Spectral and biological studies of newly synthesized organotin(IV) complexes of 4-({[(E)-(2-hydroxyphenyl)methylidene]amino}methyl)cyclohexane carboxylic acid Schiff base

Article abstract of DOI:10.1007/BF03245860

The new organotin(IV) complexes with 4-({[(E)-(2-hydroxyphenyl)methylidene]amino}methyl)cyclohexane carboxylic acid (HL, Schiff base) were synthesized by the reaction of diand triorganotin salts in the presence of triethylamine as base or dioctyltin oxide using Dean and Stark trap for the removal of azeotropic water. All complexes were characterized by elemental analysis, IR, NMR (¹H and ¹³C) and mass spectrometry. The IR data indicate that in both diand triorganotin(IV) carboxylates, the ligand moiety -COO acts as a bidentate group in solid state. Multinuclear NMR data show that triorganotin complexes exhibit the four-coordinated geometry, while diorganotin(IV) complexes show the coordination number greater than four, probably five or six, in solution state. These compounds were screened for antibacterial activities against six pathogenic bacterial strains. The activities were measured in terms of inhibition zones (mm). Antifungal activity was determined against six pathogenic fungal strains, cytotoxicity by the brine shrimp lethality assay. Results for antibacterial and antifungal activity, and cytotoxicity of these compounds demonstrate that complexes exhibit significant biological activity with few exceptions.

Full text of DOI:10.1007/BF03245860

J. Iran. Chem. Soc., Vol. 7, No. 1, March 2010, pp. 59-68.
JOUIRrNaAnLiaOnF THE
Chemical Society
Spectral and Biological Studies of Newly Synthesized Organotin(IV) Complexes of
4-({[(E)-(2-Hydroxyphenyl)methylidene]amino}methyl)cyclohexane Carboxylic Acid
Schiff Base
F.A. Shaha, S. Alia,* and S. Shahzadib,*
aDepartment of Chemistry, Quaid-i-Azam University, Islamabad, 45320, Pakistan
bDepartment of Chemistry, GC University, Faisalabad, Pakistan
(Received 18 September 2008, Accepted 21 November 2008)
The new organotin(IV) complexes with 4-({[(E)-(2-hydroxyphenyl)methylidene]amino}methyl)cyclohexane carboxylic acid
(HL, Schiff base) were synthesized by the reaction of di- and triorganotin salts in the presence of triethylamine as base or
dioctyltin oxide using Dean and Stark trap for the removal of azeotropic water. All complexes were characterized by elemental
analysis, IR, NMR (1H and 13C) and mass spectrometry. The IR data indicate that in both di- and triorganotin(IV) carboxylates,
the ligand moiety -COO acts as a bidentate group in solid state. Multinuclear NMR data show that triorganotin complexes exhibit
the four-coordinated geometry, while diorganotin(IV) complexes show the coordination number greater than four, probably five
or six, in solution state. These compounds were screened for antibacterial activities against six pathogenic bacterial strains. The
activities were measured in terms of inhibition zones (mm). Antifungal activity was determined against six pathogenic fungal
strains, cytotoxicity by the brine shrimp lethality assay. Results for antibacterial and antifungal activity, and cytotoxicity of these
compounds demonstrate that complexes exhibit significant biological activity with few exceptions.
Keywords: Organotin(IV) carboxylates, Schiff base, Spectral characterization, Biological activity
INTRODUCTION
such as bactericides [3], as an anti-tumour [5], as an anti-
inflammatory agent [6], and as an antituberclosis [7,8].
The chemistry of organotin(IV) derivatives is a field of
growing interest [1] because of their great structural diversity,
the nature of organic ligand and the ratio of the reactant [2].
The increasing importance of organotin(IV) compounds is not
only because of its extensive commercial use [3] in industry
such as PVC stabilizing agent and anti-neoplastic agent, and in
agriculture such as a wood preservative, fungicide and
pesticide, but also due to the environmental consequences of
the widespread use of these complexes [4]. The organotin(IV)
compounds are also used for pharmacological applications
Many Schiff bases are biologically active and show
significant anti-microbial and anti-tumor activities [9,10].
These compounds also possess a wide range of structural
diversity. Molecules having hetero-atoms, other than nitrogen,
can be easily synthesized and successfully used for metal
complexation [11,12]. The role of Schiff base as extractant in
radioisotope
enrichment
and
manufacturing
of
radiopharmaceutical is worth mentioning [13]. Due to the
clinical importance of tranexamic acid and in order to pursue
our studies of biologically active organotin(IV) derivatives
[14,15], we attempted to synthesize the Schiff base by using
tranexamic acid as reactant (Fig. 1) and then their organotin(IV)
*Corresponding author. E-mail: drsa54@yahoo.com

Shah et al.
NH2
HOOC
+
CHO
N
HOOC
OH
C
Ethanol
100 ml
reflux for 3-4 h
OH
Fig. 1. 4-({[(E)-(2-Hydroxyphenyl)methylidene]amino}
methyl)cyclohexane carboxylic acid (Schiff
base).
N
HOOC
C
OH
Scheme 1
complexes assuming that the complexes can be used as new
prodrug of tranexamic acid. To check this, we screened these
complexes against different bacterial and fungal strains and
also checked their cytotoxicity. These complexes were
characterized by IR, NMR and mass spectrometry.
solution was kept at room temperature for 48 h to get the
yellow solid product (Scheme 1).
Synthesis of Organotin(IV) Complexes of 4-({[(E)-(2-
Hydroxyphenyl)methylidene]amino}methyl)cyclohex-
ane Carboxylic Acid
EXPERIMENTAL
Materials and Methods
a.
4-({[(E)-(4-Hydroxyphenyl)methylidene]amino}
All the glass apparatus with standard quick fit joints was
used throughout the work after cleaning and drying at 120 °C.
2-Hydroxybenzaldehyde, organotin(IV) chlorides and
organotin(IV) oxide from Aldrich and toluene from Fluka
were purchased. Solvents were purified by standard methods
[16], while other chemicals were used as supplied. Melting
points were determined with a Mitamura Rikero Kogyo
(Japan) and are uncorrected. Mass spectra were recorded on a
MAT 8500 Finngin (Germany). Elemental analysis was
carried out with a Perkin-Elmer 2400 Series II instrument. IR
spectra in the range 4000-400 cm-1 were recorded as neat
liquids, using KBr pellets (for solid compounds) on a Bio-Rad
FT-IR spectrometer. The 1H and 13C NMR spectra were
recorded on a Bruker AM-300 MHz spectrometer using CDCl3
as internal reference.
methyl)cyclohexane carboxylic acid (1 g, 3.83 mmol) was
suspended in 250 ml round bottom two necked flask in dry
toluene (100 ml) and treated with triethylamine (0.386 ml,
3.83 mmol). The mixture was refluxed for 2-3 h. Then 2 mmol
diorganotindichloride (R2 = Me2, Bu2, Ph2 and Oct2) or 1
mmol triorganotinchloride (R3 = Me3, Bu3 and Ph3) was added
as solid to a reaction flask with constant stirring and reaction
mixture was refluxed for 8-10 h. The reaction mixture
contained Et3NHCl and was filtered off in such a way that
filtrate had the organotin derivative. The solvent was removed
through rotary apparatus. The mass left behind was
recrystallized from CHCl3 and n-hexane mixture (1:1).
b. 4-({[(E)-(4-Hydroxyphenyl)methylidene]amino}
methyl)cyclohexane carboxylic acid (1 g, 3.83 mmol) was
suspended in dry toluene, (100 ml). To this solution, Oct2SnO
(dioctyltin(IV) oxide) (0.67 g, 1.91 mmol) was added as solid
with constant stirring and refluxed for 8-10 h. Water formed
during the reaction was removed via Dean and Stark trap. The
solvent was removed under reduced pressure through rotary
apparatus and the product obtained was recrystallized in
CHCl3:n-hexane (1:1) mixture.
Synthesis of 4-({[(E)-(2-Hydroxyphenyl)methylidene]
amino}methyl)cyclohexane Carboxylic Acid (Schiff
Base)
An aqueous hot (100 °C) solution (100 ml) of tranexamic
acid (1 mmol) was added dropwise to an ethanolic (100 ml)
solution of 4-hydroxybenzaldehyde (1 mmol) in round bottom
flask equipped with water condenser with constant stirring.
Reaction mixture was left under reflux for 3-4 h and then the
The resulting organotin(IV) complexes of 4-({[(E)-
(2-hydroxyphenyl)methylidene]amino}methyl)cyclohexane
carboxylic acid are 1 (Me2), 2 (Bu2), 3 (Ph2), 4 (Oct2), 5 (Me3),
60

Spectral and Biological Studies of Newly Synthesized Organotin(IV) Complexes
6 (Bu3) and 7 (Ph3). Some typical synthetic routs for the
organotin(IV) complexes of the Schiff base HL are as follows:
band due to ꢀ(OH) stretching frequency in the organotin(IV)
derivatives and the presence of ꢀ(Sn-O) stretching frequency
at 403-459 cm-1 is indicative of complex formation [18].
The values of IR stretching vibration frequencies of
i) Toluene
R2SnCl2 + 2Et3NHL
carboxylic group [(ꢀ(COOasym
)
and ꢀ(COOsym)] in
ii) Reflux for 8-10 hrs
(1)
(2)
(3)
organotin(IV) carboxylates are helpful in elucidation of the
structure and bonding behaviour of the ligand [19-21]. In all
complexes the difference ꢁꢀ is less than 200 cm-1 which
indicates the bidentate nature of the ligand. Diorganotin(IV)
dicarboxylates exhibit the hexa coordinated geometry, while
triorganotin(IV) carboxylates show the trigonal bipyramidal
geometry in solid state. Polymeric structure is supported by
trigonal bipyramidal geometry.
R2SnL2 + 2Et3NHCl
R3SnCl + Et3NHL
i) Toluene
ii) Reflux for 8-10 hrs
R3SnL + Et3NHCl
Oct2SnO + 2HL i) Toluene
ii) Reflux for 8-10 hrs
Oct2SnL2 + H2O
1H NMR Spectroscopy
The characteristic resonance peaks for the reported
complexes (1)-(7) have been recorded in CDCl3 and data are
given in Table 3. The expected resonances are assigned by
their peak multiplicity, intensity pattern and integration. The
integration of spectra shows good agreement with the
composition of the compounds.
RESULTS AND DISCUSSION
The Schiff base ligand is yellow in color and is soluble in
almost all organic solvents. While, the corresponding metal
complexes obtained in 1:1 and 1:2 molar ratios (Eqs. 1-3)
were found to be dark yellow in color. The reported
compounds (1)-(7) were prepared by the reaction of ligand
acid with organotin(IV) halides or oxide in the presence of
triethylamine. All the synthesized compounds were stable
having sharp melting points and were soluble in common
organic solvents. The complexes were analyzed by IR, MS
and NMR to propose their geometry in the solid and solution
state. The physical data are given in Table 1.
1
The H NMR spectral data of the ligand show single
resonance at 11.4 ppm, which is absent in the spectra of the
complexes, indicating the replacement of the carboxylic acid
proton by the organotin(IV) moiety.
In addition, the resonance appearing in the range 5.20-5.21
ppm as a singlet is attributed to the -N=CH proton and
aromatic protons appearing in the expected region as doublets
and triplets. However, cyclohexyl protons appear at relatively
upfield shift value in the range of 1.20-1.73 ppm, while four
protons of aromatic ring of the ligand appear as doublet and a
triplet with 3J(1H,1H) 8.1 and 8.2 Hz, respectively. The phenyl
groups attached to metal atom come into view as a multiplet at
7.26-7.30 and 7.28-7.39 ppm for compound (3) and (7),
respectively.
Infrared Spectroscopy
IR spectra of the complexes (1)-(7) were recorded as KBr
pellets or neat liquid (for liquid sample) in the range 4000-400
cm-1. The collected data are summarized in Table 2. The
ꢀ(C=N) band of Schiff base appears in the range 1613-1622
cm-1 which is in close agreement with the values reported in
literature for such systems [17].
Assignment of different vibrational bands was made by the
comparison of free acid spectrum with the organotin(IV)
derivatives. The absorption bands ꢀ(Sn-C) in the spectra of the
reported compounds lie in the range of 510-526 cm-1 which
indicate the presence of Sn-C bond. The absence of a broad
The CH2 protons of di-n-butyltin compound (2) are
3
significant as a triplet at 0.87 ppm with J[1H,1H] = 7.5 Hz,
while -CH2-CH2- protons appear as a multiplet. Terminal
protons of di-butyltin(IV) also show a triplet at 0.95 ppm with
3J [1H,1H] = 7.8 Hz.
1
The most important information obtained from H NMR
values is 2J[119Sn-1H] coupling constant values in these
compounds. The coupling value of 81 Hz in compound (1)
61

Shah et al.
Table 1. Physical Parameters of Organotin(IV) Complexes of Schiff Base
Compound Empirical formula
m.p.
(ºC)
Yield
(%)
Molecular
weight
Elemental analysis; calculated (found)
(%)
C
H
N
HL
C15H19O3N
120
168
154
143
-
-
261
669
753
793
857
424
550
610
68.96
(68.93)
57.39
6.89
(6.92)
6.27
5.36
(5.32)
4.18
(1)
C32H42O6N2Sn
C38H54O6N2Sn
C42H46O6N2Sn
80
75
79
70
81
83
80
(57.33)
(6.23)
(4.22)
60.55
(60.50)
63.55
7.17
(7.20)
5.80
3.71
(3.75)
3.53
(2)
(3)
(4)
(63.50)
(5.82)
(3.57)
C46H62O6N2Sn
C18H27O3NSn
C27H45O3NSn
C33H33O3NSn
64.41
(64.37)
50.94
(50.90)
58.90
(58.86)
64.91
7.23
(7.19)
6.36
(6.40)
8.18
(8.21)
5.40
3.26
(3.22)
3.30
(3.35)
2.54
(2.58)
2.29
166
67
(5)
(6)
(7)
134
(64.96)
(5.37)
(2.23)
Table 2. Characteristic Infrared Bands (cm-1) for Organotin(IV) Complexes of Schiff Base
Compound
ꢀasym(COO)
ꢀsym(COO)
ꢀꢀ
ꢀ(Sn-C)
ꢀ(Sn-O)
HL
(1)
(2)
1635
1641
1634
1372
1447
1450
263
194
184
-
-
516
525
403
459
(3)
(4)
(5)
(6)
1645
1633
1635
1637
1452
1449
1495
1488
193
184
140
149
-
456
452
449
457
526
510
520
(7)
1645
1480
165
-
453
demonstrates that diorganotin(IV) derivatives show the
coordination number greater than four, probably five or six, in
non-coordinating solvent. The coupling value of 57 Hz in the
compound (5) signifies that triorganotin(IV) derivatives show
distorted tetrahedral geometry [22,23] in the solution form.
Furthermore, it is observed that the aldehyde phenyl protons
appear upfield as a two doublet and a triplet due to the electron
donating effect of the hydroxy group. The hydroxy proton
gives singlet in the range of 5.1-5.3 ppm for the complexes
(1)-(7).
13C NMR Spectroscopy
The characteristic resonance peaks in the 13C NMR spectra
of the complexes (1)-(7) recorded in CDCl3, are reported in
Table 4. The position of the phenyl carbons of the ligand
undergo a minor variation in the complexes as compared to
62

Spectral and Biological Studies of Newly Synthesized Organotin(IV) Complexes
1
Table 3. H NMR Dataa,b (ppm) for Organotin(IV) Complexes of Schiff Base
4
3
2
5
13
HOOC
6
11
9
N
10
1
C
8
7
12
OH
H No.
2
HL
(1)
(2)
(3)
(4)
(5)
(6)
(7)
6.93d
(8.1)
6.94t
(8.3)
6.95t
(8.3)
6.93d
(8.2)
5.20s
1.57s
1.20m
1.62m
1.72m
1.80m
11.4s
5.1s
6.92d
(8.1)
6.91t
(8.3)
6.92t
(8.1)
6.94d
(8.1)
5.20s
1.58s
1.22m
1.61m
1.70m
1.83m
-
6.91d
(8.1)
6.92t
(8.3)
6.93t
(8.1)
6.93d
(8.1)
5.20s
1.57s
1.21m
1.60m
1.71m
1.82 m
-
6.92d
(8.1)
6.94t
(8.3)
6.95t
(8.1)
6.94d
(8.1)
5.21s
1.58s
1.23m
1.61m
1.71m
1.81m
-
6.90d
(8.1)
6.91t
(8.3)
6.91t
(8.1)
6.92d
(8.1)
5.20s
1.59s
1.21m
1.62m
1.72m
1.82 m
-
6.94d
(8.1)
6.93t
(8.3)
6.94t
(8.1)
6.94d
(8.1)
5.20s
1.57s
1.20m
1.61m
1.72m
1.81m
-
6.93d
(8.1)
6.92t
(8.3)
6.93t
(8.1)
6.93d
(8.1)
5.21s
1.58s
1.21m
1.60m
1.71m
1.83m
-
6.91d
(8.1)
6.93t
(8.3)
6.91t
(8.1)
6.94d
(8.1)
5.20s
1.58s
1.22m
1.60m
1.73m
1.84m
-
3
4
5
7
8
9
10
11
12
COOH
OH
5.3s
5.2s
5.1s
5.2s
5.2s
5.2s
5.1s
aCompound (1): Sn-CH3, 0.27s 2J[81]. Compound (2): Sn-CH2CH2CH2CH3, 0.87t (7.5), 1.30-1.41m.
Compound (3): Sn-C6H5, 7.26-7.30m. Compound (4): Sn-CH2CH2CH2CH2CH2CH2CH2CH3, 0.91-1.82m.
Compound (5): Sn-CH3, -0.05s [57]. Compound (6): Sn-CH2CH2CH2CH3, 0.95t (7.8), 1.31-1.42m.
Compound (7): Sn-C6H5, 7.28-7.39m. bChemical shifts (ꢂ) 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.
2
1
1
those observed in free acid. The carboxylate carbon shows a
downfield shift in the complexes, indicating the contribution
of the carboxylic group (COO) in coordination to tin(IV) [24].
The coupling constants, nJ[119Sn,13C] are important parameters
for the structure characterization of organotin(IV) compounds.
calculated from the J[119Sn, H] and J[119Sn, 13C] values,
using the literature methods [25]. Since the geometry of the
diorganotin dicarboxylates in non-coordinating solvents is
concerned from J[119Sn,13C] coupling value, as in case of
1
compound (3), it is not defined with certainty because of the
fluxional behavior of the carboxylate oxygen in their
coordination with the tin atom. However, most of alkyl
diorganotin(IV) dicarboxylates appear as skew trapezoidal
geometry which is in between five and six coordination
1
For triorganotin compound (5), the magnitude of J[119Sn,13C]
coupling values is 397 Hz, which suggests the typical
tetrahedral geometry around the tin atom in solution [24]. This
is further supported by the C-Sn-C bond angles (Table 5)
63

Shah et al.
Table 4. 13C NMR Dataa,b (ppm) for Organotin(IV) Complexes of Schiff Base
4
3
2
5
13
HOOC
6
11
9
N
10
1
C
8
7
12
OH
C No.
1
2
3
4
5
6
7
8
HL
(1)
(2)
(3)
(4)
(5)
(6)
(7)
138.2
129.3
125.2
120.6
129.2
137.8
122.6
31.2
138.3
129.2
125.1
120.7
129.4
137.7
122.8
31.5
138.4
129.2
125.4
120.5
129.1
137.5
122.7
31.4
138.8
129.3
125.4
120.4
129.3
137.6
122.8
31.5
138.2
129.1
125.3
120.3
129.2
137.5
122.6
31.6
138.3
129.4
125.4
120.6
129.2
137.1
122.2
31.5
138.4
129.2
125.4
120.7
129.3
137.7
122.5
31.3
138.4
129.2
125.4
120.5
129.1
137.5
122.2
31.4
9
38.2
34.8
34.2
33.6
38.5
34.6
34.4
33.5
38.3
34.5
34.3
33.5
38.3
34.6
34.1
33.5
38.2
34.6
34.2
33.4
38.3
34.5
34.3
33.2
38.4
34.6
34.3
33.3
38.3
34.6
34.3
33.6
10
11
12
13
180.1
182.7
182.4
182.3
182.3
182.7
182.6
182.9
aCompound (1): Sn-CH3, (C-ꢃ)-2.23 1J[641,664]. Compound (2): Sn-CH2CH2CH2CH3, (C-ꢃ) 28.6,
(C-ꢄ) 27.4 2J[22], (C-ꢅ) 26.8 3J[63], (C-ꢂ) 14.5. Compound (3): Sn-C6H5, (C-ꢃ) 138.4, (C-ꢄ) 137.7 2J[48],
(C-ꢅ) 136.5, (C-ꢂ) 130.2. Compound (4): Sn-CH2CH2CH2CH2CH2CH2CH2CH3, (C-ꢃ) 37.6 1J[555, 580],
(C-ꢄ) 31.3 2J[37] (C-ꢅ) 30.5 3J [91], (C-ꢂ) 29.8 (C-ꢃ*) 29.3, (C-ꢄ*) 26.4, (C-ꢅ*), 22.1, (C-ꢂ*) 14.8.
Compound (5): Sn-CH3, (C-ꢃ)-2.3 1J[377, 397]. Compound (6): Sn-CH2CH2CH2CH3, (C-ꢃ) 29.2, (C-ꢄ)
27.3 2J[22], (C-ꢅ) 26.4 3J[63], (C-ꢂ) 14.6. Compound (7): Sn-C6H5, (C-ꢃ) 138.8, (C-ꢄ) 137.9 2J[47],
(C-ꢅ) 136.9, (C-ꢂ) 130.8. bChemical shifts (ꢂ) in ppm. nJ[119Sn, 13C] in Hz are listed in square brackets.
Table 5. (C-Sn-C) Angles (o) Based on NMR Parameters of Selected Organotin(IV)
Complexes of Schiff Base
Angle (°)
Compound
1J[119Sn, 13C] (Hz)
2J[119Sn, 1H] (Hz)
1J
-
2J
(1)
(5)
-
81
57
132.1
110.5
397
111.6
numbers [24]. Deshielding of C(13) observed in complexes
(1)-(7) should be related to the electrophilicity of the tin.
compounds (1)-(7) have been reported in Table 6. It can be
observed that large organotin molecules suffer considerable
fragmentation in the mass spectrometer, while small
organotin(IV) molecules often show the molecular ion peaks.
Molecular ion peak is not observed for the reported complexes
Mass Spectrometry
The fragment ions with their m/z (%) values for
64

Spectral and Biological Studies of Newly Synthesized Organotin(IV) Complexes
Table 6. Mass Spectral Data for Organotin(IV) Complexes of Schiff Base
(1)
(2)
(3)
m/z(%)
263(90)
216(70)
174(65)
134(100)
121(25)
216(32)
260(70)
-
(4)
(5)
(6)
(7)
Fragment ion
m/z(%)
263(90)
216(70)
174(35)
134(100)
121(25)
216(42)
260(25)
-
77(18)
-
150(11)
135(6)
m/z(%)
263(87)
216(45)
174(39)
134(100)
121(20)
216(45)
260(88)
57(44)
77(18)
-
m/z(%)
263(15)
216(18)
174(18)
134(55)
121(55)
216(17)
260(35)
57(24)
77(100)
-
m/z(%)
263(38)
216(60)
174(10)
134(45)
121(20)
216(65)
260(100)
-
m/z(%)
263(21)
216(50)
174(10)
134(20)
121(18)
216(18)
260(25)
57(64)
77(100)
291(31)
234(17)
177(9)
m/z(%)
263(92)
216(40)
174(30)
134(48)
121(20)
216(29)
260(55)
-
77(100)
351(24)
274(16)
197(10)
[C15H19NO3]+
[C14H18NO]+
[C11H12NO]+
[C8H8NO]+
[SnH]+
[C5H4O2Sn]+
[C8H12O2Sn]+
[C4H9]+
[C6H5]+
77(35)
-
274(15)
197(7)
77(8)
[R3Sn]+
165(22)
150(13)
135(4)
[R2Sn]+
234(21)
177(14)
346(14)
233(11)
[RSn]+
(1)-(7). In these compounds, primary decomposition is due to
either loss of group or ligand, while secondary
by hydrolysis [29].
R
The synthesized reported compounds were screened for
antibacterial activity by the agar well diffusion method [28] at
concentration of 10 mg ml-1 of DMSO. The zone of inhibition
diameter was measured in mm and the reference drug used
was Imipenum. All bacterial strains have clinical implication;
Escherichia coli, infection of wounds, urinary tract and
dysentery; Bacillus subtilis, food poisoning; Shigella flexenari,
blood diarrhea with fever and severe prostration;
Staphlococcus aureus, food poisoning, scaled skin syndrome,
endrocarditis; Pseudomonas aeruginosa, infection of wounds,
eyes, septicemia and Salmonella typhi, typhoid fever, localized
infection. The antibacterial data are given in Table 9.
Compound (2) shows excellent activity and compounds (6)
and (7) show good activity against all of these tested becteria.
From the biological screeing results, it is concluded that (i)
triphenyltin(IV) derivative has high toxicity but good
antifungal activity, (ii) trimethyltin(IV) derivative is least toxic
as well as good antifungal, (iii) compound (2) is excellent
antibacterial and has no fungal activity.
decomposition is a consequence of loss of either R group or
CO2 molecules [26,27]. However, the latter is the more
frequent and probable pathway. Base peak for compounds (1)-
(3) is observed due to [C8H8NO]+ fragment, while for
compounds (4), (6) and (7) it is due to [C6H5]+.
Biological Studies
The cytotoxicity (LD50) data have also been determined
using the Brine-shrimp (Artemia salina) method [28], and
results are listed in Table 7. The highest toxicity is observed
for compound (7), whereas compounds (5) and (6) were found
to be the least and moderate toxic, respectively, and the other
synthesized compounds showed no cytotoxicity.
All synthesized complexes of Schiff base were evaluated
for their microbial toxicity against a set of fungal strain. The
antifungal results of the investigated compounds are given in
Table 8. Compounds (5) and (7) are found to show significant
antifungal activity against the test fungi. Compound (3) also
shows good antifungal activity. Compounds (2) and (4) show
no fungal activity. The activity varies with variation of R
groups, attached with the Sn. Apparently, the function of the
ligand is only to support the transport of the active
organotin(IV) moiety to the site of action where it is released
Proposed Structure
The possible structures for organotin(IV) complexes of
Schiff base HL, concluded based on the spectroscopic data
given in Tables 2-6, are given in Fig. 2.
65

Shah et al.
Table 7. Brine Shrimp (Artemia Salina) Lethality Bioassay for Organotin(IV) Complexes of Schiff Base
Dose
(ꢆg ml-1
100
10
No. of
Shrimps
30
No. of
Standard
drug
LD50
LD50 (ꢆg ml-1)
Compound
)
Survivors
(ꢆg ml-1)
0
0
1
HL
-
Etoposide
Etoposide
Etoposide
Etoposide
Etoposide
Etoposide
Etoposide
7.46
7.46
7.46
7.46
7.46
7.46
7.46
30
1
100
10
1
100
10
1
100
10
1
100
10
1
100
10
1
100
10
30
30
22
24
27
24
25
27
26
26
28
24
24
29
0
(1)
(2)
(3)
(4)
(5)
(6)
30
-
30
30
30
-
-
30
30
30
30
30
30
-
30
30
30
1
1.12
3.72
30
18
0
0
30
30
1
30
0
100
30
0
(7)
5.98
Etoposide
7.46
10
1
30
30
0
1
Table 8. Antifungal Activitya-c (%Inhibition) for Organotin(IV) Complexes of Schiff Base
Inhibition (%)
Fungus
(ATCC No.)
MIC
(ꢆg ml-1)
HL
(1)
(2)
(3)
(4)
(5)
(6)
(7)
Trichophyton longifusus
0
30
0
80
0
80
20
80
70.0
110.8
20.0
(22397)
Candida albicans (2192)
Aspergillus flavis (1030)
Microsporum canis (9865)
Fusarium solani (11712)
Candida glaberata
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
20
50
80
50
20
0
90
90
80
40
90
50
0
50
0
80
0
98.4
50
73.2
0
0
20
110.8
aConcentration: 100 ꢆg ml-1 of DMSO. bMIC: Minimum inhibitory concentration. cPercent inhibition (standard drug) = 100.
66

Spectral and Biological Studies of Newly Synthesized Organotin(IV) Complexes
Table 9. Antibacterial Activitya-c (Diameter of Inhibition Zone after 20 h) for Organotin(IV) Complexes
of Schiff Base
Bacterium
(ATCC No.)
Inhibition zone diameter (mm)
Reference
drug
HL
(1)
(2)
(3)
(4)
(5)
(6)
(7)
Escherichia coli
-
15
22
0
0
0
12
12
35
Bacillus subtilis
(11774)
-
-
0
0
24
17
0
0
0
0
0
0
12
12
12
12
38
Shigella flexenari
32
38
29
(700390)
Stephlococcus aureus
(25923)
Pseudomonas
aeruginosa (10145)
Salmonella typhi
(10749)
-
0
18
0
0
0
0
0
-
-
12
10
14
20
12
16
0
23
20
14
18
15
22
10
28
c
aIn vitro, agar well diffusion method, conc. 3 mg ml-1 of DMSO. bReference drug, Imipenum. Clinical
Implication: Escherichia coli, infection of wounds, urinary tract and dysentery; Bacillus subtilis, food
poisoning; Shigella flexenari, blood diarrhea with fever and severe prostration; Staphlococcus aureus,
food poisoning, scaled skin syndrome, endrocarditis; Pseudomonas aeruginosa, infection of wounds,
eyes, septicemia, Salmonella typhi, typhoid fever, localized infection.
R
R
O
O
O
R
O
CONCLUSIONS
O
O
R
C
Sn
C
R
Sn
R
R
O
O
R
Elemental analysis shows a good agreement between the
calculated and observed % of C, H and N. The FT-IR spectra
clearly demonstrate that the organotin(IV) moieties react with
[O,O] atoms of the ligand and ligand behaves as bidentate for
coordination to tin. Detailed studies of the reported complexes
in solution state indicate that their structure is tetrahedral for
triorganotin(IV) complexes, while the polymeric structure was
exhibited by triorganotin(IV) complexes having a penta
coordinated geometry around tin atom. Diorganotin(IV)
complexes show the coordination number greater than four,
probably five or six, in solution state. Mass spectral data are
also in agreement with the proposed molecular formulae of all
the synthesized compounds with no molecular ion peak.
Organotin(IV) complexes are found to be active against tested
Brine Shrimp larvae, bacteria and fungi with few exceptions.
(a)
(b)
R
O
O
R
R
R
R
O
O
Sn
O
O
R
Sn
R
R
R
(c)
(d)
R
R
O
R
Sn
R
O
(e)
where R` =
N
C
ACKNOWLEDGEMENT
OH
Fig. 2. Proposed structures (a), (b) for diorganotin(IV)
derivatives, and (c), (d), (e) for triorganotin(IV)
carboxylates.
SA is thankful to Quaid-i-Azam University, Islamabad for
financial support.
67

Shah et al.
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