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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)
844 J IRAN CHEM SOC (2014) 11:839–846
123
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
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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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HL 40 30 10 50
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(lg/mL)
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