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Synthetic spectral as well as in vitro antimicrobial studies on some bismuth(III) bis(N N-dialkyldithiocarbamato) alkylenedithiophosphates.

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Full Paper
Received: 28 May 2009
Revised: 14 November 2009
Accepted: 14 November 2009
Published online in Wiley Interscience: 28 January 2010
(www.interscience.com) DOI 10.1002/aoc.1609
Synthetic, spectral as well as in vitro
antimicrobial studies on some bismuth(III)
bis(N,N-dialkyldithiocarbamato)
alkylenedithiophosphates
H. P. S. Chauhan∗, Abhilasha Bakshi and Sumit Bhatiya
Mixed sulfur donor ligand complexes of the type bismuth(III) bis(N,N-dialkyldithiocarbamato) alkylenedithiophosphate,
[R2 NCS2 ]2 BiS2 POGO [where R = CH3 and C2 H5 ; G = -CH2 -C(C2 H5 )2 -CH2 -, -CH2 -C(CH3 )2 -CH2 -, -CH(CH3 )-CH(CH3 )- and -C(CH3 )2 C(CH3 )2 -] were synthesized in 1 : 1 molar ratio of bismuth(III) bis(N,N-dialkyldithiocarbamate) chloride and ammonium
alkylenedithiophosphate in refluxing benzene and characterized by melting point, molecular weight determinations, elemental
analysis (C, H, N, Bi and S) and spectral [UV, IR,NMR (1 H,13 C and 31 P) and powder X ray diffraction] studies; all these studies
were in good agreement with the synthesized complexes. These newly synthesized derivatives are yellow and brown colored
solids and are soluble in common organic solvents like benzene, chloroform, dichloromethane and DMF. Based on the
physicochemical and spectral studies, a tentative structure of these newly synthesized complexes was assigned and the average
particle size of the synthesized complexes determined by powder XRD, showing that nano range polycrystalline particles were
formed with a monoclinic crystal system. These complexes were also screened for their antimicrobial activities using the well
diffusion method. The free ligands as well as their mixed metal complexes were tested in vitro against four bacterial strains:
two Gram-positive, Staphylococcus aureus (ATCC 9144) (G+ ) and Bacillus subtilis (ATCC 6051), (G+ ) and two Gram-negative,
Escherichia coli (ATCC 9637) (G− ) and Pseudomonas aeruginosa (ATCC 25619) (G− ) to assess their antimicrobial properties. The
results were indeed positive and exhibited good antibacterial effects. Chloroamphenicol used as a standard for comparison and
synthesized complexes showed good antibacterial effects over chloroamphenicol. On the basis of these studies, the synthesized
complexes help to understand the different structural and biological properties of main group elements with sulfur donor
c 2010 John Wiley & Sons, Ltd.
ligands. Copyright Keywords: bismuth(III); dithiocarbamate; dithiophosphate; UV; IR; NMR (1 H; 13 C and 31 P); powder XRD; in vitro antimicrobial activities
Introduction
Appl. Organometal. Chem. 2010, 24, 317–325
Experimental
Materials and Methods
Sodium/ammonium dialkyldithiocarbamates and bismuth trichloride (E. Merck) were used as received. The reactants, such as
ammonium alkylenedithiophosphates[24] and bismuth(III) bis(N,Ndialkyldithiocarbamate) chloride,[22] were prepared by reported
methods. Solvents (benzene, acetone, dichloromethane, hexane,
diethyl ether, alcohol, etc.) were purified and dried by standard
methods before use.[25]
Physical Measurements
Melting points were determined on a B10 Tech India melting
point apparatus and are uncorrected. Bismuth was estimated
∗
Correspondence to: H. P. S. Chauhan, School of Chemical Sciences, Devi Ahilya
University, Takshashila Campus, Khandwa Road, Indore 452 017, India.
E-mail: hpsc@rediffmail.com
School of Chemical Sciences, Devi Ahilya University, Takshashila Campus,
Khandwa Road, Indore 452001, India
c 2010 John Wiley & Sons, Ltd.
Copyright 317
Dithiolato moieties like dithiocarbamates[1 – 6] and alkylenedithiophosphates[7 – 11] are versatile ligands and display a broad
variety of coordination patterns, leading to a great diversity
of molecular and supramolecular structures. With regards to
structural studies, these ligands often display bidentate coordination patterns, which may be isobidentate (symmetrical) or
anisobidentate (unsymmetrical) both in chelating and bridging
situations. In addition to peculiar structural properties, these
ligands continue to attract attention owing to their diverse
range of applications, such as dithiocarbamates, which have
useful applications as a sulfur source for vapor deposition and
nanoparticle growth of metal sulfide materials,[12,13] as singlesource precursors for metallo-organic chemical vapour deposition
(MOCVD) of nanosized particles of tin[14] and bismuth[15] sulfide thin films along with dithiocarbamates, alkylenedithiophosphates are well known for their antifungal and antibacterial[16,17]
properties. On the other hand despite being a heavy metal,
bismuth finds many applications in medicines and in the treatment of gastrointestinal disorders,[18,19] and has anticancer
and antitumor[20] properties. In view of the above and interesting results obtained in our laboratory[21 – 24] with mixed
sulfur ligand complexes, it is considered of interest to extend the present course of investigations to synthetic, spectral
and in vitro antimicrobial studies on some bismuth(III) bis(N,
N-dialkyldithiocarbamato)alkylenedithiophosphates.
H. P. S. Chauhan, A. Bakshi and S. Bhatiya
Table 1. Analytical and physicochemical data of bismuth(III) bis(N,N-dialkyldithiocarbamato)alkylenedithiophosphates complexes
Compound
no.
Compound (empirical formula)
1
2
Analysis (%) found (calcd)
Yield
(%)
Color
and m.p. (◦ C)
98%
Yellow
710
27.88
4.68
3.78
28.54
26.26
136
(730.04)
(27.94)
(4.69)
(3.83)
(28.60)
(26.32)
77%
Molecular weight
found (calcd)
C
H
N
Bi
S
Yellow
690
25.58
4.21
3.92
29.69
27.31
132
(702.01)
(25.64)
(4.30)
(3.99)
(29.74)
(27.37)
3
72%
Brown
691
26.75
4.44
3.84
29.11
26.79
82
(716.03)
(26.81)
(4.50)
(3.91)
(29.16)
(26.84)
4
54%
Brown
673
24.37
4.04
4.00
30.29
27.88
74
(688.00)
(24.42)
(4.10)
(4.07)
(30.34)
(27.93)
Yellow
662
23.09
3.83
4.08
30.92
28.46
150
(673.99)
(23.14)
(3.88)
(4.15)
(30.97)
(28.51)
Yellow
635
20.34
3.37
4.28
32.26
29.72
190
(645.95)
(20.43)
(3.43)
(4.33)
(32.32)
(29.75)
5
6
7
56%
58%
52%
complexometrically and sulfur was estimated gravimetrically
as barium sulfate.[26] Molecular weights were determined
cryoscopically in benzene. Elemental analysis (C, H and N)
was performed on a Carlo Erba 1108 C, H, N analyzer at the
Sophisticated Analytical Instrumentation Facility, CDRI, Lucknow,
India. Infrared spectra were recorded on a Perkin Elmer Model
Spectrum GX in the range 4000–400 cm−1 . The UV spectra
were recorded in chloroform solution at room temperature on a
Shimadzu UV-1700 UV–vis spectrophotometer within the range
400–200 nm. NMR spectra were recorded in CDCl3 solution on
a Bruker Avance II 400 NMR spectrometer, operated at 400.13,
100.62 and 161.9 MHz for 1 H, 13 C and 31 P, respectively, using TMS
and H3 PO4 as standards. Powder X-ray diffraction patterns of a few
complexes were recorded on diffractometer system XPERT-PRO
using CuKα radiation at a wavelength of 1.54 Å.
Brown
652
21.75
3.60
4.19
31.58
28.07
160
(659.97)
(21.82)
(3.66)
(4.24)
(31.63)
(29.12)
removed by filtration. The solvent was stripped off under reduced
pressure to obtain a pale yellow solid, which was crystallized
in 1 : 1 benzene–n-hexane mixture (yield = 0.60 g, 98%, m.p. =
136 ◦ C). All other complexes were synthesized by adopting similar
methods. The pertinent analytical and physicochemical data for
these complexes are summarized in Table 1.
Antimicrobial Studies
Test microorganism strains
Strains of four human pathogenic bacterial species, two Grampositive [Staphylococcus aureus (ATCC 9144) (G+ ) and Bacillus
subtilis (ATCC 6051) (G+ )] and two Gram-negative [Escherichia
coli (ATCC 9637) (G− ) and Pseudomonas aeruginosa (ATCC 25619)
(G− )] were screened for their in vitro antimicrobial studies.
Synthesis of Bismuth(III) bis(N,N-diethyldithiocarbamato)-2,
2-diethylpropylenedithiophosphate
Method
To the benzene solution of ∼30 ml of bismuth(III) bis(N,Ndiethyldithiocarbamate) chloride (0.45 g, 0.83 mmol) was added
the ammonium-2,2-diethylpropylenedithiophosphate (0.20 g,
0.83 mmol) and the contents were refluxed for ∼6 h. The
contents were cooled and precipitated ammonium chloride was
The compounds were screened for their in vitro antimicrobial
studies by the well diffusion method.[24] The compound was
dissolved in DMF to obtain a 200-µg ml−1 solution. Further
progressive double dilutions were performed to obtain the
required concentrations of 100 and 50 µg ml−1 . At first nutrient
318
Scheme 1. Reaction of bismuth(III) bis(N,N-dialkyldithiocarbamate) chloride with ammonium salts of alkylenedithiophosphate in an equimolar
ratio.
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c 2010 John Wiley & Sons, Ltd.
Copyright Appl. Organometal. Chem. 2010, 24, 317–325
Studies on some bismuth(III) bis(N,N-dialkyldithiocarbamato)alkylenedithiophosphates
Scheme 3. Zone of inhibition observed against P. aeruginosa
{at 200 µg ml−1 of compound [(C2 H5 )2 NCS2 ]2 BiS2 POGO, G = CH2 − C(Et)2 − CH2 -}.
Scheme 2. Zone of inhibition observed against S. aureus {at 200 µg ml−1
of compound [(CH3 )2 NCS2 ]2 BiS2 POGO, G = -CH2 − C(Et)2 − CH2 -}.
agar media and broth were prepared in the required amounts. A
0.5 ml aliquot of the investigated microorganism cultured in broth
was added to a sterile nutrient agar just before solidification, then
poured into sterile Petri dishes (12 cm in diameter) and left to
solidify. Using a sterile cork borer (6 mm in diameter), three holes
were made in each dish and then 0.1 ml of the tested compound
dissolved in DMF (50,100 and 200 µg ml−1 ) was poured into these
holes. Finally the Petri dishes were incubated at 37 ◦ C for 24 h.
Distinct or light inhibition zones were observed, as shown in
Scheme 2 to Scheme 5, around each hole, which were measured
in millimeters as the diameter of inhibition zones by taking the
mean Dimethyl formamide (DMF) exhibiting no effect on the
organism tested.
Results and Discussion
Scheme 4. Zone of inhibition observed against S. aureus {at 100 µg ml−1
of compound [(CH3 )2 NCS2 ]2 BiS2 POGO, G = -CH2 − C(Et)2 − CH2 -}.
Synthesis
Mixed bismuth(III) bis(N,N-dialkyldithiocarbamato)alkylenedithiophosphates were synthesized by the reactions of bismuth(III)
bis(N,N-dialkyldithiocarbamate) chloride with ammonium salts of
respective alkylenedithiophosphoric acids in an equimolar ratio in
refluxing benzene for ∼6 h (Scheme 1). These compounds are yellow and brown colored solids and are soluble in common organic
solvents like benzene, chloroform, DMF and dichloromethane.
These compounds along with their analytical and physicochemical
data are summarized in Table 1.
Electronic Spectra
Appl. Organometal. Chem. 2010, 24, 317–325
Infrared Spectra
The IR spectra of these complexes recorded in the range
4000–400 cm−1 and the assignments, made on the basis of
previous reports,[21 – 24] are summarized in Table 2. All these
complexes showed a single band in the region 1496–1545 cm−1
due to ν(C–N) and another band at 1010–1050 cm−1 due to
ν(C–S) indicating anisobidentate behavior of the carbamate
group in these complexes.[21,22] The bands of medium to sharp
intensity present in the region 950–998 and 791–850 cm−1
were assigned to (P)–O–C and P–O–(C) stretching vibrations,
c 2010 John Wiley & Sons, Ltd.
Copyright www.interscience.wiley.com/journal/aoc
319
The electronic absorption spectral data of bismuth(III) bis(N,Ndialkyldithiocarbamato)-alkylenedithiophosphate complexes are
listed in Table 2. Tentative assignments have been made with the
help of earlier publications.[21,27,28] In all the bismuth complexes,
the π –π ∗ and n–π ∗ transitions are due to dithiophosphate
moieties and π –π ∗ intramolecular charge transfer transitions
due to dithiocarbamate moieties[24] overlapping and exhibiting
the most intense broad band in the range 240–305 nm with peak
maxima at 270, 260 and 250 nm. The second band of comparatively
low intensity appears in the range 300–375 nm and is attributed
to π –π ∗ transition in the dithiocarbamate group[24] and n–π ∗ or
charge transfer transition due to dithiocarbamate moiety, in which
we get peak maxima at 310, 325, 330 and 340 nm.
H. P. S. Chauhan, A. Bakshi and S. Bhatiya
present in the region 510–562 cm−1 were due to P–S stretching
vibrations.[30]
1 H NMR
Scheme 5. Zone of inhibition observed against E. coli {at 50 µg ml−1 of
compound [(C2 H5 )2 NCS2 ]2 BiS2 POGO, G = -C(Me)2 − C(Me)2 -}.
Table 2. UV spectral data of bismuth(III) bis(N,N-dialkyldithiocarbamato)alkylenedithiophosphate complexes
UV spectral data (in nm)
Compound no.
1
2
3
4
5
6
7
I
II
270
260
260
260
250
250
250
330
330
340
330
340
325
310
respectively.[29] A sharp band in the region 910–927 cm−1 was
assigned to the ring vibrations of the dioxaphospholane and
dioxaphosphorinane rings.[29] The bands for νP S were found in
the region 650–685 cm−1 and it was observed that, in comparison
with spectra of the parent alkylenedithiophosphoric acids, there
is shifting of ∼35 cm−1 towards lower frequencies. This shifting
indicates most probably a bidentate chelation of thiophosphoryl
sulfurs to bismuth.[28] The bands of weak to medium intensities
1 H NMR spectral data (Table 3) of bismuth(III) bis(N,Ndialkyldithiocarbamate) complexes with alkylenedithiophosphate showed the characteristic proton resonance for the
corresponding N,N-dialkyldithiocarbamate[21,22,28,31] as well as
alkylenedithiophosphate[21,23,24] protons. The dimethyldithiocarbamate complexes showed a singlet at 3.32–3.44 ppm due
to NCH3 proton resonance while diethyldithiocarbamate complexes showed generally a complex pattern at 1.07–1.49 due
to overlapping of CH3 protons of carbamate with CH3 protons of alkylenedithiophosphate. However, a few cases showed
triplets separately for CH3 protons of carbamate, singlets for
CH3 protons of alkylenedithiophosphate and a quartet at
3.63–3.84 ppm due to NCH2 proton resonance of dithiocarbamate. The appeareance of a doublet in the six-membered
ring and a multiplet in the five-membered ring of dithiophosphate complexes was due to the coupling of OCH2 and OCH
protons with 31 P nuclei, respectively. Alkylene protons of 2,2diethylpropylenedithiophosphate showed a triplet at 0.85 for
diethyl and dimethylcarbamate groups. Dimethyldithiophosphate
group showed a singlet at 1.07 and at 1.06 for diethyl and dimethyl
carbamate groups, while 2,3-dimethyl butane showed a complex
pattern for diethyl and a singlet for dimethyldithiocarbamate
group along with this simple butane, giving a complex pattern at
1.07–1.36 ppm.
13 C NMR
The proton-decoupled 13 C NMR spectra (Table 3) of all these
complexes were recorded in CDCl3 and assignments were
made on the basis of previously reported data.[21 – 24,28] The 13 C
spectral data of the dimethyldithiocarbamate derivatives showed
a signal in the range 43.2–44.0 ppm due to methyl carbon. The
corresponding diethyldithiocarbamate showed two signals, one at
11.76–12.34 ppm and the other at 48.0–48.86 ppm due to CH3 and
NCH2 carbons, respectively. Most of these complexes showed a
weak signal at 197.16–199.20 ppm due to NCS2 carbon resonance.
The very weak signals were also observed for quaternary carbons in
a six-membered ring.[21,22,24] In the six-membered ring complexes
OCH2 carbon resonance appeared as doublet due to coupling with
phosphorus nuclei.
320
Figure 1. Powder X-ray diffraction pattern of bismuth(III) bis(N,N-diethyldithiocarbamato)-2,3-dimethylbutanedithiophosphate.
www.interscience.wiley.com/journal/aoc
c 2010 John Wiley & Sons, Ltd.
Copyright Appl. Organometal. Chem. 2010, 24, 317–325
Studies on some bismuth(III) bis(N,N-dialkyldithiocarbamato)alkylenedithiophosphates
Table 3.
1 H, 13 C and 31 P NMR spectral data for bismuth(III) bis(N,N-dialkyldithiocarbamato)alkylenedithiophosphate complexes
Compound
no.
13 C chemical shift
Compound (empirical formula)
1
1
H chemical shift (in ppm)
0.85, t, 6H (CH3 of dtp)
J = 7.8 Hz
1.35, t, 12H (CH3 of dtc)
J = 7.3 Hz
1.47, q, 4H (CH2 of dtp)
J = 7.8 Hz
3.72, q, 8H (NCH2 of dtc)
J = 7.3 Hz
4.2, d, 4H (P–O–CH2 of
dtp)J∗ = 16.1 Hz
(in ppm)
31 P chemical shift
(in ppm) (free acid)
7.0 8(CH3 of dtp)
99.05
12.25 (CH3 ofdtc)
(77.80)
22.99 (CH2 of dtp)
37.61 (q C of dtp)
48.75(CH2 of dtc)
76.5, d, (OCH2 of dtp)
J∗ = 8.1 Hz
197.9 (NCS2 of dtc)
2
1.07, s, 6H (CH3 of dtp)
1.36, t, 12H (CH3 of dtc)
J = 7.1 Hz
3.70, q, 8H (NCH2 of dtc)
J = 7.1 Hz
4.14, d, 4H (P–O–CH2 of
dtp)j∗ = 15.8 Hz
12.32 (CH3 of dtc)
21.84 (CH3 of dtp)
101.29
(78.58)
32.75 (q C of dtp)
48.84 (CH2 of dtc)
75.7, d, (OCH2 of dtp)
J∗ = 8.0 Hz
197.9(NCS2 of dtc)
3
1.34–1.49, m, 24H (CH3 of dtc
and dtp)
3.71, q, 8H (NCH2 of dtc)
J = 7.1 Hz
12.30 (CH3 of dtc)
113.24
24.53 (CH3 of dtp)
(93.07)
48.77 (CH2 of dtc)
90.03 (OC of dtp)
198.20 (NCS2 of dtc)
4
1.07–1.36, m, 18H (CH3 of dtc
and dtp)
3.65, q, 8H (NCH2 of dtc)
J = 7.1 Hz
4.65–4.71, m, 2H (P–O–CH of
dtp)
11.77 (CH3 of dtc)
114.83
15.14 (CH3 of dtp)
(95.49)
48.12 (CH2 of dtc)
77.6 (OCH of dtp)
197.79 (NCS2 of dtc)
5
0.85, t, 6H (CH3 of dtp)
J = 7.5 Hz
1.48, q, 4H (CH2 of dtp)
J = 7.5 Hz
3.42, s, 12H (NCH3 of dtc)
4.25,d, 4H (P–O–CH2 of dtp)
J∗ = 15.4 Hz
7.17 (CH3 of dtp)
100.46
23.01(CH2 of dtp)
(77.80)
37.6 3(q C of dtp)
44.05(NCH3 of dtc)
76.81 (OCH2 of dtp)
6
1.06, s, 6H (CH3 of dtp)
3.35, s, 12H (NCH3 of dtc)
4.1, d, 4H (P–O–CH2 of dtp)
J∗ = 15.9 Hz
7
1.41, s, 12H (CH3 of dtp)
3.36, s, 12H (NCH3 of dtc)
99.64
(78.58)
24.48 (CH3 of dtp)
43.89 (NCH3 of dtc)
89.79 (OC of dtp)
199.20 (NCS2 of dtc)
112.83
(93.07)
s = singlet, d = doublet, t = triplet, q = quartet, q C = quaternary carbon, dtc = dialkyldithiocarbamate and dtp = alkylenedithiophosphate, J = H–H
coupling constant, J∗ = P–O–C–H coupling constant.
321
Appl. Organometal. Chem. 2010, 24, 317–325
c 2010 John Wiley & Sons, Ltd.
Copyright www.interscience.wiley.com/journal/aoc
H. P. S. Chauhan, A. Bakshi and S. Bhatiya
Figure 2. Powder X-ray diffraction pattern of bismuth(III) bis(N,N-diethyldithiocarbamato)-2,2-diethylpropylenedithiophosphate.
Table 4. The experimental data and the calculated results for
powder X-ray diffraction pattern of the bismuth(III) bis(N,Ndiethyldithiocarbamato)-2,3-dimethylbutanedithiophosphate
2θ in
degrees
d-spacing
in angstrom,
observed
d-spacing
in angstrom,
calculated
Relative
intensity
(%)
h
k
l
10.586
11.854
17.035
25.059
26.945
28.283
31.150
33.985
36.392
69.746
78.017
8.35
7.47
5.20
3.55
3.31
3.16
2.87
2.63
2.46
1.34
1.22
8.53
7.49
5.19
4.41
3.39
3.78
2.87
3.43
2.75
0.78
0.70
100
67.09
20.74
17.18
24.20
22.93
34.71
12.14
15.63
1.20
0.75
0
0
0
1
2
1
2
2
1
8
7
1
0
2
1
0
2
1
1
0
4
9
1
2
0
2
2
2
3
1
5
9
9
Lattice parameters and angle calculated are: a = 7.87 Å or 0.78 nm,
b = 10.4 Å or 1.04 nm, c = 14.98 Å or 1.498 nm, β = 94.25◦ .
Unit cell volume of the complex: 1222.40 × 10−8 cm3 .
Table 5. The experimental data and the calculated results for
powder X ray diffraction pattern of the bismuth(III) bis(N,Ndiethyldithiocarbamato)-2,2-diethylpropylenedithiophosphate
2θ in
degrees
d-spacing in
angstrom,
observed
d-spacing
in angstrom,
calculated
Relative
intensity
(%)
h
k
l
7.664
11.035
13.123
15.259
18.908
23.062
33.300
35.944
45.097
54.845
60.500
68.484
11.53
8.02
6.75
5.80
4.69
3.86
2.69
2.50
2.01
1.67
1.53
1.37
11.52
8.03
7.8
5.80
5.2
4.0
2.28
3.05
1.71
1.30
1.25
1.20
100
14.05
25.85
14.18
21.76
17.65
4.39
3.45
1.73
0.16
0.54
0.12
1
0
0
0
0
0
4
1
6
8
8
9
1
0
1
9
1
0
3
0
4
0
4
7
0
2
2
0
3
4
4
5
4
5
6
4
Lattice parameters and angle calculated are: a = 11.82 Å or 1.18 nm,
b = 52.2 Å or 5.2 nm, c = 16.08 Å or 1.6 nm, β = 94.35◦ . Unit cell
volume of the complex: 9891.66 × 10−8 cm3 .
31 P NMR
The 31 P NMR chemical shift values (Table 3) appeared to
be dependent on the size of the heterocyclic rings. In the
spectra of these derivatives the 31 P NMR signal showed
downfield shifting of about 19–23 ppm in the corresponding dioxaphosphorinane (six-membered rings) and dioxaphospholane (five-membered rings) with respect to their parent alkylenedithiophosphoric acids,[29] 77.80–78.58 ppm for
dioxaphosphorinane (six-membered ring) and 93.07–95.49 ppm
for dioxaphospholane (for five-membered ring)], indicating
the bidentate mode of attachment of alkylenedithiophosphate
ligand.
1
1
=
d2
sin2 β
Powder X ray Diffraction Study
322
X ray powder diffraction patterns for two of the
complexes, bismuth(III) bis(N,N-diethyldithiocarbamato)-2,3dimethylbutanedithiophosphate and bismuth(III) bis(N,Ndiethyldithiocarbamato)-2,2-diethylpropylenedithiophosphate,
were recorded and are shown in Figs 1 and 2, respectively.
Average particle size of the synthesized complexes was determined with the help of the Scherrer formula,[32] in which
particle size D is defined as 0.9λ/B cosθ , where 0.9 = constant,
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λ = wavelength, B = angular width and θ = diffraction angle.
Average particle sizes of the complex determined were 34.8
and 37.9 nm respectively. Diffraction data of the complexes are
listed in Tables 4 and 5. Both of our synthesized complexes had a
monoclinic crystal lattice and XRD patterns showed that both are
polycrystalline in nature. The largest relative deviation between
the calculated and experimental d values was nearly equal to
one, which indicates that both the synthesized complexes are
multiphase complexes. Interplanar d spacing and unit cell volume
of the synthesized complexes were calculated by the formulae:
h2
k2 sin2 β
l2
2hl cos β
+
+ 2 −
2
2
ac
a
b
c
V = abcsinβ.
As our synthesized compounds are complexes, and due to the
lone pair of electrons, distortion occurs due to which it undergoes
lower symmetry, yet the characteristic and prominent peaks of
complexes and the crystal system have been identified, which are
equal and in some cases nearly match the standard diffraction
card JCPDS 48–2458 and the literature.[33 – 35] Along with these
c 2010 John Wiley & Sons, Ltd.
Copyright Appl. Organometal. Chem. 2010, 24, 317–325
Studies on some bismuth(III) bis(N,N-dialkyldithiocarbamato)alkylenedithiophosphates
Figure 3. Schematic molecular representation of bismuth(III) bis(N,N-dialkyldithiocarbamato)Alkylenedithiophosphates.
formulae, other information related to our synthesized complexes
was collected from standard books.[32]
Structural Elucidation
In IR spectra of all these bismuth complexes, the presence of a
strong and broad signal in the region 1496–1545 cm−1 due to
ν(C–N) and another band at 1010–1050 cm−1 due to ν(C S)
indicates the anisobidentate nature of dithiocarbamate ligands.
A band due to ν(P S) at 650–685 cm−1 was observed to be
shifted by ∼35 cm−1 towards lower frequency in comparison
to the parent alkylenedithiophosphoric acids, indicating anisobidentate chelation of these moieties with bismuth, which was
further confirmed by presence of only one proton decoupled 31 P
chemical shift in the range 96.68–109.69 ppm (in dioxaphosphorinane) and 102.65–114.83 ppm (in dioxaphospholane) complexes,
respectively. Hence distorted octahedral geometry, with a stereochemically active lone pair of electrons occupying one of the
triangular face of the octahedra, has been tentatively proposed
for these complexes (Figure 3).
Antimicrobial Activity
The antimicrobial activities[24] of all complexes were assayed at
the concentrations 50,100 and 200 µg ml−1 against four bacterial
species, two Gram-positive [Staphylococcus aureus (ATCC 9144)
(G+ ) and Bacillus subtilis (ATCC 6051) (G+ )] and two Gram-negative
[Escherichia coli (ATCC 9637) (G− ) and Pseudomonas aeruginosa
(ATCC 25619) (G− )]. The inhibitory effects of these complexes
against bacterial species are given in Table 6. Chloroamphenicol
was used as a standard drug for comparison. The impact of
the bismuth was found in the antimicrobial activity against
the tested bacterial species. The results obtained by the well
diffusion method indicated that the coordination compounds
have enhanced activity compared with the ligands. This indicates
that the coordinated bismuth(III) atom increases the antimicrobial
effects mainly in higher concentrations.
Results obtained by comparison with the antimicrobial activities of chloroamphenicol, free ligands and previously formed
complexes are summarized as follows:
Appl. Organometal. Chem. 2010, 24, 317–325
Conclusion
Newly synthesized mixed sulfur donor ligand complexes of
the type bismuth(III) bis(N,N-dialkyldithiocarbamato)alkylenedithiophosphates show good agreement with synthetic,
physicochemical, spectral and structural aspects. In addition,
newly synthesized complexes have nano range crystallite
sizes with a monoclinic crystal system and exhibit enhanced
antibacterial properties over free ligands, the standard antibiotic
c 2010 John Wiley & Sons, Ltd.
Copyright www.interscience.wiley.com/journal/aoc
323
1. All the metal complexes have higher or equal activity against
all micro-organisms as compared with the free ligands.
2. All the dialkyldithiocarbamate ligands possess a pronounced
antibacterial effects against all tested Gram-positive bacteria
and have less or equal activity against Gram-negative bacteria
than the antibiotic (chloroamphenicol) used. On the other
hand the free alkylenedithiophosphate ligands also exhibited
pronounced and in some cases equal or less activity against
Gram-positive bacteria than the antibiotic (chloroamphenicol)
used, while having no effect against Gram-negative bacteria.
3. All the tested complexes have greater activity than standard antibiotic and in a few cases lesser activity than
chloroamphenicol, and also exhibited greater activity against
bacterial species in comparison to free ligands.
4. As compared with bismuth(III) bis(N,N-diethyldithiocarbamato)alkylenedithiophosphates, the inhibition zones of
bismuth(III) bis(N,N-dimethyldithiocarbamato)alkylenedithiophosphates are more distinct and larger in size.
5. In some cases complexes with different concentrations
also showed equal activities against bacterial species. By
comparison of antibacterial activities of these synthesized
complexes with chloroamphenicol and their corresponding
free ligands, we found that these complexes exhibited greater
antibacterial effects over free ligands and corresponding
antibiotic used.
6. As compared with previously reported complexes,[24] these
newly synthesized derivatives showed pronounced inhibitory effect mainly at higher concentrations and a distinct inhibition zone even up to 25 mm, while some
cases showed nearly equal results with previously reported
complexes.
7. (N,N-dialkylldithiocarbamato)alkylenedithiophosphate complexes of bismuth have comparatively greater antibacterial
activity over 1,2 dithiolato complexes.[36]
H. P. S. Chauhan, A. Bakshi and S. Bhatiya
Table 6. Antibacterial activity of free ligands and their bismuth(III) bis(N,N-dialkyldithiocarbamato)alkylenedithiophosphates complexes
Zone of inhibition (in mm) by taking known concentration of complexes
Bacterial concentration in µg ml−1
+
B. subtilis (G+ )
S. aureus (G )
Compound
E. coli (G− )
P. aeruginosa (G− )
50
100
200
50
100
200
50
100
200
50
100
200
Dtc 1
8
(++)
11
(+++)
13
(+++)
8
(++)
9
(++)
12
(+++)
3
(+)
6
(++)
8
(++)
4
(+)
6
(++)
8
(++)
Dtc 2
8
(++)
11
(+++)
14
(+++)
7
(++)
9
(++)
13
(+++)
4
(+)
6
(++)
9
(++)
4
(+)
6
(++)
8
(++)
Dtp1
3
(+)
6
(++)
9
(++)
2
(+)
4
(+)
7
(++)
0
0
0
0
0
0
Dtp 2
2
(+)
4
(+)
7
(++)
2
(+)
7
(++)
9
(++)
0
0
0
0
0
0
Dtp 3
2
(+)
3
(+)
5
(+)
1
(+)
3
(+)
5
(+)
0
0
0
0
0
0
Dtp 4
2
(+)
3
(+)
5
(+)
2
(+)
4
(+)
8
(++)
0
0
0
0
0
0
1
11.5
(+++)
14.5
(+++)
15
(+++)
10.5
(++)
13
(+++)
15.7
(+++)
7
(++)
9
(++)
10.5
(++)
12.5
(+++)
15
(+++)
17.5
(++++)
2
8.5
(++)
10.7
(++)
11.2
(+++)
10.2
(++)
12
(+++)
ND
7
(++)
10
(++)
13
(+++)
18.5
(++++)
19
(++++)
23
(+++++)
3
11.3
(+++)
12.1
(+++)
12.5
(+++)
ND
10.5
(++)
10.6
(++)
10
(++)
12
(+++)
15
(+++)
12.5
(+++)
15.6
(+++)
22.5
(+++++)
4
12
(+++)
13
(+++)
17
(++++)
9
(++)
10
(++)
13
(+++)
11
(+++)
12
(+++)
ND
16
(++++)
16.5
(++++)
20
(++++)
5
15
(+++)
15.5
(+++)
17
(++++)
7
(++)
9
(++)
ND
11.2
(+++)
13
(+++)
23
(+++++)
18.6
(++++)
20
(++++)
25
(+++++)
6
18
(++++)
15
(+++)
3
(+)
22
(+++++)
17
(++++)
5
(+)
25
(+++++)
22
(+++++)
7
(++)
10.5
(++)
11
(+++)
2
(+)
11.5
(+++)
11.5
(+++)
4
(+)
15.6
(+++)
11.6
(+++)
8
(++)
14.5
(+++)
9
(++)
3
(+)
16.3
(++++)
11
(+++)
7
(++)
19.3
(++++)
19.7
(++++)
11
(+++)
17
(++++)
7
(++)
6
(++)
17
(++++)
11
(+++)
11
(+++)
17.6
(++++)
13
(+++)
12
(+++)
7
X
ND = not detected, X = chloroamphenicol, Dtc1 = (CH3 )2 NCS2 Na, Dtc2 = (C2 H5 )2 NCS2 Na, Dtp1 = OCH2 C(C2 H5 )2 CH2 OPS2 NH4 , Dtp2 =
OCH2 C(CH3 )2 CH2 OPS2 NH4 , Dtp3 = OC(CH3 )2 C(CH3 )2 OPS2 NH4 , Dtp4 = OCH(CH3 )CH(CH3 )OPS2 .
Inhibition values beyond control are + = 1–5 mm, ++ = 6–10 mm, +++ = 11–15 mm, ++++ = 16–20 mm and +++++ = 21–25 mm, 0 =
not active.
chloroamphenicol and some previously reported compounds.
These complexes have structural diversities and biological
properties which help in understanding the structural chemistry
and biological properties of main group elements with mixed
sulfur donor ligand complexes.
Acknowledgments
324
Financial assistance from the University Grant Commission,
New Delhi is gratefully acknowledged. We also thank the
Sophisticated Analytical Instrument Facility (SAIF) of Panjab
University, Chandigarh (for spectral data), the Central Drug
Research Institute (CDRI), Lucknow (for elemental analysis), CSMCRI
Bhavnagar (for IR studies) and the Microbiology Department
of Holkar Science College, Indore for providing antimicrobial
studies.
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