Synthesis, spectroscopic characterization, antimicrobial, pesticidal and nematicidal activity of some nitrogen-oxygen and nitrogen-sulfur donor coumarins based ligands and their organotin(IV) complexes

Article abstract of DOI:10.1002/aoc.1813

Series of new tin complexes are synthesized by classical thermal and microwave-irradiated techniques. The biologically potent ligands 3-formyl-4-chlorocoumarin semicarbazone (L¹H) and 3-formyl-4-chlorocoumarin thiosemicarbazone (L²H), were prepared by the condensation of semicarbazide hydrochloride and thiosemicarbazide in ethanol with the particular ketone by using microwave as well as conventional methods. The tin(IV) complexes have been prepared by mixing Ph₃SnCl/Me ₃SnCl/Me₂SnCl₂ in 1:1 and 1:2 molar ratios with monofunctional bidentate ligands. The structures of the ligands and their tin complexes were confirmed by the elemental analysis, melting point determinations, molecular weight determinations, IR, ¹H NMR, ¹³C NMR, ¹¹⁹Sn NMR, UV, mass spectral and X-ray powder diffraction studies. On the basis of these studies it is clear that the ligands coordinated to the metal atom in a monobasic bidentate mode, by X ^∩ N donor system. Thus, suitable trigonal bipyramidal geometry for penta-coordinated state and octahedral geometry for hexa-coordinated state have been suggested for the 1:1 and 1:2 metal compounds. Both the ligands and their complexes have been screened for their antimicrobial, pesticidal and nematicidal activities. Copyright

Full text of DOI:10.1002/aoc.1813

Full Paper
Received: 11 January 2011
Revised: 18 May 2011
Accepted: 18 May 2011
Published online in Wiley Online Library: 10 August 2011
(wileyonlinelibrary.com) DOI 10.1002/aoc.1813
Synthesis, Spectroscopic Characterization,
Antimicrobial, Pesticidal and Nematicidal
Activity of Some Nitrogen-Oxygen and
Nitrogen-Sulfur donor Coumarins based
Ligands and their Organotin(IV) Complexes
Latika Dawara and R.V. Singh∗
Series of new tin complexes are synthesized by classical thermal and microwave-irradiated techniques. The biologically
potent ligands 3-formyl-4-chlorocoumarin semicarbazone (L1H) and 3-formyl-4-chlorocoumarin thiosemicarbazone (L2H),
were prepared by the condensation of semicarbazide hydrochloride and thiosemicarbazide in ethanol with the particular
ketone by using microwave as well as conventional methods. The tin(IV) complexes have been prepared by mixing
Ph3SnCl/Me3SnCl/Me2SnCl2 in 1 : 1 and 1 : 2 molar ratios with monofunctional bidentate ligands. The structures of the
ligands and their tin complexes were confirmed by the elemental analysis, melting point determinations, molecular weight
determinations, IR, 1H NMR, 13C NMR, 119Sn NMR, UV, mass spectral and X-ray powder diffraction studies. On the basis of these
studies it is clear that the ligands coordinated to the metal atom in a monobasic bidentate mode, by X∩ N donor system. Thus,
suitable trigonal bipyramidal geometry for penta-coordinated state and octahedral geometry for hexa-coordinated state have
been suggested for the 1 : 1 and 1 : 2 metal compounds. Both the ligands and their complexes have been screened for their
c
antimicrobial, pesticidal and nematicidal activities. Copyright ꢀ 2011 John Wiley & Sons, Ltd.
Keywords: Tin(IV) complexes; Antimicrobial; Pesticidal and Nematicidal activities.
Introduction
the formation of a five-membered chelate ring. Semicarbazones
and thiosemicarbazones also have attracted special attention due
to their biological activities. These compounds present a wide
variety of biological activity such as fungicidal, bactericidal and
antiviral[11]. In the past few years organotin compounds of the
types R3SnX and R2SnX2 became well known as broad spectrum
biocides, toxic additive in molluscicides, fungicides and other
type of pesticides[12] and appeared in the literature[13] dealing
with various applied aspects. Increasing attention has also been
devoted to the organotin(IV) complexes with the Schiff base
According to the need of the society, we are increasingly aware for
the environmental impact of human activity and consequently
of the need to develop cleaner and more energy-efficient
technologies in chemical synthesis. Solvent-free reactions have
played strategic roles in methodologies of organic as well as
inorganic syntheses[1,2]. Among the most promising pathways,
microwave-assisted technique has been commonly used since
1986 for organic synthesis[3,4] and since 1989 for inorganic
synthesis[5]. The use of microwave ovens in chemical synthesis and
analysis is gaining importance, due to its ability to reduce reaction
time, improve yield and simplify procedures[6]. Schiff bases and
their structural analogues as ligating compounds containing
acyclic and cyclic imine >C N bonds are of great importance
in modern coordination chemistry[7]. Metallic complexes of Schiff
bases are biologically important and also serve as catalysts
in various chemical and photochemical reactions[8]. Coumarins
are known to exhibit anti-cancer, anti-bacterial, aggregation,
anti-mutagenic, anti-oxidant, anti-inflammatory and anti-ulcerous
activities as well as behave as lipoxygenase and cycloxygenase
inhibitors. The coumarin crux has also been reported to inhibit
DNA gyrase and T-cell activation[9]. The Schiff base complexes of
main group elements containing ligands such as semicarbazones
and thiosemicarbazones have remained a topic of considerable
current research interest[10]. They can show tautomerism and
can exist in keto/thione or enol/thiol form. Usual coordination
through oxygen or sulfur and azomethine nitrogen is observed in
ligands in view of their special antitumor activities[14–18]
.
Encouraged by the above findings, during the course of the
present investigations, synthesis of several new tin derivatives of
monofunctional bidentate ligands are reported and biological and
inorganic aspects of the resulting complexes have been studied
and discussed in brief in this paper.
Experimental
Materials and methods
Metal salts, Ph3SnCl, Me3SnCl and Me2SnCl2 as well as 4-hydroxy
coumarin were purchased from Alfa Aesar and used as such.
Ł
Correspondence to: R.V. Singh, Department of Chemistry, University of
Rajasthan, Jaipur 302004, India. E-mail: rvsjpr@hotmail.com
Department of Chemistry, University of Rajasthan, Jaipur 302004, India
c
Appl. Organometal. Chem. 2011, 25, 643–652
Copyright ꢀ 2011 John Wiley & Sons, Ltd.

L. Dawara and R. V. Singh
OH
O
Cl
O
CHO
POCl3/DMF
O
O
R-NH2
2 drops of conc. H2SO4
H
Cl
R
C
N
O
O
O
S
Where, L1H = R =
NH
C
L2H = R =
NH
C
NH2
NH2
(L1H)
3-Formyl-4-chlorocoumarinsemicarbazone
Figure 1. Synthesis and structures of the ligands.
(L2H)
3-Formyl-4-chlorocoumarinthiosemicarbazone
Solvents of analytical grade were distilled from appropriate drying
agents immediately prior to use. Molecular weights were deter-
mined by the Rast Camphor method[19]. Chlorine was estimated
by Volhard’s method. Tin was determined gravimetrically as SnO2.
Nitrogen was estimated by the Kjeldahl’s method and Sulfur was
estimated by the Messenger’s method[20]. Carbon and hydrogen
analyses of the ligands and their tin complexes were carried out
at CDRI, Lucknow. U.V. Spectra of the ligands and their complexes
were recorded with the help of 752 UV spectrophotometer. In-
frared spectra of the ligands and their complexes were recorded
with the help of Nicolet Megna FTIR-550 spectrophotometer on
KBr pellets. 1H NMR spectra were recorded on a JEOL-AL-300
FTNMR spectrometer in DMSO-d6. using TMS as the internal stan-
dard. Mass spectrum of the complex was carried out at IIT Chennai.
X-Ray powder diffraction was recorded with the help of panalytical
system having CuKα as a radiation source of wavelength 1.542AŽ
with 2 Theta 10–70Ž.
poured onto crushed ice and neutralized with sodium carbonate.
A solid product was immediately formed which was crystallized
from ethanol to give a yellow solid (80%), m.p. 115 ŽC[21]
.
Microwave assisted synthesis
The ligands were prepared by the condensation of 3-formyl-
4-chlorocoumarin (0.01 mol) with semicarbazide hydrochloride
(0.01 mol) in the presence of sodium acetate and thiosemicar-
bazide (0.01 mol). The reaction mixture was irradiated inside a
microwave oven by taking 2–3 mL of solvent. The reactions were
completed in a short period of 5–7 min. The resulting precipitate
was recrystallized with alcohol and dried under vacuum. These
were characterized and analysed before use. Elemental analyses
were conducted using the methods mentioned above and the
results were found to be in good agreement with the calcu-
lated values. The structures of the ligands have been shown in
Fig. 1.
Preparation of the ligands
Conventional thermal method
Two different routes were employed for the synthesis of the
ligands.
For comparison purpose, the above ligands were also synthesized
by the thermal method. In this method, instead of few drops of
ethanol, 100 mL of ethanol was used to dissolve the starting
materials of the ligands and the contents were refluxed for
nearly 3–4 h. The residue formed was separated out, filtered
off, washed with water, recrystallized from ethanol and finally
dried in vacuum over fused calcium chloride. A comparison
between thermal method and microwave method is given in
Table 1.
3-Formyl-4-chlorocoumarin: Phosphorus oxychloride (10 mL)
was added dropwise to a solution of dimethylformamide (DMF)
(20 mL) keeping the temperature below 5 ŽC. Solution of 4-
hydroxycoumarin (4.0 g) in DMF (10 mL) was then gradually added
tothemixturewithconstantstirringandmaintingthetemperature
of the reaction mixture below 5 ŽC. The reaction mixture was then
allowed to stand at room temperature for 2 h and then heated
on a steam bath for 1 h. After cooling, the reaction mixture was
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Synthesis, Spectroscopic Characterization, Antimicrobial, Pesticidal and Nematicidal Activity
Table 1. Comparison between microwave and thermal method
Yield (%)
Solvent(mL)
Microwave
Time
Compound
Thermal
Microwave
Thermal
Thermal(h)
Microwave(min)
L1H
83
73
73
74
77
82
69
70
69
70
85
81
82
89
86
88
82
85
80
82
100
45
40
50
50
4
2
3
3
2
3
3
2
3
2
3
17
17
12
13
4
5
8
5
5
5
7
5
6
7
6
Ph3Sn(L1)
Me3Sn(L1)
Me2SnCl(L1)
Me2Sn (L1)2
L2H
100
40
50
40
50
Ph3Sn(L2)
Me3Sn(L2)
Me2SnCl(L2)
Me2Sn (L2)2
15
13
14
17
Table 2. Analytical data and physical properties of the ligands and their metal complexes
Found (Calcd.)(%)
Melting
Mol.Wt
Found (Calcd.)
Compound
Colour
Point( ŽC)
C
H
N
S
Cl
Sn
–
(C11H8ClN3O3) L1H
(C29H22 ClN3O3Sn)
(C14H16ClN3O3Sn)
(C13H13Cl2N3O3Sn)
(C24H20Cl2N6O6Sn)
Yellow
132–135 48.65(49.73) 2.95(3.04) 15.56 (15.82)
92–95 65.23(66.67) 3.12(3.61) 6.12(6.84)
–
–
–
–
–
13.06 (13.35)
5.36(5.77)
265.23(265.81)
Light Brown
19.25(19.31) 614.54(614.78)
27.13(27.71) 428.23(428.45)
Light Yellow 147–152 38.56(39.25) 3.13(3.76) 9.18(9.81)
Light Orange 162–165 33.38(34.78) 2.38(2.92) 9.05(9.36)
8.15(8.27)
15.02(15.80) 26.13(26.45) 448.39(448.78)
10.21(10.46) 17.23(17.51) 677.95(678.06)
Yellow
112–116 41.56(42.51) 2.46(2.97) 12.03(12.39)
(C11H8ClN3O2S) L2H Brown
125–128 45.23(46.90) 2.00(2.86) 14.34(14.92) 11.13(11.8) 12.36(12.58)
–
281.35 (281.71)
(C29H22 ClN3O2SSn) Green
136–139 54.16(55.22) 2.96(3.52) 6.31(6.66)
129–133 36.84(37.83) 3.01(3.63) 9.16(9.45)
4.96(5.08) 5.36(5.62)
7.11(7.21) 7.36(7.98)
18.36(18.82) 630.25(630.73)
26.16(26.70) 444.15(444.52)
(C14H16ClN3O2SSn)
Orange
(C13H13Cl2N3O2SSn) Light Brown 146–149 32.78(33.58) 2.18(2.82) 9.00(9.04)
6.32(6.90) 15.12(15.25) 25.01(25.53) 464.35(464.94)
8.96(9.03) 9.26(9.98) 16.25(16.72) 710.06(710.19)
(C24H20Cl2N6O4S2Sn) Brown
152–156 38.26(40.59) 2.31(2.84) 11.25(11.83)
Preparation of the metal complexes
Microbiological studies
Antifungal activity
Microwave method
The antifungal activity of the standard fungicide (Flucanazone),
ligandsandcomplexesweretestedfortheireffectonthegrowthof
microbial cultures and studied for their interaction with Aspergillus
niger andFusariumoxysporumusingCzapek’sagarmediumhaving
the composition, glucose 20 g, starch 20 g, agar-agar 20 g and
distilled water 1000 mL. To this medium was added requisite
amount of the compounds after being dissolved in methanol so
as to get the certain concentrations (50, 100 and 200 ppm). The
medium then was poured into petri plates and the spores of fungi
were placed on the medium with the help of inoculum’s needle.
These petri plates were wrapped in polythene bags containing a
few drops of alcohol and were placed in an incubator at 30 š 2 ŽC.
The controls were also run and three replicates were used in each
case. The linear growth of the fungus was recorded by measuring
the diameter of the fungal colony after 96 h and the percentage
inhibition was calculated by the equation:
For the synthesis of the complexes, Ph3SnCl/Me3SnCl/Me2SnCl2
and sodium salt of the ligands (prepared by adding the cor-
responding weight of sodium to 3-formyl-4-chlorocoumarin
semicarbazone/thiosemicarbazone) in 5 mL of dry methanol
in 1 : 1 and/or 1 : 2 molar ratios were irradiated inside a mi-
crowave oven 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 chloride formed
during the course of the reaction was removed by filtration,
and the filtrate was dried under reduced pressure. The result-
ing product was repeatedly washed with petroleum ether and
then finally dried at 40–60 ŽC/0.5 mmHg for 3–4 h. The purity
was further checked by thin layer chromatography using silica
gel-G.
Conventional thermal method
% Inhibition D (C ꢁ T/C) 100
These Sn(IV) complexes were also synthesized by the thermal
method. The reaction mixtures were heated under reflux for
12–17 h and filtered to remove NaCl and the solvent was
removed by the same procedure mentioned above, which
was adopted to get the complexes. The physico-chemical
properties and analytical data of these complexes are listed in
Table 2.
Where C and T are the diameters of the fungal colony in the
control and the test plates, respectively[22]
.
Antibacterial activity
Antibacterial activity was tested against Escherichia coli and
Bacillus subtilis using the paper disc plate method[23]. Each of
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Appl. Organometal. Chem. 2011, 25, 643–652
Copyright ꢀ 2011 John Wiley & Sons, Ltd.
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L. Dawara and R. V. Singh
the compounds was dissolved in methanol and solutions of the
concentrations (500 and 1000 ppm) were prepared separately.
Paper discs of Whatman filter paper (No. 42) of uniform diameter
(2 cm) were cut and sterilized in an autoclave. The paper discs
soaked in the desired concentration of the complex solutions
were placed aseptically in the petri dishes containing nutrient
agar media (agar 20 g C beef extract 3 g C peptone 5 g) seeded
with E. coli and B. subtilis bacteria separately. The petri dishes
were incubated at 37 ŽC and the inhibition zones were recorded
after 24 h of incubation. The antibacterial activity of common
standard antibiotic Streptomycin was also recorded using the
same procedure as above at the same concentrations and solvent.
The%ActivityIndexforthecomplexwascalculatedbytheformula
as under:
poured in each petri plate (90 mm) with the help of micropipette.
Petri plates with test solution were rotated for uniformity and
were allowed to dry for 3–5 minutes. Each concentrations as
well as control in methanol were replicated thrice. 20 adults
(2–5 days old) were released in each petri plates and were kept
at 27 š 1 ŽC and 70% relative humidity. Mortality was observed
after 96 h. Adults were considered dead if they failed to respond
to stimulus by touch. Control mortality was corrected by using
Abbott’s formula[28] and LC50 is obtained by graphical method. X2
is calculated by statistical analysis.
Nematicidal activity
Preparation of inoculum[29]
Egg masses were isolated in sterile water and the eggs were
allowed to incubate in a Baermann funnel for 48–72 h. As
the juveniles hatched out of eggs, they passed through the
double layers of tissue papers and collected in a tube below. The
suspension was diluted with sterile water,stirred with a magnetic
stirrer to obtained a homogenous suspension; 5 mL of it contained
the desired number of juveniles. Nematode inculation was done
when brinjal seedlings; afterwards the holes were plugged with
soil.ThepurecultureofnematodeMeloidogyneincognitachitwood
was maintained and multiplied on brinjal plants. Fertilizer used
was Hoaglands’s complete nutrient solution, 25 mL/pot once in a
week.
% Activity Index
Zone of inhibition by test compound (diameter) ð 100
D
Zone of inhibition by standard (diameter)
Determination of Minimum Inhibitory Concentration (MIC):
Minimum Inhibitory Concentration, MIC, is the lowest concentra-
tion of the test agent that inhibits visible growth of bacteria after
18 h incubation at 37 ŽC. The determination of the MIC involves a
semi quantitative test procedure, which gives an approximation
to the least concentration of an antimicrobial needed to prevent
microbial growth. The minimum inhibitory concentration was
determined by liquid dilution method[24]. Stock solutions of the
ligands and their complexes with 10–50 mg/mL concentrations
were prepared with aqueous methanol. Inoculum of the overnight
culture was prepared. In a series of tubes, 1 mL each of complex
solutions with different concentrations were taken and 0.4 mL of
theinoculumwasaddedtoeachtubes. Further3.5 mLofthesterile
water was added to each of the test tubes. These test tubes were
incubated for 18 h and observed for the presence of turbidity. The
absorbance of the suspension of the inoculum was observed with
spectrophotometer at 555 nm. The end result of the test was the
minimum concentration of antimicrobial (test materials) which
Isolation of egg masses
Brinjal plants were uprooted after 60 days and the galls with egg
masses were washed with sterile water.Egg masses were hand-
picked out in watch glasses containing distilled water. Eggs were
counted with the help of a nematode counting dish in each egg
mass. These eggs were further treated with different 25, 50 and
100 ppm concentrations of ligands and their complexes, along
with the untreated control. The solvents used were methanol and
water.
gave a clear solution, i.e., no visual growth[25,26]
.
Results and Discussion
Insecticidal activity
The reactions of triphenyltin chloride, trimethyltin chloride and
dimethyltin dichloride with the sodium salt of ligands L1H and
L2H have been carried out in unimolar and/or bimolar ratios,
which led to the isolation of Ph3Sn(L1), Me3Sn(L1), Me2SnCl(L1),
Me2Sn(L1)2, Ph3Sn(L2), Me3Sn(L2) Me2SnCl(L2) and Me2Sn(L2)2
solids. These are soluble in DMF and DMSO. The reactions were
carried out in perfectly dry methanol and proceed smoothly with
the precipitation of NaCl.
Many insects cause damage to the stored products and other
commodities such as food, grain, paper, books, furniture, timber,
and clothing.The greatest importance of insects lies in their being
pests of crops and animals. A pest is an animal whose population
increases above certain level of economic injury and its existence
conflicts with human welfare, convenience and profit[27]
.
Larva of Corcyra cephalonica were obtained from stock culture
maintained at the storage section of Division of Entomology,
Agricultural Research Institute, Jaipur. Insects were reared on
grains of wheat at 27 š 1 ŽC and 70% relative humidity. Glass jars
containing 500 g of wheat grains were labeled to indicate the
date of introduction of larva and new emergence. At alternate
day’s larva were shifted to fresh jars so that successive rearing
jars can be maintained and insects of known age can be obtained
regularly. Insecticidal activity of the synthesized compounds was
tested by ‘Dipping’ and ‘Spray’ methods. All synthetic compounds
were weighed and dissolved in methanol to prepare 1000 mg Lꢁ1
stock solution. Further concentrations viz., 900, 800, 700, 600, 500,
400, 300, 200 and 100 mg Lꢁ1 were prepared by serial dilution.
One mL of each concentration of various compounds was directly
The low values of molar conductivity (9–17 ohmꢁ1 cm2 molꢁ1
)
of the resulting metal complexes in anhydrous DMF show them to
be non-electrolytes.
UV Spectra
The electronic spectra of the ligands show a band due to the
>C N chromophore observed at 365 nm and shifts to the lower
wave length region in the spectra of the complexes. Such a shift
in the n-πŁ band is probably due to the donation of the lone
pair of electrons by the nitrogen of the ligand to the central
metal atom. Two bands at 319–320 and 298–300 nm assigned
to π –πŁ transitions, within the benzene and coumarin rings and
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Synthesis, Spectroscopic Characterization, Antimicrobial, Pesticidal and Nematicidal Activity
2CH3OH
methanol
CH3O-Na+
2Na
+
-H2
sodium methoxide
H
Cl
H
C
X-Na+
NH2
Cl
O
XH
C
N
C
CH3O-Na+
N
C
+
NH2
N
N
O
O
O
sodium salt of the ligand
enolic form of the ligand
Methanol
1:1
R2SnCl2 + N X.Na
R2SnCl (N X) + NaCl
Methanol
1:2
R2SnCl2 + 2 N X.Na
R2Sn (N X)2 + 2 NaCl
R3Sn (N X) + NaCl
Methanol
1:1
R3SnCl + N X.Na
(Where, R = Ph or Me and X = O or S)
azomethine linkage also show some shifting in their position due
to bond formation (Table 3).
of azomethine nitrogen upon complexation. The bands due to
(>C S) and (>C O) are shifted towards lower frequencies in
the complexes indicating coordination of sulfur and oxygen to
the central metal atom. The spectra of the free ligands display
two sharp bands at 3340–3500 and 3350–3490 cmꢁ1 due to
asym and sym vibrations of NH2 group, respectively, which
remain at almost the same positions in the spectra of the
complexes, suggesting that the NH2 group is not involved in
chelation. Two medium intensity bands observed in the far IR
region of the tin complexes at (404–413) and (352–356) cmꢁ1
are assigned to (Sn N) and (Sn-Cl) modes respectively
which are not observed in the spectra of the ligands. The
medium to sharp intensity bands are observed at 590 and
530 cmꢁ1 and may be assigned to the asymmetric and symmetric
modes of Sn-C stretching vibrations.One strong to medium
intensity band appeared in the spectra of the complexes in the
region 1220–1170 cmꢁ1 has been assigned to Sn-CH3 stretching
vibrations.
IR Spectra
Thetentativeabsorptionfrequenciesoftheligandsandtheirmetal
complexes along with their assignments are listed in Table 4. The
IR spectra of the free ligands L1H and L2H display absorption
bands at 3150–3250, 1630–1635 and 1080/1715 cmꢁ1 assigned
to -(NH), (>C N), and (>C S)/(>C O), respectively. The bands
at ca. 1735 cmꢁ1 due to (>C O) of lactone moiety of the
ligands remain almost unchanged in the complexes indicating
their non-involvement in complexation. The broad band due
to – (NH) vibrations, disappears in the spectra of the complexes,
indicating the deprotonation of this group on coordination with
the metal atom. The negative shift (10–20 cmꢁ1) of (>C N)
band observed in all the complexes indicates the involvement
1H- NMR and 13C- NMR Spectra
Table 3. U.V. Spectroscopic analysis of the ligands and their
corresponding complexes
Further evidence for the coordinating mode of the ligands
was obtained from 1H NMR spectra. The 1H NMR spectra of
the ligands recorded in DMSO-d6 exhibit a broad peak at
δ 8.59–8.69 ppm due to–NH proton(Table.4). The–NH proton
signal of the ligands disappears in the complexes. The absence
of this signal in these complexes suggest that this proton has
been lost via thioenolization and ketoenolization of >C S and
>C O groups and coordination of sulfur and oxygen to the
metal atoms, respectively, has taken place. The >CH N proton
moves downfield in the complexes in comparison with its original
positions in the ligand due to coordination of >C N to the metal
atom. In the case of 13C NMR spectra the considerable shifts in the
positionofthecarbonatomsattachedtothedifferentparticipating
groups clearly indicate the bonding of azomethine nitrogen to the
n-πŁλmax/nm
(>C N)
π –πŁ/nm
C6H5ꢁring
π –πŁ/nm
(>C N)
Compound
L1H
365
348
361
360
358
364
349
360
359
350
319
325
320
326
324
320
330
332
325
328
300
274
279
282
275
298
272
280
282
276
Ph3Sn(L1)
Me3Sn(L1)
Me2SnCl(L1)
Me2Sn (L1)2
L2H
Ph3Sn(L2)
Me3Sn(L2)
Me2SnCl(L2)
Me2Sn (L2)2
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L. Dawara and R. V. Singh
Table 4. IR (cmꢁ1) and 1H NMR (δ, ppm) spectral data of the ligands and their corresponding complexes
IR spectral data (cmꢁ1 1H NMR spectral data (δ, ppm)
)
Compound
(>C N)
(Sn N)
V(-NH)
(Sn-Cl)
–NH
-CH
N
–NH2
Aromatic protons (m)
L1H
1630
1624
1625
1624
1622
1635
1625
1630
1628
1626
–
3150–3240
–
–
8.59
6.7
3.45
3.43
3.42
3.47
3.44
3.46
3.47
3.48
3.38
3.41
6.42–8.22
6.45–8.12
6.48–8.35
6.72–8.06
6.73–8.19
6.72–8.15
6.71–8.10
6.76–8.46
6.65–8.11
6.85–8.16
Ph3Sn(L1)
Me3Sn(L1)
Me2SnCl(L1)
Me2Sn (L1)2
L2H
406
410
412
413
–
–
–
–
6.9
6.9
6.8
6.8
6.7
6.8
6.9
7.0
6.9
–
–
–
352
–
–
–
–
3150–3250
–
8.69
–
Ph3Sn(L2)
Me3Sn(L2)
Me2SnCl(L2)
Me2Sn (L2)2
404
408
410
413
–
–
–
–
–
–
–
356
–
–
–
R
Table 5. Angles and coupling constants of organotin(IV) compounds
N
N
X
Estimated
R
R
1J (119Sn,13C) 2J (119Sn,13C) 3J (119Sn,13C) C-Sn-C
Compound
(Hz)
(Hz)
(Hz)
angle θ
Sn
Sn
R
S
Ph3Sn(L1)
546
578
569
666
542
574
566
689
41.82
77.90
76.80
87.60
39.56
76.50
78.30
86.80
126.00
122.56
126.00
125.85
136.92
128.23
124.00
127.45
134.58
Me3Sn(L1)
Me2SnCl(L1)
Me2Sn (L1)2
Ph3Sn(L2)
–
X
N
–
R
Where, X= O or S and R = Me or Ph
–
129.30
Me3Sn(L2)
Me2SnCl(L2)
Me2Sn (L2)2
–
–
–
Figure 2. Structures of tin complexes.
diffraction studies. The observed interplanar spacing values
(‘d’ in Å) have been measured from the diffractogram of the
compound and the Miller indices h, k and l have been assigned
to each d value and 2-Theta angles are reported. The results
show that the compound belongs to ‘monoclinic’ crystal system
having unit cell parameters as a D 9.3565, b D 10.2356, c D
25.569, maximum deviation of 2-Theta D 0.039and Alpha D
90, Beta D 90, Gama D 120 at the wavelength D 1.540598.
We have tried to isolate single crystal of tin(IV) complex for
suitable X-ray crystal study but could not succeed. However.Yanga
et al.[30] have recently reported the single crystal structure of
Sn atom. (Table 6). The chemical shift values relative to the TMS
peak are shown in Tables 4–6.
119Sn NMR Spectra
119Sn NMR spectra recorded for the di and triorganotin(IV)
derivatives exhibit sharp signals at δ-115.13–155.54 ppm and
δ-335.41–362.30 ppm and thus strongly support the penta-
and hexa-coordination around the tin atom. Thus on the
basis of the results discussed and the analytical as well as
the spectral data, suitable trigonal bipyramidal geometry for pentacoordinated tin(IV) complex in which the ligand adopts
penta-coordinated state and octahedral geometry for hexa- the most stereochemically favourable orientation (Table 7 and
coordinated state have been suggested for the 1 : 1 and 1 : 2 Graph-I).
metal compounds.
Onthebasisoftheabovediscussion,followingstructuresshown
in Figs. 2 and 3 have been proposed for the complexes.
Mass Spectra
The EI mass spectrum of the Me3Sn(L2) complex was studied
as a representative case. The molecular ion peak for the
complex Me3Sn(L2) was observed at m/z 444.95 and this is in
good agreement with its molecular weight, which suggests the
monomeric nature of the complex. The tin containing fragments
[C14H16ClN3O2SSn]Cž, [C14H14ClN2O2SSn]C, [C13H11ClN2O2SSn]C
and [C11H6ClN2O2SSn]C are observed at 444.95, 428.43, 413.95
and 384.85, respectively which are accompanied by other isotopic
combinations.
Antimicrobial assay
The ligands and their microwave synthesized tin(IV) complexes
wereevaluatedfortheirantimicrobialactivityagainsttwobacteria,
Escherichia coli and Bacillus subtilis and two fungi, Aspergillus
niger and Fusarium oxysporum. The results were compared
with those of the standard drugs Streptomycin for bacteria and
Flucanazole for fungi. Both the ligands were found potentially
active against the fungal and bacterial strains. The antimicrobial
screening data show that both the ligands and their complexes
individually exhibited varying degrees of inhibitory effects on the
growth of the tested bacterial and fungal species. The antibacterial
X-Ray structure determination
The possible lattice dynamics of the finely powdered product, (Graph II) and antifungal (Graph III) results evidently show that
[Ph3Sn(L2)] has been deduced on the basis of X-ray powder the activity of the ligands became more pronounced when
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Appl. Organometal. Chem. 2011, 25, 643–652

Synthesis, Spectroscopic Characterization, Antimicrobial, Pesticidal and Nematicidal Activity
Table 6. 13C NMR (δ, ppm) spectral data of the ligands and their corresponding complexes
C2
C7
C3
C8
C4
C9
C5
C6
–
Compound
L1H
Azomethine
153.35
>C O/>C
S
Sn-CH3
–
C10
163.50
161.95
129.56
160.26
128.98
159.23
129.07
160.14
129.01
161.02
129.32
162.03
129.95
161.90
129.23
161.25
129.00
161.23
128.95
161.66
129.27
100.36
115.36
102.01
114.65
101.56
115.23
101.02
114.95
102.03
115.52
101.56
116.32
101.88
115.65
101.90
116.0
158.91
154.32
157.32
153.26
158.25
154.03
158.32
154.84
157.65
154.01
159.65
154.98
158.32
153.85
159.00
154.23
158.69
154.00
158.23
154.05
127.58
133.56
126.36
132.85
125.98
133.06
126.56
132.99
125.65
133.01
128.08
133.96
127.56
132.65
128.00
132.45
128.05
133.00
128.00
132.85
125.36
–
Ph3Sn(L1)
Me3Sn(L1)
Me2SnCl(L1)
Me2Sn (L1)2
L2H
150.98
149.65
148.32
144.95
152.65
149.98
148.36
147.95
143.25
–
–
124.58
–
–
16.06
16.85
18.23
–
125.01
–
–
124.69
–
–
125.00
–
170.86
126.54
–
Ph3Sn(L2)
Me3Sn(L2)
Me2SnCl(L2)
Me2Sn (L2)2
–
–
–
–
–
126.00
–
125.95
–
16.23
16.56
18.69
101.82
115.58
102.16
115.67
125.92
–
126.01
–
8
O
O
2
O
C
9
7
6
N
11
12
NH2
N
H
3
10
C
4
5
H
Cl
Table 7. X-Ray diffraction data of the complex Ph3Sn(L2)
Table 8. Minimum inhibitory concentration mg/mL of the ligands
and their complexes
2Theta 2Theta 2Theta
(Exp.) (Calc.) (Diff.)
d
d
Intensity
(Exp.)
h
K
l
(Exp.)
(Calc.)
Compound
E. coli
B. subtilis
A. niger
F. oxysporum
L1H
25
18
20
21
19
22
16
18
17
15
27
21
22
20
18
24
18
19
16
14
35
29
31
29
27
34
22
24
20
19
37
26
21
19
17
35
23
18
19
20
ꢁ2
ꢁ2
ꢁ2
ꢁ2
ꢁ2
ꢁ1
ꢁ2
1
2
2
0
0
0
3
0
2
1
2
2
0
4
1
5
6
21.282 21.320 ꢁ0.038 4.17163 4.16420
22.117 22.162 ꢁ0.045 4.01584 4.00780
22.93
0.54
8.75
1.03
5.87
6.92
18.54
16.86
4.13
4.15
Ph3Sn(L1)
Me3Sn(L1)
Me2SnCl(L1)
Me2Sn (L1)2
L2H
23.012 23.009
0.003 3.86164 3.86218
21.902 21.920 ꢁ0.019 4.05488 4.05148
26.016 26.018 ꢁ0.001 3.42216 3.42203
26.690 26.652
28.065 28.076
34.640 34.601
0.039 3.33726 3.34203
0.001 3.17691 3.17562
0.038 2.58745 2.59023
Ph3Sn(L2)
Me3Sn(L2)
Me2SnCl(L2)
Me2Sn (L2)2
ꢁ3 3 13 57.086 57.089 ꢁ0.003 1.61213 1.61204
ꢁ3 63.588 63.625 ꢁ0.037 1.46204 1.46128
7
0
coordinated to the metal. The increased activity of the metal
chelates can be explained on the basis of chelation theory[31]
degree of inhibition; as the concentration increases, the activity
increases.
,
according to which the polarities[32,33] of the ligands and the
central metal atoms are reduced through charge equilibration
over the whole chelate ring. This increases the lipophilic character
of the metal chelate and favours its permeation through the
lipid layer of the bacterial membranes[34]. The variation in the
effectiveness of different compounds against different organisms
depends either on the impermeability of the cells of the microbes
or the difference in ribosomes of microbial cells. It has also been
proposed that concentration plays a vital role in increasing the
Minimum inhibitory concentration (MIC)
MIC values calculated for the ligands and their tin(IV) complexes
have been shown in Table 8, which indicated that the ligands
and their metal complexes were the most active in inhibiting
the growth of the tested organisms between 15–40 minimum
inhibitory concentration (mg/mL) against selected bacteria and
fungi.
c
Appl. Organometal. Chem. 2011, 25, 643–652
Copyright ꢀ 2011 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

L. Dawara and R. V. Singh
Graph I. X-Ray diffraction screening of the complex [Ph3Sn(L2)].
Figure 3. 3D Molecular structures of Ph3Sn(L1) and Me2Sn(L2)2.
Graph II. Antibacterial screening of the ligands and their complexes.
Graph III. Antifungal screening of the ligands and their complexes.
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Appl. Organometal. Chem. 2011, 25, 643–652

Synthesis, Spectroscopic Characterization, Antimicrobial, Pesticidal and Nematicidal Activity
Conclusion
Table 9. Pesticidal data of the ligands and their metal complexes
Microwave irradiation is an efficient and environmentally-benign
method to accomplish various inorganic syntheses to afford
products in higher yields in shorter reaction periods. Both
the ligands behave as monofunctional bidentate with the
metal atom in different reaction conditions. Tin(IV) complexes
synthesized in 1 : 1 and 1 : 2 molar ratios with monofunctional
bidentate ligands were found to be penta and hexacoordinated.
Antimicrobial, pesticidal and nematicidal activity of the complexes
and the ligands showed that the tin(IV) complexes are more
active than the parent ligands. The results showed that the
compounds are more active than ligands but less active than
thesestandarddrugsandthiswasourmainobjectiveforbiological
screening.
Compounds
Correct motility (%)
X2
LC50 mgLꢁ1
L1H
44.44
55.55
50.00
61.11
66.66
50.00
61.11
66.66
72.22
77.77
–
0.144
0.275
0.694
0.278
0.620
0.540
0.202
0.471
0.242
0.162
1.142
610
260
295
305
190
405
240
250
280
160
–
Ph3Sn(L1)
Me3Sn(L1)
Me2SnCl(L1)
Me2Sn (L1)2
L2H
Ph3Sn(L2)
Me3Sn(L2)
Me2SnCl(L2)
Me2Sn (L2)2
Control
Acknowledgment
Table 10. Nematicidal action of ligands and their Sn(IV) complexes
The authors are thankful to U.G.C New Delhi for financial assistance
through grant no. 34-324/08/(SR-I).
(recorded percentage of hatching after 24 h)
Compounds
25 ppm
50 ppm
100 ppm
L1H
29.36
23.27
24.95
21.36
20.12
23
21.23
17.43
18.23
19.25
16.23
19.85
17.23
16.85
18.56
14.23
16.56
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Ph3Sn(L1)
Me3Sn(L1)
Me2SnCl(L1)
Me2Sn (L1)2
L2H
Very low
Very low
Very low
Very low
14.69
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