
Powder X-ray diffraction pattern for compound 1, 2 and 4 have
been obtained are shown in Figs. 1, S4 and S5 and results summa-

234
H.P.S. Chauhan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 130 (2014) 230–237
Table 4
Positive-ion ESI-Mass spectra of [(CH3)2NCS2]2SbSCH2COOH (M)
m/z (%)[Possible formula of the fragments]: 419.6 (40)
[MAH3O2]+, 417.0 (10) [MAH5O2]+, 412.9 (4) [MAC4H5]+, 360.7
(100) [MASCH2COOH]+, 338.3 (5) [MAC5H12COO]+, 320.3 (4)
[MAC6H16NO2]+, 305.5 (3)[MAC6H17N2O2]+, 285.0 (4) [MAC5H18N2S2]+,
243.2 (2) [MAC6H19N2OS2]+, 212.2 (2) [MAC6H16N2OS3]+, 200.2 (2)
[MAC7H16N2OS3]+, 186.1 (2) [MAC8H17N2O2S3]+.
The experimental data and the calculated results for powder X-ray diffraction pattern
of compound 1.
S.
no.
2
d Spacing
d Spacing
(calculated)
Relative
intensity (I/I0)
h
k
l
Theta (observed)
1
2
3
4
5
6
7
8
9
12.89 6.86
13.09 6.76
15.51 5.71
16.49 5.37
19.28 4.60
21.03 4.22
22.15 4.01
23.64 3.76
24.17 3.68
26.11 3.41
27.59 3.23
28.68 3.11
29.96 2.98
30.59 2.92
32.05 2.79
33.67 2.66
34.06 2.63
35.16 2.55
37.12 2.42
38.27 2.35
39.67 2.27
40.61 2.22
41.79 2.16
43.92 2.06
44.37 2.04
45.55 1.99
46.04 1.97
47.57 1.91
48.38 1.88
49.50 1.84
50.67 1.80
51.91 1.76
5.77
5.69
4.89
4.84
4.60
3.60
3.58
3.38
3.27
2.85
2.79
2.72
2.70
2.51
2.61
2.19
2.31
2.21
2.15
2.14
2.03
1.90
1.85
1.82
1.83
1.83
1.82
1.73
1.62
1.64
1.75
1.46
68.81
37.99
30.85
27.66
22.83
14.39
17.29
22.36
15.52
72.66
10.92
12.33
12.27
18.45
16.99
46.54
9.04
8.42
9.71
7.46
100.00
9.15
9.30
7.44
7.59
8.47
0
1
0
0
0
1
1
2
2
2
2
1
0
2
1
3
2
3
2
3
1
3
4
2
0
2
3
3
4
4
5
4
2
5
3
1
0
1
0
0
1
0
1
1
0
1
0
0
1
1
2
1
2
2
1
1
0
1
1
2
2
1
1
2
2
1
3
ꢂ1
Positive-ion ESI-Mass spectra of [(CH3)2NCS2]2SbSCH2CH2CH3 (M)
m/z (%) [Possible formula of the fragments]: 421.0 (2)
[MACH3]+, 417.0 (9) [MACH7]+, 393.2 (2) [MAC3H7]+, 364.9
(19) [MAC5H13]+, 360.7 (100) [MASCH2CH2CH3]+, 332.4 (8)
[MASC5H13]+, 303.8 (2) [MASC7H19]+, 199.5 (3) [MAC8H17N2S3]+,
186.2 (2) [MAC9H19N2S3]+.
0
0
1
ꢂ1
1
2
1
2
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
1
Thermogravimetric analysis (TG & DTA)
ꢂ2
ꢂ1
ꢂ2
1
Thermal behavior of three of the synthesized complexes (1, 2
and 4) has been analyzed in inert atmosphere in a range of
25–600 °C as shown in Table 5. Thermal degradation of the
complexes by which we analyze a change in the weight of the sub-
stance as a function of temperature or time indicates the formation
of antimony sulfide as a final decomposition product [57,58]. It
supports to the facts that the synthesized complexes may be used
as a single source precursor to obtaining such type of materials
having lots of commercial applications.
The TG and DTA curves in Figs. S6, 2 and 3 show two, four and
five steps weight losses corresponded to the compounds 1, 2 and 4,
respectively. Fig. S6 exhibits two steps weight losses. The curve
indicates that, the decomposition starts at 70 °C and continues to
decompose till 295 °C. This step corresponds to the loss of C6H5-
COO group and some other organic part of the compound. The
expected and observed mass losses are 54.01% and 55.24%, respec-
tively. The final step corresponding to the decomposition of NC
part of the dithiocarbamate and subsequent formation of ½
Sb2S3, lies in the temperature range 295–400 °C. The total expected
and observed mass losses, after complete formation of ½ Sb2S3 are
64.77% and 65.17%, respectively. The DTA profile of steps I and II
are shown as endothermic peak at 250 and 313 °C.
First step (70–195 °C) of compound 2 (Fig. 2) related to the
removal of absorbed water molecule and in second step (195–
310 °C) the CH2COOH and 4 CH3 groups have been removed with
expected (26.27%) and observed (25.68%) mass losses. The third
step (310–430 °C) corresponded to the degradation of sulfur
atoms. The final step (430–580 °C) indicates the degradation 2
NC groups followed by the formation of ½ Sb2S3. The total expected
and observed mass losses, after the complete formation of ½ Sb2S3
are 66.50% and 67.29%, respectively. The DTA profile of steps I, II, III
and IV are shown as endothermic peaks at 176, 275, 333 and
550 °C, respectively.
In the case of complex 4, we observed five steps weight losses as
shown in Fig. 3. First step of decomposition occurs within a range
of 75–180 °C with the removal of trapped water. Second step (180–
260 °C) deals with the removal of C3H7 fragment of thiopropanoate
ligand with expected (9.84%) and observed (10.28%) values of mass
losses. Third step (260–325 °C) indicates the elimination of 4 CH3
and S atoms with expected (24.69%) and observed (25.46%) mass
losses. The forth step (325–405 °C) corresponded to the removal
of 2 S atoms from the 2 NCS residues of third step. The expected
and calculated values of mass losses are 14.64 and 14.63%, respec-
tively. Final step, which corresponded to the removal of 2 NC res-
idues of the dithiocarbamate and subsequent conversion of Sb(III)
to ½ Sb2S3 lies in the temperature range (405–562 °C). The total
observed mass loss after the completion of this step was 66.72%,
while the expected mass loss was 65.19%. In the DTA curves the
decomposition of the ligands represented by the endothermic
1
ꢂ1
0
2
3
ꢂ3
2
1
ꢂ1
ꢂ2
ꢂ1
1
6.48
7.48
7.08
6.65
5.07
5.54
2
0
ꢂ3
Lattice parameter calculated a = 6.76 Å, b = 9.21 Å and c = 6.86 Å; angle b = 122.73°.
Unit cell volume V = 400.07 ꢄ 10ꢂ8 cmꢂ3; particle size = 20.82 nm.
ESI-Mass spectral studies
ESI-Mass spectra of three of the complexes, 1, 2 and 4 have
been recorded. ESI-Mass spectrometry is one of the most impor-
tant tools to determine molecular weight of the complexes [53–
55] and to identify the fragments formed during electrospray
ionization, which reveal composition and properties of the par-
ticular moiety of the complexes. Two important peaks observed
in the ESI-Mass spectrum are the base peak and the molecular
ion peak (indicating the molecular mass of the complex). In
the case of these complexes the molecular ion peak does not
appear, which may be due to the pyrolytic decomposition at
the relatively high temperature, or due to the fragmentation of
molecular ion in the ionization chamber [56]. However, all of
the three compounds show the base peak at m/z 360.7 indicating
the fragmentation of metal–ligand bond as well as strong chelat-
ing property of the dithiocarbamate than other ligands used. The
possible formulae of the fragments and their m/z ratios are as
follows:
Positive-ion ESI-Mass spectra of [(CH3)2NCS2]2SbOOCC6H5 (M)
m/z (%)[Possible formula of the fragments]: 530.4 (5)
[M+C3H9]+, 498.4 (4) [M + CH3]+, 454.3 (5) [MAC2H5]+, 417.0 (11)
[MAH2S2]+, 364.9 (13) [MAC6HCOO]+, 362.8 (64) [MAC6H3COO]+,
360.8 (100) [MAC6H5COO]+, 347.1 (23) [MAC7H8COO]+, 303.1
(10) [MAC10H17COO]+, 371.0 (26) [MAC10H18CO2S]+, 257.1 (45)
[MAC10H18CNO2S]+, 239.0 (10) [MAC10H22CN2O2S]+, 225.0 (14)
[MAC11H24CN2O2S]+, 207.0 (6) [MAC10H17N2S3]+, 193.0 (8)
[MAC11H18N2S3]+, 181.0 (6) [MAC10H17N2S3]+, 153.4 (17)
[MAC13H19N2OS3]+.

H.P.S. Chauhan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 130 (2014) 230–237
235
Table 5
164)] (Fig. S9) at three different concentrations (50, 100 and
200
g mLꢂ1).
Thermogravimetric (TG & DTA) data of compounds 1, 2 and 4.
l
Chloramphenicol and terbinafine have been used as standard
drugs and their activities have been compared with the activities
of free ligands and their antimony(III) complexes. A considerable
impact of the central metal atom of the complexes has been found
against the tested bacterial (Table S3) and fungal species (Table S4).
The results obtained by disc diffusion method indicate that, the
synthesized metal complexes have enhanced activities compared
to the free ligands, which supports that, the coordination of
ligands to the metal center increases the biochemical activities. A
comparison has been made between the antimicrobial activities
of the free ligands and their metal complexes with chlorampheni-
col (standard antibacterial drug) and terbinafine (standard anti-
fungal drug) are as follows:
Compound Steps Decomposition Mass losses
Remaining
fragments
DTAmax
(°C)
temp. range
(°C)
(%) found
(calc.)
1
2
I
II
70–295
295–400
55.24 (54.01) 2NC + ½ Sb2S3
9.93 (10.76)
250d
313d
150d
a
½ Sb2S3
I
II
70–195
195–310
4.14 (3.98)
–
25.68 (26.27) 2NCS + ½S3 + ½ 275d
Sb2S3
III
IV
310–430
430–580
25.29 (24.71) 2NC + ½ Sb2S3
12.18 (11.47) ½ Sb2S3
333d
550d
110d
218d
b
4
I
75–180
3.69 (4.12)
–
II
180–260
260–325
325–405
405–562
10.28 (9.84)
C6H12N2S5Sb
III
IV
V
25.46 (24.69) 2NCS + ½ Sb2S3 280d
14.64 (14.53) 2NC + ½ Sb2S3
12.65 (11.89) ½ Sb2S3
334d
517d
c
a
b
c
(i) The results showed that, the metal complexes exhibiting
higher antibacterial and antifungal activities than the free
ligands. It is noticeable here that, Gram-negative bacteria
E. coli shows resistance to free ligands (1–4 and 6) and P.
aeruguinosa and S. aureus to ligand 1 and 6.
Remaining material, found (calc.) = 34.83 (35.14).
Remaining material, found (calc.) = 36.84 (37.46).
Remaining material, found (calc.) = 36.97 (38.87).
Endothermic reaction.
d
(ii) It has also been observed that, the free ligands and anti-
mony(III) complexes inhibit the growth of bacteria to a
greater extent as the concentration is increased.
peaks at 228, 280, 334 and 517 °C corresponded to the second,
third, fourth and fifth step, respectively.
(iii) All the complexes showed greater or equal activities against
bacterial and fungal species than the standard drugs, chlor-
amphenicol and terbinafine.
In vitro antimicrobial studies
To evaluate the antimicrobial activities of free ligands and their
antimony(III) complexes [38], these have been screened in vitro
against four human pathogenic bacterial species [S. aureus (ATCC
9144) (G+), B. subtilis (ATCC 6051) (G+), E. coli (ATCC 9637) (Gꢂ)
and P. aeruguinosa (ATCC 25619) (Gꢂ)] (Figs. S7 and S8) and two
plant fungal species [A. niger (ATCC 9029) and T. ressie (ATCC
Structure elucidation
On the basis of strong intensity bands in the range of 1021–
1027 cmꢂ1 due to
t(CAS) indicating anisobidentate behavior of
Fig. 2. TG and DTA curves of compound 2.

236
H.P.S. Chauhan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 130 (2014) 230–237
Fig. 3. TG and DTA curves of compound 4.
dithiocarbamate group and the NMR spectra explaining the
structural framework, it may be tentatively concluded that, the
complexes adopted distorted octahedral geometry with stereo-
chemically active lone pair of electrons occupying one of the trian-
gular face of octahedra (Fig. 4). In addition, powder X-ray diffraction
studies show that, the complexes are crystalline in nature,
nano-ranged particle size (11.51–20.82 nm) and having monoclinic
crystal system, which supports to distorted octahedral geometry
and indicate the lower symmetry of the complexes.
Conclusion
The mixed bis(N,N-dimethyldithiocarbamato-S,S0)antimony(III)
complexes with oxo or thio ligands have been synthesized and
characterized by a number of physicochemical, spectral techniques
and thermal analysis as well as the biochemical activity screening
test performed against some bacterial and fungal species. It is con-
cluded on the basis of above studies that the complexes adopted
distorted octahedral geometry in which the lone pair of electrons
occupying one of the triangular face of octahedral, crystalline in
nature, nano-ranged particle size with monoclinic crystal system.
The ESI-Mass and thermal studies provided fragmentation patterns
and final degradation product as highly pure antimony sulfide.
The biochemical screening activity test results that, the com-
plexes are exhibiting higher antibacterial and antifungal activities
than the free ligands as well as these showed greater or equal activ-
ities than the standard drugs (S.D.) chloramphenicol and terbinafine.
Acknowledgements
The authors thank to University Grant Commission (UGC), New
Delhi for financial support [F.39-801/2010(SR)] for the accomplish-
ment of this work. We are also thankful to CSMCRI, Bhavanagr,
Gujarat; Sophisticated Analytical Instrumentation Facility (SAIF),
Chandigarh and SAIF, Mumbai for TGA/DTA; ESI-Mass and far IR
spectral studies, respectively. IISER, Bhopal and UGC–DAE–CSR,
Indore are gratefully acknowledged for NMR (1H and 13C) and
Powder XRD studies, respectively.
Appendix A. Supplementary material
Fig. 4. Proposed structure for (a) bis(N,N-dimethyldithiocarbamato-S,S0)anti-
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2014.03.054.
mony(III) benzoate
1 and (b) di-l-ethane-1,2-dithiolatobis(N,N-dimethyldithio-
carbamato-S,S0)antimony(III) 7.

H.P.S. Chauhan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 130 (2014) 230–237
237
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