Catalytic, biological and DNA binding studies of organotin(IV) carboxylates of 3-(2-fluorophenyl)-2-methylacrylic acid: Synthesis, spectroscopic characterization and X-ray structure analysis

Article abstract of DOI:10.1016/j.poly.2013.04.026

A new series of organotin(IV) carboxylates [Me₂SnL₂] (1), [Bu₂SnL₂] (2), [Oct₂SnL₂] (3), [Me₃SnL] (4), [Bu₃SnL] (5) and [Ph₃SnL] (6), where L = 3-(2-fluorop

Full text of DOI:10.1016/j.poly.2013.04.026

Polyhedron 57 (2013) 127–137
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Polyhedron
journal homepage: www.elsevier.com/locate/poly
Catalytic, biological and DNA binding studies of organotin(IV) carboxylates of
3-(2-fluorophenyl)-2-methylacrylic acid: Synthesis, spectroscopic characterization
and X-ray structure analysis
a,
b
c
d
Muhammad Tariq a, , Saqib Ali , Naseer Ali Shah , Niaz Muhammad , Muhammad Nawaz Tahir ,
⇑
⇑
Nasir Khalid e, Muhammad Rashid Khan b
a Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
b Department of Biochemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
c Department of Chemistry, Abdul Wali Khan University, Mardan, Pakistan
d Department of Physics, University of Sargodha, Sargodha, Pakistan
e Chemistry Division, Pakistan Institute of Nuclear Science and Technology, P.O. Nilore, Islamabad, Pakistan
a r t i c l e i n f o
a b s t r a c t
Article history:
A new series of organotin(IV) carboxylates [Me2SnL2] (1), [Bu2SnL2] (2), [Oct2SnL2] (3), [Me3SnL] (4),
[Bu3SnL] (5) and [Ph3SnL] (6), where L = 3-(2-fluorophenyl)-2-methylacrylate have been synthesized
and characterized by FT-IR, CHNS and NMR (1H, 13C). The crystal structures of complexes (1) and (4) were
also analyzed by single crystal X-ray analysis. The complex (1) adopted distorted octahedral geometry
while complex (4) exhibited distorted trigonal bipyramidal geometry. The catalytic activity of the com-
plexes was assessed in the production of biodiesel. Biodiesel is the monoalkyl ester of long chain fatty
acids derived from the renewable feed stock, such as vegetable oil and is produced by a transesterification
of vegetable oil with methanol. The results revealed that triorganotin(IV) complexes showed better cat-
alytic activity than their diorganotin(IV) analogues. The complexes were also screened for their biological
activities such as antibacterial, antifungal and cytotoxicity. The complexes 4–6 showed significant activ-
ity than the complexes 1–3. DNA interactions studies of ligand and complexes were investigated by UV–
Vis absorption spectroscopy. The results showed that both ligand and complexes interact with DNA via
intercalation as well as minor groove binding.
Received 3 March 2013
Accepted 11 April 2013
Available online 19 April 2013
Keywords:
Organotin(IV) carboxylate
Antibacterial activity
Antifungal activity
Transesterification
Crystal structure
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
triorganotin(IV) carboxylates of the type R4ꢀnSnLn where R = Me,
n-Bu, Ph, L = 3-(2-fluorophenyl)-2-methylacrylate and n = 1 or 2.
The organotin compounds have been used as pesticides, fungi-
cides, bactericides, homogeneous catalysts and in the synthesis of
polyesters, polyurethanes etc. [1–7]. The broad spectrum biological
and non-biological applications depend on both nature of molecule
and coordination number of tin atom [8–11]. Otera used organo-
stannyl and organodistannoxnae isothioscynanates as catalysts in
transesterification of ester with alcohol [12]. However, less atten-
tion has been devoted on catalytic activity of organotin(IV) carbox-
ylates in transesterification of triglycerides (vegetable oil) into fatty
acid methyl esters (biodiesel). Biodiesel is the monoalkyl ester of
long chain fatty acids derived from the renewable feed stock, such
as vegetable oil or animal fats and is usually produced by a transe-
sterification of triglycerides (vegetable oil) with methanol [13–15].
In view of the biocidal and catalytic activities of organotin(IV)
These complexes were characterized by FT-IR, CHNS, NMR (1H,
13C) and single X-ray crystal analysis. The catalytic activity of the
complexes was assessed in transesterification of triglycerides (veg-
etable oil) into fatty acid methyl esters (biodiesel). The complexes
were screened for their anti-bacterial, anti-fungal and cytoxicity.
DNA interaction studies were also performed using UV–Vis spec-
trophotometer to find out drug–DNA mechanism.
2. Experimental
2.1. Materials and methods
All the di- and triorganotin(IV) precursors were purchased from
Sigma–Aldrich and were used without further purification. All the
solvents purchased from Merck (Germany) were of analytical grade
and dried according to reported procedures before use [16]. The
melting points were measured on a Gallenkamp (UK) electrother-
mal melting point apparatus. Microanalyses were done using a
carboxylates, we have synthesized
a
series of di and
⇑
Corresponding authors. Tel.: +92 51 90642130; fax: +92 51 90642241.
E-mail addresses: mtnazir@yahoo.com (M. Tariq), drsa54@yahoo.com (S. Ali).
0277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2013.04.026

128
M. Tariq et al. / Polyhedron 57 (2013) 127–137
Leo CHNS 932 apparatus. IR spectra were recorded in the range
from 4000 to 400 cmꢀ1 using a Thermo Nicolet-6700 FT-IR Spectro-
photometer using KBr discs. 1H and 13C NMR spectra were recorded
at room temperature in CDCl3 on a Bruker Avance Digital 300 MHz
NMR spectrometer (Switzerland). The X-ray diffraction data were
collected on a Bruker SMART APEX CCD diffractometer, equipped
with a 4 K CCD detector set 60.0 mm from the crystal. The crystals
were cooled to 100 1 K using the Bruker KRYOFLEX low tempera-
ture device and intensity measurements were performed using
graphite monochromated Mo K
a radiation from a sealed ceramic
diffraction tube (SIEMENS). Generator settings were 50 kV/40 mA.
The structure was solved by Patterson method and extension of
the model was accomplished by direct method using the program
DIRDIF or SIR2004. Final refinement on F^2 was carried out by full ma-
trix least square techniques using SHELXL-97, a modified version of
the program PLUTO (preparation of illustrations) and PLATON package.
The absorption spectra were recorded on a Shimadzu 1800 UV–Vis
spectrophotometer. The sesame seeds were purchased from a local
market. The seeds were washed with distilled water to remove the
dirt and were oven dried at 60 °C till constant weight. The oil was
extracted by using German made electric oil expeller (KEK P0015-
10127).
.
2.2.3. Dimethyltin(IV) bis[(3-(2-fluorophenyl)-2-methylacrylate)] (1)
The sodium salt R0COONa (0.404 g, 2.0 mmol), was refluxed
with dimethyltin(IV) dichloride (0.219 g, 1.0 mmol) in dry toluene
contained in a 250 mL two necked round bottom flask for 10 h. A
turbid solution obtained, was left overnight at room temperature.
The sodium chloride formed was filtered off and the filtrate was ro-
tary evaporated. The resultant solid mass was recrystallized from
chloroform and n-hexane (4:1) mixture. Yield: 0.41 g, 82%. M.p.
117–118 °C. Anal. Calc. for C22H22F2O4Sn: C, 52.11; H, 4.37. Found:
C, 52.01; H, 4.28%. IR (KBr, cmꢀ1): 1573
(OCO)sym, ( (Sn–C), 448.0
= 121 cmꢀ1), 524.0
NMR (CDCl3, ppm): 7.89 (s, H3, 2H), 7.09–7.42 (m, Ar–H6–9, 8H),
2.10 (s, H10, 6H), 1.12 (s, H
, 6H, 2J(119/117Sn–1H) = 83/80 Hz). 13C
m
(OCO)asym
, 1452
2.2. Syntheses
m
D
m
m
m
(Sn–O). 1H
2.2.1. Synthesis of 3-(2-fluorophenyl) 2-methylacrylic acid
a
The mixture of 2-fluorobenzaldehyde (3.47 g, 28 mmol), meth-
ylmalonic acid (6.61 g, 56 mmol) and piperidine (4.76 g, 56 mmol)
in molar ratios of 1:2:2 (scheme 1) was refluxed in two neck round
bottom flask in pyridine as solvent for 24 h on steam bath. After
cooling, the reaction mixture was poured into ice water and added
conc. HCl until pH 3. The precipitates formed were filtered, washed
with water, recrystallized in ethanol and dried.
NMR (CDCl3, ppm): 177.2 (C-1), 123.6 (C-2), 140.7 (C-3), 130.5
(C-4), 162.0, 158.7 (C-5), 115.5 (C-6), 133.5 (C-7), 123.8 (C-8),
130.2 (C-9), 14.5 (C-10), 4.6 (C-a
), 1J(119/117Sn–13C) = 760 Hz.
2.2.4. Dibutyltin(IV) bis[(3-(2-fluorophenyl) 2-methylacrylate)] (2)
Compound 2 was prepared in the same way as 1, using R0COONa
(0.404 g, 2.0 mmol) and dibutyltin(IV) dichloride (0.303 g,
1.0 mmol). The product was recrystallized from chloroform and
n-hexane (4:1) mixture. Yield: 0.45 g, 76%. M.p. 102–104 °C. Anal.
Calc. for C28H34F2O4Sn: C, 56.88; H, 5.80. Found: C, 56.18; H,
Yield: 3.49 g, 69.3%. M.p. 75–77 °C. Anal. Calc. for C10H9O2F: C,
66.66; H, 5.03. Found: C, 66.23; H, 5.0%. IR (KBr, cmꢀ1): 3321
m
(OH), 1672 m(OCO)asym, 1421 m(OCO)sym, (Dm
= 251 cmꢀ1). 1H
NMR (CDCl3, ppm): 11.00 (s, H1, 1H), 7.90 (s, H3, 1H), 7.10–7.45
Ar–H (m, H6–9, 4H), 2.10 (s, H10, 3H). 13C NMR (CDCl3, ppm):
173.8 (C-1), 123.4 (C-2), 140.5 (C-3), 129.9 (C-4), 162.0, 158.7 (C-
5), 115.6 (C-6), 133.9 (C-7), 130.4 (C-8), 130.6 (C-9) 13.9 (C-10).
5.65%. IR (KBr, cmꢀ1): 1574
= 122 cmꢀ1), 525
(Sn–C), 447
ppm): 7.88 (s, H3, 2H), 7.06–7.42 (m, Ar–H6–9, 8H), 2.10 (s, H10
6H), 1.78 (t, H
, 4H), 1.48–1.41 (m, Hb– , 8H), 0.92 (t, Hd, 6H). 13C
m
(OCO)asym
, 1452 m(OCO)sym,
(
D
m
m
m
(Sn–O). 1H NMR (CDCl3,
,
a
c
NMR (CDCl3, ppm): 177.6 (C-1), 123.8 (C-2), 141.0 (C-3), 126.8
F
2.2.2. Synthesis of Na-salt of 3-(2-fluorophenyl)-2-methylacrylic acid
The sodium salt of ligand, R0COONa, was prepared by dropwise
addition of an equimolar amount of sodium hydrogen carbonate
solution to a methanolic solution of ligand acid (R0COOH). The
solution was stirred for 2 h at room temperature, evaporated under
reduced pressure to give a white solid and was vacuum dried.
Scheme 2 represents numbering in ligand and R groups at-
tached to Sn atom for 1H and 13C NMR interpretation
10
6
5
1
3
2
4
CH
C
COOH
7
8
9
Scheme 2.
CH3
COOH
F
CH3
F
a)pyridine
b)piperidine
CO2
+
H2O
+
CHO
+
H
COOH
C
c)24 h stirring
d) 100 oC
COOH
Scheme 1.

M. Tariq et al. / Polyhedron 57 (2013) 127–137
129
(C-4), 162.0, 158.7 (C-5), 115.8 (C-6), 133.0 (C-7), 123.9 (C-8), 129.7
(C-9), 14.6 (C-10), 21.4 (C- ), 25.4 (C-b), 29.1(C- ), 13.5 (C-d).
2.3. Antibacterial studies
a
c
The antibacterial activity of ligand HL and its organotin(IV)
complexes were tested against four bacterial strains; two Gram-
Positive (Micrococcus luteus and Staphylococcus aureus) and three
Gram-negative (Escherichia coli and Bordetella bronchiseptica). The
agar well-diffusion method was used in which Broth culture
(0.75 mL) containing ca. 106 colony forming units (CFU) per mL
of the test strain was added to 75 mL of nutrient agar medium at
45 °C, mixed well, and then poured into a 14 cm sterile petri plate
[17]. The media was allowed to solidify, and 8 mm wells were dug
with a sterile metallic borer. Then a DMSO solution of test sample
2.2.5. Dioctyltin(IV) bis[(3-(2-fluorophenyl) 2-methylacrylate)] (3)
Compound 3 was prepared by using ligand acid, R0COOH (0.36 g,
2.0 mmol) and dioctyltin(IV) oxide (0.36 g, 1.0 mmol). The reactant
mixture was suspended in 100 mL dry toluene in a single necked
round bottom flask (250 mL), equipped with a Dean–Stark appara-
tus. The mixture was refluxed for 10 h and water formed during
the condensation reaction was removed at regular intervals. A clear
solution thus obtained, was cooled to room temperature and sol-
vent was removed under reduced pressure. The solid obtained
was recrystallized from chloroform and n-hexane (4:1) mixture.
Yield: 0.48 g, 68%. M.p. gel. Anal. Calc. for C36H50F2O4Sn: C, 61.46;
(100 lL) at 1 mg/mL was added to the respective wells. DMSO
served as negative control, and the standard antibacterial drugs
Roxyithromycin (1 mg/mL) and Cefixime (1 mg/mL) were used as
positive control. Triplicate plates of each bacterial strain were pre-
pared which were incubated aerobically at 37 °C for 24 h. The
activity was determined by measuring the diameter of zone show-
ing complete inhibition (mm).
H, 7.16. Found: C, 60.25; H, 7.02%. IR (KBr, cmꢀ1): 1574
(OCO)asym
= 121 cmꢀ1), 522.5 (Sn–O). 1H
1453 (OCO)sym, ( (Sn–C), 441 m
m
,
m
D
m
m
NMR (CDCl3, ppm): 7.88 (s, H3, 2H), 7.08–7.43 (m, Ar–H6–9, 8H),
0
2.11 (s, H10, 6H), 1.78–1.27 (bs, H
28H), 0.85 (t, Hd ,
a
,b,c
,d,a0,b0,c0
6H). 13C NMR (CDCl3, ppm): 177.6 (C-1), 123.7 (C-2), 140.8 (C-3),
130.0 (C-4), 162.0, 158.7 (C-5), 115.5 (C-6), 133.0 (C-7), 124.0 (C-
2.4. Antifungal studies
8), 130.6 (C-9), 14.7 (C-10), 25.6 (C-
a), 24.4 (C-b), 33.9 (C-c), 31.8
(C-d), 29.7 (C-a0), 29.0 (C-b0), 22.5 (C-c0), 14.0 (C-d0).
Antifungal activity against four fungal strains (Aspergillus Flavus,
Aspergillus niger, Fusarium solani and Aspergillus fumigatus) was
determined by using agar tube dilution method [18]. Screw capped
test tubes containing Sabouraud dextrose agar (SDA) medium
(4 mL) were autoclaved at 121 °C for 15 min. Tubes were allowed
2.2.6. Trimethyltin(IV) 3-(2-fluorophenyl) 2-methylacrylate (4)
Compound 4 was prepared in the same way as 1, using R0COONa
(0.404 g, 2.0 mmol) and trimethyltin(IV) chloride (0.398 g,
2.0 mmol). The product was recrystallized from chloroform and
n-hexane (4:1) mixture. Yield: 0.56 g, 81%. M.p. 125–126 °C. Anal.
Calc. for C13H17FO2Sn: C, 45.52; H, 5.0. Found: C, 45.13; H, 4.90%.
to cool at 50 °C and non solidified SDA was loaded with 66.6
of compound from the stock solution (12 mg/mL in DMSO) to make
200 g/mL final concentration. Tubes were then allowed to solidify
lL
IR (KBr, cmꢀ1): 1574 = 187 cmꢀ1),
m(OCO)asym, 1387 m(OCO)sym, (Dm
l
524.0 m(Sn–C), 444 m
(Sn–O). 1H NMR (CDCl3, ppm): 7.72 (s, H3, 1H),
in slanting position at room temperature. Each tube was inoculated
with 4 mm diameter piece of inoculum from seven days old fungal
culture. The media supplemented with DMSO and Turbinafine
7.06–7.40 (m, Ar–H6–9, 4H), 2.05 (s, H10, 3H), 0.62 (s, H , 9H) 2J(119/
a
117Sn–1H) = [58/56 Hz]. 13C NMR (CDCl3, ppm): 173.3 (C-1), 123.6
(C-2), 141.2 (C-3), 129.6 (C-4), 161.9, 158.6 (C-5), 115.4 (C-6),
(200 lg/mL) were used as negative and positive control, respec-
132.3 (C-7), 124.4 (C-8), 130.9 (C-9), 14.8 (C-10), ꢀ2.3 (C-
a
), 1J
tively. The tubes were incubated at 28 °C for 7 days and growth
was determined by measuring linear growth (mm) and growth
inhibition was calculated with reference to growth in vehicle con-
trol as shown in equation.
(
119Sn–C) = [396/378 Hz].
2.2.7. Tributyltin(IV) 3-(2-fluorophenyl)-2-methylacrylate (5)
ꢀ
ꢁ
Compound 5 was prepared in the same way as 1, using R0COONa
(0.404 g, 2.0 mmol) and tributyltin(IV) chloride (0.650 g,
2.0 mmol). The product was recrystallized from chloroform and
n-hexane (4:1) mixture. Yield: 0.72 g, 76%. M.p. 139–141 °C. Anal.
Calc. for C22H35FO2Sn: C, 56.31; H, 7.52. Found: C, 55.98; H,
Linear growth in test sample ðmmÞ
Linear growth in control ðmmÞ
% Growth inhibition ¼ 100 ꢀ
ꢁ 100
2.5. Cytotoxic studies
7.14%. IR (KBr, cmꢀ1): 1560
= 187 cmꢀ1), 522.2
(Sn–C), 441
ppm): 7.88 (s, H3, 1H), 7.08–7.42 (m, Ar–H6–9, 4H), 2.09 (s, H10
m
(OCO)asym
, 1373 m(OCO)sym,
(D
m
m
m
(Sn–O). 1H NMR (CDCl3,
Cytotoxicity was studied by the brine-shrimp lethality assay
method [17]. Brine-shrimp (Artemia salina) eggs were hatched in arti-
ficial sea water (3.8 g sea salt/L) at ambient temperature of 23 1 °C.
After 2 days these shrimps were transferred to vials containing 5 mL
,
3H), 1.82–1.79 (t, Ha, 6H), 1.47–1.40 (m, Hb, c, 12H), 0.94 (t, Hd,
9H). 13C NMR (CDCl3,): 177.6 (C-1), 123.4 (C-2), 140.3 (C-3),
129.3 (C-4), 162.0, 158.7 (C-5), 115.6 (C-6), 130.5 (C-7), 123.8 (C-
of artificial sea water (10 shrimps per vial) with 10, 100 and 500 lg/
8), 130.4 (C-9), 14.5 (C-10), 25.7 (C-a), 29.5 (C-b), 32.8 (C-c), 14.2
(C-d).
mL final concentrations of each compound taken from their stock
solutions of 12 mg/mL in DMSO. After 24 h number of surviving
shrimps was counted. Data was analyzed with a Biostat 2009 com-
puter programme (Probit analysis) to determine LD50 values.
2.2.8. Triphenyltin(IV) 3-(2-fluorophenyl)-2-methylacrylate (6)
Compound 6 was prepared in the same way as 1, using R0COONa
(0.404 g, 2.0 mmol) and triphenyltin(IV) chloride (0.77 g,
2.0 mmol). The product was recrystallized from chloroform and
n-hexane (4:1) mixture. Yield: 0.82 g, 78%. M.p. 146–148 °C. Anal.
Calc. for C28H23FO2Sn: C, 63.55; H, 4.38. Found: C, 63.18; H,
2.6. Catalytic experiment
Transesterification of sesame oil was carried out using organo-
tin(IV) carboxylate as catalysts in molar ratio of 400:100:1 (meth-
anol:oil:catalyst) [5]. 0.01 mol sesame oil was transesterified using
0.04 mol methanol and 0.1 mmol catalyst in a 100 mL three neck
round bottom flask equipped with reflux condenser, magnetic stir-
rer, thermometer and sampling outlet. Before the reaction, the
organotin catalyst was solubilized in 0.5 mL chloroform. The reac-
tion mixture was refluxed with constant stirring. The sample was
taken after 1, 8, 16 and 24 h and was analyzed by 1H NMR to check
4.08%. IR (KBr, cmꢀ1): 1643
= 161 cmꢀ1), 443
1H), 7.16–7.47 (m, Ar–H6–9, 4H), 2.17 (s, H10, 3H), 7.80–7.71 (Hb,
, Hd 15H). 13C NMR (CDCl3, ppm): 175.7 (C-1), 123.2 (C-2),
140.1 (C-3), 130.4 (C-4), 161.5, 158.6 (C-5), 115.3 (C-6), 133.6 (C-
7), 124.1 (C-8), 130.5 (C-9), 14.1 (C-10), 139.7 (C- ), 137.2 (C-b),
129.7 (C- ), 130.3 (C-d).
m
(OCO)asym
, 1482 m(OCO)sym,
(D
m
m
(Sn–O). 1H NMR (CDCl3, ppm): 7.68 (s, H3,
Hc
a
c

130
M. Tariq et al. / Polyhedron 57 (2013) 127–137
the % age conversion of triglycerides in sesame oil into fatty acid
methyl esters (biodiesel).
with the protons calculated from incremental method. The satel-
lites due to (119/117Sn, 1H) coupling are helpful in finding geome-
try around tin in solution. The methyl protons of dimethyltin(IV)
(1) and trimethyltin(IV) (4) derivative appear as sharp singlets
with well defined satellites in the range 0.99–1.26 and 0.53–
0.72 ppm having coupling constants of 83/80 and 58/56 Hz [2J
2.7. DNA interaction studies by UV–Vis spectroscopy
0.2 g of SS-DNA (salmon sperm) was dissolved in 100 mL of
double deionized water and kept at 4 °C. Solutions of DNA in
20 mM Tris–HCl (pH 7.4) gave the ratio of UV absorbance at 260
and 280 nm, A260/A280, of 1.86 indicating that the DNA is suffi-
ciently free from protein [19]. The DNA concentration was deter-
mined via absorption spectroscopy using the molar absorption
coefficient of 6600 Mꢀ1 cmꢀ1 at 260 nm [20], and was found as
7.45 ꢁ 10ꢀ5 M. From this stock solution 3, 6, 9, 12, 15, 18, 21, 24
(
119/117Sn, 1H)], respectively. The determined 2J values indicate
five or six coordination for compound (1) and four co-ordination
for compound (4) around tin atom in solution state. The protons
of n-butyltin(IV) derivative mostly show a complex pattern and
were assigned according to the literature [25,26]. Despite the
complex pattern of 1H NMR spectra of di- (2) and tri-n-butyl-
tin(IV) (5) derivatives, a clear triplet due to terminal methyl
group appears in the range of 0.92–0.94 ppm. The methylene pro-
tons (CH2) of n-octyltin(IV) derative (3) exhibit somewhat differ-
ent behavior compared with the n-butyl groups of the respective
complexes. All the CH2 protons of n-octyl groups give broad/mul-
tiplet signals in the range 0.85–1.78 ppm.
and 27 lM working solutions were prepared by dilution method.
The ligand HL, complexes 1 and 4 were dissolved in 10% DMSO
at a concentration of 5 ꢁ 10ꢀ5 M. The UV absorption titrations
were performed by keeping the complexes concentration fixed
while varying the concentration of DNA. Equivalent solutions of
DNA were added to the complex and reference solutions to elimi-
nate the absorbance of DNA itself. Compound-DNA solutions were
allowed to incubate for 30 min at ambient temperature before
measurements were made. Absorption spectra were recorded
using cuvettes of 1 cm path length.
3.3.2. 13C NMR studies
In 13C NMR, the carbon signals of synthesized ligand and its
organotin(IV) derivatives are in good agreement with expected val-
ues. The carbon attached to flouro group and others in its vicinity
gave doublets due to heteronuclear coupling of [13C, 19F]. The car-
bons bonded to Sn atom have satellites due to 1J [119Sn, 13C] cou-
plings which are important parameters for characterization of
organotin(IV) compounds and geometry around tin atom. For di-
methyl derivative (1), the value of 1J [119Sn, 13C] is 760 Hz while
for trimethyltin(IV) (4), it is 388 Hz which confirm six co-ordina-
tion geometry around the tin in solution for (1) and four coordina-
tion for (4), respectively, [27,28].
3. Results and discussions
3.1. Syntheses of complexes 1–6
Diorganotin dichloride and triorganotin chloride with NaL in
1:2 and 1:1 M ratios, respectively while R2SnO with HL in 1:2 M ra-
tios give complexes according to the following equations
R2SnCl2 þ 2NaL ! R2SnL2 þ 2NaCl
ð1Þ
3.4. Crystal structures of complexes 1 and 4
R ¼ CH3ð1Þ; n-C4H9ð2Þ;
The dimeric structure and packing diagram of complex 1 are
shown in Figs. 1 and 2 while the crystal data, selected bond lengths
and bond angles of complex 1 are listed in Tables 1 and 2, respec-
tively. The four oxygen atoms from two carboxylate ligands are in
planar position. The carboxylate moiety COOꢀ of ligand is bonded
in anisobidentate mode with two shorter bonds (Sn1–O1, Sn1–O3)
and two longer bonds (Sn1–O2 and Sn1–O4) in asymmetric way as
depicted in Table 2. The longer Sn–O distances (Sn1–O2 = 2.6543 Å
and Sn1–O4 = 2.575 Å) are significantly less than the sum of the
van der Waal’s radii (3.68 Å) [29]. The asymmetric mode of coordi-
nation of the carboxylate ligands is further confirmed by unequal
C–O bond distances; O1–C1 = 1.298(3) Å, O2–C1 = 1.224(3) Å and
R2SnO þ 2HL ! R2SnL2 þ H2O
ð2Þ
R ¼ n-C8H17ð3Þ
R3SnCl þ NaL ! R3SnL þ NaCl
ð3Þ
R ¼ CH3ð4Þ; n-C4H9ð5Þ; C6H5ð6Þ
3.2. FT-IR analysis
The binding mode of ligand to tin atom was determined using
FT-IR spectra in the range 4000–400 cmꢀ1 by the difference be-
tween the asymmetric and symmetric carboxylate stretching
vibrations [
lieved that the difference in
D
m
=
m
asym(COOꢀ) ꢀ
m
sym(COOꢀ)] [21]. It is generally be-
Dm
between asymmetric (COOꢀ) and
symmetric (COOꢀ) absorption frequencies below 200 cmꢀ1 indi-
cates the bidentate carboxylate moiety, but greater than
200 cmꢀ1 indicates the unidentate carboxylate moiety [22]. The
magnitudes of
D
m
[(
m
asym(COOꢀ) ꢀ
m
sym(COOꢀ)] for complexes
1–6 are within range of 121–187 cmꢀ1 which indicate the presence
of bidentate carboxylate groups in these complexes [23]. The
absorption bands in the 441–470 cmꢀ1 region are assigned to the
stretching mode of the Sn–O linkage which indicates the formation
of complexes [24].
3.3. NMR studies
3.3.1. 1H NMR studies
The chemical shift, multiplicities pattern in 1H NMR spectra
are helpful in elucidation of structures of the synthesized com-
pounds. All the protons present in the synthesized ligand and
compounds (1–6) were identified by the position and number
Fig. 1. Dimeric ORTEP diagram of complex 1.

M. Tariq et al. / Polyhedron 57 (2013) 127–137
131
[5,34,35]. The 2-fluorophenyl ring (C18a–C23a/F2a and C18b–
C23b/F2b) is disordered over two sites with refined occupancy
ratio of 0.711(7):0.289(7). The disordered benzene rings were
idealized as regular hexagon of bond length 1.39 Å and these
C-atoms were treated having equal anisotropic thermal parame-
ters. In a similar manner the disordered F-atoms were treated
having equal anisotropic thermal parameters. The geometry
around Sn can be deduced by the value of
is the largest and is the second largest basal angles around
the Sn atom [36]. The angle values = b = 180° correspond to
value equal to zero for a perfect square-pyramidal and the value
of = 120° and b = 180° correspond to value equal to 1 for a per-
fect trigonal–bipyramidal geometry. The calculated value for
s
= (bꢀ
a)/60, where b
a
a
s
a
s
s
complex 4 is 0.81 which indicates distorted trigonal–bipyramidal
geometry around the Sn atom.
Fig. 2. Platon dimeric diagram of complex 1.
3.5. Biological studies
O3–C11 = 1.295(3) Å, O4–C11 = 1.232(3) Å as shown in Table 2.
The two methyl groups attached to tin atom occupy axial position
with C21–Sn–C22 angle 143.95(12)° which shows that methyl
groups do not occupy the exact axial positions. The two methyl
groups in distorted axial position and four oxygen atoms from
the two chelating carboxylate ligands in basal plane represent
skew-trapezoidal or distorted octahedral geometry around tin
[5,30]. The geometry, bond lengths and angles are comparable with
literature values [5,31–33].
The dimeric structure and polymeric bridiging diagram of com-
plex 4 are shown in Figs. 3 and 4, while the crystal data, selected
bond length and bond angles are listed in Tables 1 and 3, respec-
tively. The complex 4 showed polymeric structure with distorted
trigonal bipyramidal geometry. The three methyl groups attached
to tin atom are in trigonal plane having C–Sn–C angle 113.2° to
126.6° while two oxygen atoms of bridging carboxylate ligands
occupy axial position with O–Sn–O angle 175.06°. Thus carboxyl-
ate ligand bridges the two symmetry related Sn atoms and gives
rise to the unequal Sn–O bond distances which is further reflected
from C–O bond lengths, the shorter C–O bond is involved in the
longer Sn–O interaction and vice versa. These bond lengths and
polymeric bridging behavior are comparable with literature
3.5.1. Antibacterial studies
In vitro antibacterial activity tests of the ligand HL and its organo-
tin(IV) complexes (1–6) were carried out against four bacterial
strains; two Gram-Positive (Micrococcus luteus and Staphylococcus
Table 2
Selected bond lengths (Å) and bond angles (°) of complex 1.
Bond lengths (Å)
Sn1–C21
Sn1–C22
Sn1–O1
Sn1–O2
Sn1–O3
Sn1–O4
O2–C1
2.086(3)
2.092(3)
2.0757(19)
2.6543(18)
2.0857(17)
2.575(2)
O3–C11
O4–C11
Sn2–O5
Sn2–O6
Sn2–O7
Sn2–O8
Sn2–C44
1.295(3)
1.232(4)
2.566(2)
2.0781(17)
2.0780(19)
2.6698(19)
2.088(3)
1.224(3)
O1–C1
1.298(3)
Bond angles (°)
O1–Sn1–O2
O1–Sn1–O3
O2–Sn1–O3
O2–Sn1–O4
O1–Sn1–O4
C21 Sn1 C22
53.18(6)
81.99(7)
135.16(7)
169.74(6)
136.36(7)
143.95(12)
O1–Sn1–C21
O1–Sn1–C22
O2–Sn1–C21
O2–Sn1–C22
O3–Sn1–C21
O3–Sn1–C22
104.90(10)
101.72(10)
90.84(9)
85.97(9)
101.27(10)
106.18(9)
Table 1
Crystal data and structure refinement parameters for complexes 1 and 4.
Compound
1
4
Chemical formula
Formula mass (g molꢀ1
Crystal system
Space group
Unit cell dimensions
a (Å)
C
22H22F2O4Sn
C13H17FO2Sn
342.96
)
507.11
monoclinic
P21/c
triclinic
ꢀ
P1
13.5161(3)
23.0786(6)
13.9395(3)
90.00
96.976(1)
90.00
9.8854(3)
11.5996(5)
13.9493(6)
99.922(2)
109.989(1)
101.495(2)
1421.92(10)
2
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
4316.00(17)
8
Z
T (K)
296(2)
1.561
1.225
296(2)
1.602
1.797
Dcalc (g cmꢀ3
)
Absorption coefficient (mmꢀ1
)
F(000)
2032
0.71073
680
0.71073
Radiation (A0) (Mo K
Index ranges
a
)
ꢀ166h616, ꢀ286k628, ꢀ176l617
ꢀ126h612, ꢀ146k614, ꢀ176l617
h (°) Min max
Total reflections
1.52–26.0
8485
1.86–26.0
5570
Restraints/parameters
Rall, Rgt
0/531
0/316
0.0396, 0.0261
0.0649,0.0583
1.004
0.0466, 0.0351
0.0945, 0.0865
1.053
wRref, wRgt
Goodness-of-fit (GOF) on F2

132
M. Tariq et al. / Polyhedron 57 (2013) 127–137
Table 3
Selected bond lengths (Å) and bond angles (°) of complex 4.
Bond lengths (Å)
Sn1–C11
Sn1–C12
Sn1–C13
O1–C1
2.107(6)
2.107(5)
2.103(6)
1.292(6)
1.225(6)
Sn1–O1
Sn2–O2
Sn2–O3
Sn2–C24
Sn2–C25
Sn2–C26
2.109(4)
2.728(4)
2.119(4)
2.114(7)
2.114(6)
2.104(5)
O2–C1
Bond angles (°)
O2–Sn2–O3
O1–Sn1–C11
O1–Sn1–C12
O1–Sn1–C13
C12–Sn–C11
175.06(13)
91.34(19)
99.18(19)
99.2(2)
C13–Sn–C12
C13–Sn–C11
C25–Sn2–C26
C24–Sn2–C26
C24–Sn2–C25
126.6(2)
113.2(2)
125.8(2)
116.7(2)
113.4(2)
116.0(2)
Fig. 3. Dimeric ORTEP diagram of complex 4.
3.5.2. Antifungal studies
The ligand HL and its organotin(IV) complexes (1–6) were
screened for antifungal activity against four fungal strains (Asper-
gillus flavus, Aspergillus niger, Aspergillus fumigatus and Fusarium
solani) by using agar tube dilution method [18]. The results are
shown in Fig. 6. Terbinafine was used as standard drug in this assay.
Criteria for activity is based on percent growth inhibition; more
than 70% was considered as significant activity, 60–70% as good,
50–60% as moderate while below 50% was considered as non-
significant [37]. The antifungal data showed that compound 4
exhibited 100% growth inhibition against Aspergillus niger, Aspergil-
lus fumigatus and Fusarium solani while significant against Aspergil-
lus flavus. The compound 6 exhibited 100% growth inhibition
against Aspergillus niger and Aspergillus fumigates while significant
against Aspergillus flavus and Fusarium solani. The compound 5
showed good to significant activity against Aspergillus niger, Asper-
gillus fumigatus and Fusarium solani. The compounds 1–3 showed
non-significant to moderate activity against all the tested fungal
strains. Like antibacterial activity, triorganotin(IV) compounds
aureus) and two Gram-negative (Escherichia coli and Bordetella bron-
chiseptica). The experiment was performed in triplicate by agar well-
diffusion method [17]. Roxyithromycin and Cefixime were used as
positive control. The results are shown in Fig. 5. Criteria for activity
is based on zone of inhibition (mm); inhibition zone more than
20 mm shows significant activity, for 18–20 mm inhibition activity
is good, 15–17 mm is low, and below 11–14 mm is non-significant
[37]. The antibacterial study demonstrates that compound 4 exhib-
ited significant activity against Gram-negative bacteria (Escherichia
coli and Bordetella bronchiseptica) and also greater than both refer-
ence drugs used while compounds 5 and 6 showed significant activ-
ity against all tested bacterial strains or even greater against some
strains. The compounds 1–3 and ligand HL showed low to significant
activity. In general, triorganotin(IV) compounds showed greater
antibacterial activity than di-analogues which may be due to greater
lipophilicity and permeability through the cell membrane which is
consistent with literature [5,38,39].
Fig. 4. Polymeric structure of complex 4.

M. Tariq et al. / Polyhedron 57 (2013) 127–137
133
Fig. 5. Antibacterial activity of HL and its organotin(IV) complexes (1–6).
Fig. 7. Cytotoxicity of HL and its organotin(IV) complexes (1–6) against brine-
shrimps (in vitro).
Fig. 6. Antifungal activity of HL and its organotin(IV) complexes (1–6).
In the present study, the transesterification reaction of triglyc-
erides in sesame oil was carried out in molar ratio of 400:100:1
(methanol:oil:catalyst) to assess the catalytic activity of organo-
tin(IV) carboxylates [5]. The experimental conditions were not
optimized and no attempt was made to remove the added catalyst
from the reaction mixture. However, the effect of reaction time on
% age conversion of triglycerides into fatty acid methyl esters (bio-
diesel) was studied but was not optimized to get the maximum %
age conversion because the aim was to assess the catalytic activity
of different organotin(IV) carboxylates. The sample was taken from
the reaction mixture at regular interval of 1, 8, 16 and 24 h and was
analyzed by 1H NMR to calculate % age conversion of triglycerides
into fatty acid methyl esters (biodiesel). The results are shown in
Fig. 8. The equation used to quantify the extent of transesterifica-
tion [42,43] was:
showed greater antifungal activity than di-analogues which is also
consistent with literature [5,40,41].
3.5.3. Cytotoxic studies
In vitro cytotoxicity of ligand HL and organotin(IV) complexes
(1–6) was studied against the brine-shrimp lethality method [17]
by using reference drug MS-222 (Tricaine Methanesulfonate) and
the results are summarized in Fig. 7. The data is based on mean va-
lue of two replicates each of 10, 100 and 500
data exhibited that compound 4–6 showed greater toxicity having
LD50 values 0.008(4), 0.20(6) and 2.59(5)
g mLꢀ1 while com-
pounds 1–3 exhibited less toxicity having LD50 values 313.1(1),
403(3) and 736(2)
g mLꢀ1
l
g mLꢀ1. The LD50
l
l
.
2AMe
C ¼
ꢁ 100
3.6. Catalytic activity of organotin(IV) carboxylates
3ACH
2
Organotin(IV) carboxylates were used as catalyst in a transeste-
rification reaction of triglycerides in sesame oil with methanol to
produce biodiesel (Fatty acid methyl esters – the chemical name
of biodiesel). The organotin(IV) carboxylates were selected due to
the Lewis acid character of tin atom. The tin atom has the property
of coordination expansion which may play an important role in the
catalytic activity of different substituted organotin compounds.
Since Lewis acid can activate carbonyl groups which lead to in-
crease in the electrophilicity of the carbonyl carbon in triglycerides
and a subsequent interaction with tin atom.
where C = percentage conversion of triglycerides to corresponding
methyl esters, AMe = integration value of the methoxy protons of
the methyl esters,ACH = integration value of
a-methylene pro-
2
tons.The representative 1H NMR spectrum showing % age conver-
sion (80.9%) of oil (triglycerides) into biodiesel (fatty acid methyl
esters) is shown in Fig. 9. The characteristic peak of methoxy pro-
tons was observed as a strong singlet at 3.65 ppm and a triplet of
a-CH2 protons at 2.26 ppm. These two peaks are the distinct peaks
for the confirmation of conversion of oil (triglycerides) into biodie-
sel (fatty acid methyl esters) [13]. The results demonstrated that

134
M. Tariq et al. / Polyhedron 57 (2013) 127–137
due to presence of small methyl groups causing less hindrance dur-
ing attack on bulky triglyceride molecules.
3.7. DNA binding studies
The binding interaction of the SS-DNA with ligand HL and com-
plexes 1 and 4 was investigated by comparing their absorption
spectra with and without SS-DNA. Both the ligand HL and com-
plexes 1 and 4 showed minor bathochromic shift of the spectral
band with significant hypochromicity, suggesting mainly interca-
lating mode of binding as well as groove binding tendency of the
compounds to the DNA helix (Figs. 10–12). This may be attributed
to the presence of phenyl group that facilitates the interaction with
double stranded DNA [43]. After 24 h, the spectrum was again ta-
ken and obtained the same results which confirm the stability of
drug–DNA adduct.
The intrinsic binding constant K of the ligand HL and complexes
1 and 4 were calculated in order to compare binding strengths of
ligand–DNA and complex-DNA by using Benesi–Hildebrand equa-
tion [20]:
Fig. 8. % Age conversion of sesame oil triglycerides into FAMEs (biodiesel).
catalytic activity was increased with increase in time interval and
triorganotin(IV) carboxylates (compounds 4–6) gave better % con-
version than diorganotin(IV) carboxylates. Out of triorganotin(IV)
carboxylates (compounds 4–6), the compound 4 (trimethyltin(IV)
derivative) gave highest conversion 80.9% in 24 h which may be
A0
eG
eG
e0 eHꢀG
1
¼
þ
ꢁ
A ꢀ A0 eHꢀG
ꢀ
ꢀ eG K½DNAꢂ
Fig. 9. 1H NMR spectrum showing formation of biodiesel with 80.9% conversion of oil (triglycerides) into biodiesel (fatty acid methyl esters).

M. Tariq et al. / Polyhedron 57 (2013) 127–137
135
Fig. 10. Absorption spectra of 20
l
M HL in the absence (a) and presence of 3
lM, (b) 6
l
M, (c) 9
lM, (d) 12
l
M, (e) 15
l
M, (f) 18
lM, (g) and 21
lM, (h) DNA. The arrow
direction indicates increasing concentrations of DNA. Inside graph is the plot of A0/(AꢀA0) vs. 1/[DNA] for the determination of binding constant and Gibb’s free energy of HL–
DNA adduct.
Fig. 11. Absorption spectra of 20 lM complex 1 in the absence (a) and presence of 3 lM, (b) 6 lM, (c) 9 lM, (d) 12 lM, (e) 15 lM, (f) 18 lM, (g) and 21 lM, (h), DNA. The
arrow direction indicates increasing concentrations of DNA. Inside graph is the plot of A0/(AꢀA0) vs. 1/[DNA] for the determination of binding constant and Gibb’s free energy
of complex 1–DNA adduct.

136
M. Tariq et al. / Polyhedron 57 (2013) 127–137
Fig. 12. Absorption spectra of 20 lM complex 4 in the absence (a) and presence of 3 lM, (b) 6 lM, (c) 9 lM, (d) 12 lM, (e) 15 lM, (f) 18 lM, (g) 21 lM, (h) and 24 lM, (i)
DNA. The arrow direction indicates increasing concentrations of DNA. Inside graph is the plot of A0/(AꢀA0) vs. 1/[DNA] for the determination of binding constant and Gibb’s
free energy of complex 4–DNA adduct.
where K = binding constant, A0 = absorbance of the drug, A = absor-
bance of the drug and its complex with DNA, G = absorption coef-
H–G = absorption coefficient of the drug–DNA
shown more toxicity having LD50 values in the range 0.008–
2.59
g mLꢀ1. The significant hypochromicity was observed in
e
l
ficient of the drug,
complex.
e
DNA binding studies of ligand HL and complexes 1 and 4 which
may be due to minor groove as well as intercalating mode of bind-
ing with base pairs of DNA. The triorganotin(IV) carboxylates 4–6
were shown better catalytic activity than their di- analogues 1–2.
Out of triorganotin(IV) carboxylates 4–6, the complex 4 (trimethyl-
tin(IV) derivative) showed greater catalytic activity which may be
due to presence of small methyl groups causing less hindrance dur-
ing attack on bulky triglyceride molecules.
The binding constants were obtained from the intercept-to-
slope ratios of A0/(AꢀA0) verus 1/[DNA] plots. The binding con-
stants were found to be 1.59 ꢁ 103 Mꢀ1 (HL), 3.0 ꢁ 104 Mꢀ1 (1)
and 5.6 ꢁ 103 Mꢀ1 (4).
The Gibb’s free energy (DG) of the ligand HL and complexes 1
and 4 were determined by using the following equation:
D
G ¼ ꢀRT lnK
Acknowledgment
where R is general gas constant (8.314 J Kꢀ1molꢀ1) and T is the
temperature (298 K). The Gibb’s free energies were found ꢀ18.25
(HL), ꢀ25.52 (1), and ꢀ21.3 kJ molꢀ1 (4), indicating spontaneous
interaction of the compounds with DNA.
M. Tariq (Pin No. 074-0616-Ps4-099) is thankful to higher edu-
cation commission of Pakistan for financial support during the
present study.
4. Conclusions
Appendix A. Supplementary data
A series of six organotin(IV) carboxylate complexes of 3-(2-
flourophenyl)-2-methylacrylic acid were synthesized and charac-
terized by FT-IR, NMR (1H and 13C). The complexes 1 and 4 were
also analyzed by single crystal X-ray analysis. The complex 1 has
shown hexa co-ordinated behaviour with distorted octahedral
geometry in both solution and solid state. The complex 4 has
shown four co-ordinated behavior in solution state while five coor-
dinated with distorted trigonal bipyramidal geometry in solid
state. The antimicrobial results showed that triorganotin(IV) car-
boxylates 4–5 exhibited greater antibacterial and antifungal activ-
ity than diorganotin(IV) carboxylates 1–3. The greater
antimicrobial activity of triorganotin(IV) deravatives may be due
to greater lipophilic character which cause easy passage of organo-
tin moieties into the microbial cells leading to death of pathogen
cells. The cytotoxic studies revealed that complexes 4–6 were
CCDC 910965 and 910967 contains the supplementary crystal-
lographic data for 1 and 4. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336 033; or e-mail:
deposit@ccdc.cam.ac.uk.
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