Microwave synthesis, spectral studies, antimicrobial approach, and coordination behavior of antimony(III) and bismuth(III) compounds with benzothiazoline

Article abstract of DOI:10.1134/S1070328409030038

The reaction of 2-hydroxy-N-phenylbenzamide with 2-aminobenzenethiol yielded 2-hydroxy-N-phenylbenzamidebenzothiazoline (H₂-Saly ? BTZ/HONSH). The reaction of H₂-Saly ? BTZ with PhSbCl ₂, SbCl₃, and BiCl₃

Full text of DOI:10.1134/S1070328409030038

ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2009, Vol. 35, No. 3, pp. 179–185. © Pleiades Publishing, Ltd., 2009.
Microwave Synthesis, Spectral Studies, Antimicrobial Approach,
and Coordination Behavior of Antimony(III) and Bismuth(III)
Compounds with Benzothiazoline1
K. Mahajan, M. Swami, and R. V. Singh*
Department of Chemistry, University of Rajasthan, Jaipur, 302004, India
*e-mail: rvsjpr@hotmail.com
Received January 25, 2008
Abstract—The reaction of 2-hydroxy-N-phenylbenzamide with 2-aminobenzenethiol yielded 2-hydroxy-N-phe-
nylbenzamidebenzothiazoline (H2-Saly · BTZ/HO∩N∩SH). The reaction of H2-Saly · BTZ with PhSbCl2, SbCl3,
and BiCl3 under varied reaction conditions (microwave, as well as conventional method) gave corresponding anti-
mony(III) and bismuth(III) Schiff base compounds (substitution along with addition) in different coordination
environments. These complexes were characterized by elemental analysis, IR and NMR (1H and 13C) spectral
studies. The ligand was found to bifunctional tridentate, as well as monodentate for different starting materials of
metal (Sb/Bi), as well as for different reaction conditions, hence, suitable coordination environments and pseudot-
rigonal bipyramidal geometry for the antimony and bismuth complexes have been proposed. Their biological
activities have also been checked against many fungi and bacteria. The complexes were found to be more toxic
than the corresponding ligand.
DOI: 10.1134/S1070328409030038
1
INTRODUCTION
exhibit fungicidal [5], bactericidal [5], antifertility [5],
and pharmacological activities [6]. The coordination
chemistry, biological effects, and toxicology of antimony
and bismuth complexes, such as their requirements in
pharmacological activities, are areas of increasing
research interest [7, 8]. Antimony compounds exhibit a
broad spectrum of biological activities [9], chemothera-
peutic applications [10], and cytotoxic activities [11].
Bi(III) exhibits variable coordination numbers and often
an irregular coordination geometry. In view of the diver-
sified chelating behavior of benzothiazolines, as well as
novel biological importance of antimony and bismuth
complexes [12], it has been considered worthwhile to
synthesize, characterize some new antimony(III) and
bismuth(III) derivatives of benzothiazolines and to
investigate their physicochemical and structural features
as well as the biological activity. A comparative study
has also been made on the basis of microwave radiation
effects on compound synthesis, reports of which are
rather few in the literature. In continuation of our work,
we have studied the coordination behavior of benzothia-
zoline towards the Sb and Bi metals.
The present day industrialization has led to immense
environmental deterioration. The increasing environ-
mental consciousness throughout the world has put a
pressing need to develop an alternate synthetic approach
for biologically and synthetically important compounds.
This requires a new approach, which will reduce the
material and energy intensity of chemical processes and
products, minimize or eliminate the dispersion of harm-
ful chemicals in the environment in a way that enhances
the industrially benign approach and meets the chal-
lenges of green chemistry [1]. Microwave-assisted syn-
thesis is a branch of green chemistry. In other words,
requirement of few amount of solvents coupled with
high yields and short reaction times is often associated
with the reactions of this type and makes these proce-
dures very attractive for synthesis. In the present discus-
sion, we describe the synthesis of the metal complexes
with one Schiff base using microwave assisted tech-
nique. Benzothiazolines constitute an important class of
–NC6H4S– containing ligands. Usually benzothiazoline
ring opening is catalyzed by the presence of a metal ion
[2]. However, some reactions with benzothiazolines are
reported [3] to form addition products also. In general
biological activity of such type of ligands enhances con-
siderably on complexation with the metal atom [4]. Ben-
EXPERIMENTAL
The PhSbCl2 was prepared according to the litera-
zothiazolines and their metal chelates have been found to ture method [13]. 2-Hydroxybenzamide, 2-aminoben-
zenethiol, and trichlorobismuthane were purchased
and used as such. All the chemicals were dried and
1
The article is published in the original.
179

180
MAHAJAN et al.
purified before use. All the preparations were done
under anhydrous conditions. The purity was checked zothiazoline (L) was carried out by the condensation of
by thin layer chromatography.
Synthesis of 2-hydroxy-N-phenylbenzamideben-
2-hydroxy-N-phenylbenzamide with 2-aminothiophe-
nol in a 1 : 1 molar ratio using ethanol.
H
O
H
O
S
HS
–H2O
+
C
O
C
N
H
NH
NH
H N
2
(L)
For C19H16N2SO (HO∩N∩SH)
The reaction mixture was stirred for 3–4 h, and the
solid separated out was filtered, purified by recrystalli-
zation from ethanol, and dried in vacuo. Product is
sandy brown, m.p. 110°C, FW (found/calcd)
298.3/320.4.
anal. calcd, %:
Found, %:
N, 8.7;
N, 8.1;
S, 10.0.
S, 9.8.
The parent ligand exists in the tautomeric forms
(benzothiazoline ring as well as Schiff base):
H
O
H
O
HS
S
C
C N
N
H
N
H
N
H
(Ring form)
(Azomethine form)
For the comparison purpose, two different routes 40–60°C/0.5 mmHg for 3–4 h. The purity was further
were employed for the synthesis of the antimony and bis- checked by thinlayer chromatography using silica gelG.
muth compounds (thermal and microwave) (Table 1).
The details of these reactions and the analysis of the
resulting products are recorded in Table 1.
Synthesis of the organo-, chloroantimony(III)-,
and chlorobismuth(III)-complexes [PhSb(O«N«S) (I),
SbCl(O«N«S) (II), and BiCl(O«N«S)] (III).
Thermal method. These organo- and chloroanti-
mony(III) and chlorobismuth(III) complexes were also
synthesized by the thermal method. The reaction mix-
tures were heated under reflux for 10–15 h and filtered to
remove NaCl and the solvent was removed by the same
procedure mentioned above, which was adopted to get
the complexes.
Synthesis of antimony trichloride and bismuth
trichloride adducts MCl3 · (HO«N«SH) (M = Sb(IV),
Bi(V)).
Microwave method [14]. For the synthesis of com-
plexes, dichloromonophenylantimony(III) (or SbCl3 or
BiCl3), and sodium salt of H2-Saly · BTZ (prepared by
adding the corresponding weight of sodium to 2-hydroxy-
N-phenylbenzamidebenzothiazoline) in 5 ml of dry
methanol in 1 : 1 molar ratio were irradiated inside a micro-
wave oven at 700 W for about 5–8 min. The products were
recovered from the microwave oven and dissolved in few
ml of dry methanol. The white precipitate of sodium
Microwave method. In microwave-assisted synthesis,
chloride formed during the course of the reaction was the reaction mixtures were taken in an open borosil bea-
removed by filtration, and the filtrate was dried under ker and then irradiated for 4–7 minutes. A drastic reduc-
reduced pressure. The resulting product was repeatedly tion in the reaction time was observed due to the rapid
washed with petroleum ether and then finally dried at heating capability of microwaves. Finally, the adducts
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MICROWAVE SYNTHESIS, SPECTRAL STUDIES, ANTIMICROBIAL APPROACH
181
Table 1. Comparison of data of microwave and conventional methods
Yield, %
microwave
Solvent, ml
Time
thermal, h microwave, min
Compound
thermal
thermal
microwave
PhSb(O∩N∩S)
55
46
43
57
58
79
80
79
84
86
15
15
15
15
10
5
5
3
2
5
14
13
12
14
12
8
10
3
SbCl(O∩N∩S)
SbCl3 · (HO∩N∩SH)
BiCl(O∩N∩S)
BiCl3 · (HO∩N∩SH)
10
3
Table 2. Analytical and physical characteristics of the ligand and its antimony and bismuth derivatives
Reactant, g
starting
Contents (found/calcd), %
Cl
M.w.
(found/
calcd)
M.p.,
Compound
HO∩N∩SH
Color
°C
ligand Na
C
H
N
S
Sb
Bi
material
Sandy
brown
110
8.1/8.7 9.8/
10.0
298.3/
320.4
518.43/
517.26
476.11/
475.61
533.12/
532.53
PhSb(O∩N∩S)
SbCl(O∩N∩S)
PhSbCl2 0.869 0.125 Brown
(0.732)
178* 57.78/ 3.53/ 5.12/ 6.11/
58.05 3.70 5.42 6.20
23.19/
23.54
SbCl3
(0.461)
0.648 0.093 Red
184 47.55/ 2.45/ 5.34/ 6.45/ 7.34/ 25.45/
47.98 2.97 5.89 6.74 7.45 25.60
169 42.26/ 2.97/ 5.23/ 5.88/ 19.43/ 23.91/
42.85 3.03 5.26 6.02 19.97 23.86
SbCl3 · (HO∩N∩SH) SbCl3
(0.531)
0.746
Light
yellow
BiCl(O∩N∩S)
BiCl3
(0.823)
0.836 0.120 Gray
132 40.15/ 2.33/ 4.88/ 5.66/ 6.05/
40.55 2.50 4.98 5.70 6.30
Creamish 156 35.78/ 2.45/ 4.23/ 4.78/ 16.64/
35.90 2.54 4.41 5.04 16.73
36.98/ 562.42/
37.13 562.83
32.01/ 636.45/
32.87 635.75
BiCl3 · (HO∩N∩SH) BiCl3
(0.813)
0.826
* Decomposition temperature.
were recovered from the microwave oven, washed the oxidation of Sb(III) to Sb(V) on heating with
repeatdly with n-hexane, then with petroleum ether, and
finally dried at 40–60°C/0.5 mmHg for 3–4 h. The purity
was further checked by TLC using silica gelG.
KMnO4, the excess of which was decolorized with
H2O2. The remaining H2O2 was decomposed, and
Sb(V) was then determined iodimetrically [16]. Elec-
tronic spectra of the complexes were recorded in
methanol on a UV–160A Shimadzu spectrophotome-
ter in the range 200–600 nm. Infrared spectra of the
ligands and its complexes were scanned in the range
4000–200 cm–1 with the help of a model Nicolet Megna
FTIR–550 spectrophotometer and a model FTIR–8400 S
spectrophotometer on KBr pellets. The NMR spectra
were recorded using a JEOL-AL–300 FT NMR spec-
trometer in DMSO-d6 using TMS as the internal stan-
dard. The conductivity of the resulting derivatives was
determined at room temperature in dry DMF by the
Systronics conductivity bridge (Model 305) using a cell
having a cell constant of 0.5 cm−1. Carbon and hydrogen
analyses were performed at the Central Drug Research
Institute (Lucknow, India).
Thermal method. In this method, adducts were pre-
pared under anhydrous conditions. Diethyl ether and car-
bon tetrachloride solution of BiCl3 and SbCl3, respec-
tively, were added dropwise to a benzene solution of
H2-Saly · BTZ in a unimolar ratio at room temperature
with constant stirring. A creamish to light yellow-colored
precipitate was obtained after 12 h continuously stirring.
The precipitate was filtered off and washed with the parent
solvent twice or thrice and then with dry n-hexane.
Finally, adducts were dried under reduced pressure to
yield the desired product.
Analytical and physical characteristics of antimony
and bismuth complexes are given in Table 2.
Physical measurements and analytical methods.
The molecular weights were determined by the Rast
camphor method. Sulfur and nitrogen were estimated
gravimetrically (Messenger’s method) as BaSO4 and by
Kjeldahl’s method, respectively. Chlorine was deter-
mined by Volhard’s method. Bismuth was estimated
Antifungal screening. The antifungal activity was
evaluated against Fusarium oxysporum and Alternaria
alternata using the agar plate technique. The compounds
were directly mixed with the medium in different con-
complexometrically [15]. Antimony was estimated by centrations. Controls were also run, and three replicates
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 35 No. 3 2009

182
MAHAJAN et al.
Table 3. IR spectral data (cm–1) of the ligand and its antimony(III) and bismuth(III) derivatives
Compound
HO∩N∩SH
ν(Ph–OH)
ν(>C=N)
ν(NH)
ν(M–N)*
ν(M–O)*
ν(M–S)*
3405
3310
PhSb(O∩N∩S)
SbCl(O∩N∩S)
SbCl3 · (HO∩N∩SH)
BiCl(O∩N∩S)
BiCl3 · (HO∩N∩SH)
1620
1505
400
430
450
320
332
515
505
380
391
3310
3404
3275
3260
1630
445
230
* M = Sb or Bi.
were used in each case. The linear growth of the fungus molar ratio. The reaction proceeded with the formation
was recorded by measuring the diameter of the fungus of molecular adducts. It is shown below in Eqs. (3):
colony after four days. The amount of growth inhibition
CCl4/diethyl ether
in each of the replicates was calculated by the equation: MCl3 + HO∩N∩SH
100 × (C–T) C–1, where C and T are the diameters of the
MCl3 · (HO∩N∩SH),(3)
where M = Sb(IV), Bi(V), and HO∩N∩SH is the donor
set of the ligand.
fungus colony in the control and the test plates, respec-
tively [17].
The resulting colored solids are monomeric in nature,
as evidenced by their molecular weight determinations,
and are soluble in most of common organic solvents. Their
low molar conductivity values (8–10 Ohm–1 cm2 mol–1)
show that they are nonelectrolyte in nature. The unimolar
reaction of H2-Saly · BTZ with SbCl3 and BiCl3 in
CCl4/diethyl ether solvents at room temperature resulted
in the precipitation of simple addition compounds. Libera-
tion of HCl gas was not observed even under reflux. These
observations show that the benzothiazoline ring is not
opened during the reaction. These addition compounds
are creamish-colored to yellow solid powders. They are
soluble in common organic solvents and on heating tend
to decompose with charring.
Antibacterial screening. Antibacterial activity was
evaluated against Pseudomonas aeruginosa and
Escherichia coli by the paper disc plate method. The
nutrient agar medium (0.5% peptone, 0.15 yeast,
0.15 beef extract, 0.35 NaCl, and 0.13% KH2PO4) in dis-
tilled water (1000 cm3) was autoclaved for 20 min at
15 psi before inoculation. The 5-mm diameter paper
discs of Whatman no. 1 were soaked under different
solutions (500 and 1000 ppm) of the compounds, dried,
and then placed in the Petri plates previously seeded with
the test organisms. The plates were incubated for 24 h at
28 2°C, and the inhibition zone around each disc was
measured [17].
The UV spectrum of the benzothiazoline HO∩N∩SH
consists of two broad bands centered at 260 and 310 nm
characteristics of the cyclic forms of the ligand. These
bands arise out of π–π* (benzenoid) transitions. The
band in the range of 320–398 nm due to the n–π* elec-
tronic transition of the azomethine group is observed in
the spectra of the substitution complexes I–III, which
remains absent in the free ligand, thus proving the ring
form of the benzothiazoline present in L.
RESULTS AND DISSCUSSION
The elemental analysis and spectral data are consis-
tent with the formulation of compounds I–V. The unimo-
lar reactions of SbCl3, PhSbCl2, and BiCl3 with the
sodium salt of the H2-Saly · BTZ in a methanol solution
proceed with the formation of M
N, M–S, and M–O
bonds, yielding the substitution products. The reaction
proceeds as shown in Eqs. (1)–(2):
The IR spectral data of the synthesized compounds
are represented in the Table 3. Absence of the ν(SH)
mode at 2610–2540 cm–1 and the presence of ν(NH)
mode at 3310 cm–1 in the spectrum of the ligand
HO∩N∩SH indicates the presence of the benzothiazoline
ring structure [18] in the ligand. The IR-spectra of the
complexes I–III show the disappearance of the NH
stretching band. In these complexes, the phenolic OH
stretching band also disappeared which was present at
~3405 cm–1 in the spectrum of the ligand, indicating the
M–O bond formation during complexation. Some new
bands observed in the regions 1630–1505, 400–450,
PhSbCl2 + HO∩N∩SH + 2Na
MeOH
PhSb(O∩N∩S) + 2NaCl,
(1)
(I)
MeOH
MCl3 + HO∩N∩SH + 2Na
MCl(O∩N∩S) + 2NaCl.
(2)
(M = Sb(II), Bi(III))
In another type of reactions, metal chlorides (SbCl3
and or BiCl3) react with the benzothiazoline in 1 : 1 505–515, 380–391, 320–332, 230–265, and 445 cm–1 for
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MICROWAVE SYNTHESIS, SPECTRAL STUDIES, ANTIMICROBIAL APPROACH
Table 4. H NMR spectral data (δ, ppm) of the ligand and its antimony(III) and bismuth(III) derivatives*
183
1
Compound
Ph–OH (bs.)
12.0
–NH (free) (bs.)
–NH (ring) (bs.)
5.20
Aromatic (m.)
HO∩N∩SH
10.60
10.58
10.60
10.61
10.57
10.62
6.54–7.59
6.58–7.65
7.26–8.03
6.58–8.06
6.71–8.05
6.81–7.95
PhSb(O∩N∩S)
SbCl(O∩N∩S)
SbCl3 · (HO∩N∩SH)
BiCl(O∩N∩S)
12.0
12.1
6.25 (deshielded)
6.17 (deshielded)
BiCl3 · (HO∩N∩SH)
* bs. – broad singlet; m. – multiplet.
ν(>C=N), ν(Sb
ν(Bi
N) [19], ν(Sb–O) [20], ν(Sb–S) [21], appreciable shift has been observed in the position of the
N) [22], ν(Bi–S) [23], and ν(Bi–O) [24],
phenolic proton (Ar–OH) signal on complexation indi-
cating that this group does not participate in bonding.
respectively. The band at 450–470 cm–1 may be assigned
to ν(Sb–Ph) [14] vibrations in PhSb(O∩N∩S) complex.
This may be interpreted in terms of the benzothiazoline
ring opening and the formation of Schiff base complexes
by the rearrangement of the ring.
The ligand (HO∩N∩SH) shows multiplets in a region
of δ 6.54–8.06 ppm attributable to aromatic protons,
which appear almost in the same position in their respec-
tive complexes.
In the case of the adducts IV and V, the presence of
ν(NH) mode of vibration indicates that the benzothiazo-
line ring remains intact [25] in the said adducts. This
band due to ν(NH) mode appears with the lowering of
~20–35 cm–1 in its position in the synthesized adducts.
This indicates the participation of the NH group in bond-
ing. This is further supported by the appearance of a new
A comparative study of the 13C NMR spectra of the
benzothiazoline ligand with the antimony and bis-
muth(III) derivatives provides useful information about
the mode of bonding. In the spectra of complexes I–III,
a downfield shift of the >C–N carbon signal, which
appears at ~162.54 ppm, confirming the formation of
M
N band. This confirms the coordination in these
adducts, taking place through nitrogen only and also
showing the monodentate behavior of the H2-Saly · BTZ
ligand. It is shown below:
M
N=C (Sb/Bi) by the rearrangement of benzothiazo-
line ring. A downfield shift in the position of the Ph–C–O
group on complexation indicates the M–O bond forma-
tion (M = Sb/Bi). The substituted phenyl ring carbons
are observed in the range δ 125.13–177.36 ppm. The
–NC6H4S– carbon signals are observed in the range
δ 127.16–150.56 ppm. A new set of signals was
observed in ranges of δ 142.36, 124.72, 127.96, 128.98,
127.34, and 123.26 ppm for complex I, assigned to the
phenyl ring carbons attached to antimony atom.
OH
H
N
C
Cl
S
HN
M
Cl
Cl
13
In the C NMR spectra of the addition compounds
1 : 1 Adduct,
IV andV, a small shift was observed in the position of the
>C–N signal as compared to the free ligand. This indi-
cates the involvement of nitrogen atom of the benzothia-
zoline in bonding. No appreciable shift has been
observed in the position of >C–OH group carbon on
complexation indicating that this group does not partici-
pate in bonding.
where M = Sb or Bi atom
1
The H NMR spectral data are represented in the
Table 4. The signal observed at δ 5.20 ppm due to the
–NH proton in the spectrum of HO∩N∩SH is found to be
absent in the complexes I–III indicating the deprotona-
tion of the NH proton during complex formation. The
phenolic (Ar–OH) proton appears at δ 12.0 ppm in the
benzothiazoline and disappears in its complexes, show-
ing the deprotonation of phenolic proton and confirming
the M–O bond formation. This clearly indicates the tri-
dentate behavior of the H2-Saly · BTZ (L). In the spectra
of compounds IV and V, NH proton becomes deshielded
and shows a downfield shift. This supports the formation
In view of the monomeric nature of these derivatives
and bifunctional tridentate I–III as well as monodentate
(adducts IV and V), behavior of the ligand in the com-
pounds as evident from the observed spectral data
(Tables 3 and 4), the following structure in which the
of the M
NH bond during adduct formation. No central atom (Bi/Sb) aquires pseudotrigonal bipyramidal
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MAHAJAN et al.
Table 5. Antifungal screening and antibacterial screening data of the ligand and its antimony(III) and bismuth(III) derivatives
Average antifungal screening (%) Average antibacterial screening (%)
(inhibition zone (mm) after 4 day; concentration in ppm) (inhibition zone (mm) after 24 h; concentration in ppm)
Compound
Fusarium oxysporum Alternaria alternata Escherichia coli Pseudomonas aeruginosa
50
100
200
50
100
200
500
1000
500
1000
HO∩N∩SH
PhSb(O∩N∩S)
SbCl(O∩N∩S)
SbCl3 · (HO∩N∩SH)
BiCl(O∩N∩S)
BiCl3 · (HO∩N∩SH) 42
34
42
41
47
54
51
49
59
50
69
85
80
71
87
70
37
43
42
35
49
47
48
52
51
53
61
68
81
71
64
82
74
7
9
9
11
10
6
9
9
13
11
8
7
7
9
48
10
8
14
10
10
15
12
geometry appears to be highly plausible. It is shown zymes. Metals can coordinate to active site residues to
below:
block substrate interaction or coordinate to residues out-
side the active site to affect structural integrity. The coor-
dination ability of metal also holds the attractive promise
of forming stronger attachments through covalent and
ionic bonds [27].
The results reveal that there is a considerable increase
in the toxicity of the complexes as compared to the
ligands. On giving a closer look at these results, a com-
mon feature, which appears is that the bioactivity
enhances due to the following points.
O
N
S
X
M
1 : 1 complex,
1. The chelation reduces the polarity and increase the
lipophilic nature of the central metal atom, which subse-
quently favors its permeation through the lipid layer of
the cell membrane. This can be well ascribed to
Tweedy’s chelation theory [28].
2. Solubility and concentration of the compounds
also play an important role in biological activity. It is
seen that lower concentration of compounds can check
the sporulation in fungi, and a higher concentration
inhibits the growth of organisms almost completely.
3. The enhanced activity of the complexes depends on
fineness of the particle size of the metal ion and the pres-
ence of the bulkier organic moieties. Furthermore, halo-
gen atoms directly attached to metal ion increases toxic-
ity to some extent and, when this halogen atom is being
replaced by a bulky ligand moiety, it enhances the activ-
ity of the whole molecule to a considerable extent [29].
4. The toxicity of antibacterial compounds against
different species of bacteria depends either on the differ-
ence in ribosomes, or the impermeability of the cell to
the antimicrobial agent [30].
where M = Sb or Bi atom, X = Ph/Cl and
HO∩N∩SH/H2-Saly · BTZ ligand.
The ligand L and its metal complexes have been
screened in vitro for their antibacterial and antifungal
activities. The results are indicative of the fact that these
compounds exhibit antimicrobial properties. These data
are represented in the Table 5. Antimicrobials can attack
various targets in microorganism, as a consequence of
which the organisms are either destroyed or have their
growth inhibited. Since the complexes inhibit the growth
of microorganisms, it is assumed that the production of
the enzymes is being affected and, hence, the microor-
ganisms are unable to utilize the food for themselves, or
the intake of ion decreases and, consequently, the growth
ceases. At lower concentrations when the enzyme
leaches out, the growth of the microorganism is arrested,
although a very small amount of enzyme is being pro-
duced, but the amount is sufficient to suffice the need of
the microorganism to grow, while higher concentrations
destroy the enzyme mechanisms by blocking any of the
metabolism pathways (viz., lipid, carbohydrate, and ami-
noacids), and the organism dies [26]. Furthermore,
enzymes seem to be a natural target for inorganic drugs,
since metals play a key structural role for many enzymes,
such as zinc metalloenzymes perturbing an endogenous
metal that is vital to enzymatic action can render such an
enzyme inactive. These disturbances can arise from
actions such as coordination of exogenous ligands to the
metal, substitution of the metal, or removal of the metal.
CONCLUSIONS
Microwave irradiation is an efficient and environ-
mentally-benign method to accomplish various inor-
ganic syntheses to afford products in higher yields in
shorter reaction periods.
N-Phenylbenzamidebenzothiazoline (HO∩N∩SH)
Inorganic complexes can also affect nonmetalloen- ligand behaves as tridentate, as well as monodentate,
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MICROWAVE SYNTHESIS, SPECTRAL STUDIES, ANTIMICROBIAL APPROACH
185
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Antimicrobial activity of the complexes and the
ligand L showed that the former are more active than the
parent ligand.
The data given in Table 5 reveal that the
PhSb(O∩N∩S) (I) and BiCl(O∩N∩S) (III) complexes
were found to be more toxic than the other complexes
and the bismuth complexes display better results than the
antimony complexes.
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AKNOWLEDGMENTS
Int. J. Chem. Sci., 2007, vol. 5, p. 1417.
The authors are grateful to Dr. Gyan Singh Shekha-
wat (Department of Bioscience and Biotechnology, Ban-
asthali University, Rajasthan) for help in interpreting the
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RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 35 No. 3 2009