Syntheses, structural characteristics, and antimicrobial activities of new organotin(IV) 3-(4-bromophenyl)-2-ethylacrylates

Article abstract of DOI:10.1080/00958972.2012.718076

New organotin(IV) carboxylates, [n-Bu2SnL2] (1), [Et₂SnL ₂] (2), [Me₂SnL₂] (3), [n-Oct ₂SnL₂] (4), [n-Bu₃SnL]_n (5), [Me₃SnL]_n (6), and [Ph₃SnL]_n (7), where L=3-(4-bromophenyl)-2-ethylacrylate, were synthesized and characterized by elemental analysis, FT-IR, and multinuclear NMR (¹H, ¹³C, and ¹¹⁹Sn). Spectroscopic studies confirm coordination of L to the organotin moiety via COO group. Single-crystal X-ray analysis reveals bridging mode of coordination in 6. Packing diagram established a supramolecular cage-like structure for 6 due to Sn-O interactions (3.287 A). Subsequent antimicrobial activities proved them to be active biologically.

Full text of DOI:10.1080/00958972.2012.718076

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
Syntheses, structural characteristics, and
antimicrobial activities of new organotin(IV) 3-(4-
bromophenyl)-2-ethylacrylates
Niaz Muhammad , Zia-Ur-Rehman , Shaukat Shujah , Afzal Shah , Saqib Ali ,
Auke Meetsma & Zahid Hussain
To cite this article: Niaz Muhammad , Zia-Ur-Rehman , Shaukat Shujah , Afzal Shah , Saqib Ali ,
Auke Meetsma & Zahid Hussain (2012) Syntheses, structural characteristics, and antimicrobial
activities of new organotin(IV) 3-(4-bromophenyl)-2-ethylacrylates, Journal of Coordination
Chemistry, 65:21, 3766-3775, DOI: 10.1080/00958972.2012.718076
To link to this article: http://dx.doi.org/10.1080/00958972.2012.718076
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Date: 09 June 2016, At: 03:57

Journal of Coordination Chemistry
Vol. 65, No. 21, 10 November 2012, 3766–3775
Syntheses, structural characteristics, and antimicrobial activities
of new organotin(IV) 3-(4-bromophenyl)-2-ethylacrylates
NIAZ MUHAMMADyz, ZIA-UR-REHMANy, SHAUKAT SHUJAHy,
AFZAL SHAHy, SAQIB ALI*y, AUKE MEETSMAx and ZAHID HUSSAIN{
yDepartment of Chemistry, Quaid-i-Azam University, Islamabad-45320, Pakistan
zDepartment of Chemistry, Abdul Wali Khan University, Mardan, Pakistan
xCrystal Structure Center, Chemical Physics, Zernike Institute for Advanced Materials,
University of Groningen, Nijenborgh 4, NL-9747 AG GRONINGEN, The Netherlands
{Institute of Industrial Biotechnology, G.C. University, Lahore, Pakistan
(Received 17 May 2012; in final form 17 July 2012)
New organotin(IV) carboxylates, [n-Bu2SnL2] (1), [Et2SnL2] (2), [Me2SnL2] (3), [n-Oct2SnL2]
(4), [n-Bu3SnL]n (5), [Me3SnL]n (6), and [Ph3SnL]n (7), where L ¼ 3-(4-bromophenyl)-2-
ethylacrylate, were synthesized and characterized by elemental analysis, FT-IR, and
multinuclear NMR (1H, 13C, and 119Sn). Spectroscopic studies confirm coordination of L to
the organotin moiety via COO group. Single-crystal X-ray analysis reveals bridging mode of
coordination in 6. Packing diagram established a supramolecular cage-like structure for 6 due
˚
to Sn–O interactions (3.287 A). Subsequent antimicrobial activities proved them to be active
biologically.
Keywords: Organotin(IV) carboxylate; Crystal structure; Antimicrobial
1. Introduction
Drug resistance in microbial strains is a serious public health concern [1–6] and
demands urgent development of new and more efficient antibacterial and antifungal
agents. Organotin(IV) complexes with carboxylate ligands have been the subject of
interest due to their numerous biological activities [7–15]. Antifungal and antibacterial
properties of a range of organotin(IV) carboxylates have been evaluated, with improved
properties of organotin(IV) carboxylates over parent ligands [7, 12, 13]. This enhanced
activity may be attributed to a variety in coordination number, geometries, thermo-
dynamic, and kinetic stability of organotin(IV) carboxylates. Although data are
available, work is in progress for development of more effective compounds in terms of
biological activity, stability, and compromised solubility in both aqueous and lipid
layers. From structural and biological diversity of organotin carboxylates and in
connection with our interest in coordination chemistry of organotin compounds with
different carboxylic acids [7, 16], herein we report the synthesis, characterization,
*Corresponding author. Email: drsa54@yahoo.com
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online ß 2012 Taylor & Francis
http://dx.doi.org/10.1080/00958972.2012.718076

Organotin(IV) ethylacrylates
3767
antibacterial, and antifungal activities of organotin(IV) 3-(4-bromophenyl)-2-
ethylacrylates.
2. Experimental
Organotin(IV) precursors, 4-bromobenzaldehyde and ethylmelonic acid were purchased
from Aldrich and used without purification. Solvents were dried according to reported
procedures [17]. Melting points were recorded on an electrothermal melting point
apparatus, model MP-D mitamura Riken Kogyo (Japan). Microanalyses were done
using a Leco CHNS 932 apparatus. IR spectra were recorded with KBr pellets from
4000 to 400 cmꢀ1 using a Bio-Rad Excalibur FT-IR, model FTS 300 MX spectrometer
1
(USA). H and 13C-NMR spectra were recorded at room temperature in CDCl3 on a
Bruker Avance Digital 300 MHz NMR spectrometer (Switzerland) and a Varian Unity
500-MHz instrument [119Sn; SnMe4 (ext) ref].
2.1. Synthesis
2.1.1. 3-(4-bromophenyl)-2-ethylacrylic acid (HL). Synthesis and single-crystal analy-
sis of 3-(4-bromophenyl)-2-ethylacrylic acid (HL) were reported [18], while other
spectroscopic data are given below. Yield: 65%;. m.p. 138.5–139.5ꢁC. Anal. Calcd for
C11H11BrO2 (%): C, 51.76; H, 4.31. Found: C, 51.76; H, 4.33. IR (cmꢀ1): 3328–2529
1
ꢀ(OH), 1663 ꢀ(OCO)asym, 1409 ꢀ(OCO)sym, 254 Dꢀ. H-NMR (CDCl3 ppm): 11.68
0
0
(s, H1, 1H); 7.73 (s, H3, 1H); 7.29 (d H5,5 , 2H); 7.56 (d, H6,6 , 2H); 2.58 (q, H8, 2H); 1.23
(t, H9, 3H). 13C-NMR (CDCl3 ppm), 173.8 (C-1), 134.3 (C-2), 139.5 (C-3), 134.6, 131.8,
130.9, 123.0 (Ar–C), 20.6 (C-8), 13.7 (C-9).
2.1.2. Na-salt of 3-(4-bromophenyl)-2-ethylacrylate (NaL). The sodium salt of ligand,
NaL, was prepared by dropwise addition of an equimolar amount of sodium hydrogen
carbonate dissolved in distilled water to a methanolic solution of HL. The solution was
stirred for 2 h at room temperature and evaporated under reduced pressure to give a
white solid.
2.1.3. Di-n-butyltin(IV) bis[3-(4-bromophenyl)-2-ethylacrylate] (1). NaL (1.38 g,
5 mmol) was refluxed for 10 h with dibutyltin(IV) dichloride (0.76 g, 2.5 mmol) in dry
toluene contained in a 250 mL two neck round bottom flask. A turbid solution obtained
was left overnight at room temperature. The precipitated sodium chloride was filtered
off and the filtrate was rotary evaporated. The resultant solid was recrystallized from
chloroform and n-hexane (4 : 1). Yield: 71%; m.p. gel. Anal. Calcd for C30H38Br2O4Sn
(%): C, 48.52; H, 5.12. Found: C, 48.56; H, 5.13. IR (cmꢀ1): 1560 ꢀ(OCO)asym, 1411
1
ꢀ(OCO)sym, 149 Dꢀ, 575 ꢀ(Sn–C), 452 ꢀ(Sn–O). H-NMR (CDCl3 ppm): 7.72 (s, H3,
0
0
2H); 7.29 (d, H5,5 , 4H); 7.55 (d, H6,6 , 4H); 2.57 (q, H8, 4H); 1.21 (t, H9, 6H); 1.77–1.72
(m, Hꢁ, ꢂ, 8H); 1.48–1.41 (m, Hꢃ, 4H); 0.94 (t, Hꢄ, 6H). 13C-NMR (CDCl3 ppm), 177.0
(C-1), 134.6 (C-2), 138.6 (C-3), 135.2, 131.7, 130.8, 122.7 (Ar–C), 21.0 (C-8), 13.7 (C-9),
25.3 (C-ꢁ), 26.8 (C-ꢂ), 26.4 C-ꢃ, 13.6 (C-ꢄ).119Sn-NMR (CDCl3, ppm): ꢀ161.3.

3768
N. Muhammad et al.
2.1.4. Diethyltin(IV) bis[3-(4-bromophenyl)-2-ethylacrylate] (2). Compound 2 was
prepared and recrystallized in the same way as 1 using NaL (1.38 g, 5 mmol) and
diethyltin(IV) dichloride (0.62 g, 2.5 mmol). Yield: 89%; m.p. 90–92ꢁC. Anal. Calcd for
C26H30Br2O4Sn (%): C, 45.48; H, 4.37. Found: C, 45.43; H, 4.40. IR (cmꢀ1): 1559
1
ꢀ(OCO)asym, 1407 ꢀ(OCO)sym, 152 Dꢀ, 573 ꢀ(Sn–C), 437 ꢀ(Sn–O). H-NMR (CDCl3
0
0
ppm): 7.74 (s, H3, 2H); 7.30 (d, H5,5 , 4H); 7.54 (d, H6,6 , 4H); 2.57 (q, H8, 4H); 1.21
(t, H9, 6H); 1.76 (q, Hꢁ, 4H); 1.38 (t, Hꢂ, 6H). 13C-NMR (CDCl3 ppm), 177.9 (C-1),
134.7 (C-2), 138.6 (C-3), 135.2, 131.7, 130.8, 122.6 (Ar–C), 21.1 (C-8), 13.8 (C-9), 17.6
(C-ꢁ), 9.0 (C-ꢂ). 119Sn-NMR (CDCl3, ppm): ꢀ165.8.
2.1.5. Dimethyltin(IV) bis[3-(4-bromophenyl)-2-ethylacrylate] (3). Compound 3 was
prepared and recrystallized in the same way as 1 using NaL (1.38 g, 5 mmol) and
dimethyltin(IV) dichloride (0.55 g, 2.5 mmol). Yield: 67%; m.p. 101–103ꢁC. Anal. Calcd
for C24H26Br2O4Sn (%): C, 43.77; H, 3.95. Found: C, 43.80; H, 4.10. IR (cmꢀ1): 1553
1
ꢀ(OCO)asym, 1400 ꢀ(OCO)sym, 153 Dꢀ, 579 ꢀ(Sn–C), 438 ꢀ(Sn–O). H-NMR (CDCl3
2
1
ppm), J[(119Sn, H), Hz]: 7.73 (s, H3, 2H); 7.27 (d, H5,5 , 4H); 7.54 (d, H6,6 , 4H); 2.56
(q, H8, 4H); 1.20 (t, H9, 6H); 1.10 {(s, Hꢁ, 3H) [82]}. 13C-NMR (CDCl3 ppm): 177.7
(C-1), 134.6 (C-2), 138.9 (C-3), 135.1, 131.8, 130.8, 122.7 (Ar–C), 21.1 (C-8), 13.7 (C-9),
4.7 (C-ꢁ). 119Sn-NMR (CDCl3, ppm): ꢀ133.4.
0
0
2.1.6. Di-n-octyltin(IV) bis[3-(4-bromophenyl)-2-ethylacrylate] (4). HL (1.28 g,
5 mmol) and dioctyltin(IV)oxide (0.90 g, 2.5 mmol) were suspended in dry toluene
(100 mL) in a single-neck round-bottom flask (250 mL) equipped with a Dean-Stark
apparatus. The mixture was refluxed for 10 h and water formed during the conden-
sation was removed at regular intervals. A clear solution thus obtained was cooled to
room temperature and solvent was removed under reduced pressure. The solid obtained
was recrystallized from chloroform and n-hexane (4 : 1). Yield: 78%; m.p. gel. Anal.
Calcd for C38H54Br2O4Sn (%): C, 53.40; H, 6.32. Found: C, 53.37; H, 6.29. IR (cmꢀ1):
1560 ꢀ(OCO)asym, 1410 ꢀ(OCO)sym, 150 Dꢀ, 576 ꢀ(Sn–C), 447 ꢀ(Sn–O). 1H-NMR
0
0
(CDCl3 ppm): 7.72 (s, H3, 2H); 7.29 (d, H5,5 , 4H); 7.54 (d, H6,6 , 4H); 2.57 (q, H8, 4H);
0
1.20 (t, H9, 6H); 1.41–1.18 (bs, Hꢁ,ꢂ, 8H); 1.41–1.18 (bs, Hꢃ–ꢃ , 20H); 0.87 (t, Hꢄ, 6H).
13C-NMR (CDCl3 ppm), 177.8 (C-1), 134.7 (C-2), 138.4 (C-3), 135.4, 131.7, 130.8, 122.6
(Ar–C), 21.1 (C-8), 13.8 (C-9), 25.6 (C-ꢁ), 24.6 (C-ꢂ), 33.3 (C-ꢃ), 32.0 (C-ꢄ), 29.2 (C-ꢁ0),
29.0 (C-ꢂ0), 22.7 (C-ꢃ0), 14.1 (C-ꢄ0). 119Sn-NMR (CDCl3, ppm): ꢀ161.3.
2.1.7. Tri-n-butyltin(IV) 3-(4-bromophenyl)-2-ethylacrylate (5). Compound 5 was
prepared in the same way as 1 using equimolar molar amounts of NaL (1.38 g,
5 mmol) and tributyltin(IV) chloride (1.62 g, 5 mmol). The product was recrystallized
from chloroform and n-hexane (4 : 1). Yield: 82%; m.p. gel. Anal. Calcd for
C23H37BrO2Sn (%): C, 50.64; H, 6.79. Found: C, 50.58; H, 6.84. IR (cmꢀ1): 1593
ꢀ(OCO)asym, 1390 ꢀ(OCO)sym, 203 Dꢀ, 567 ꢀ(Sn–C), 444 ꢀ(Sn–O) (%): 1H-NMR
0
0
(CDCl3 ppm): 7.55 (s, H3, 1H); 7.25 (d, H5,5 , 2H); 7.51 (d, H6,6 , 2H); 2.52 (q, H8, 2H);
1.16 (t, H9, 3H); 1.76–1.61 (m, Hꢁ, 6H); 1.44–1.27 (m, Hꢂ,ꢃ, 12H); 0.94 (t, Hꢄ, 9H).
13C-NMR (CDCl3 ppm), J[(119/117Sn, 13C), Hz]: 173.2 (C-1), 135.4 (C-2), 137.4 (C-3),
n
136.0, 131.5, 130.7, 122.0 (Ar–C), 21.4 (C-8), 13.7 (C-9), 16.6 {(C-ꢁ), [359/342]}, 27.9
{(C-ꢂ), [21]}, 27.1 {(C-ꢃ), [65]}, 13.6 (C-ꢄ). 119Sn-NMR (CDCl3, ppm): 107.9.

Organotin(IV) ethylacrylates
3769
2.1.8. Trimethyltin(IV) 3-(4-bromophenyl)-2-ethylacrylate (6). Compound 6 was pre-
pared in the same way as 1 using equimolar molar amounts of NaL (1.38 g, 5 mmol) and
trimethyltin(IV) chloride (1.00 g, 5 mmol). Yield: 79%; m.p. 128–130ꢁC. Anal. Calcd for
C14H19BrO2Sn (%): C, 40.10; H, 4.53. Found: C, 40.15; H, 4.55. IR (cmꢀ1): 1587
1
ꢀ(OCO)asym, 1398 ꢀ(OCO)sym, 189 Dꢀ 545 ꢀ(Sn–C); 463 ꢀ(Sn–O). H-NMR (CDCl3
ppm), 2J[(119/117Sn, 1H), Hz]: 7.58 (s, H3, 1H); 7.25 (d, H5,5 , 2H); 7.52 (d, H6,6 , 2H); 2.52
(q, H8, 2H); 1.17 (t, H9, 3H); 0.62 {(s, Hꢁ, 3H), [58/56]}. 13C-NMR (CDCl3 ppm),
1J[(119/117Sn, 13C), Hz]: 173.2 (C-1), 135.2 (C-2), 138.9 (C-3), 136.5, 131.6, 130.7,
122.1 (Ar–C), 21.3 (C-8), 13.8 (C-9), ꢀ2.3 {(C-ꢁ), [398/380]}. 119Sn-NMR (CDCl3, ppm):
132.3.
0
0
2.1.9. Triphenyltin(IV) 3-(4-bromophenyl)-2-ethylacrylate (7). Compound 7 was pre-
pared in the same way as 1 using equimolar molar amounts of NaL (1.38 g, 5 mmol) and
triphenyltin(IV) chloride (1.93 g, 5 mmol). Yield: 75%; m.p. 320ꢁC (dec.). Anal. Calcd
for C29H25BrO2Sn (%): C, 57.52; H, 4.13. Found: C, 57.47; H, 4.13. IR (cmꢀ1): 1577
ꢀ(OCO)asym, 1398 ꢀ(OCO)sym, 179 Dꢀ, 443 ꢀ(Sn–O). 1H-NMR (CDCl3 ppm): 7.58
0
0
(s, H3, 1H); 7.26 (d H5,5 , 2H); 7.52 (d, H6,6 , 2H); 2.51 (q, H8, 2H); 1.16 (t, H9, 3H);
n
7.80–7.68 (m, Hꢂ,ꢃ,ꢄ, 15H). 13C-NMR (CDCl3 ppm), J[(119Sn, 13C), Hz]: 174.3 (C-1),
135.3 (C-2), 137.4 (C-3), 136.5, 131.5, 130.7, 122.0 (Ar–C), 21.3 (C-8), 13.8 (C-9), 137.7
{(C-ꢁ), [642]}, 136.8 {(C-ꢂ), [48]}, 129.2 {(C-ꢃ), [63]}, 130.2 {(C-ꢄ), [12]}. 119Sn-NMR
(CDCl3, ppm): ꢀ119.1.
2.2. X-ray crystallographic studies
A crystal fragment, cut to fit in the homogeneous part of the X-ray beam, was mounted
on top of a glass fiber and aligned on a Bruker SMART APEX CCD diffractometer
(Platform with full three-circle goniometer). The crystal was cooled to 100(1) K using
the Bruker KRYOFLEX low-temperature device. Intensity measurements were
performed using graphite monochromated Mo-Ka radiation from a sealed ceramic
diffraction tube (SIEMENS). Data integration and global cell refinement were
performed with SAINT [19]. The program suite SAINTPLUS was used for space
group determination (XPREP) [19]. The structure was solved by the Patterson method;
extension of the model was accomplished by direct methods and applied to difference
structure factors using DIRDIF [20]. Refinement calculations and graphics were
performed with SHELXL, PLUTO, and PLATON package.
3. Results and discussion
3.1. Syntheses of 1–7
Reaction of R3SnCl/R2SnCl2/n-Oct2Sn with NaL/HL in 1 : 1/1 : 2/1 : 2 molar ratios,
respectively, led to formation of complexes according to equations (1)–(3) in scheme 1.
The resulting complexes were obtained in good yield (67–89%). All the complexes were
white solids/gel, stable in air, and soluble in CHCl3 and DMSO. The numbering scheme
of ligand and alkyl/aryl groups attached to Sn is shown in scheme 1.

3770
N. Muhammad et al.
Scheme 1. Synthesis of organotin(IV) derivatives, 1–7, and numbering scheme of ligand and organic groups
attached to Sn atom.
3.2. IR spectra
In IR spectra of 1–7, the absence of a band at 3328–2529 cmꢀ1 due to –OH stretch in the
free ligand acid signifies metal–ligand bond formation via this site. This is further
supported by the absorption at 463–437 cmꢀ1, characteristic of an Sn–O bond [21, 22].
The bonding mode of the ligand was confirmed by Dꢀ, {ꢀasym(COO) – ꢀsym(COO)} [23].
The Dꢀ values signified that ligand coordination is a chelated bidentate (1–4) and
bridging bidentate (5–7). The conclusions drawn from the IR data are consistent with
the X-ray structure for 6.
3.3. NMR spectra
Assignment of proton resonances were made by peak multiplicities, intensity pattern,
and comparison of integration values of protons with the expected composition. In
spectra of 1–7, 1H resonances of protons attached to the ꢁ-alkyl of the ligand appear as
quartets (for CH2) and triplet (for CH3), whereas olefinic protons of the ligand resonate
as a sharp singlet, of E-configuration at 7.74–7.55 ppm [24–26]. The aromatic part of
the ligand gave two doublets due to two non-equivalent sets of protons. Protons of
alkyl/aryl groups attached to Sn presented signals as expected [27, 28]. Coordination
around Sn was deduced from [2J (119Sn, 1H)] coupling constants. For 3 and 6, the values
were 82 and 58 Hz, respectively, consistent with CSnC angles of 133.42ꢁ and 111.00ꢁ,
thus confirming five- and four-coordinate Sn, respectively, in solution [29]. In spectra of
all complexes, the presence of the exact number of carbon resonances for ligand and
alkyl as anticipated from the structures validate formation of 1–7. Furthermore, signal
of the carboxylic carbon of the ligand shifted downfield upon complexation. Greater
downfield shift of C-1 in dialkyltin derivatives shows higher coordination number of tin
1
and corresponds to deshielding of C-1. The J [119/117Sn, 13C] coupling constant can be
used to assess the coordination number of Sn in organotin compounds. The calculated
coupling constants were 359/342 Hz for tributyltin 5, 398/380 Hz for trimethyltin 6, and

Organotin(IV) ethylacrylates
3771
642 Hz for triphenyltin 7, consistent with the range reported for four-coordinate Sn [30].
1
The H and 13C-NMR spectra of the complexes were found to exhibit no additional
resonances and thus reflect the purity of complexes. The ꢄ(119Sn) values define the
coordination number of tin [7]. For 1–4, the ꢄ(119Sn) values fall in the range þ200 to
ꢀ60 ppm, showing five-coordinate tin. ꢄ(119Sn) signals for 5–7 show a four-coordinate
tetrahedral geometry in solution.
3.4. Crystal structure of 6
Compound 6 crystals were obtained from chloroform and n-hexane (4 : 1) mixture, and
the structure is shown in figure 1. Crystal data and selected interatomic parameters are
collected in tables 1 and 2, respectively. X-ray diffraction investigation of 6 shows that it
Figure 1. Molecular structure of 6.
Table 1. Crystal data and structure refinement parameters for 6.
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
C14H19BrO2Sn
417.92
100(1)
Monoclinic
P21/c
ꢁ
˚
Unit cell dimensions (A, )
a
b
c
6.8387(6)
9.7596(8)
23.547(2)
95.4929(14)
1564.4(2), 4
0.82
1.774
816
ꢂ
Volume (A ), Z
3
˚
ꢅ
Calculated density (g cmꢀ3
F(000)
)
Crystal size (mm3)
0.44 ꢂ 0.20 ꢂ 0.13
ꢆ range for data collection (ꢁ)
Limiting indices
Total data
2.72–28.28
ꢀ9 ꢃ h ꢃ 8; ꢀ13 ꢃ k ꢃ 13; ꢀ26 ꢃ l ꢃ 31
14,003
Unique data
Final R indices [Fo 4 /4ꢇ(Fo)]
3870[R(int) ¼ 0.0291]
R1 ¼ 0.0301, wR2 ¼ 0.0737

3772
N. Muhammad et al.
is an infinite zigzag polymeric chain with trimethyltin centers being linked by bridging
carboxylates. Each tin is five-coordinate, axially by two oxygen atoms and equatorially
by three methyl groups, thus resulting in a distorted trigonal bipyramidal geometry. Each
˚
O–Sn–O unit is associated with unequal Sn–O bond distances (2.1795(19), 2.411(2) A).
˚
These values are closer to the Sn–O covalent bond length (2.13 A), but are much shorter
˚
than the sum of the van der Waals radii of connected atoms (3.68 A) [31]. This asymmetry
may be due to involvement of oxygen in inter- and intramolecular Sn–O non-covalent
˚
interactions (3.287 A). These interactions also render a supramolecular cage-like
˚
structure to 6 (figure 2). The interactions are 0.1 A less than the van der Waals radii
and were drawn by using Hg-2.2 software. The dissimilarity in Sn–O bonds is clearly
evident in the associated C–O bond lengths: the longer C–O bond is associated with
˚
shorter Sn–O interaction and vice versa. Sn–C bond lengths (2.119(3)–2.125(3) A) are
consistent with those reported for other triorganotin derivatives [7].
ꢁ
˚
Table 2. Selected bond lengths (A) and angles ( ) of 6.
Sn–O1
Sn–O2
Sn–C12
O2–C1
2.1795(19)
2.411(2)
2.131(3)
1.252(3)
Sn–C13
Sn–C14
O1–C1
2.119(3)
2.125(3)
1.288(3)
O1–Sn–C12
O1–Sn–C13
O1–Sn–C14
O1–Sn–O2
C12–Sn–C13
C12–Sn–C14
92.22(10)
87.90(10)
99.35(10)
171.96(7)
116.07(13)
120.48(13)
C12–Sn–O2
C13–Sn–C14
C13–Sn–O2
C14–Sn–O2
Sn–O1–C1
90.65(10)
122.48(13)
84.1(10)
85.62(10)
123.79(17)
˚
Figure 2. Cage-like supramolecular structure of 6 mediated by intermolecular Sn–O interaction (3.287 A).

Organotin(IV) ethylacrylates
3773
Table 3. Antibacterial activity data of organotin(IV) derivatives of 3-(4-bromophenyl)-2-ethylacrylic
acid (HL).a,b
Zone of inhibition (mm)
Ref. drugs
B
Name of bacterium
HL
1
2
3
4
5
6
7
A
C
E. coli
B. subtilis
Erwenia sp.
14
12
25
10
13
23
12
15
20
26
20
33
12
11
09
13
52
30
20
24
33
7
12
14
28
35
30
40
26
33
32
21
35
aConcentration: 1 mg mLꢀ1 of DMSO; bReference drugs: Ofloxacin (A), Ciprofloxacin (B), and Ampicillin (C).
3.5. Antimicrobial studies
3.5.1. Antibacterial activity. The parent acid and complexes were evaluated for their
antibacterial activities using the agar well diffusion method [32]. The in vitro
antibacterial activity was performed against Bacillus subtilis, Escherichia coli, and
Erwenia sp. and the activity is shown in terms of zone of inhibition (mm) in table 3. In
order to compare the results obtained, Ofloxacin, Ciprofloxacin, and Ampicillin were
used as standard drugs. A comparative study of the ligand acid and its organotin(IV)
derivatives indicates that complexes exhibit higher or comparable antibacterial activity
than the free ligand, in general. In some cases activity is higher than standard drug,
especially for 5 against B. subtilis.
Improved activity of the complexes can be explained on the basis of Overtone’s
concept [33] and Tweedy’s chelation theory [34–36], which requires increased
lipophilicity for antimicrobial activity. The observed variation in activity of the
synthesized complexes against the tested bacteria may be due to differences in cell wall
and/or membrane construction, nature of complex, number, and lengths of alkyl groups
attached to tin. Triorganotin(IV) derivatives are more active than the diorganotin(IV)
derivatives, attributed to greater lipophilic character. Also, activity decreases with
increasing length of alkyl group, which may be due to slow movement and greater
hydrophobic character of bulky groups. This trend shows dependence of antibacterial
activity on number and nature of alkyl group attached to tin.
3.5.2. Antifungal activity. The complexes were checked for antifungal activity against
different pathogens by using Agar tube dilution protocol [32] and the data collected are
listed in table 4. Generally, complexes show markedly higher antifungal activity than
the ligand. Like antibacterial activities no clear patterns were observed for complexes
against fungal strains.
Antimicrobial results of this study are almost comparable with the promising findings
of Amin et al. [37].
4. Conclusion
The outcome of this study is that the di- and triorganotin(IV) 3-(4-bromophenyl)-2-
ethylacrylates demonstrated different structural motifs in solution and solid states.

3774
N. Muhammad et al.
Table 4. Antifungal activity data of organotin(IV) derivatives of 3-(4-bromophenyl)-2-ethylacrylic
acid (HL).a,b
Percent inhibition
Name of fungus
HL
1
2
3
4
5
6
7
Standard drug
Saccharomyces cerevisiae
Kluyveromyces fragilis
Aspergillus niger
47
27
33
18
43
24
40
50
50
82
47
55
43
73
40
63
40
30
33
25
37
42
60
50
40
30
43
70
40
30
40
75
100
100
100
100
Aspergillus oryzae
aConcentration: 400 mg mLꢀ1 of DMSO; bStandard drug: Travogen.
These compounds are active biologically; however, this property not only depends on
structure of complex but also on type of antimicrobial study in consideration.
Difference in behavior toward bacterial and fungal strains suggests a different mode of
action and activity controlling factors in either case.
Supplementary material
Crystallographic data for the structural analysis are available from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK on request,
quoting the deposition number 882 214.
Acknowledgments
We thank the Higher Education Commission of Pakistan for the financial support.
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