ORIGINAL PAPER

Synthesis, spectroscopic characterization, X-ray crystal structure,biological screening and catalytic studies of organotin(IV)carboxylates of 3-(4-cyanophenyl) acrylic acid

Muhammad Tariq • Saqib Ali • Muhammad Nawaz Tahir •

Nasir Khalid • Jafir Hussain Shirazi

Received: 14 July 2013 / Accepted: 19 September 2013 / Published online: 4 October 2013

� Iranian Chemical Society 2013

Abstract A series of six organotin(IV) carboxylates

[Me2SnL2] (1), [n-Bu2SnL2] (2), [n-Oct2SnL2] (3),

[Me3SnL] (4), n-Bu3SnL (5) and [Ph3SnL] (6), where

L = 3-(4-cyanophenyl) acrylic acid have been synthesized

and characterized by elemental analysis, FT-IR and NMR

(1H, 13C). The complex (4) was also analyzed by single

crystal X-ray analysis which showed distorted trigonal

bipyramidal geometry with polymeric bridging behavior.

The complexes 1–6 were screened for antimicrobial

activities and cytotoxicity. The results showed significant

activity with few exceptions. The catalytic activity of

complexes was assessed in transesterification reaction of

Brassica campestris oil (triglycerides) to produce biodiesel

(fatty acid methyl esters). The results showed that

triorganotin(IV) complexes exhibited good catalytic

activity than their di-analogues.

Keywords Organotin(IV) carboxylate � Antimicrobial

activity � Transesterification � Biodiesel

Introduction

Organotin(IV) carboxylates have been studied due to their

biocidal, pharmaceutical and catalytic properties [1–4].

The significant antifungal, antibacterial and antitumor

activities of organotin(IV) carboxylates [5–7] might be

related to the number and nature of the organic groups

attached to the central Sn atom and also on carboxylate

ligand which enhances fat-solubility and plays an

important role for the transportation of the organotin(IV)

moiety to an active site. The free carboxylic acid ligand

and the parent organotin(IV) precursors show less anti-

microbial activities than the organotin(IV) carboxylates.

The high activities of carboxylates relative to their parent

organotin(IV) precursors and the free carboxylic acid

ligands appear to be an additive (not a synergistic) effect

of the metal ions and the carboxylate groups. Usually

triorganotin(IV) complexes display a higher biological

activity than their di- and monoorganotin(IV) analogues,

which has been related to their ability to bind to proteins

[8–10]. Owing to greater scope in this area of research, in

the present article, we report synthesis and characteriza-

tion of six di- and triorganotin(IV) carboxylates of the

type R4-nSnLn (R = Me, n-Bu, n-Oct, Ph) where L = 3-

(4-cyanophenyl) acrylic acid and n = 1 or 2. The com-

plexes synthesized were tested for their antibacterial,

antifungal, cytotoxicity and catalytic activities.

Electronic supplementary material The online version of thisarticle (doi:10.1007/s13738-013-0355-9) contains supplementarymaterial, which is available to authorized users.

M. Tariq (&) � S. Ali

Department of Chemistry, Quaid-i-Azam University,

Islamabad 45320, Pakistan

e-mail: mtnazir@yahoo.com

S. Ali

e-mail: drsa54@yahoo.com

M. N. Tahir

Department of Physics, University of Sargodha, Sargodha,

Pakistan

N. Khalid

Chemistry Division, Pakistan Institute of Nuclear Science and

Technology, Nilore, Pakistan

J. H. Shirazi

Department of Microbiology, Quaid-i-Azam University,

Islamabad 45320, Pakistan

123

J IRAN CHEM SOC (2014) 11:839–846

DOI 10.1007/s13738-013-0355-9

Experimental

Materials and methods

All the di-, triorganotin(IV) precursors and 3-(4-cyano-

phenyl) acrylic acid (HL) were purchased from Sigma-

Aldrich and were used without further purification. All the

solvents used were of analytical grade and dried according to

reported procedures before use [11]. The melting points were

measured on a Gallenkamp (UK) electrothermal melting

point apparatus. Microanalyses were done using a Leo CHNS

932 apparatus. FT-IR spectra were recorded in the range

from 4,000 to 400 cm-1 using a Thermo Nicolet-6700 FT-IR

Spectrophotometer using KBr discs. 1H and 13C NMR

spectra were recorded at room temperature in CDCl3 on a

Bruker Avance Digital 300 MHz NMR spectrometer (Swit-

zerland). 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 temperature device and intensity measurements were

performed using graphite monochromated Mo–Ka radiation

from a sealed ceramic diffraction tube (SIEMENS). Gener-

ator settings were 50 kV/40 mA. The structure was solved by

Patterson method and extension of the model was accom-

plished by direct method using the program DIRDIF or

SIR2004. Final refinement on F^2 carried out by full matrix

least squares techniques using SHELXL-97, a modified

version of the program PLUTO (preparation of illustrations)

and PLATON package. The brassica plant seeds were pur-

chased 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 using

German made electric oil expeller (KEK P0015-10127).

Syntheses

Synthesis of Na-salt of 3-(4-cyanophenyl) acrylic acid

The sodium salt of ligand, R0COONa, was prepared by

dropwise addition of an equimolar amount of sodium hydro-

gen carbonate solution to a methanolic solution of ligand acid

(R0COOH). The solution was stirred for 2 h at room temper-

ature, evaporated under reduced pressure to give a white solid

and was vacuum dried. The Scheme 1 represents numbering

in sodium salt of ligand acid and organic groups attached to Sn

atom for 1H and 13C-NMR interpretation.

Dimethyltin(IV) bis[(3-(4-cyanophenyl) acrylic acid)] (1)

The sodium salt R0COONa (0.4 g or 2 mmol) was refluxed

with dimethyltin(IV) dichloride (0.22 g or 1 mmol) in

molar ratio of 2:1 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

rotary evaporated to get the white solid mass. Yield: 78 %.

M.p. 171–173 �C. Anal. Calcd for C22H18N2O4Sn (%): C,

53.59, H 3.68, N 5.68. Found (%): C, 53.55, H 3.65, N

5.70. IR (KBr, cm-1): 1,551 m(OCO)asym, 1,421 m(OCO)-

sym, (Dm = 130 cm-1), 576 m(Sn–C), 449 m(Sn–O). 1H-

NMR (CDCl3, ppm): 6.51 (d, H2, 2H, 3Jtrans = 16.2), 7.75

(d, H3, 2H, 3Jtrans = 15.9), 7.69 (d, H5,50, 4H), 7.47(d, H6,60,

4H), 0.98 (s, Ha, 6H), 2J(119/117Sn–1H) = 83/80 Hz). 13C-

NMR (CDCl3, ppm): 171.1 (C-1), 128.5 (C-2), 144.3 (C-3),

138.5 (C-4), 126.3 (C-5), 132.7 (C-6), 113.6 (C-7), 118.3

(C-8), 5.1 (C-a, 1J(119Sn–13C) = 705 Hz, C–Sn–C,

138.5�).

Dibutyltin(IV) bis[(3-(4-cyanophenyl) acrylic acid)] (2)

Complex 2 was prepared in the same way as 1, using

R0COONa (0.30 g or 1.53 mmol) and dibutyltin(IV)

dichloride (0.23 g or 0.76 mmol) in molar ratio of 2:1.

Yield: 75 %. M.p. 76–78 �C. Anal. Calcd for

C28H30N2O4Sn (%): C, 58.26, H 5.24, N 4.85. Found (%):

C, 58.29, H 5.22, N 4.81. IR (KBr, cm-1): 1,550

m(OCO)asym, 1,412 m(OCO)sym, (Dm = 138 cm-1), 567

m(Sn–C), 455 m(Sn–O). 1H-NMR (CDCl3, ppm): 6.56 (d,

H2, 2H, 3Jtrans = 15.9), 7.78 (d, H3, 2H, 3Jtrans = 16.2),

O

+Na-O

N

1 2

3

4

5

5/

6

6/

7 8

H

H

Scheme 1 Numbering scheme of sodium salt of ligand acid (NaL)

and organic groups attached to Sn atom in complexes

840 J IRAN CHEM SOC (2014) 11:839–846

123

7.69 (d, H5,50, 4H), 7.48 (d, H6,60, 4H), 1.79–1.63 (m, Ha,

4H), 1.46–1.37 (m, Hb, 4H), 1.20–1.15 (m, Hc, 4H), 0.90 (t,

Hd, 6H). 13C-NMR (CDCl3, ppm): 175.5 (C-1), 128.3 (C-

2), 146.9 (C-3), 138.5 (C-4), 127.3 (C-5), 132.4 (C-6),

113.5 (C-7), 118.3 (C-8), 22.5 (C-a), 27.1 (C-b), 32.5 (C-

c), 13.5 (C-d).

Dioctyltin(IV) bis[(3-(4-cyanophenyl) acrylic acid)] (3)

Complex 3 was prepared using ligand acid, R0COOH

(0.21 g 1.16 mmol) and dioctyltin(IV) oxide (0.21 g or

0.58 mmol) in molar ratio of 2:1. The reactant mixture was

suspended in 100 mL dry toluene in a single necked round

bottom flask (250 mL), equipped with a Dean–Stark

apparatus. 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, solvent was removed under reduced

pressure and gel product was obtained. Yield: 70 %. M.p.

gel. Anal. Calcd for C36H46N2O4Sn (%): C, 62.71, H 6.72,

N 4.06. Found (%): C, 62.68, H 6.75, N 4.15. IR (KBr,

cm-1): 1,536 m(OCO)asym, 1,391 m(OCO)sym,

(Dm = 145 cm-1), 545 m(Sn–C), 467 m(Sn–O). 1H-NMR

(CDCl3, ppm): 6.56 (d, H2, 2H, 3Jtrans = 15.9), 7.77 (d, H3,

2H, 3Jtrans = 16.2), 7.68 (d, H5,50, 4H), 7.48 (d, H6,60, 4H),

1.74–1.24 (bs, Ha,b,c,a0,b0,c0, 28H), 0.82 (t, Hd0, 6H). 13C-

NMR (CDCl3, ppm): 175.3 (C-1), 128.4 (C-2), 146.9 (C-3),

138.6 (C-4), 126.4 (C-5), 132.4 (C-6), 111.7 (C-7), 118.6

(C-8), 33.9, 32.6 (C-b), 31.8 (C-c), 29.7 (C-d), 25.9 (C-a0),24.3 (C-b0), 22.2 (C-c0), 14.1 (C-d0).

Trimethyltin(IV) 3-(4-cyanophenyl) acrylic acid (4)

Complex 4 was prepared in the same way as 1, using

R0COONa (0.4 g or 2 mmol) and trimethyltin(IV) chloride

(0.41 g or 2 mmol) in molar ratio of 2:1. The product was

recrystallized from chloroform and n-hexane (4:1) mixture.

Yield: 80 %. M.p. 135–137 �C. Anal. Calcd for

C13H15NO2Sn (%): C, 46.47, H 4.50, N 4.17. Found (%): C,

46.41, H 4.55, N 4.20. IR (KBr, cm-1): 1,570 m(OCO)asym,

1,382 m(OCO)sym, (Dm = 188 cm-1), 553 m(Sn–C), 439

m(Sn–O). 1H-NMR (CDCl3, ppm): 6.53 (d, H2, H,3Jtrans = 15.9), 7.76 (d, H3, H, 3Jtrans = 15.9), 7.69 (d, H5,50,

2H), 7.49 (d, H6,60, 2H), 0.72 (s Ha, 9H), 2J(119/

117Sn–1H) = 58/56 Hz, C–Sn–C, 110.0o). 13C-NMR

(CDCl3, ppm): 171.1 (C-1), 128.2 (C-2), 141.6 (C-3), 139.3

(C-4), 127.3 (C-5), 132.3 (C-6), 111.4 (C-7), 118.5 (C-8), -

2.2 (C-a), 1J (119/117Sn–C) = 396/378 Hz, C–Sn–C, 111.5�).

Tributyltin(IV) 3-(4-cyanophenyl) acrylic acid (5)

Complex 5 was prepared in the same way as 1, using

R0COONa (0.3 g or 1.53 mmol) and tributyltin(IV)

chloride (0.5 g or 1.53 mmol) in molar ratio of 1:1. Yield:

69 %. M.p. 67–69 �C. Anal. Calcd for C22H33NO2Sn (%):

C, 57.17, H 7.20, N 3.03. Found (%): C, 57.20, H 7.26, N

3.05. IR (KBr, cm-1): 1,556 m(OCO)asym, 1,376 m(OCO)-

sym, (Dm = 180 cm-1), 572 m(Sn–C), 443 m(Sn–O). 1H-

NMR (CDCl3, ppm): 6.56 (d, H2, H, 3Jtrans = 15.9), 7.77

(d, H3, H, 3Jtrans = 15.9), 7.68 (d, H5,50, 2H), 7.48 (d, H6,60,

2H), 1.81–1.72 (m, Ha, 6H), 1.45–1.36 (m, Hb, 6H), 1.35-

1.30 (m, Hc, 6H), 0.92 (t, Hd, 9H). 13C-NMR (CDCl3,):

172.2 (C-1), 128.4 (C-2), 145.4 (C-3), 139.1 (C-4), 127.4

(C-5), 132.2 (C-6), 111.7 (C-7), 118.5 (C-9), 26.3 (C-a),

27.6 (C-b), 30.2 (C-c), 13.8 (C-d).

Triphenyltin(IV) 3-(4-cyanophenyl) acrylic acid (6)

Complex 6 was prepared in the same way as 1, using

R0COONa (0.3 g or 1.53 mmol) and triphenyltin(IV)

chloride (0.59 g or 1.53 mmol) in molar ratio of 1:1. Yield:

76 %. M.p. 126–127 �C. Anal. Calcd for C28H21NO2Sn

(%): C, 64.40, H 4.05, N 2.68. Found (%): C, 64.45, H

4.10, N 2.66. IR (KBr, cm-1): 1,582 m (OCO) asym, 1,387 m(OCO) sym, (Dm = 195 cm-1), 460 m (Sn–O). 1H-NMR

(CDCl3, ppm): 6.55 (d, H2, H), 7.77 (d, H3, H), 7.68 (d,

H5,50, 2H), 7.39 (d, H6,60, 2H), 7.71–7.45 (H-b, H-c, Hd

18H]. 13C-NMR (CDCl3, ppm): 171.8 (C-1) 128.7 (C-2),

142.3 (C-3), 138.7 (C-4), 127.4 (C-5), 132.6 (C-6), 111.3

(C-7), 118.3 (C-8), 131.2 (C-a), 139.3 (C-b), 129.7 (C-c),

129.6 (C-d).

Antimicrobial activities

The antibacterial activity of ligand HL and its organo-

tin(IV) complexes were tested against four bacterial

strains; two gram-positive (Micrococcus luteus and

Staphylococcus aureus) and two gram-negative (Esche-

richia coli and Bordetella bronchiseptica). The agar well-

diffusion method was used [12]. Antifungal activity against

four fungal strains (Aspergillus Flavus, Aspergillus niger,

Fusarium solani, and Aspergillus fumigatus) was deter-

mined using agar tube dilution method [13].

Cytotoxic studies

Cytotoxicity was studied by the brine–shrimp lethality

assay method [13]. Brine–shrimp (Artemia salina) eggs

were hatched in artificial sea water (3.8 g sea salt/L) at

ambient temperature of 23 ± 1 �C. After 2 days, these

shrimp were transferred to vials containing 5 mL of arti-

ficial sea water (10 shrimp per vial) with 10, 100 and

1,000 lg/mL final concentrations of each complex taken

from their stock solutions of 12 mg/mL in DMSO. After

24 h, the number of surviving shrimp was counted. Data

J IRAN CHEM SOC (2014) 11:839–846 841

123

were analyzed with a Biostat 2009 computer program

(Probit analysis) to determine LD50 values.

Catalytic transesterification

Transesterification of Brassica campestris oil was carried

out using organotin(IV) carboxylates as catalysts in molar

ratio of 400:100:1 (methanol:oil:catalyst) [14] in a 100 mL

three neck round bottom flask equipped with reflux con-

denser, magnetic stirrer, thermometer and sampling outlet.

Before the reaction, the organotin(IV) complexes as cata-

lysts, were solubilized in 0.5 mL chloroform. The reaction

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 the % age conversion of oil into biodiesel.

Results and discussion

Syntheses of complexes 1–6

Diorganotin dichloride and triorganotin chloride with NaL

(L = 3-(4-cyanophenyl) acrylic acid) in 1:2 and 1:1,

respectively, while R2SnO with HL in 1:2 molar ratios give

complexes according to the following equations

R2SnCl2 þ 2NaL! R2SnL2 þ 2NaCl ð1ÞR ¼ CH3 1ð Þ; n� C4H9 2ð Þ;R2SnOþ 2HL! R2SnL2 þ H2O ð2ÞR ¼ n� C8H17 3ð ÞR3SnClþ NaL! R3SnLþ NaCl ð3ÞR ¼ CH3 4ð Þ; n� C4H9 5ð Þ; C6H5 6ð Þ

FT-IR analysis

FT-IR spectra of synthesized complexes range were

recorded in the range 4,000–400 cm-1, to determine the

mode of the carboxylate moiety coordination to the tin

centre. The difference between the asymmetric and sym-

metric carboxylate stretches [Dm = masym(COO-) - msym(-

COO-)] vibrations gives the mode of binding of COO-

moiety to tin centre [15, 16]. It is generally believed that

Dm below 200 cm-1 corresponds to bidentate while greater

than 200 cm-1 corresponds to unidentate mode of coordi-

nation of carboxylate moiety to tin atom [17]. Moreover, a

Dm value between 150 and 250 cm-1 indicates a bridging

behavior while a value \150 cm-1 exhibits a chelate

structure. The magnitudes of Dm for complexes 1–6 are

within range of 130–195 cm-1 which indicate the presence

of bidentate carboxylate groups in these complexes [18].

On the basis of Dm values, the carboxylate ligand surrounds

the Sn(IV) atom in chelated bidentate mode of binding

giving octahedral geometry to the complexes 1–3 which is

consistent with literature [5, 8, 14]. While the Dm values for

complexes 4–6 are compatible with the bridging bidentate

mode of binding giving trigonal bipyramidal geometry

with five coordinated Sn(IV) atom in solid state and are

consistent with single crystal X-ray structure of complex 4

as well as with literature [5, 8, 14]. The absorption bands in

the 439–467 cm-1 region for complexes 1–6 are assigned

to the stretching mode of the Sn–O linkage which indicates

the formation of complexes [19].

NMR studies

The chemical shift, multiplicities pattern in 1H NMR spectra

are helpful in elucidation of structures of the synthesized

complexes. All the protons present in the complexes (1–6)

were identified by the position and number with the protons

calculated from incremental method The satellites due to

(119/117Sn,1H) coupling are helpful in finding geometry

around tin in solution. The methyl protons of dimethyl-

tin(IV) (1) and trimethyltin(IV) (4) derivative appear as

sharp singlets with well-defined satellites at 0.98 and

0.72 ppm having coupling constants of 83/80 and 58/56 Hz

[2J (119/117Sn,1H)], respectively. The determined 2J values

indicate five or six coordination (due to the fluxional

behavior) for complex (1) and four coordination for complex

(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 [19, 20]. Despite

the complex pattern of 1H NMR spectra of di- (2) and tri-n-

butyltin(IV) (5) derivatives, a clear triplet due to terminal

methyl group appears at 0.90 and 0.92 ppm, respectively.

The methylene protons (CH2) of n-octyltin(IV) derivative

(3) exhibit somewhat different behavior as compared with

the n-butyl groups of the respective complexes. All the CH2

protons of n-octyl groups give broad/multiplet signals in the

range 1.74–1.24 ppm.

In 13C NMR, the carbon signals of organotin(IV) com-

plexes 1–6 have been found in good agreement with

expected values. The carbons bonded to Sn atom have

satellites due to 1J [119Sn,13C] couplings which are

important parameters for characterization of organotin(IV)

complexes and geometry around tin atom. For dimethyl

derivative (1), the value of 1J [119Sn,13C] is 705 Hz while

for trimethyltin(IV) (4), it is 396 Hz which indicates five or

six coordination geometry around the tin in solution for (1)

which may be due to the fluxional behavior and four

coordination for (4), respectively, [21, 22].

Crystal structure of complex 4

The molecular and polymeric bridging structure of com-

plex 4 is shown in Figs. 1, 2, respectively. The crystal data,

842 J IRAN CHEM SOC (2014) 11:839–846

123

selected bond length and bond angles of complex 4 are

listed in Tables 1, 2, respectively. The Fig. 1 showed that

Sn1 atom is bonded with three methyl groups which have

C–Sn–C bond angles C11–Sn1–C12 = 117.78(17) A,

C11–Sn1–C13 = 117.07(17) A, C12–Sn1–C13 = 124.28

(15) A. These three methyl groups attached to Sn1 atom

make trigonal plane. The Sn1 atom is also bonded with

oxygen atoms from carboxylate moiety having Sn1–O1 and

Sn1–O2 bond distances 2.194(2) and 2.366(3), respec-

tively, showing former bond is covalent bond (covalent

bond length, 2.13 A) and latter is coordinate covalent

(shorter than the sum of the van der Waals radii of con-

nected atoms, 3.68 A). The two oxygen atoms bonded with

Sn1 have occupied axial positions with angle O1–Sn1–

O2 = 174.38�(9) and three methyl groups are in equatorial

positions suggest that the geometry around Sn1 is distorted

trigonal bipyramidal. The geometry around Sn can also be

deduced by the value of s = (b - a)/60, where b is the

largest and a is the second largest basal angles around the

Sn atom [23]. The calculated s value for complex 4 is 0.835

which indicates distorted trigonal-bipyramidal geometry

around the Sn1 atom.

Antimicrobial activity

In vitro antibacterial activity tests of the ligand HL and its

organotin(IV) complexes (1–6) were carried out against

four bacterial strains; two gram-positive (Micrococcus

luteus and Staphylococcus aureus) and two gram-negative

(Escherichia coli and Bordetella bronchiseptica). Roxi-

thromycin and Cefixime were used as positive control. The

results are shown in Table 3. Criteria for activity are 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 [24]. The antibacterial study demonstrates

that complexes 2, 4–6 exhibited significant activity against

various tested bacterial strains while complexes 1, 3 and

ligand HL showed zero or non-significant activity against

all tested bacterial strains.Fig. 1 Molecular structure of complex 4

Fig. 2 Polymeric structure of

complex 4

J IRAN CHEM SOC (2014) 11:839–846 843

123

The ligand HL and its organotin(IV) complexes (1–6)

were screened for antifungal activity against four fungal

strains (Aspergillus flavus, Aspergillus niger, Aspergillus

fumigatus and Fusarium solani). The results are shown in

Table 4. Terbinafine was used as standard drug in this

assay. Criteria for activity are based on percentage of

growth inhibition; more than 70 % was considered as

significant activity, 60–70 % as good, 50–60 % as mod-

erate while below 50 % was considered as non-significant

[24]. The antifungal data showed that complexes along

with ligand HL showed significant to non-significant

activity against all the tested fungal strains.

Cytotoxic studies

The cytotoxicity of ligand HL and organotin(IV) com-

plexes (1–6) was studied in vitro against the brine–shrimp

lethality method [25] using reference drug MS-222 (Tri-

caine Methanesulfonate) and the results are shown in

Table 5. The data are based on mean value of 2 replicates

each of 10, 100 and 1,000 lg mL-1. The LD50 data

exhibited that complexes 2 and 5 are toxic while complexes

1, 3, 4, and 6 are less toxic.

Catalytic activity of organotin(IV) carboxylates

The transesterification reaction of triglycerides in Bras-

sica campestris oil was carried out in molar ratio of

400:100:1 (methanol:oil:catalyst) to assess the catalytic

activity of organotin(IV) carboxylates [14, 15]. 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 (biodiesel) 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 biodiesel (FAMEs). The results are

shown in Fig. 3. The equation used to quantify the extent

of transesterification [26] was:

C ¼ 2AMe

3ACH2

� 100

where C = percentage conversion of triglycerides to cor-

responding methyl esters

AMe = integration value of the methoxy protons of the

methyl esters and

ACH2= integration value of a-methylene protons

The results demonstrated that catalytic activity was

increased with increase in time interval and triorgano-

tin(IV) carboxylates gave more % conversion than dior-

ganotin(IV) carboxylates. Out of triorganotin(IV)

carboxylates, the complex 4 (trimethyltin(IV) derivative)

gave highest conversion 75.3 % in 24 h which may be due

to presence of small methyl groups causing less hindrance

during attack on bulky triglyceride molecules.

Table 1 Crystal data and structure refinement parameters for com-

plex 4

Compound 4

Chemical formula C13H15NO2Sn

Formula mass (g mol-1) 335.95

Crystal system Monoclinic

Space group P21/c

Unit cell dimensions

a (A) 12.1841 (10)

b (A) 9.9220 (7)

c (A) 12.5081 (11)

a (�) 90

b (�) 103.949 (3)

c (�) 90

Volume (A3) 1,467.5 (2)

Z 4

Temperature (K) 296 (2)

Density (calculated) (g cm-3) 1.521

Absorption coefficient (mm-1) 1.732

F(000) 664

Radiation (A) (Mo K/a) 0.71073

Index ranges h: -15 ? 15; k: -12 ? 11;

l: -15 ? 15

h (�) Lin Lax 1.72–26.0

Total reflections 2,873

Restraints/parameters 0/157

Rall, Rgt 0.0485, 0.0298

WRref, WRgt 0.0659, 0.0591

Goodness-of-fit 1.006

Table 2 Selected bond lengths (A) and bond angles (�) of complex 4

Bond lengths (A)

Sn1–C11 2.123 (4) Sn1–O1 2.194 (2)

Sn1–C12 2.113 (4) Sn1–O2 2.366 (3)

Sn1–C13 2.114 (4) O1–C1 1.264 (4)

O2–C1 1.251 (5)

Bond angles (�)

O1–Sn1–C11 89.77 (11) O2–Sn1–C13 88.33 (12)

O1–Sn1–C12 95.73 (12) C11–Sn1–C12 117.78 (17)

O1–Sn1–C13 93.55 (12) C11–Sn1–C13 117.07 (17)

O2–Sn1–C11 84.66 (11) C12–Sn1–C13 124.28 (15)

O2–Sn1–C12 87.56 (12) O1–Sn1–O2 174.38 (9)

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Conclusions

Six organotin(IV) complexes of 3-(4-cyanophenyl) acrylic

acid were synthesized and characterized by elemental

analysis, FT-IR and NMR (1H and 13C). The complex 4

was also analyzed by single crystal X-ray analysis. The

complex 4 has shown distorted trigonal bipyramidal

geometry with polymeric bridging behavior. The antimi-

crobial results showed that triorganotin(IV) carboxylates

4–5 exhibited greater antibacterial and antifungal activity

than diorganotin(IV) carboxylates 1–3. The triorgano-

tin(IV) carboxylates 4–6 were shown comparatively better

catalytic activity than their di-analogues 1–2.

Acknowledgments M. Tariq (Pin No. 074-0616-PS4-099) is

thankful to higher education commission of Pakistan for financial

support.

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Table 3 Antibacterial activity

data of organotin(IV)

complexes of 3-(4-cyanophenyl)

acrylic acid

Average zone of inhibition (mm)

Complex no. Staphylococcus

aureus

Escherichia

coli

Bordetella

bronchiseptica

Micrococcus

luteus

HL 0 10 0 06

1 0 12 08 0

2 10 18 0 18

3 0 0 10 0

4 10 16 0 10

5 20 12 0 18

6 0 16 14 22

Cefixime 22 22 25 20

Roxythromycin 25 20 25 22

Table 4 Antifungal activity data of organotin(IV) complexes of 3-(4-

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Mean value of percent growth inhibition (%)

Complex no. Aspergillus

Flavus

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HL 40 30 10 50

1 80 60 70 65

2 15 40 10 0

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Terbinafine 100 100 100 100

Table 5 Cytotoxicity data of organotin(IV) complexes of 3-(4-cya-

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(lg/mL)

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4 8 5 0 661.2

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Fig. 3 % age conversion of Brassica campestris oil triglycerides into

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