Synthesis, spectral characterization and X-ray crystal structure of biologically active organotin(IV) 3-[(3',5'-dimethylphenylamido)]propanoates

Article abstract of DOI:10.1007/s13738-012-0109-0

A new ligand was prepared by reacting 3,5- dimethylaniline with succinic anhydride in glacial acetic acid at room temperature. A series of organotin(IV) carboxylates were prepared by reacting the ligand with R₂SnCl ₂/R₃SnCl (R = Me, Bu, Ph, Oct) in 1:2/1:1 molar ratio. The synthesized complexes were characterized by elemental analyses, FT-IR, multinuclear magnetic resonance (¹H and ¹³C) and mass spectrometry. The structures of the ligand (HL) and complex (5) were determined by single crystal X-ray diffraction analysis. FT-IR data shows that the coordination takes place through both carboxylate oxygen atoms. NMR data confirm the tetrahedral geometry in solution. In the crystal structure of ligand (HL), centrosymmetrically related molecules are linked into dimers by N-H.O hydrogen bonding interactions, while in complex (5) coordination around the tin atom is trigonal bipyramidal, with the carbon atoms of the methyl groups occupying the equatorial plane and the O atoms of symmetry- related ligands at the apices. Organotin(IV) complexes were also screened for their antibacterial and antifungal activities, and the results suggested that the synthesized complexes are better antimicrobial agents as compared to the free ligand. Iranian Chemical Society 2012.

Full text of DOI:10.1007/s13738-012-0109-0

J IRAN CHEM SOC (2012) 9:923–932
DOI 10.1007/s13738-012-0109-0
ORIGINAL PAPER
Synthesis, spectral characterization and X-ray crystal
structure of biologically active organotin(IV)
3-[(30,50-dimethylphenylamido)]propanoates
•
•
•
•
F. A. Shah S. Ali S. Shahzadi C. Rizzoli
S. Ahmad
Received: 9 February 2012 / Accepted: 16 May 2012 / Published online: 16 June 2012
ꢀ Iranian Chemical Society 2012
Abstract A new ligand was prepared by reacting 3,5-
dimethylaniline with succinic anhydride in glacial acetic
acid at room temperature. A series of organotin(IV) car-
boxylates were prepared by reacting the ligand with
R2SnCl2/R3SnCl (R = Me, Bu, Ph, Oct) in 1:2/1:1 molar
ratio. The synthesized complexes were characterized by
elemental analyses, FT-IR, multinuclear magnetic reso-
nance (1H and 13C) and mass spectrometry. The structures
of the ligand (HL) and complex (5) were determined by
single crystal X-ray diffraction analysis. FT-IR data shows
that the coordination takes place through both carboxylate
oxygen atoms. NMR data confirm the tetrahedral geometry
in solution. In the crystal structure of ligand (HL), cen-
trosymmetrically related molecules are linked into dimers
by N–H…O hydrogen bonding interactions, while in
complex (5) coordination around the tin atom is trigonal
bipyramidal, with the carbon atoms of the methyl groups
occupying the equatorial plane and the O atoms of sym-
metry-related ligands at the apices. Organotin(IV) com-
plexes were also screened for their antibacterial and
antifungal activities, and the results suggested that the
synthesized complexes are better antimicrobial agents as
compared to the free ligand.
Keywords Organotin(IV) carboxylates ꢀ FT-IR ꢀ NMR ꢀ
Mass ꢀ XRD ꢀ Biological activities
Introduction
Among organotin(IV) compounds, organotin carboxylates
are highly important and have been receiving more atten-
tion in recent years. Organotin(IV) carboxylates form an
important class of compounds which find many applica-
tions in chemistry and biology, such as catalysts, stabiliz-
ers, biocides, antifouling agents and wood preservatives
[1]. Mostly, organotins are species specific and a general
pattern revealed that their toxicity is a function of the
organic group attached to the tin atom.
The biological investigations of organotin carboxylates
have attracted considerable attention owing to their sig-
nificant cytotoxic effect and relatively high antitumor
activity [2, 3]. It may yield new leads for the development
of antitumor drugs, which can display another spectrum of
antitumor activity. For instance, they show non-cross
resistance with platinum drugs and possess less toxicity
than platinum compounds [4].
The structural diversity of organotin carboxylates is well
recognized and a wide variety of coordination geometries
have been reported [5, 6]. It is generally believed that a
combination of steric and electronic factors determine the
specific structure adopted by a particular organotin car-
boxylate [7]. This is supported by the observation of
monomeric, dimeric, tetrameric, oligomeric ladder, cyclic
and drum structure [5–7]. Therefore, synthesis of new
organotin(IV) carboxylates with different structural fea-
tures is beneficial in the development of pharmaceutical
organotin and in other properties and applications. In view
of the various applications of organotin carboxylates and as
F. A. Shah ꢀ S. Ali (&) ꢀ S. Ahmad
Department of Chemistry, Quaid-i-Azam University,
Islamabad 45320, Pakistan
e-mail: drsa54@yahoo.com
S. Shahzadi (&)
Department of Chemistry, GC University, Faisalabad, Pakistan
e-mail: sairashahzadi@hotmail.com
C. Rizzoli
Dipartimento di Chimica Generale ed Inorganica, Chimica
Analitica, Chimica Fisica, Parco Area delle Scienze 17/A,
43124 Parma, Italy
123

924
J IRAN CHEM SOC (2012) 9:923–932
FT-IR spectrophotometer. Mass spectral data was collected
1
H3C
on a Finnigan MAT-311A spectrometer. The H and 13C
H
N
O
C
H
C
H
H
C
H
O
C
NMR spectra were recorded on a Bruker ARX 300 MHz-X
Spectrometer at room temperature operating at 300 and
75.3 MHz, respectively. X-ray single crystal diffraction
data for the ligand (HL) was collected on a Siemens AED
diffractometer using graphite monochromated Cu–Ka
radiation, while that for complex (5) was collected on a
Bruker APEX-II CCD diffractometer using graphite
monochromated Mo–Ka radiation.
OH
H3C
Fig. 1 3-[(30,50-Dimethylphenylamido)]propanoic acid (HL)
a continuation of our studies of biologically active or-
ganotin(IV) derivatives [8, 9], we synthesized some novel
organotin(IV) derivatives of 3-[(30,50-dimethylphenylamido)]
propanoic acid (Fig. 1). These complexes were characterized
by elemental analysis, infrared, NMR (1H, 13C), mass spec-
trometry and X-ray diffraction studies. Their biological
activity data has also been investigated.
Synthesis
Synthesis of 3-[(30, 50-dimethylphenylamido)]propanoic
acid (HL)
A solution of 3,5-dimethylaniline (1 mmol) in glacial
acetic acid was added to a solution of succinic anhydride
(1 mmol) in glacial acetic acid followed by continuous
overnight stirring at room temperature. The resulting white
solid product was subsequently filtered and washed with
cold distilled water (400 mL). The product thus obtained
was recrystallized from acetone (Scheme 1).
Experimental
Materials and instrumentation
3,5-Dimethylaniline, succinic anhydride, organotin(IV)
chlorides and dioctyltin(IV) oxide were purchased from
Aldrich Chemical (USA). Glacial acetic acid, acetone,
toluene, diethyl ether and chloroform were obtained from
Merck (Germany). Acetone, toluene, diethyl ether and
chloroform were purified before use by reported procedures
[10, 11].
General procedure for the synthesis of complexes
Procedure (a)
3-[(30,50-Dimethylphenylamido)]propanoic acid (4.6 mmol,
1 g) was suspended in dry toluene (100 mL) and treated
with Et3N (4.6 mmol, 0.63 mL). The mixture was refluxed
for 2–3 h and to this solution diorganotin dichloride
(2.3 mmol) or triorganotin chloride (4.6 mmol) was added
as solid (or liquid in case of Bu3SnCl) with constant stir-
ring and then refluxed for 8 h. The reaction mixture
Melting points of the synthesized compounds were
recorded by the electrothermal melting point apparatus
MP-D Mitamura Riken Kogyo (Japan) and are uncorrected.
Elemental analysis was carried out using a Leco CHNS-
932 analyzer. The IR spectra of the synthesized complexes
were obtained using KBr pallets on a Bio-Rad Excaliber
O
Scheme 1
H
N
O
C
H
C
H
H
C
H
O
C
i) Glacial Acetic Acid
ii) Overnight Stirring
R
NH2
+
O
R
OH
O
Where
H3C
R =
H3C
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J IRAN CHEM SOC (2012) 9:923–932
925
Table 1 Physical data of 3-[(30,50-dimethylphenylamido)]propanoic
acid and its organotin(IV) complexes
i) Toluene
R2SnCl2 + 2Et3NHL
R2SnL2 + 2Et3NHCl
R3SnL + Et3NHCl
ii) Reflux for 8-10 hrs
Comp. Mol. formula
no.
m.p.
(ꢁC)
% Elemental analysis
yield % calculated (found)
i) Toluene
R3SnCl + Et3NHL
ii) Reflux for 8-10 hrs
C
H
N
(HL)
(1)
C12H15NO3
195–196 74
65.16
6.78
6.33
i) Toluene
(65.12) (6.74) (6.29)
52.97 5.77 4.75
(52.93) (5.74) (4.73)
57.05 6.83 4.16
(57.08) (6.81) (4.20)
60.58 5.32 3.92
(60.55) (5.29) (2.95)
61.14 7.89 3.56
(61.10) (7.85) (3.53)
46.87 5.89 3.64
(46.84) (5.92) (3.67)
56.47 8.03 2.74
(56.43) (8.05) (2.70)
63.15 5.08 2.45
(63.14) (5.03) (2.47)
Oct2SnO + 2HL
Oct2SnL2 + H2O
ii) Reflux for 8-10 hrs
C
C
C
C
C
C
C
26H34N2O6Sn 163–165 70
32H46N2O6Sn 140–142 67
36H38N2O6Sn 128–129 60
40H62N2O6Sn 145–146 69
(2)
R
Me2
(1)
Bu2
(2)
Ph2
(3)
Ph3
(7)
Oct2
Comp. No
R
(4)
-
(3)
Me3
(5)
Bu3
(6)
(4)
Comp. No
-
(5)
15H23NO3Sn 98–100
71
Scheme 2
(6)
24H41NO3Sn 121–122 68
30H29NO3Sn 210–211 66
containing Et3NHCl was filtered off leaving the organo-
tin(IV) derivative in the filtrate. Solvent was removed by
rotary evaporator and the precipitate was recrystallized
from a chloroform/methanol (4:1 v/v) mixture (Eqs. 2 and
3 in Scheme 2).
(7)
comparing the spectra of ligand and complexes. The –NH
group does not participate via intra- or intermolecular
modes of interactions, as confirmed by the presence of
characteristic strong band at 3,300–3,340 cm-1, which
does not show any shift after complexation [12]. The
description of the coordination modes was based on
the difference between (COO)sym and (COO)asym and the
corresponding band position [13].
In all the synthesized complexes, Dm is \200 cm-1
which confirms the bidentate nature of the ligand. In the
spectra of the compounds, new bands confirming the
complexation [14] appear in the region 465–423 cm-1 [for
(1), (2), (4)–(6)] and 540–512 [for (1)–(7)] cm-1 and were
assigned to Sn–O and Sn–C bonds, respectively. For the
phenyl derivatives (3) and (7), the Sn–C band appears at
244 and 253 cm-1, respectively.
Procedure (b)
3-[(30,50-Dimethylphenylamido)]propanoic acid (4.6 mmol,
1 g) was suspended in dry toluene (100 mL). To this
solution, Oct2SnO (2.3 mmol, 0.8 g) was added as solid
with constant stirring and the mixture refluxed for 8–10 h.
Water formed during the reaction was removed via Dean
and Stark trap. The solvent was evaporated through rotary
apparatus and the product obtained was recrystallized
by a chloroform:n-hexane (4:1 v/v) mixture (Eq. 4 in
Scheme 2).
Results and discussion
All complexes (1)–(7) are solid, generally with sharp
melting points, which are stable in light and dry air. They
are soluble in polar solvents. Physical data are reported in
Table 1.
1H NMR spectra
1H NMR spectra for the investigated compounds were
obtained in deuterated chloroform at room temperature.
Different protons were assigned on the basis of their
multiplicity and intensity patterns. The integration of
spectra was in accordance with the number of protons
proposed for each molecular fragment. The 1H NMR
spectra of the complexes exhibit the useful features and the
observed chemical shifts are reported in Table 3. In the
complexes, the COOH resonance of the ligand at 10.4 ppm
is absent which suggests the deprotonation of the
IR spectra
Characteristic FT-IR vibrations ligand (HL) and its or-
ganotin(IV) complexes are summarized in Table 2. The
complexation of tin with the ligand through the –COO
group is confirmed by the absence of a broad –OH band in
the region of 2,650 cm-1. The values of different vibra-
tional frequencies were assigned to different bonds by
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J IRAN CHEM SOC (2012) 9:923–932
Table 2 Assignment of characteristic FT-IR vibrations (cm-1) of 3-[(30,50-dimethylphenylamido)]propanoic acid and its organotin(IV)
complexes
Comp. no.
IR peak (cm-1
)
mOH
mNH
mC=O
mCOO
Dm
mSn–C
mSn–O
Asymm
Symm
(HL)
(1)
3,416
3,326
3,317
3,334
3,320
3,300
3,302
3,337
3,340
1,748
1,746
1,740
1,735
1,754
1,736
1,745
1,736
1,532
1,550
1,560
1,554
1,568
1,570
1,565
1,575
1,310
1,432
1,444
1,416
1,429
1,433
1,450
1,456
222
118
116
138
139
164
115
119
–
526
540
244
513
512
534
253
–
486
460
454
445
465
423
474
–
–
–
–
–
–
–
(2)
(3)
(4)
(5)
(6)
(7)
1
Table 3 H NMR data of 3-[(30,50-dimethylphenylamido)]propanoic acid and its organotin(IV) complexes
Proton
no.
Chemical shift (ppm)
(HL)
(1)
(2)
(3)
(4)
(5)
(6)
(7)
2/6
4
6.65s
7.23s
2.22s
6.65s
7.20s
2.21s
6.65s
7.22s
2.20s
6.68s
7.25s
2.25s
6.65s
7.21s
2.21s
6.64s
7.2s
6.63s
7.21s
2.20s
6.66s
7.21s
2.22s
7/8
10
2.21s
7.52–7.54d
[6.0]
7.20–7.23d
[6.0]
7.20–7.23d
[6.0]
7.43–7.45d
[6.0]
7.20–7.22d 7.45–7.43d 7.46–7.49d 7.48–7.50d
[6.0]
[6.0]
[6.0]
[6.0]
11
7.53–7.55d
[6.0]
7.50–7.53d
[6.0]
7.50–7.53d
[6.0]
7.50–7.52d
[6.0]
7.50–7.48d 7.52–7.50d 7.51–7.49d 7.51–7.53d
[6.0]
[6.0]
9.7s
[6.0]
9.7s
[6.0]
9.6s
NH
9.8s
9.7s
9.7s
9.7s
9.8s
a
2
Compound (1) Sn–CH3, 0.95s J[96]; Compound (2) Sn–CH2CH2CH2CH3, 0.85–1.20m, 0.23t (7.2); Compound (3) Sn–C6H5, 7.40–7.92m;
Compound (4) Sn–CH2CH2CH2CH2 CH2CH2CH2CH3, 0.82–1.18m; Compound (5) Sn–CH3, 0.83s 2J[82]; Compound (6) Sn–CH2CH2CH2CH3,
0.82–1.39m, 0.23t (7.2); Compound (7) Sn–C6H5, 6.84–7.08m
b
Chemical shifts (d) in ppm 2J[119Sn,1H] and 3J(1H,1H) in Hz are listed in square brackets and parenthesis, respectively. Multiplicity is given as:
s singlet, d doublet, t triplet, m multiplet
7
H3C
2
H
N
O
H
C
H
H
C
O
3
1
4
C
C
O
10
11
9
12
H
5
6
H3C
8
carboxylic acid by the organotin(IV) moiety, as charge
donation from the COO- donor to the tin atom decreases
the electron density and results in deshielding of the ligand
protons. The NH group does not show any significant shift
upon complexation indicating that the NH group does not
contribute to the coordination of the tin metal atom.
In the case of dimethyl (1) and trimethyl (5) organo-
tin(IV) derivatives, the methyl protons gave a characteristic
singlet at 0.95 and 0.83 ppm, respectively. In the n-butyl
derivatives, a triplet for the terminal methyl group of the
butyl chain at 0.85 ppm for the dibutyltin (2) and at
0.82 ppm for the tributyl (5) derivatives. For other protons
of the butyl chain in (2) and (5), the multiplets were
observed (Table 3).
The nJ(119Sn, 1H) for dimethyl and trimethyltin(IV)
derivatives have approximately the same value, confirming
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J IRAN CHEM SOC (2012) 9:923–932
927
13C NMR spectra
According to 13C NMR data, the involvement of the car-
boxylate group in bonding to Sn is confirmed by the res-
onance of the carboxylic carbon in all the compounds,
which exhibits a lower shift after coordination as compared
to the ligand, suggesting the coordination of the ligand
through a carboxylic oxygen to the organotin(IV) moiety.
The remaining carbons do not shift significantly after
complexation. The spectral data is given in Table 4.
The carbon of phenyl and alkyl groups attached to tin
are observed at almost similar positions in the experimental
data with respect to that calculated from the incremental
method [17] and reported in the literature [18, 19].
The tributyltin and trimethyltin complexes exhibit
nJ(13C–117/119Sn) coupling satellites in the range 349–396
Hz in CDCl3 solution, suggesting that the tin atom is four-
coordinated in solution [20, 21].
Fig. 2 Suggested structure of the complexes
the tetrahedral coordination environment in solution, i.e.,
carboxylate groups act as monodentate in solution. The
aromatic proton resonances were assigned by comparing
the experimental chemical shifts with those calculated by
the incremental method [15]. In triorganotin carboxylates,
2J[119Sn–1H] for triorganotin compounds suggest a tetra-
hedral geometry (Fig. 2a) of the tin atom.
Unlike the triorganotin carboxylates in solution, the
geometry of diorganotin dicarboxylates cannot be defined
with certainty because of dynamic processes involving
different modes of carboxylate oxygen coordination to the
tin atom [16]. However, in the solid state, the tin atom is
mostly hexa-coordinated in such systems (Fig. 2b) [17].
Mass spectrometry
Mass spectra for the investigated compounds were recor-
ded at 70 eV for all di- and triorganotin(IV) derivatives.
The molecular ion peaks of very low intensity are observed
13
Table 4 C NMR data of 3-[(30,50-dimethylphenylamido)]propanoic acid and its organotin(IV) complexes
Carbon
(HL)
(1)
(2)
(3)
(4)
(5)
(6)
(7)
1
138.03
117.18
139.60
124.91
21.53
138.03
117.08
139.67
124.84
21.85
138.03
117.38
139.69
124.18
21.55
138.17
117.12
139.80
124.97
21.63
138.50
117.92
139.56
124.18
21.61
138.91
117.19
139.67
124.95
21.58
138.80
117.20
139.80
124.99
21.62
138.03
117.18
139.61
124.92
21.59
2/6
3/5
4
7/8
9
170.39
29.28
170.69
29.26
170.43
29.29
170.90
29.75
170.47
29.02
170.27
29.49
170.97
29.14
170.39
29.98
10
11
12
31.48
31.38
31.26
31.04
31.62
31.09
31.64
31.49
174.34
177.4
176.25
176.28
177.50
176.39
176.38
177.43
n
Chemical shifts (d) in ppm: J[119Sn, 13C] in hertz is listed in parenthesis
a
Compound (1): Sn–CH3, (C-a) 29.6; Compound (2): Sn–CH2CH2CH2CH3, (C-a) 29.5, (C-b) 27.4, (C-c) 26.2, (C-d) 13.9; Compound (3): Sn–
C6H5, (C-a) 137.9 1J[635], (C-b) 135.0, (C-c) 136.0, (C-d) 129.2; Compound (4): Sn–CH2CH2CH2CH2CH2CH2CH2CH3, (C-a) 33.5, (C-b) 31.7,
1
(C-c) 30.1, (C-d) 29.3, (C-a*) 29.1, (C-b*) 28.8, (C-c*) 22.6, (C-d*) 14.40; Compound (5): Sn–CH3, (C-a) 2.7 J[396]; Compound (6): Sn–
CH2CH2CH2CH3, (C-a) 31.3 [349], (C-b) 27.4 2J[21], (C-c) 28.7 3J[63], (C-d) 14.2; Compound (7): Sn–C6H5, (C-a) 138.0 1J[640], (C-b) 133.0
2J[49.0], (C-c) 130.0, (C-d) 125.1
7
H3C
2
H
N
O
H
C
H
H
C
O
3
1
4
C
C
O
10
11
9
12
H
5
6
H3C
8
123

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J IRAN CHEM SOC (2012) 9:923–932
Table 5 Mass spectral data of 3-[(30,50-dimethylphenylamido)]propanoic acid and its organotin(IV) complexes
Fragment ion
(1)
m/z (%)
(2)
m/z (%)
(3)
m/z (%)
(4)
m/z (%)
(5)
m/z (%)
(6)
m/z (%)
(7)
m/z (%)
[SnL]
[C11H14ONSn]?
[R2Sn]?
340 (6)
296 (8)
150 (8)
120 (10)
120 (25)
204 (100)
162 (43)
105 (12)
77 (6)
340 (40)
296 (12)
234 (8)
120 (8)
120 (19)
204 (100)
162 (29)
105 (13)
77 (9)
340 (10)
296 (18)
274 (27)
120 (25)
120 (38)
204 (100)
162 (22)
105 (12)
77 (18)
340 (16)
296 (18)
345 (27)
120 (12)
120 (38)
204 (100)
162 (53)
105 (6)
340 (13)
296 (11)
150 (95)
120 (25)
120 (70)
204 (100)
162 (42)
105 (28)
77 (30)
340 (20)
296 (19)
234 (28)
120 (30)
120 (14)
204 (59)
162 (24)
105 (30)
77 (22)
340 (32)
296 (13)
274 (31)
120 (10)
120 (14)
204 (59)
162 (24)
105 (30)
77 (22)
[Sn]?
[C8H10N]?
[C12H14O2N]?
[C10H12ON]?
[C8H9]?
[C6H5]?
77 (10)
[C4H9]?
57 (6)
57 (33)
57 (6)
57 (19)
57 (19)
57 (98)
57 (98)
in few complexes [22]. In di- and triorganotin(IV) deriva-
tives, a rather similar pattern of fragmentation is observed.
For the synthesized complexes, the fragmentation takes
place by the loss of alkyl or aryl groups followed by the
elimination of CO2. The second route of fragmentation is
the loss of CO2 and other neutral species which ultimately
gives [C6H5?] in the last step. Another possible route is
disintegration of the ligand and stepwise elimination of R
groups to Sn? or SnH? as a residue. Some common and
different peaks (with m/z and % abundance) which were
observed in di- and triorganotin(IV) derivatives are repor-
ted in Table 5.
Table 6 Crystal data and structure refinement parameters for (HL)
and compound (5)
Crystal structures
(HL)
(5)
Crystal data and structure refinement parameters for ligand
(HL) and complex (5) are given in Table 6, and selected
bond angles and lengths are listed in Table 7.
Emp. formula
Formula weight
Crystal system
Space group
C12H15 NO3
221.25
C15H23NO3Sn
384.03
Monoclinic
P 21/n
Monoclinic
P 21/c
˚
a (A)
14.355 (2)
5.0170 (10)
17.858 (4)
90.00
17.168 (8)
10.925 (6)
9.623 (7)
90.00
˚
b (A)
˚
Table 7 Selected bond lengths (A) and bond angles (ꢁ) for (HL) and
compound (5)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
(HL)
111.980 (15)
90.00
101.48 (5)
90.00
N1–C4
1.340(12)
1.411(14)
1.508(18)
129.78(9)
119.64(12)
O3–C4
1.239(11)
1.513(17)
1.324(12)
122.24(10)
122.62(9)
N1–C5
C9–C12
O2–C1
3
˚
V (A )
1,192.6 (4)
4
1,768.8 (18)
4
C7–C11
Z
C4–N1–C5
C6–C7–C11
(5)
O3–C4–N1
O3–C4–C3
Crystal size (mm)
T (K)
0.28 9 0.22 9 0.18 0.14 9 0.10 9 0.08
295 (2)
1.54178
2,332
295 (2)
0.71073
3,498
˚
k (A)
Sn1–C15
2.109(8)
2.112(8)
2.120(7)
2.203(4)
126.3(3)
116.1(3)
116.9(3)
97.0(3)
Sn1–O2
2.358(5)
1.274(8)
1.246(8)
1.209(8)
86.2(3)
Total reflections
Sn1–C14
O1–C1
Independent reflections 2,263
(all)
3,285
Sn1–C13
O2–C1
Sn1–O1
O3–C4
Final R indices [I [ 2r R1 = 0.039
R1 = 0.054
wR2 = 0.125
R1 = 0.092
wR2 = 0.135
1.004
(I)]
C15–Sn1–C14
C15–Sn1–C13
C14–Sn1–C13
C15–Sn1–O1
C14–Sn1–O1
C13–Sn1–O1
C15–Sn1–O2
C14–Sn1–O2
C13–Sn1–O2
O1–Sn1–O2
C1–O1–Sn1
O2–C1–O1
wR2 = 0.089
88.1(3)
R indices (all data)
R1 = 0.047
wR2 = 0.097
1.038
87.4(2)
176.1(18)
115.2(4)
121.8(6)
Goodness-of-fit
91.8(3)
h range for data
collection (ꢁ)
3.4–70.1
3.1–25.5
89.2(2)
123

J IRAN CHEM SOC (2012) 9:923–932
929
with those found in the literature for related compounds
[23]. The carbonyl O1 and O3 oxygen atoms are in trans
position with respect to the C1–C4 butyl group (Fig. 3).
The C(O2)C2C(O)N fragment is approximately planar
˚
(maximum deviation 0.0547(10) A for atom C3) and is
tilted by 8.12(4)ꢁ to the benzene ring. In the crystal
structure, centrosymmetrically related molecules are
linked into dimers by N–H…O hydrogen bonding inter-
i
˚
˚
actions [N1–H1N, 0.946(15) A; H1N…O1 , 1.940(15) A;
i
i
˚
N1…O1 , 2.879(1) A; N1–H1N…O1 , 172.0(14)ꢁ; sym-
metry code: (i) 2 - x, -y, -z]. The dimers are further
connected into layers parallel to the (101) plane by
intermolecular O–H…O hydrogen bonds [O2–H1O,
Fig. 3 ORTEP drawing of 3-[(30,50-dimethylphenylamido)]propa-
noic acid (HL) showing 50 % displacement ellipsoids
0.911(14) A; H1O…O3ii, 1.738(14) A; O2…O3ii,
˚
˚
ii
˚
2.628(1) A; O2–H1O…O3 , 164.9(14)ꢁ; symmetry code:
Crystal structures of ligand (HL)
(ii) 5/2 - x, -1/2 ? y, 1/2 - z]. A packing diagram of
(HL) approximately viewed along the b axis is given in
Fig. 4.
In the crystal structure of the free ligand (HL), all bond
lengths and angles are unexceptional and in agreement
Fig. 4 Packing diagram of
(HL) approximately viewed
along the b axis. Intermolecular
hydrogen bonds are shown as
dashed lines
123

930
J IRAN CHEM SOC (2012) 9:923–932
Crystal structure of complex (5)
dihedral angle of 23.6(6)ꢁ formed by the plane of the
carboxylic group with the mean plane through the C2–C4/
N1/O3 atoms. The dihedral angle between this plane and
the benzene ring is 11.6(3)ꢁ. In the crystal structure
(Fig. 6), interchain N–H…O hydrogen bonds link the
polymers into layers parallel to the (100) plane [N1–H2N,
Coordination around the metal is trigonal bipyramidal, with
the carbon atoms of the methyl groups occupying the
equatorial plane and the O1 and O2 atoms of symmetry-
related ligands at the apices (Fig. 5). In complex (5), the
carboxylic oxygen atoms of the ligand bridge adjacent tin
metal atoms to form zigzag polymeric chains parallel to the
crystallographic c axis (Fig. 6). According to the literature
[24], trigonality around the Sn atom can be described by the
index s = (b - a)/60, where b is the largest of the basal
angles and a isthe secondlargestangle. The calculateds value
is 0.16, which indicates a slightly distorted trigonal bipyra-
midal arrangement. The sum of the equatorial C–Sn–C angles
H2N…O3iii,
N1…O3iii,
˚
0.914(8) A;
˚
2.18(8) A;
iii
˚
3.088(8) A; N1–H2 N…O3 , 170(6)ꢁ; symmetry code:
(iii) x, -1/2 - y, -1/2 ? z].
Antibacterial activity
The antibacterial activity of the compounds was studied
by using agar well diffusion method [27]. Bacterial
strains, e.g., E. coli, B. subtilis, S. flexneri and P. aeru-
ginosa were selected to study the antibacterial activity of
the ligand (HL) and complexes (1)–(7) (concentration of
1 mg/mL of DMSO). Imipenem was used as a standard
drug and the zone of inhibition was measured in milli-
meter. Antibacterial data obtained from the experiment
are presented in Table 8. The data indicated that the
ligand showed no activity against tested bacterial strains.
Complex (5) showed significant activity against E. coli,
B. subtilis and S. flexneri among the synthesized com-
plexes, possibly due to its lipophilicity. This balance of
hydrophobic and hydrophilic forces helped the complex
(2) in the penetration through cell membrane and per-
turbation on growth, respiration and membrane physical
properties [28]. The data obtained in this study, which are
consistent with those reported in literature [29, 30],
seems to suggest a strong link between the biological
activity and the alkyl groups attached to the tin metal
rather than ligand, whose role is merely to transport the
organotin(IV) species to the site of the action where it is
released by hydrolysis.
˚
is 359.3ꢁ. The Sn–C [2.109(8) - 2.120(7) A] and Sn–O bond
˚
lengths [2.109(8) - 2.358(5) A] are in agreement with
those reported for related triorganotin(IV) carboxylates
[25, 26]. With respect to the free ligand (HL), the planarity
of the C(O2)C2C(O)N fragment is lost, as indicated by the
Fig. 5 ORTEP drawing of complex (5) showing 50 % displacement
ellipsoids [symmetry codes: (i) x, 1/2 - y, 1/2 ? z; (ii) x, ‘ -y,
-1/2 ? z)]
Fig. 6 Packing diagram of
complex (5) approximately
viewed along the b axis.
Interchain hydrogen bonds are
shown as dashed lines.
Hydrogen atoms not involved in
hydrogen bonding are omitted
for clarity
123

J IRAN CHEM SOC (2012) 9:923–932
931
Table 8 Antibacterial activity data of 3-[(30,50-dimethylphenylami-
do)]propanoic acid and its organotin(IV) complexes
biological activity. This anomalous behavior can be
explained on the basis of the anionic ligand group that
generally plays a secondary role. In some cases, however, it
may also play important role to enhance the biocidal
activity of organotin(IV) compounds [32].
Compound
Zone of inhibition (mm)
E. coli
B. subtilis
S. flexneri
P. aeruginosa
(HL)
(1)
0
10
17
0
0
11
19
16
14
0
0
0
0
0
Conclusion
(2)
17
0
12
10
14
14
16
0
(3)
Di- and triorganotin(IV) complexes of 3-[(30,50-dim-
ethylphenylamido)]propanoic acid have been synthesized
and characterized. Detailed studies of the reported com-
plexes indicate that triorganotin compounds exhibit a tri-
gonal bipyramidal geometry which is also confirmed by the
crystal structure of complex (5), while a six-coordination
geometry is preferred by diorganotin compounds in the
solid state. The structure of ligand acid (HL) was also
determined by XRD. Multinuclear NMR data shows that
the synthesized complexes exhibit tetrahedral geometry in
solution.
(4)
11
12
0
10
12
9
(5)
(6)
11
10
37
(7)
15
30
13
36
Imipenem
32
Concentration: 1 mg/mL of DMSO
Antifungal activity
The in vitro antifungal properties of the (HL) and its
synthesized complexes were evaluated against representa-
tive fungi using a literature method [27]. The percent
growth inhibition (%) of the synthesized ligand and the
compounds are listed in Table 9. The ligand showed no
potency against the selected strains of fungus. The higher
activity of tin(lV) complexes as compared to the ligand
owed to the chelate formation, in which the ligand coor-
dinated to the central tin atom through the carboxylate
oxygen. The tin metal atom caused apoptosis which
increased fungitoxic action. Data obtained showed that
triorganotin(IV) carboxylates were more active than dior-
ganotin(IV) carboxylates [31]. This situation is in sharp
contrast to the earlier assessment that increase in the
number of R groups on the tin(IV) atom enhances its
Supplementary material
CCDC nos. 859832 and 859833 contains the supplemen-
tary crystallographic data for (HL) complexes (5),
respectively. These data can be obtained free of charge
from The Cambridge Crystallographic Data Center via
http://www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgments SA is thankful to Quaid-i-Azam University,
Islamabad for financial support.
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123