Synthesis, spectral analysis, and molecular modeling of bioactive Sn(II)-complexes with oxadiazole Schiff bases

Article abstract of DOI:10.1080/00958972.2011.569541

Sn(II)-complexes of seven 2-amino-5-substituted-aryl-1,3,4-oxadiazole Schiff bases have been synthesized and characterized by various physico-chemical studies. Their structures have been confirmed by elemental analyses, infrared, 1H NMR, UV-Vis, and mass

Full text of DOI:10.1080/00958972.2011.569541

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Synthesis, spectral analysis, and
molecular modeling of bioactive Sn(II)-
complexes with oxadiazole Schiff bases
Abdalla M. Khedr a , Sudha Jadon b & Vipin Kumar b
a Department of Chemistry, Faculty of Science , Tanta University ,
Tanta , Egypt
b Department of Chemistry , Agra College , Agra-282002, U.P. ,
India
Published online: 08 Apr 2011.
To cite this article: Abdalla M. Khedr , Sudha Jadon & Vipin Kumar (2011) Synthesis, spectral
analysis, and molecular modeling of bioactive Sn(II)-complexes with oxadiazole Schiff bases,
Journal of Coordination Chemistry, 64:8, 1351-1359, DOI: 10.1080/00958972.2011.569541
To link to this article: http://dx.doi.org/10.1080/00958972.2011.569541
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Journal of Coordination Chemistry
Vol. 64, No. 8, 20 April 2011, 1351–1359
Synthesis, spectral analysis, and molecular modeling of
bioactive Sn(II)-complexes with oxadiazole Schiff bases
ABDALLA M. KHEDR*y, SUDHA JADONz and VIPIN KUMARz
yDepartment of Chemistry, Faculty of Science, Tanta University, Tanta, Egypt
zDepartment of Chemistry, Agra College, Agra-282002, U.P., India
(Received 27 December 2010; in final form 21 February 2011)
Sn(II)-complexes of seven 2-amino-5-substituted-aryl-1,3,4-oxadiazole Schiff bases have been
synthesized and characterized by various physico-chemical studies. Their structures have been
confirmed by elemental analyses, infrared, 1H NMR, UV-Vis, and mass spectral studies as well
as thermal decomposition. Conductance measurements in methanol show these complexes to be
non-electrolytes, and the molecular weight determinations support the proposed molecular
formulae. The molecular structures of the complexes have been optimized by CS Chem 3-D
Ultra Molecular Modeling and Analysis Program showing tetrahedral geometry. The
bio-efficacy of the complexes has been examined against the growth of bacteria (Escherichia
coli and Staphylococcus aureus) and fungi (Aspergillus flavus and Candida albicans) in vitro to
evaluate their anti-microbial potential.
Keywords: Sn(II)-complexes; Oxadiazole Schiff bases; Molecular modeling; Antimicrobial
activity
1. Introduction
Schiff bases are an important class of compounds reported to possess various biological
activities [1], including antibacterial [2], antifungal [3], anti-inflammatory [4], antipyretic
[5], antitumor [6, 7], and anticancer [8] activities. Therapeutic activities of coordination
compounds offer a variety of geometries and reactivity for use in drug design [9]. Schiff
bases are widely used as ligands in the synthesis of transition metal complexes [10, 11],
due to their stability under a variety of oxidative and reductive conditions and due to
the fact that imine ligands are borderline hard and soft Lewis bases [12]. Tin is
extensively used as fungicides in crops, in food packaging, in some veterinary
formulations, in wood preservation, as stabilizer for polyvinylchloride, as polymeriza-
tion initiators and catalysts [13, 14]. In order to find cheap and effective antimicrobial
agents, we report the synthesis, characterization, and molecular modeling of seven new
Sn(II) complexes involving oxadiazole-based Schiff bases, SB1ꢀSB7 (figure 1), and
screening of these complexes for antimicrobial activities against bacteria (Escherichia
coli and Staphylococcus aureus) and fungi (Candida albicans and Aspergillus flavus).
*Corresponding author. Email: abkhedr2001@yahoo.com
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online ß 2011 Taylor & Francis
DOI: 10.1080/00958972.2011.569541

1352
A.M. Khedr et al.
N
C
N
H
C
R„
N
C
R
O
Figure 1. Structural formula of Schiff bases (SB1ꢀSB7). R¼R0¼H (SB1); R¼H, R0¼4-NO2 (SB2); R¼3-Br,
R0¼3-Br (SB3); R¼3-Cl, R0¼3-Cl (SB4); R¼4-F, R0¼4-OH (SB5); R¼3-NO2, R0¼3-NO2 (SB6); R¼4-OCH3,
R0¼4-NO2 (SB7).
2. Experimental
2.1. Materials and methodology
All chemicals were of analytical grade and used as procured. The Schiff bases, SB1ꢀSB7
(figure 1), were prepared by condensation of 2-amino-5-substituted-aryl-1,3,
4-oxadiazole (10 mmol) with substituted aryl aldehyde (10 mmol) in ethanol. These
were recrystallized from the same solvent and dried in vacuo. Microanalyses (C, H, and
N) were performed on a Perkin-Elmer 2400 elemental analyzer. Metal content was
determined by EDTA titration after decomposition with nitric and perchloric acids [15].
Molar conductivities were measured in CH3OH solutions, employing a conductance
bridge of the type 523 conductometer at ambient temperature. Mass spectra were
obtained using a Shimadzu LCMS-2010 eV mass spectrometer using the electron spray
ionization (ESI) method at Gakushuin University (Japan). Infrared (IR) spectra from
4000 to 200 cmꢀ1 were obtained as KBr discs with a Perkin-Elmer (model 1430) IR
spectrophotometer at the Micro-analytical unit of Tanta University. A Bruker DMX
750 (500 MHz) spectrometer was used for obtaining 1H NMR spectra, employing
DMSO-d6 as the solvent and TMS as the internal standard. Electronic spectra (in
methanol) were taken on a Cary-400 double beam recording spectrophotometer.
Heating of the complexes was performed in a muffle furnace at 100ꢁC, 300ꢁC, 500ꢁC,
and 750ꢁC.
2.2. Synthesis of tin(II) complexes
To a weighed amount of anhydrous tin(II) chloride, the calculated amount of the Schiff
bases was added in a 1 : 1 molar ratio using ethanol as the reaction medium. The color
of the contents immediately changed and the resulting mixture was refluxed for 4–6 h on
a water bath. The complex was precipitated, filtered off, and finally dried in vacuo over
anhydrous calcium chloride after being repeatedly washed with hot water and ether to
remove excess ligand and tin salt.
2.3. Molecular modeling
3-D molecular modeling of the structures of the complexes was performed using CS
Chem 3-D Ultra Molecular Modeling and Analysis Program [16], an interactive
graphics program that allows rapid structure building, geometry optimization with
minimum energy, and molecular display. The program has the ability to handle
transition metal complexes [17]. The correct stereochemistry was assured through

Sn(II) oxadiazole Schiff bases
1353
manipulation and modification of the molecular coordinates to obtain reasonable, low-
energy molecular geometries. The potential energy of the molecule was the sum of the
following terms:
E ¼ Estr þ Eang þ Etor þ Evdw þ Eoop þ Eele,
where all E’s represent the energy values corresponding to the given types of interaction
(Kcal molꢀ1). The subscripts str, ang, tor, vdw, oop, and ele denote bond stretching,
angle bonding, torsion, van der Waals interactions, out-of-plane bending and electronic
interaction, respectively. The molecular mechanics describe the application of classical
mechanics for the determination of molecular equilibrium structures. It enables the
calculation of the total static energy of a molecule in terms of deviations from reference
unstrained bond lengths, angles, and torsions plus non-bonded interactions. It has been
found that off-diagonal terms are usually largest when neighboring atoms are involved,
and so we have to take account of non-bonded interactions, but only between next-
nearest neighbors [18].
2.4. Biological activity: antibacterial and antifungal screening
In vitro antibacterial and antifungal activities of the complexes against E. coli, S. aureus,
A. flavus, and C. albicans were carried out using the modified Kirby–Bauer disc
diffusion method [19] at the micro-analytical unit of Cairo University. Briefly, 100 mL of
the test bacteria/fungi were grown in 10 mL of fresh media until they reached
108 cells mLꢀ1 for bacteria or 105 cells mLꢀ1 for fungi [20]. Hundred microliters of
microbial suspension was spread onto agar plates corresponding to the broth in which
they were maintained. Isolated colonies of each organism was selected from primary
agar plates and tested for susceptibility by the disc diffusion method [21]. From the
many media available, NCCLS recommends Mueller–Hinton agar since it results in
good batch-to-batch reproducibility. The disc diffusion method for filamentous fungi
was tested using approved standard method (M38-A) which was developed by the
NCCLS [22] for evaluating the susceptibilities of filamentous fungi to antifungal agents.
The disc diffusion method for yeasts was developed using approved standard method
(M44-P) by the NCCLS [23]. Plates were inoculated with filamentous fungi, A. flavus, at
25ꢁC for 48 h; Gram (þ) bacteria, S. aureus, and Gram (ꢀ) bacteria, E. coli. They were
incubated at 35–37ꢁC for 24–48 h and yeast as C. albicans was incubated at 30ꢁC for
24–48 h, and then the diameters of the inhibition zones were measured in millime-
ters [24]. Standard discs of tetracycline (antibacterial agent) and amphotericin B
(antifungal agent) served as positive controls for antimicrobial activity but filter discs
impregnated with 10 mL of solvent (distilled water, DMSO) were used as a negative
control. The agar used is Meuller–Hinton agar that is rigorously tested for composition
and pH. Further the depth of the agar in the plate is a factor to be considered in the disc
diffusion method. This method is well-documented and standard zones of inhibition
have been determined for susceptible and resistant values. Blank paper discs (Schleicher
& Schuell, Spain) with a diameter of 8.0 mm were impregnated with 10 mL of tested
concentration of the stock solutions. When a filter paper disc impregnated with a tested
chemical is placed on agar the chemical will diffuse from the disc into the agar. This
diffusion will place the chemical in the agar only around the disc. The solubility of
the chemical and its molecular size will determine the size of the area of chemical

1354
A.M. Khedr et al.
infiltration around the disc. When an organism is placed on the agar it will not grow in
the area around the disc if it is susceptible to the chemical. This area of no growth
around the disc is known as a ‘‘zone of inhibition’’ or ‘‘clear zone’’. For the disc
diffusion, the zone diameters were measured with slipping calipers of the National
Committee for Clinical Laboratory Standards [24]. Agar-based methods such as Etest
and disc diffusion can be good alternatives because they are simpler and faster than
broth-based methods [25, 26].
3. Results and discussion
All the complexes are air stable, colored, microcrystalline solids which are insoluble in
water but soluble in methanol, ethanol, DMF, and DMSO. Composition and identity
of the assembled compounds were deduced from elemental analyses, spectroscopic
1
techniques (IR, UV-Vis, H NMR, ESI-MS), and thermal studies. The analytical data
of the complexes (table 1) indicated 1 : 1 metal to ligand stoichiometry. The
satisfactory analytical data (table 1) and spectral studies revealed that the ligands
and complexes were of good purity. Low values of molar conductance (DM ¼ 8.99–
11.35 ꢀꢀ1 cm2 molꢀ1) show these complexes to be non-electrolytes [27].
3.1. ESI-MS studies
ESI-MS of [SnL1Cl2] ꢂ 4H2O ꢂ C2H5OH, [SnL3Cl2], [SnL4Cl2] ꢂ 5H2O, and [SnL7Cl2] ꢂ
H2O ꢂ 2C2H5OH showed a molecular ion peak Mþ at m/z 557.0, 597.0, 598.0, and 623.9,
respectively, that is equivalent to its molecular weight. The spectra of [SnL2Cl2] ꢂ
Table 1. Physical properties and microanalyses of tin(II) complexes.a
Elemental analysis
Compound
(Empirical formula)
M. wt.
(Cal. M. wt.)
No.
Color (Ãm)
%C
%H
%N
%M
1
2
3
4
5
6
7
[SnSB1Cl2] ꢂ 4H2O ꢂ C2H5OH 557.0 (556.99) Deep Yellow
(C17H25Cl2N3O6Sn) (10.11)
36.24
4.66
7.84
21.54
(36.66) (4.52) (7.54) (21.31)
31.76 4.74 6.24 18.25
(32.00) (4.42) (6.59) (18.60)
34.60 2.82 7.51 19.61
(34.22) (2.53) (7.04) (19.89)
31.34 2.95 7.45 19.69
(30.14) (3.20) (7.03) (19.85)
30.90 3.61 6.92 20.11
(31.01) (3.82) (7.23) (20.43)
31.32 2.42 12.45 20.80
(30.91) (2.59) (12.01) (20.36)
38.81 3.86 9.15 19.44
(38.49) (4.20) (8.98) (19.02)
[SnSB2Cl2] ꢂ 6H2O ꢂ C2H5OH 639.4 (638.03) Reddish orange
(C17H28Cl2N3O10Sn)
[SnSB3Cl2]
(11.35)
597.0 (596.66) Faint yellow
(10.42)
598.0 (597.83) Deep yellow
(8.99)
582.0 (580.95) Buff
(9.23)
584.0 (582.91) Red
(11.24)
(C17H15Br2Cl2N3O2Sn)
[SnSB4Cl2] ꢂ 5H2O
(C15H19Cl4N3O6Sn)
[SnSB5Cl2] ꢂ 6H2O
(C15H22Cl2FN3O8Sn)
[SnSB6Cl2] ꢂ 3H2O
(C15H15Cl2N5O8Sn)
[SnSB7Cl2] ꢂ H2O ꢂ 2C2H5OH 623.9 (624.04) Brown
(C20H26Cl2N4O7Sn) (9.84)
The yield for the synthesized complexes was 80–82%.
M. Wt. ¼ molecular weight obtained from mass spectral measurements; (Cal. M. Wt.) ¼ calculated molecular weight;
Ãm ¼ molar conductance (ꢀꢀ1 cm2 molꢀ1).
aAll the synthesized complexes decompose with out melting above 280ꢁC.

Sn(II) oxadiazole Schiff bases
1355
6H2O ꢂ C2H5OH, [SnL5Cl2] ꢂ 6H2O, and [SnL6Cl2] ꢂ 3H2O displayed peaks at m/z 639.4,
582.0, and 584.0, respectively, corresponding to [M]þþ1. Tin(II) complexes (1–7)
decompose via abstraction of the ligand, which give rise to the presence of molecular ion
peaks attributable to [L]þ, besides other peaks due to different fragmentation processes
of the complexes (scheme 1). This is a common behavior for metal ion complexes
containing different ligands (ML) which decompose during spray ionization through
cleavage of the metal-ligand bond [28, 29]. For example, 4 gave fragment ion peaks m/z
561.1, 544.0, 526.0, 508.0, and 318.0, due to loss of two, three, four, five water
molecules, and L4, respectively (scheme 1). The results of mass spectra are in
satisfactory agreement with elemental analyses confirming the constitutions and purities
of the prepared Sn(II) complexes (table 1).
3.2. IR spectral studies
Comparison of IR spectra of the ligands with those of their complexes (table 2) resulted
in the following information regarding various groups. IR spectra of the Schiff bases
exhibited strong bands at 1602–1591 cmꢀ1, assigned to ꢀ(C¼N) of azomethine.
demetallization
–2H2O
–3H2O
.
.
SB4
m/z 318.00 (318.16)
–5H2O
[SnSB4Cl2] 5H2O
[SnSB4Cl2] 3H2O
m/z 598.00 (597.83)
m/z 561.10 (561.80)
–4H2O
.
.
[SnSB4Cl2] 2H2O
[SnSB4Cl2] H2O
[SnSB4Cl2]
m/z 544.00 (543.78)
m/z 508.00 (507.75)
m/z 526.00 (525.77)
Scheme 1. Fragmentation pathways of [SnSB4Cl2] ꢂ 5H2O.
Table 2. IR and 1H NMR and UV-Vis spectral data of the Schiff bases (SB1–SB7) and their Sn(II) complexes.
IR spectra (cmꢀ1
)
1H NMR spectra (ppm)
ꢀ(H2O) or ꢀ(C¼N) ꢀ(C¼N)
UV-Vis
spectra
Complex
ꢀ(EtOH)
(ring)
(imine)
ꢀ(M–N) ꢀ(M–Cl)
ꢁAr–H
ꢁCH¼N
SB1
1
SB2
2
SB3
3
SB4
4
SB5
5
SB6
6
SB7
7
–
3301
–
3397
–
3293
–
3295
–
3317
–
3408
–
1652
1657
1647
1657
1651
1662
1653
1654
1662
1654
1646
1662
1658
1659
1591
1601
1597
1599
1597
1598
1596
1597
1597
1595
1598
1580
1602
1605
–
397
–
395
–
419
–
438
–
360
–
418
–
–
326
–
329
–
308
–
321
–
289
–
307
–
7.24–7.99
7.35–7.80
6.47–7.98
7.22–7.80
7.31–7.87
7.33–7.89
7.32–7.89
7.33–7.75
6.28–8.04
7.24–7.84
6.50–7.98
7.43–8.31
7.03–8.39
7.04–8.38
10.23
–
207, 277
213, 283
211, 272
217, 280
207, 281
226, 292
204, 283
219, 295
206, 276
217, 282
211, 267
215, 272
214, 273
216, 285
10.24
10.16
10.01
10.22
8.68
10.32
9.77
9.78
10.45
10.40
10.13
10.14
3318
379
302

1356
A.M. Khedr et al.
In comparison with spectra of the Schiff bases, all Sn(II) complexes exhibited this band
at 1605–1580 cm–1; the shift of this band indicates tꢀh1at azomethine nitrogen is
coordinated [30]. In addition, the band at 1662–1646 cm in the Schiff bases due to
ꢀ(C¼N) group of the oxadiazole ring shifted by 5–16 cmꢀ1 in complexes, confirming
participation of C¼N of ring in coordination with tin [31]. The new bands at 438–
360 cmꢀ1 in spectra of the complexes are assigned to Sn–N stretching frequencies [32].
Another new band at 329–289 cmꢀ1 is ascribed to Sn–Cl bond formation [33]. Thus the
IR spectral results provide strong evidence for bidentate Schiff bases. The broad bands
at 3408–3295 cm–1 in spectra of hydrated complexes are assigned to ꢀ(OH) of water or
ethanol attached to tin(II).
3.3. 1H NMR spectral studies
1H NMR spectra of the Schiff bases and their tin(II) complexes are collected in table 2.
The signal for the azomethine proton at 8.68–10.45 ppm in the ligands shifts downfield
in spectra of the tin(II) complexes. This de-shielding is probably due to donation of the
lone pair of electrons on the azomethine nitrogen to tin, resulting in the formation of a
coordinate bond [34]. The multiplets observed at 6.28–8.39 ppm in spectra of SB1–SB7
due to aromatic protons have downfield shifts in spectra of the complexes, attributed to
1
increased conjugation upon complex formation [29, 35]. Thus the H NMR results
support the IR inferences.
3.4. Electronic spectral studies
Electronic absorption spectra of the Schiff bases and their Sn(II) complexes were
recorded in methanol (table 2). The spectra of the free ligands exhibit two absorptions
at 204–214 and 277–289 nm assigned to high energy ꢂ–ꢂ* transition corresponding to
1
the La–1A in the aromatic moiety [36] and n–ꢂ* transition within the CH¼N [37],
respectively. The shift of these bands to longer wavelength in spectra of all Sn(II)
complexes is a good evidence of complex formation [38]. It has been reported that the
metal is capable of forming dꢂ–pꢂ bonds with ligands containing nitrogen as donor.
Tin has its 5d orbital completely vacant and, hence, N!Sn bonding can take place by
the acceptance of the pair of electrons from nitrogen of the ligand. Sn!N bonding can
occur by partial transfer of electrons of the 4d orbitals of the stannous ion to the vacant
p-orbitals of nitrogen of the ligand [34].
3.5. Thermal decomposition studies
Complexes 1–7 were heated at four temperatures (100ꢁC, 300ꢁC, 500ꢁC, and 750ꢁC) in a
muffle furnace for 20–30 min. The resulting weights were measured. The weight loss at
100ꢁC corresponds to loss of lattice water or ethanol from the complexes [39]. No
measured weight loss after heating at 300ꢁC indicates that the complexes do not contain
coordinated water (table 1). On heating at 500ꢁC, the weight indicates loss of parts of
the ligand. The weight of the pyrolysis product after heating at 750ꢁC corresponds to tin
oxide [40].

Sn(II) oxadiazole Schiff bases
1357
Figure 2. 3-D molecular modeling of complex [SnSB3Cl2] (3).
3.6. 3-D molecular modeling and analysis of bonding modes
Molecular mechanics attempts to reproduce molecular geometries, energies, and other
features by adjusting bond length, bond angles, and torsion angles to equilibrium values
that are dependent on the hybridization of an atom and its bonding scheme. In order to
obtain estimates of structural details of these four-coordinate complexes, we have
optimized the molecular structure of [SnSB3Cl2] (3) as a representative compound.
For convenience, the atoms are numbered in Arabic numerals (figure 2). The details
of bond lengths and bond angles per the 3-D molecular structure are given in
‘‘Supplementary material’’. Energy minimization was repeated several times to find the
global minimum [40].
The energy minimization value for tetrahedral and without restricting the structure
for 3 is almost the same, i.e., 42.8472 Kcal molꢀ1. The tetrahedral bond lengths are
Sn(23)–N(21) 2.095, Sn(23)–Cl(24) 2.383, Sn(23)–Cl(25) 2.382, and N(10)–Sn(23)
˚
2.099 A, respectively. The molecular modeling for the modulated complex (figure 2 and
Supplementary material) shows the angles around tin are 66.987ꢁ, 113.978ꢁ, 114.147ꢁ,
115.390ꢁ, 116.064ꢁ, and 119.300ꢁ; these angles do not change for the other complexes,
indicating distorted tetrahedral geometry around Sn(II) [16, 17, 41]. Thus the proposed
structure of 3 as well as of the others is acceptable.
3.7. Antimicrobial activity
The in vitro anti-microbial activities of the compounds were tested against E. coli,
S. aureus, S. faecalis, and C. albicans by the modified Kirby–Bauer disc diffusion
method [19]. Standard drugs tetracycline and amphotericin B were also tested for their
antibacterial and antifungal activities at the same concentration and conditions of the
tested compounds. The complexes had significant antimicrobial activities against the
tested organisms (table 3). Complexes 1, 2, 6, and 7 exhibited high activity against most
of the tested bacteria and fungi, whereas 3, 4, and 5 are less active against tested

1358
A.M. Khedr et al.
Table 3. Antimicrobial activities of 1–7.
Inhibition zone diameter (mm mgꢀ1 sample)
E. coli (Gþ) S. aureus (Gꢀ) A. flavus (Fungus) C. albicans (Fungus)
Compound
Control: DMCL
Tetracycline (antibacterial agent)
Amphotericin B (antifungal agent)
Complex 1
Complex 2
Complex 3
Complex 4
Complex 5
Complex 6
Complex 7
0.0
33.0
–
13.0
14.0
12.0
11.0
12.0
13.0
13.0
0.0
30.0
–
14.0
15.0
11.0
11.0
12.0
15.0
15.0
0.0
–
0.0
–
20.0
13.0
14.0
0.0
0.0
0.0
14.0
14.0
20.0
0.0
0.0
0.0
0.0
0.0
11.0
16.0
bacteria and are completely inactive against tested fungi. Compared with standard
drugs (tetracycline and amphotericin B) the complexes were less active. The data prove
the potential of 1, 2, 6, and 7 as broad spectrum antimicrobial agents. The activity of
any compound is a complex combination of steric, electronic, and pharmacokinetic
factors. The action of the compounds may involve the formation of a hydrogen bond
through ꢀN¼C of the chelate or the ligand with the active centers of the cell
constituents resulting in interference with normal cell process [18]. The microbotoxicity
of the compounds may be ascribed to the metal ions being more susceptible toward the
bacterial cells than ligands [42]. The tin(II) complexes (table 3) with oxadiazole Schiff
bases (1–7) have higher antimicrobial activity compared to other tin(II) complexes with
ethylenediamine Schiff bases [18].
4. Conclusion
The coordination complexes of Sn(II) with seven new bidentate 2-amino-5-substituted-
aryl-1,3,4-oxadiazole Schiff bases (SB1–SB7) were synthesized and characterized by
elemental, thermal analyses, spectral, and magnetic data. The IR, 1H NMR, and UV-Vis
spectra revealed that SB1–SB7 coordinate bidentate to tin(II) through nitrogen-forming
tetrahedral complexes. Mass spectra under EI-conditions are in agreement with
elemental analyses confirming the constitutions and purities of the Sn(II) complexes.
The proposed structures of the investigated complexes were supported by 3-D molecular
modeling of 3 as a representative compound. The synthesized complexes were active
against bacteria (E. coli and S. aureus) and fungi (A. flavus and C. albicans), thus giving a
new thrust of these compounds in the field of metallo-drugs (bio-inorganic chemistry).
Acknowledgments
The authors are grateful to Dr Mohamed El-Zarie (Gakushuin University, Japan) for
1
assistance in measuring H NMR and mass spectra carried out in this work.

Sn(II) oxadiazole Schiff bases
1359
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