Diorganotin(IV) complexes of biologically potent 4(3H)-quinazolinone derived Schiff bases: Synthesis, spectroscopic characterization, DNA interaction studies and antimicrobial activity

Article abstract of DOI:10.1016/j.saa.2011.06.010

Four Schiff base ligands and their corresponding organotin(IV) complexes have been synthesized and characterized by elemental analyses, IR, ¹H NMR, MS and thermal studies. The Schiff bases are obtained by the condensation of 3-amino-2-methyl-4(

Full text of DOI:10.1016/j.saa.2011.06.010

Spectrochimica Acta Part A 81 (2011) 276–282
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Diorganotin(IV) complexes of biologically potent 4(3H)-quinazolinone derived
Schiff bases: Synthesis, spectroscopic characterization, DNA interaction studies
and antimicrobial activity
Kollur Shiva Prasada, Linganna Shiva Kumara, Shivamallu Chandanb, Basvegowda Jayalakshmic,
Hosakere D. Revanasiddappaa,∗
a Department of Chemistry, University of Mysore, Manasagangotri, Mysore 570 006, Karnataka, India
b Department of Biotechnology, University of Mysore, Manasagangotri, Mysore 570 006, Karnataka, India
c Department of Botany, Maharani’s Science College for Women, Mysore 570 005, Karnataka, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Four Schiff base ligands and their corresponding organotin(IV) complexes have been synthesized and
characterized by elemental analyses, IR, 1H NMR, MS and thermal studies. The Schiff bases are obtained by
the condensation of 3-amino-2-methyl-4(3H)-quinazolinone with different substituted aldehydes. The
elemental analysis data suggest the stoichiometry to be 1:1 ratio formation. Infrared spectral data agreed
with the coordination to the central metal ion through imine nitrogen, lactam oxygen and deprotonated
phenolic oxygen atoms. All the synthesized compounds have been evaluated for antimicrobial activity
against selected species of microorganisms. In addition, DNA binding/cleavage capacity of the compounds
was analyzed by absorption spectroscopy, viscosity measurements and gel electrophoresis methods.
© 2011 Elsevier B.V. All rights reserved.
Received 14 March 2011
Received in revised form 3 June 2011
Accepted 13 June 2011
Keywords:
3-Amino-2-methyl-4(3H)-quinazolinone
Spectral techniques
Thermal studies
DNA binding
Nuclease activity
1. Introduction
have been made to synthesize and characterize organotin com-
pounds of ligands having hetero donor atoms (O, N, S), and many
The Schiff bases are among the most widely used ligands due
to their facile synthesis, remarkable versatility and good solubility
in common solvents. Thus, they have played an important role in
the development of coordination chemistry as they readily form
stable complexes with most metals in different oxidation states. In
the area of bioinorganic chemistry, the interest in the Schiff base
complexes lies in that they provide synthetic models for the metal
containing sites in metalloproteins and enzymes [1]. Quinazolinon-
4(3H)-ones and its derivatives are versatile nitrogen heterocyclic
compounds which have long been known as a promising class of
biologically active compounds [2]. Compounds containing 4(3H)-
quinazolinone ring system have been reported to possess different
biological activities such as antibacterial [3], antifungal [4], anti-
tubercular [5], antiviral, anticancer [6] and anticonvulsant activity
depending on the substituent’s in the ring system.
studies have been focused on their structure–activity correlations
[7,8]. Several organotin(IV) compounds have been synthesized and
tested for their antitumor activity and found to be as effective
as, or even better than, traditional heavy anticancer drugs [9].
An interesting work in the field of bioinorganotin chemistry is
the introduction ligands which are bioactive [10]. Schiff bases are
potential anticancer drugs and when administered as their metal
complexes, the anticancer activity of these complexes is enhanced
in comparison to the free ligand [11]. Therefore, organotin(IV) com-
plexes of Schiff bases have received considerable attention with
respect to their potential applications in medicinal chemistry and
biotechnology [12]. Furthermore, organotin(IV) complexes with
Schiff bases present an interesting variety of structural possibili-
ties. This aspect has been attracting the attention of a number of
researchers and a multitude of structural types have been discov-
ered. Both aliphatic and aromatic Schiff bases in their neutral and
deprotonated forms have been used to react with organotin(IV)
halides; the complexes formed exhibit variable stoichiometry in
the metal to ligand ratio and different modes of coordination [13].
Still, there is a lot of scope to synthesize and characterize organ-
otin complexes with variety of ligands. Thus, the present paper
reports synthesis of four ligands and their organotin(IV) complexes,
and the prepared organotin complexes have been characterized
Over the recent decades, studies on the organotin(IV) complexes
with Schiff base ligands have received considerable attention.
Organotin(IV) complexes have played an important role in
medicine, agriculture and industry. Up to now, considerable efforts
∗
Corresponding author. Tel.: +91 821 2419669.
E-mail address: hdrevanasiddappa@yahoo.com (H.D. Revanasiddappa).
1386-1425/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2011.06.010

K.S. Prasad et al. / Spectrochimica Acta Part A 81 (2011) 276–282
277
and subjected them for biological studies. Besides, the DNA bind-
2.4.2. Viscosity measurements
ing/cleavage activities of the complexes are also reported.
Viscosity measurements were carried out in an Ostwald vis-
cometer maintained at 30.0 0.1 ◦C in a thermostatic water-bath.
The viscometric studies were carried out in buffer solution (pH
7.2). Flow time was measured by hand with digital stopwatch, each
sample was measured three times and the average flow time was
calculated. Data obtained were presented as (ꢀ/ꢀ0)1/3 vs the con-
centration of complexes, where ꢀ is the viscosity of DNA in presence
of complexes and ꢀ0 is the viscosity of DNA alone. Viscosity values
were calculated from the observed flow time of DNA-containing
solution (t > 100 s) corrected for flow time of buffer alone (to),
ꢀ = t − to/to [17].
2. Experimental
2.1. Materials and methods
All the chemicals and solvents were of analytical grade and
used as received. CT-DNA and pUC19 plasmid DNA were purchased
from Genei laboratory, Bangalore. Elemental analysis (CHNS) was
performed using a Perkin-Elmer 240 elemental analyzer. IR spec-
tra of the Schiff base ligands and their complexes were recorded
on a Shimadzu FT-IR-8300 instrument using nujol mulls method
2.4.3. Nuclease activity
in the range of 4000–200 cm−1 1H NMR spectra of the synthe-
.
The DNA cleavage experiment was conducted using supercoiled
pUC19 plasmid DNA by gel electrophoresis method. Cleavage reac-
tions were run between the metal complexes and the supercoiled
plasmid DNA, and the solutions were diluted with loading dye using
1% agarose gel. Buffer solution of 50 mmol Tris–HCl/18.2 mmol NaCl
in water (pH 7.2) was used, followed by the addition of 0.5 g of
powdered agarose and mixed well. The solution was heated to
boiling to dissolve agarose completely. The completely dissolved
agarose gel solution was kept in the water bath at 65 ◦C. Then, 3 ␮l of
ethidium bromide (0.5 ␮g/ml) was added to the above solution and
mixed well. The warmed agarose was poured and clamped imme-
diately with comb to form sample wells. After setting (30–45 min,
at room temperature) comb was removed and taped. The gel was
mounted into electrophoretic tank. Enough electrophoretic buffers
were added to cover the gel to a depth of about 1 mmol. The plasmid
DNA (10 ␮mol) and different concentrations of metal complexes
(10, 15 and 20 ␮l) in Tris–HCl/50 mmol NaCl buffer (pH 7.1) were
mixed with loading dye and loaded into the well of the submerged
gel using a micropipette. The electric current (70 V) was passed
into running buffer. The sample was running from negative to pos-
itive pole [18]. After 1 h the gel was taken out from the buffer.
After electrophoresis, the extent of cleavage was measured from
the intensities of the bands using the Alpha Innotech Gel docu-
mentation system (AlphaImager 2200).
sized compounds were recorded on Bruker DRX-300 spectrometer
using DMSO-d6 as solvent and TMS as the internal standard. Molar
conductivity measurements were recorded on a CM-82T Elico con-
ductivity bridge in DMSO. Thermogravimetric analyses data were
measured from room temperature to 700 ◦C at a heating rate
of 20 ◦C/min on a Shimadzu TG-50 Thermo Balance. Absorption
spectra were recorded using a HITACHI-3900 model spectropho-
tometer.
2.2. Synthesis of Schiff base Ligands
The Schiff base ligands were synthesized according to the
known condensation method [14]. The methanolic solution
of 3-amino-2-methyl-4(3H)-quinazolinone (1) (2.0 mmol, 25 ml)
was mixed with
a methanol solution of salicylaldehyde (to
obtain L1) or 2-pyridine carboxaldehyde (to obtain L2) or
4-hydroxy-3-methoxybenzaldehyde (to obtain L3) or 5-ethyl-2-
thiophenecarboxaldehyde (to obtain L4) (2.0 mmol, 15 ml). The
mixture was stirred magnetically for 30 min and then refluxed for
4 h. After cooling, the solution of Schiff base was filtered, washed
with hot methanol, dried in air and recrystallized from ethanol.
The purity of ligand was checked by thin layer chromatography.
The general structure of 4(3H)-quinazolinone derived Schiff base
ligands are shown in Scheme 1.
2.4.4. Antimicrobial activity
2.3. Synthesis of organotin(IV) complexes
The in vitro antimicrobial screening effects of the synthesized
ligands and their corresponding organotin(IV) complexes were
evaluated against four species of bacteria; E. coli, Staphylococcus
aureus, Ralstonia solanacearum and Xanthomonas vesicatoria as well
as fungi; Aspergillus niger, Aspergillus flavus, Fusarium oxysporum
and Alternaria solani by disk-agar diffusion method [19,20]. All the
tests were performed in triplicate and average is reported. The
minimum inhibitory concentration values of studied compounds
against tested microorganisms are also reported.
All the complexes were synthesized by adding a methanolic
solution of appropriate ligand (1 mmol, 25 ml) to a hot methanolic
solution of dimethyltin chloride salt (1 mmol, 25 ml). The resulting
solutions were stirred and heated to reflux for 4 h. The volume of the
obtained solutions was reduced to one-half by evaporation. After
one day, the colored solid of the complexes formed was filtered,
washed with hot methanol and diethyl ether and finally dried in
air. The synthesized complexes were recrystallized from ethanol.
The purity of all the complexes was evaluated by thin layer chro-
matography. Development of single crystals of these complexes
was unsuccessful.
3. Results and discussion
Organotin(IV) complexes were obtained upon reaction between
organotin and a ligand at 1:1 molar ratio. The synthesized Schiff
base ligands and their tin complexes are very stable at room tem-
perature in the solid state. The ligands and their tin complexes
are generally soluble in DMF and DMSO. The analytical and phys-
ical data of lignads and their organotin complexes are presented
in Table 1. The analytical data are in a good agreement with the
proposed stoichiometry of the complexes.
2.4. Biology
2.4.1. DNA binding studies
Electronic absorption spectroscopy is an effective method to
examine the binding mode of DNA with metal complexes [15].
The DNA concentration per nucleotide was determined adopting
absorption spectroscopy using the known molar extinction coeffi-
cient value of 6600 M−1 cm−1 at 260 nm [16]. Absorption titrations
were performed by using a fixed DNA concentration to which incre-
ments of the complex solution were added. Metal complex–DNA
solutions were incubated for 10 min before the absorption spectra
were recorded.
3.1. Molar conductivity of metal chelates
The tin complexes discussed herein were dissolved in DMF and
the molar conductivities of their 10−3 M solutions at room tempera-
ture were measured to establish the charge of the metal complexes.

278
K.S. Prasad et al. / Spectrochimica Acta Part A 81 (2011) 276–282
Fig. 1. 1H NMR spectrum of L3.
The range of conductance values (11–18 ohm−1 cm2 mol−1) listed
in Table 1 indicates that all the metal complexes have non-
electrolyte nature [21].
3.3. 1H NMR spectra
The proton NMR spectra of the ligands and their corresponding
complexes were recorded in DMSO-d6 using TMS as the internal
standard. The 1H NMR spectrum of L3 is shown in Fig. 1. The lig-
ands exhibit peaks in the region 2.72–2.61, 8.9–7.7, 7.9–7.2 and
10.8–9.8 ppm corresponds to CH3, N CH, Ar–H and OH protons,
respectively [25]. Upon comparison of 1H NMR spectra of lig-
ands with their corresponding tin(IV) complexes, the N CH signal
has been shifted downfield at around 9.21–9.06 ppm indicating
the involvement of azomethine nitrogen in the complexation. The
methyl groups in complexes attached to the central tin atom gives
a single band at a very upfield region (ca. 1.70–1.40). The 1H NMR
data concludes that the deshielding of protons is observed in all
the complexes, which is probably due to electrophilic character
of tin atom and coordination of the carbonyl oxygen atom in all
the complexes [26,27]. A comparison of 1H NMR spectra of com-
plex 1 and 3 with the L1 and L3 have shown disappearance of
signal of OH (10.8–9.8 ppm) proton on the formation of Sn–O band
[28].
3.2. IR spectra
The main vibrational bands of ligands and their organotin(IV)
complexes are shown in Table 2. Several significant changes with
respect to the ligands are observed in the corresponding tin(IV)
complexes. The spectra of the ligands show characteristic bands
due to ␯(C O) and ␯(C N) at 1682–1655 and 1655–1571 cm−1
region, respectively. In L1 and L3, ␯(OH) band appears at 3441 and
3434 cm−1, respectively. The ꢁ(C N) band has been shifted to lower
frequency (ca. 1602–1567 cm−1) in the complexes indicating the
coordination of the ligands through nitrogen atom of the azome-
thine group. Upon complexation, the band at 1682–1655 cm−1
region in ligands due to ␯(C O) has been shifted to lower frequency
(ca. 1677–1641 cm−1) indicating the involvement of lactam group
in the coordination [22]. The ꢁ(OH) band in case of L1 and L3 at 3441
and 3434 cm−1 has been disappeared in complexes 1 and 3. This
suggests the deprotonation and involvement of the phenolic oxy-
gen in chelation. Two medium to sharp intensity bands observed
in the far IR region of the tin(IV) complexes at 411–403 cm−1 and
417–413 cm−1 are assigned to ␯(Sn–N) and ␯(Sn–O) modes, respec-
tively, which are not observed in the spectra of ligands [23,24]. One
strong to medium intensity band appeared in the spectra of the
complexes in the region 513–506 cm−1 which can be attributed to
(Sn–CH3) stretching vibrations.
3.4. Mass spectra
The mass spectrum of the L4 is given in Fig. 2. Fragments at
m/z = 280 (base peak) are attributed to C16H13N3O2+ ion. The other
molecular ion peaks appeared in the mass spectra is attributed to
the fragmentation of the ligand molecule obtained from the rupture
of different bonds inside the molecule. The mass spectra of tin(IV)
Fig. 2. Mass spectrum of L4.

K.S. Prasad et al. / Spectrochimica Acta Part A 81 (2011) 276–282
279
Table 1
Analytical data and physical properties of the Schiff base ligands and their organotin(IV) complexes.
Compound
Mol. formula
Yield, %
Calculated (Found), %
Molar conductivity, S cm2 mol−1
C
H
N
S
L1
L2
L3
L4
1
2
3
4
C16H13N3O2
C15H12N4O
C17H15N3O3
77
69
81
73
58
62
49
53
68.43(68.69)
68.18(68.56)
66.01(66.45)
64.8 (64.82)
50.58(50.86)
49.39(49.87)
49.89(50.22)
48.43(48.77)
4.58(4.67)
4.28(4.39)
4.93(5.03)
5.0 (5.11)
4.21(4.63)
4.35(4.51)
4.37(4.82)
4.7 (4.92)
14.9 (15.03)
21.22(21.35)
13.58(13.72)
14.6 (14.82)
9.83 (10.23)
13.55(13.81)
9.19 (9.49)
9.41 (9.68)
–
–
–
–
–
–
–
13.7
11.1
14.9
17.8
C16H15N3OS
10.8(10.97)
–
–
–
C
18H18N3O2Sn
C17H18N4OSn
C19H20N3O3Sn
C18H21N3OSSn
7.17 (7.73)
Table 2
Infrared spectral data of the ligands and their organotin(IV) complexes.
Compound
ꢂ(C O)
ꢂ(C N)
ꢂ(O–H)
ꢂ(M–N)
ꢂ(M–O)
ꢂ(Sn–CH3)
L1
L2
L3
L4
1
2
3
4
1656
1684
1650
1702
1596
1643
1697
1581
1603
1597
1586
1609
1582
1602
1581
1593
3123
–
3117
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
407
403
411
409
414
417
415
413
511
513
507
509
complexes give a well defined parent peak at m/z = 427 (MH+), 413
(MH+), 457 (MH+) and 446 (MH+) for complexes 1, 2, 3 and 4,
respectively.
varying metal complex concentration and they are shown in
Fig. 5. The changes observed in the absorption spectra of CT-
DNA in the presence of complex, that is, the decrease in the
intensities in the range ꢃmax = 258–253 nm. This indicate that
the interaction with CT-DNA [30]. This interaction results the
direct formation of a new complex with double stranded CT-DNA
[31] which simultaneously may cause the slight change of the
conformation of DNA [32] in case of complexes. The observed
hypsochromism is due to the intercalative binding mode [33]
between the chromophores of the complexes and DNA base
pairs. Additionally, the observed blue shift of 6 nm is an evi-
dence of the stabilization of the CT-DNA duplex [34]. From the
observed spectral changes the value of the intrinsic binding con-
stant Kb were found to be 1.83 × 104 M−1 and 2.38 × 104 M−1
3.5. Thermal studies
The thermal property of complex 1 was investigated by TGA
and DTG studies. Fig. 3 presents the recorded TGA/DTG curves of
complex 1 in nitrogen atmosphere. The complex undergoes two-
step decomposition. The first-step is endothermic decomposition at
240 ◦C, corresponds to the loss of methyl groups. The ligand moiety
then decomposes exothermically at 380–430 ◦C and finally leaving
SnO as the residual product [29].
Based on the above analytical and spectral studies, following
structures are assigned for the complexes (Fig. 4).
for the complexes
1 and 2, respectively. As we know that
the extent of hypsochromism is commonly consistent with the
strength of the DNA binding interaction [35], we can rational-
ize the DNA binding affinity of the complexes by studying the
rate of hypsochromism as shown in the UV–vis spectra of the
complexes.
3.6. Biology
3.6.1. DNA binding studies
The absorption spectra of the interaction of CT-DNA with the
complexes 1and 2, have been recorded for a constant DNA by
3.6.2. Viscometric studies
The viscosity measurements of CT-DNA are regarded as the least
ambiguous and the most critical tests of a binding model in solution
in the absence of crystallographic structural data. A classical inter-
calation model demands that the DNA helix lengthens as base pairs
are separated to accommodate the bound complex, leading to the
increase of DNA viscosity [36]. Fig. 6 shows the increase in the vis-
cosity of CT-DNA up on addition of complexes 1 and 2. This result
further suggested an intercalative binding mode of the complex
with DNA.
3.6.3. Nuclease activity
The cleavage reaction on plasmid DNA was monitored by
agarose gel electrophoresis. When circular plasmid DNA was sub-
jected to electrophoresis, relatively fast migration was observed
for the intact supercoiled DNA (Form I). If scission occurs on one
strand, the supercoiled DNA will relax to generate a slower moving
open circular/nicked type (Form II). If both the strands are cleaved,
a linear form (Form III) that migrates between Form I and Form II
will be generated [37].
Fig. 3. TG and DTG curves of complex 1.

280
K.S. Prasad et al. / Spectrochimica Acta Part A 81 (2011) 276–282
Fig. 4. Proposed structures for diorganotin(IV) complexes.
Fig. 5. UV spectra of CT DNA in buffer solution (150 mM NaCl and 15 mM trisodium citrate at pH 7.0) in the presence of (a) complex 1, ([DNA] = 0.10 mM) and (b) complex
2, ([DNA] = 0.10 mM), at a complex concentration of 5.0 × 10−5 M. Dotted curve shows the absorption of DNA alone. The arrows show the intensity changes upon increasing
concentration (a–e) (20, 40, 60, 80, 100 ␮l) of complex. Plot of [DNA]/(εa − εf) vs. [DNA] for the titration of DNA (10, 20, 30, 40, 50 and 60 ␮M) with (c) 1 and (d) 2 complexes.

K.S. Prasad et al. / Spectrochimica Acta Part A 81 (2011) 276–282
281
Fig. 6. Effect of increasing amount of complexes on the relative viscosity of CT-DNA.
Fig. 7. Cleavage of supercoiled pUC19 DNA (0.5 ␮g) by complexes 1 and 2 in a buffer containing 50 mM Tris–HCl at 37 ◦C (30 min): (a) lane M: marker; lane 1: DNA control;
lane 2: 10 ␮l complex 1 + DNA; lane 3: 15 ␮l complex 1 + DNA; lane 4: 20 ␮l complex 1 + DNA. (b) Lane M: marker; lane 1: DNA control; lane 2: 10 ␮l complex 2 + DNA; lane
3: 15 ␮l complex 2 + DNA; lane 4: 20 ␮l complex 2 + DNA.
Table 3
Minimum inhibitory concentrations (MIC) (in ␮g/ml) of compounds by using macrodilution method.
Compound
Minimum inhibitory concentration values (in ␮g/ml)
Antibacterial activity
Antifungal activity
E.coli
S. aureus
R. solanacearum
X. vesicatoria
A. niger
A. flavus
F. oxysporum
A. solani
L1
L2
L3
L4
1
2
3
4
128
128
64
128
64
64
32
128
8
128
128
128
128
64
64
32
64
8
64
128
128
128
32
64
32
64
8
128
128
64
128
16
64
16
64
2
128
128
128
128
64
64
64
128
–
8
128
128
128
128
64
64
32
32
–
128
128
128
128
64
64
32
64
–
128
128
128
128
32
64
32
64
–
Chloramphenicol
Terbinafin
–
–
–
–
2
2
2
Table 4
Antimicrobial activity of Schiff bases and their corresponding organotin(IV) complexes.
Compound
Zone of inhibition (in mm)a
Antibacterial activity
Antifungal activity
E. coli
S. aureus
R. solanacearum
X. vesicatoria
A. niger
A. flavus
F. oxysporum
A. solani
L1
L2
L3
L4
1
2
3
4
18
13
21
11
15
19
23
17
34
–
12
11
20
13
22
21
33
24
35
–
09
03
11
06
12
09
21
13
32
–
12
07
15
09
19
13
27
18
29
–
11
02
13
05
13
06
19
09
–
10
03
15
08
10
07
18
11
–
12
06
17
07
13
10
26
14
–
09
03
12
06
09
05
17
10
–
Chloramphenicol
Terbinafin
22
24
29
25
aAverage of three replicates.

282
K.S. Prasad et al. / Spectrochimica Acta Part A 81 (2011) 276–282
The nuclease activity of complexes 1 and 2 has been studied
ogy for providing facilities to perform the biological and nuclease
activities.
under physiological pH and temperature by gel electrophoresis
using supercoiled pUC19 plasmid DNA as the substrate. As shown
in Fig. 7(a) and b, with increase of complex concentration, the inten-
sity of the circular supercoiled DNA (Form I) band decreases, while
that of nicked (Form II) and linear (Form III) bands increases (lanes
2–4). When the complex concentration was 20 ␮l (40 ␮M, lane 4),
all the three forms are well separated with complex 1. In com-
parison, complex 1 acts as most effective cleaving agent than the
complex 2.
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.saa.2011.06.010.
References
[1] R. Hernandez Molina, A. Mederos, in: T.J. Meyer McCleverty (Ed.), Comprehen-
sive Coordination Chemistry, vol. 1, 2nd ed., Elsevier, 2005, Chapter 19 and
references therein.
[2] B. Maggio, G. Daidone, D. Raffa, S. Plescia, L. Mantione, V. Maria, C. Cutuli,
N.G. Mangano, A. Caruso, European Journal of Medicinal Chemistry 36 (2001)
737–742.
[3] R.A. Sheldon, J.K. Kochi, Metal Catalyzed Oxidation of Organic Compounds,
Academic Press, New York, 1981.
[4] C. Pettinari, F. Marchetti, A. Cingolani, S. Bartolini, Polyhedron 15 (1996)
1263–1276.
[5] P.R. Ortiz de, Montellano, Cytochrome P-450, Structure Mechanism and Bio-
chemistry, Plenum Press, New York and London, 1986.
[6] B. Halliwll, J.M.C. Gutteridge, Free Radicals in Biology and Medicine, 2nd ed.,
Clarendon Press, Oxford, 1988.
[7] A. Tarassoli, T. Sedaghat, R.P. Irwin, Organometallic Chemistry Research Per-
spectives, Nova Science Publishers, New York, 2007.
[8] C. Di Nicola, F. Marchetti, C. Pettinari, B.W. Skelton, A.H. White, Inorganic Chem-
istry Communications 14 (2011) 133–136.
[9] M. Gielen, Applied Organometallic Chemistry 16 (2002) 481–494.
[10] C. Pellerito, L. Nagy, L. Pellerito, A. Szorcsik, Journal of Organometallic Chemistry
691 (2006) 1733–1747.
[11] M. Gielen, Coordination Chemistry Reviews 151 (1996) 41–51.
[12] S. Mishra, M. Goyal, A. Singh, Main Group Metal Chemistry 25 (2002)
437–444.
[13] H. Fu, X.W. Liu, Z.Y. Zhou, Z.W. Mao, K.C. Zheng, X.M. Chen, Inorganic Chemistry
Communications 7 (2004) 906–908.
[14] M.S. Rafat, I.M. El-Deen, H.K. Ibrahim, S. El-Ghool, Spectrochimca Acta Part A
65 (2006) 1208–1220.
[15] P.X. Xi, Z.H. Xu, X.H. Liu, F.J. Cheng, Z.Z. Zeng, Spectrochimica Acta Part A 71
(2008) 523–528.
[16] M.E. Reichmann, S.A. Rice, C.A. Thomas, P. Doty, Journal of American Chemical
Society 76 (1954) 3047–3053.
[17] S. Satyanarayana, J.C. Dabrowiak, J.B. Chaires, Biochemistry 32 (1993)
2573–2584.
[18] M.J. Pelczar, E.C.S. Chan, N.R. Krieg, Microbiology, 5th ed., New York, 1998.
[19] A.W. Bauer, W.W.M. Kirby, J.C. Sherris, M. Turck, American Journal of Clinical
Pathology 45 (1966) 493–496.
[20] M.S.A. El-Gaby, Chinese Chemical Society 51 (2004) 125–134.
[21] A. Golcu, M. Tumer, H. Demirelli, R.A. Wheatley, Inorganic Chimica Acta 358
(2005) 1785–1797.
3.6.4. Antimicrobial activity
All the synthesized ligands and their diorganotin(IV) complexes
were evaluated for their antimicrobial activity by disk-agar dif-
fusion method. Chloramphenicol and Terbinafin were used as
standard antibacterial and antifungal agents, respectively. The
compounds to be tested were dissolved in DMF at a concentration
0.25 mg/ml. The minimum inhibitory concentration (MIC), defined
as the lowest concentration of each compound that totally inhibited
visible microorganism growth, was recorded for each compound
assayed (Table 3).
Table 4 clearly shows that the ligands and their complexes
showed moderate to good antimicrobial activity. The results indi-
cate that the complexes show more activity than ligands against
same microorganisms under identical experimental conditions.
This would suggest that the chelation could facilitate the ability
of a complex to cross a cell membrane and can be explained by
Tweedy’s chelation theory [37,38]. Such a chelation could enhance
the lipophilic character of the central atom, which subsequently
favors its permeation through the lipid layer of the cell membrane.
The variation in the effectiveness of different compounds against
different organisms depends either on the impermeability of the
cells of the microbes or on differences in ribosome of microbial
cells.
L1 and L3 have greater activity than L2 and L4. This higher activ-
ity of L1 and L3 may be due the presence of hydroxyl group, which
may play an important role in antimicrobial activity [38]. All the
complexes displayed good activity than their corresponding ligands
against the tested microorganism. Among the complexes, complex
3 show higher activity against three bacteria, S. aureus, X. vesica-
toria, R. solanacearum and two fungi, A. niger and F. oxysporum.
This may be due to the presence of methoxy group. Fig. 8 shows
the antimicrobial activity of L3 and its corresponding organotin(IV)
complex 3 against X. vesicatoria.
[22] M. Muthukumar, P. Viswanathamurthi, Central European Journal of Chemistry
8 (2010) 229–240.
[23] A. Saxena, J.P. Tandon, K.C. Molloy, J.J. Zuckerman, Inorganic Chimica Acta 63
(1982) 71–74.
[24] C.A. Obafemi, J.A. Obaleya, M.S. Akanni, Synthetic-Reactivity Inorganic Metal-
loorganic Chemistry 16 (1986) 777–793.
[25] H. Naeimi, J. Safari, A. Heidarnezhad, Dyes Pigments 73 (2007)
251–253.
4. Conclusions
[26] M. Gielen, Journal of Brazalian Chemical Society 14 (2003) 870–877.
[27] S. Ali, M.N. Khokhar, M.H. Bhatti, M. Mazhar, M.J. Masood, K. Shahid, A.
Badshah, Synthetic-Reactivity Inorganic Metalloorganic Chemistry 32 (2002)
1579.
[28] T.P. Lockhart, W.F. Manders, Inorganic Chemistry 25 (1986) 892–895.
[29] S. Saydam, E. Yilmaz, Spectrochimica Acta Part A 63 (2006) 506–510.
[30] N. Raman, A. Sakthivel, R. Jeyamurugan, Central European Journal of Chemistry
8 (2010) 96–107.
[31] G.S. Son, J.A. Yeo, S.K. Kim, A. Holmen, B. Akerman, B. Norden, Journal of Amer-
ican Chemical Society 120 (1998) 6451–6457.
[32] Y.M. Song, Q. Wu, P.J. Yang, N.N. Laun, L.F. Wang, Y.M. Liu, Journal of Inorganic
Biochemistry 100 (2006) 1685–1691.
[33] A.M. Pyle, J.K. Rehmann, R. Meshoyrer, C.V. Kumar, N.J. Turror, J.K. Barton, Jour-
nal of American Chemical Society. 111 (1989) 3051–3058.
[34] E.C. Long, J.K. Barton, Accounts of Chemical Research 23 (1990) 271–273.
[35] R.G. Mali, R.R. Wadekar, Indian Journal of Pharmaceutical Science 70 (2008)
131.
Novel diorganotin(IV) complexes were synthesized using
4(3H)-quinazolinone derived Schiff bases. The ligands and their
complexes were characterized by IR, 1H NMR, MS, elemen-
tal analyses, molar conductance and thermal studies. The
complexes are non-electrolytic in nature. Complexes bind to
DNA through intercalating mode. Gel electrophoresis experi-
ment suggests that the complexes cleave supercoiled DNA at
higher concentration. The antimicrobial results indicated that
the complexes are much active compared to their corresponding
ligands.
Acknowledgements
[36] M. Ashfaq, M.M. Ahmed, S. Shaheen, H. Oku, K. Mehmood, A. Khan, S.B. Niazi,
T.M. Ansari, A. Jabbar, M.I. Khan, Inorganic Chemistry Communications 14
(2011) 5–12.
[37] D.S. Sigman, Accounts of Chemical Research 19 (1986) 180–186.
[38] B.G. Tweedy, Phytopathalogy 55 (1964) 910.
The authors are thankful to the University of Mysore, Mysore for
laboratory facilitates. One of the authors, K. Shiva Prasad is thankful
to the UGC-New Delhi for the award of meritorious fellowship. The
authors are also thankful to the Head, Department of Biotechnol-