Synthesis, spectral characterisation, electrochemical, and fluorescence studies of biologically active novel Schiff base complexes derived from E-4-(2-hydroxy-3-methoxybenzlideneamino)-N-(pyrimidin-2-yl)benzenesulfonamide

Article abstract of DOI:10.3906/kim-1301-83

A new Schiff base was prepared from 2-sulphanilamidopyrimidine and 2-hydroxy-3-methoxybenzaldehyde in ethanolic media and it was complexed with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) ions. The synthesised ligand and complexes were characterised by IR,

Full text of DOI:10.3906/kim-1301-83

Turk J Chem
Turkish Journal of Chemistry
(2014) 38: 521 – 530
¨
http://journals.tubitak.gov.tr/chem/
˙
c
⃝ TUBITAK
doi:10.3906/kim-1301-83
Research Article
Synthesis, spectral characterisation, electrochemical, and fluorescence studies of
biologically active novel Schiff base complexes derived from E-4-(2-hydroxy-3-
methoxybenzlideneamino)-N-(pyrimidin-2-yl)benzenesulfonamide
Valarmathy GOVINDARAJ∗, Subbalakshmi RAMANATHAN
PG and Research Department of Chemistry, Seethalakshmi Ramaswami College, Tiruchirappalli,
Tamil Nadu, India
Received: 01.02.2013
•
Accepted: 23.07.2013
•
Published Online: 11.06.2014
•
Printed: 10.07.2014
Abstract: A new Schiff base was prepared from 2-sulphanilamidopyrimidine and 2-hydroxy-3-methoxybenzaldehyde in
ethanolic media and it was complexed with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) ions. The synthesised ligand
and complexes were characterised by IR, UV, 1 H and 13 C NMR, elemental analysis, cyclic voltammetry, EPR, molar
conductance, and magnetic susceptibility. The reasonable shifts in FT-IR and NMR spectral signals of the complexes
with respect to the free ligand confirm good coordination of the Schiff-base ligand with the metal through imine nitrogen
and oxygen atoms of Schiff base moiety. The Schiff-base ligand and the complexes were screened for antimicrobial
activity and fluorescent behaviour. From the analytical and spectral data, the stoichiometry was found to be 1:2 for all
the complexes. An octahedral structure was proposed. All the complexes were found to be active against bacteria and
fungi.
Key words: Schiff base, 2-sulphanilamidopyrimidine, 2-hydroxy-3-methoxybenzaldehyde, metal complexes, biological
activity, fluorescent behaviour
1. Introduction
Sulpha drugs are chemotherapeutic agents whose molecular structures contain 4-aminobenzenesulfonamide
moiety.1 The antimicrobial activity of these drugs is thought to come from the structural resemblance between
sulfanilamide group and p-amino benzoic acid where the sulpha drug mimics this metabolite and blocks folic
acid synthesis in bacteria, thereby causing cell death.2 Many sulpha drugs like sulphadiazine, sulphamethoxa-
zole, and sulphamerazine possess SO2 NH moiety as an important toxophoric function.3 It has been reported
that biologically active compounds show greater activity when administered as metal complexes than as free
compounds.4 The efficacy of sulpha drugs can be enhanced upon coordination with a suitable metal ion.5 Schiff-
base compounds containing an imino group (–RC=N–) are usually formed by the condensation of a primary
amine with an active carbonyl group. Schiff bases are regarded as privileged ligands.6 Schiff bases and their
metal complexes are very popular due to their diverse chelating ability.7 They play important roles in both
synthetic and structural research because of their preparative accessibility and structural diversity.8 Metal com-
plexes of Schiff bases are extensively studied due to their synthetic flexibility, selectivity, and sensitivity towards
a variety of metal atoms.9 Schiff bases are used as pigments and dyes, catalysts, intermediates in organic syn-
∗Correspondence: valarchola@gmail.com
521

GOVINDARAJ and RAMANATHAN/Turk J Chem
thesis, and polymer stabilisers.10 A number of Schiff base molecules show biological antibacterial, antifungal,11
antidiabetic, antitumour, antiproliferative, anticancer, anticorrosion, and anti-inflammatory activities.12−14
The topical application of metal complexes of sulphadiazine has recently revived the usefulness of these
compounds in medicine.15 Indeed metal sulphadiazine complexes are now widely used to prevent bacterial
infection during burn treatments.16 The interest in metal-based sulphonamides was stimulated by the suc-
cessful introduction and preparation of Ag(I) and Zn(II) sulphadiazine complexes to prevent various bacterial
infections.17
Paralleling the same idea, this paper records the synthesis and characterisation of Mn(II), Co(II), Ni(II),
Cu(II), and Zn(II) complexes derived from 2-sulphanilamidopyrimidine and 2-hydroxy-3-methoxybenzaldehyde.
The structures of the ligand and its metal complexes were characterised by IR, UV, 1 H and 13 C NMR, ele-
mental analysis, cyclic voltammetry, ESR, molar conductance, and magnetic susceptibility measurements. The
biological activities were also studied against gram-positive and gram-negative bacterial and fungal organisms
for the Schiff-base ligand and their complexes. The structure of the Schiff-base ligand confirmed in the present
work is given in Figure 1.
N
CH
N
SO2
NH
N
OH
CH3O
Figure 1. Structure of the ligand.
2. Results and discussion
The Schiff-base ligand was synthesised by using equimolar quantities of 2-sulphanilamidopyrimidine and 2-
hydroxy-3-methoxybenzaldehyde and the complexes using metal acetates according to the following equation:
ethanol\DMF
reflux
−−−−−−−−−→
M(CH3 COO)2 .nH2 O + 2L
ML2 (H2 O)2 + 2CH3 COOH + nH2 O
The metal complexes derived varied in colour. All the complexes were stable, nonhygroscopic, and
coloured solids. The physical characteristics and microanalytical data of the ligand and metal complexes are
given in Tables 1 and 2.
Table 1. Physical characteristics of Schiff base ligand and complexes.
Ligand/
complexes
L
[MnL2(H2O)2] Sandalwood
[CoL2(H2O)2] Nut brown
[NiL2(H2O)2]
[CuL2(H2O)2] Green
[ZnL2(H2O)2]
Yield µeff
%
◦
S. no.
Colour
Orange
Molecular formula
C18H16N4O4S
MP C
CN
(BM)
-
1
2
3
4
5
6
203
75
65
65
55
75
65
-
C36H34N8O10S2Mn 235
C36H34N8O10S2Co 240
Brown yellow C36H34N8O10S2Ni 245
5.6
4.5
3.2
1.95
dia
6
6
6
6
6
C36H34N8O10S2Cu 234
C36H34N8O10S2Zn
Yellow
226
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GOVINDARAJ and RAMANATHAN/Turk J Chem
Table 2. Microanalytical data of Schiff base ligand and complexes.
Ligand/
complexes
Elemental analysis (%)(Calcd )found M % (Calcd)
found
∧
m
m2 mol−1
S. no.
C
H
N
S
(56.25) (4.17) (14.58) (8.33)
56.20 4.10 14.51 8.32
(50.41) (3.97) (13.07) (7.47)
50.41 3.96 13.0 7.43
(50.48) (3.95) (13.01) (7.43)
50.45 3.95 12.99 7.43
(50.19) (3.95) (13.01) (7.44)
50.15 3.91 13.00 7.42
(49.91) (3.93) (12.94) (7.39)
40.91 3.91 12.93 7.39
(49.80) (3.92) (12.91) (7.38)
49.79 3.91 12.90 7.38
1
2
3
4
5
6
L
-
-
(6.42)
6.41
(6.86)
6.84
(6.82)
6.82
(7.35)
7.34
[MnL2(H2O)2]
[CoL2(H2O)2]
[NiL2(H2O)2]
[CuL2(H2O)2]
[ZnL2(H2O)2]
16.7
3.44
6.0
7.86
2.9
(7.54)
7.54
2.1. Molar conductance and magnetic susceptibility measurements
The observed molar conductances of all the complexes in 10−3 MDMF solution were 2.9–16.7 ohm−1 cm2
mol−1 , showing their nonelectrolytic nature.18 This in turn suggests that the water molecules are coordinated
with the metal ions and present inside the coordination sphere in all the complexes.19 The magnetic data for
CoII and NiII complexes are consistent with octahedral geometry around the metal ion for both complexes. The
magnetic moment value of 1.95 BM for the Cu(II) complex lies in the range expected for the d9 system, which
contains one unpaired electron with octahedral geometry.20 Zn(II) complexes were found to be diamagnetic as
expected. The observed magnetic moment value of 5.60 BM for the Mn(II) complex suggests an octahedral
geometry. The probable structure of the complexes proposed in the present work is given in Figure 2.
N
NH SO2
N
H2O
OCH3
O
HC
N
M
N
CH
O
H2O
OCH3
N
N
SO2NH
Figure 2. Structure of the complex.
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GOVINDARAJ and RAMANATHAN/Turk J Chem
2.2. Infrared spectra
The infrared spectral data of the Schiff base and its metal complexes are recorded in Table 3. The Schiff base
showed a strong absorption band at 1582 cm−1 characteristic of ν (C=N), whereas the broad band at 3423 cm−1
was characteristic of hydrogen bonded ν (O-H) stretching vibrations.21 The azomethine ν(>C=N) band at 1582
cm−1 in the Schiff base is shifted to higher frequency in Co(II), Mn(II), Ni(II), Cu(II), and Zn(II) by 15, 23,
12, 10, and 12 cm−1 , respectively, which indicated the coordination of azomethine nitrogen on complexation.22
The disappearance of phenolic (OH) at 3423 cm−1 in all the complexes suggests the coordination of phenolic
oxygen after deprotonation.23 The linkage with the oxygen atom is further supported by the appearance of
a band in the region around 420–464 cm−1 , which may be assigned to ν (M–O).24 Further evidence of the
coordination of the N atom of the Schiff base with the metal atom was shown by the appearance of a new weak
frequency band at 512–578 cm−1 assigned to the metal nitrogen ν (M–N).25 These new bands were observed
only in the spectra of the metal complexes and not in the Schiff base, which confirmed the participation of
the donor groups. The bands in the ligand due to νas (SO2) and νs (SO2) appear at 1155 cm−1 and 1332
cm−1 , respectively. These bands remain almost unchanged in the complexes, indicating that this –SO2 group is
not participating in coordination.26 This is confirmed by the unchanged ν (S–N) and ν (C–S) modes appearing
around 945 cm−1 and 843 cm−1 , respectively. The ring nitrogen (=N–) of the Schiff base does not take part
in coordination, supported by the unchanged band at around 1275 cm−1
.
Table 3. IR and electronic spectral data.
Ligand/
complexes
L
[MnL2(H2O)2] 3426
[CoL2(H2O)2] 3440
[NiL2(H2O)2]
[CuL2(H2O)2] 3446
[ZnL2(H2O)2] 3399
IR spectral data, cm−1
γ (O–H) γ (C=N) γ (M–O) γ (M–N)
Electronic spectral data, (nm) cm−1
3423
1582
1597
1605
1594
1591
1594
-
-
(300, 348) 33333, 28601
(255, 272, 292) 39205, 36639, 34230
(262, 271) 38165, 36777
(255, 260, 271) 39064, 38329, 36846
(294, 302, 401) 33976, 33065, 24915
(261, 272) 38283, 36774
520
512
531
524
531
447
464
412
442
431
3450
2.3. Electronic spectra
The electronic spectrum of the ligand shows 2 high intensity bands at (300 nm) 33,333 cm−1 and (348 nm)
28,901 cm−1 , indicating n → n∗ and π → π* transitions, respectively, of the ligand moiety.27 The electronic
spectrum of the Mn(II) complex shows a band at (255 nm) 39,205 cm−1 assignable to M → L charge transfer
6
spectra and the bands at (272 nm) 36,639 and (292 nm) 34,230 cm−1 are due to A1g
→
The electronic spectra of the Co(II) complex displays bands at (262 nm) 38,165 and (271 nm)
4 T2g (D) and
6 A1g
36,777 cm−1 . The former band corresponds to intraligand transition of the organic moiety29 and the latter
→
E
4
28
g(G).
4
4
corresponds to T1g (F) → T1g (P), suggesting octahedral geometry of this complex. The Ni(II) complex
shows absorption bands at (255 nm) 39,064, (260 nm) 38,329, and (271 nm) 36,846 cm−1 . The high intensity
bands at 39,064 and 38,329 cm−1 are relatively attributed to L → M charge transfer transitions, whereas the
3
30
band at 36,846 cm−1 may be due to A2g
→
3 T2g
.
The Cu(II) complex displays bands at (292 nm) 33,976,
(302 nm) 33,065, and (401 nm) 24,915 cm−1 . The first 2 bands are attributed to intraligand transition and the
524

GOVINDARAJ and RAMANATHAN/Turk J Chem
2
third band, at 24,915 cm−1 , corresponds to E(g)
→
2 T2g . The Zn(II) complex displays high intensity bands
at (261 nm) 38,283 and (272 nm) 36,774 cm−1 . This may be due to ligand → metal charge transfer spectra.31
2.4. 1 H NMR and 13 C NMR spectra
The 1 H NMR spectra of the Schiff base and its complexes were recorded in DMSO (d6). The azomethine
proton (–CH=N–) in the Schiff base at δ = 8.5 ppm shifted downfield in metal complexes. This confirms the
coordination by azomethine nitrogen.32 The aromatic protons in the Schiff base appeared in the range at δ
6.8 to 8.1 ppm and metal complexes in the range δ 6.5 to 8.5 ppm.33 The disappearance of the phenolic –OH
proton signal at δ 12.2 ppm confirms the coordination by phenolic oxygen to metal ion. The 13 C NMR spectral
data (imine at δ 160.0 ppm, aromatic C–OH at δ 119.1 ppm, CH pyrimidine at δ 157.9 ppm) for the ligand
and (imine at δ 158.04 ppm, aromatic carbon at δ 129.4, CH pyrimidine at δ 158.0 ppm) for the complexes
support the proposed structure.
2.5. Cyclic voltammetry
Electrochemical cyclic voltammetry measurements were performed at room temperature in an airtight 3-
electrode cell by using a glassy carbon electrode with 0.071 cm2 surface area as a working electrode, while
a platinum wire served as the counter electrode and a Ag/AgCl in a saturated KCl solution as the reference
electrode. The electrochemical reaction was charged with DMF solution of all the complexes (1 × 10−4 M)
and tetrabutyl ammonium perchlorate (0.1 M) as supporting electrolyte.34 Measurements were made over a
potential range between –1.7 V and +1.7 V for Mn(II), Co(II), and Ni(II) complexes and between –1.1 V
and +1.1 V for complexes Cu(II) and Zn(II) with a scan rate of 0.1 V s−1 . Voltammetric parameters for
all compounds are summarised in Table 4. Generally the electrochemical properties of the complexes depend
on a number of factors, such as chelate ring/size, axial ligation, degree and distribution of unsaturation, and
substitution pattern in the chelate ring.35 Each voltammogram shows one electron irreversible oxidation wave
at a positive potential. The general reaction involved in the process is assigned to one electron oxidation of
the metal centre except zinc.36 The observed cyclic voltammograms are characterised as irreversible due to the
absence of a marked reduction in the peak height of the reverse scan.
Table 4. Redox potential for the complexes.
Complexes
Epc(v) Epa(v) Ipc (µA) Ipa (µA) Remarks
[MnL2(H2O)2]
[CoL2(H2O)2]
[NiL2(H2O)2]
[CuL2(H2O)2]
[ZnL2(H2O)2]
-
-
-
1.058
1.501
0.463
1.398
-
-
-
-
20
15
4.5
11.7
-
Irreversible
Irreversible
Irreversible
Irreversible
Irreversible
-
–1.357
-
–44.3
2.6. EPR spectra
The room temperature spectra of powdered samples were recorded at 9450 MHz. Both parallel and perpendicular
features of Cu are resolved in the spectra, which are characteristic of axial symmetry. The g11 and g component
⊥
for the complex were calculated as 2.22 and 2.04. The g value of the Cu(II) complex is found to be 2.1095,
confirming the presence of unpaired electrons in the dx2 -y2 orbital of Cu(II). The g value is very close to those
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GOVINDARAJ and RAMANATHAN/Turk J Chem
reported for a number of distorted Cu(II) complexes. Moreover, the observed g value is less than 2.3, suggesting
a covalent nature of metal–ligand bonds in the complex.37 The lines of this type usually observed are due either
to the intermolecular spin exchange, which may broaden the lines, or to the occupancy of the unpaired electron
in the degenerate orbital. The nature and pattern of the EPR spectra suggest an almost octahedral environment
around the Cu(II) complex.
2.7. Fluorescence spectra
The photoluminescence properties of the azo Schiff base ligand and their complexes were studied at room
temperature for 10−4 M solution for all compounds in DMSO solution. Excitation and emission slit widths
were set at 10 nm with a scan speed of 500 nm/min. The excitation spectra of the ligand show a maximum
at 300 nm and show an emission peak at 338 nm. Generally azo Schiff base systems exhibit fluorescence due
to intraligand π → π* transitions. Fluorescence spectra of the ligand solutions as 10−4 M in DMSO obtained
with the excitation at 300 nm (Figure 3). The metal complex of Mn(II) exhibits the weakest quenching. The
strongest quenching was obtained for the Cu(II) complex (Figure 4). These results show that the ligand has
potential for trace analysis of some transition metals by fluorometric method. The fluorescence data of the
complexes are summarised in Table 5.
ACIC
St.Joseph's College ( Autonomous)
Fluorescence - Report
Date: 12/19/2012
Trichy-2
Spectrum Name: L2-V.sp
5.00
4.5
4.0
338.01,3.34
3.5
3.0
2.5
2.0
1.5
1.0
0.5
312.17,0.03
0.0
-0.25
310.0 315
320
325
330
335
nm
340
345
350
355
360.0
Instrument Model: LS45
Figure 3. Fluorescence spectra for the ligand.
2.8. Antimicrobial activity
The antibacterial activity and antifungal activity of the Schiff-base ligand and its manganese, cobalt, nickel,
copper, and zinc complexes were tested by disc diffusion technique.38,39 Various gram-positive and gram-
negative bacterial organisms such as gram-negative bacteria Pseudomonas aeruginosa and E. coli, gram-positive
bacteria Staphylococcus aureus and Klebsiella aerogenes, and fungi Aspergillus niger and Mucor were used
to find out the antimicrobial activity (Table 6). Filter paper discs of diameter 6 mm were used and the
diameters of zones of inhibition formed around each disc after incubating for 72 h at 25–30 ◦ C were recorded.
Results were compared with those of the standard drug ciprofloxacin for bacteria and nystatin for fungi at the
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GOVINDARAJ and RAMANATHAN/Turk J Chem
same concentration. All the new complexes showed remarkable biological activity against bacteria and fungi40
(Figures 5a–c). From the results it is clear that the metal complexes have greater antimicrobial activity than
the parent ligand.
ACIC
St.Joseph's College ( Autonomous)
Fluorescence - Report
Trichy-2
Spectrum Name
Date: 12/19/2012
1.42
1.3
1.2
1.1
1.0
0.9
0.8
283.23,0.65
281.60,0.60
0.7
276.75
0.6
0.5
L2-Cu-V
0.4
0.3
L2-MnA
L2-Co-V
0.2
0.1
0.0
-0.11
271.2
275
280
285
nm
290
295
299.8
Instrument Model
Figure 4. Fluorescence spectra of Mn(II),Co(II), and Cu(II) complexes.
Table 5. Fluorescence characteristics of ligand and complexes.
Excitation wavelength Fluorescence wavelength
Complexes
Quantum yield
λmax (nm)
300
λmax (nm)
338
276
281
271
L
0.88
0.94
0.96
0.94
0.95
0.94
[MnL2(H2O)2] 261
[CoL2(H2O)2] 270
[NiL2(H2O)2]
[CuL2(H2O)2] 270
[ZnL2(H2O)2] 260
255
283
274
In conclusion, the coordination ability of the newly synthesised azo Schiff base was proved in complexation
reactions with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) ions. IR, UV, 1 H NMR, and magnetic measurements
of the ligand and its complexes confirm the suggested coordination of the ligand through azomethine linkage.
Based on these facts, an octahedral structure has been proposed for all complexes. The process of chelation
dominantly affects the biological activity of the complexes that are potent against pathogens. In general, all
the synthesised complexes can serve as potential photoactive materials, as indicated by their characteristic
fluorescence properties.
3. Experimental
All chemicals used were of analytical reagent (AR) grade and of the highest purity available. Solvents were
purified and dried according to the standard procedures. All metal (II) compounds were used as acetate salts.
IR spectra of the complexes were recorded in KBr pellets with a PerkinElmer RX1 FT-IR spectrophotometer
in the 4000–400 cm−1 range. The electronic spectra were recorded in DMF on a PerkinElmer Lambda 35
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GOVINDARAJ and RAMANATHAN/Turk J Chem
Table 6. Antimicrobial activity of Schiff base ligand and complexes.
Ligand and
complexes
Ligand (L)
[MnL2(H2O)2] +++
[CoL2(H2O)2] +++
[NiL2(H2O)2]
[CuL2(H2O)2] +++
[ZnL2(H2O)2] +++
Staphylococcus Klebsiella
Pseudomonas
aeruginosa
++
+++
++
++
++
+++
Aspergillus
niger
++
+++
+++
+++
+++
+++
E. coli
Mucor
aureus
++
aerogenes
+++
+++
+++
+++
+++
+++
+++
+++
++
+++
+++
+++
++
+++
+++
+++
+++
+++
++
Standard = ciprofloxacin 5 g/disc for bacteria; nystatin = 100 units/disc for fungi. Highly active = +++ (inhibition
zone > 15 mm); moderately active = ++ (inhibition zone > 10 mm); slightly active = + (inhibition zone > 5 mm);
inactive = – (inhibition zone < 5 mm)
Figure 5. a) Activity of Cu(II) and Zn(II) complex against gram-positive bacterium E. coli. b) Activity of ligand
and Mn(II),Co(II), and Ni(II) complexes against fungus Mucor. c) Activity of ligand and Mn(II),Co(II), and Ni(II)
complexes against fungus Pseudomonas aeruginosa.
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GOVINDARAJ and RAMANATHAN/Turk J Chem
spectrophotometer in the 190–1100 nm range. The 1 H and 13 C NMR spectra were recorded on a Bruker
400 MHz FT-PMR spectrometer (DMSO-d6). Elemental analysis of the ligand and complexes was performed
using an Elementar Vario EL CHN rapid analyser. Cyclic voltammetric measurements for the complexes
were obtained using a Princeton Applied Research Multichannel VersaSTAT-II. The X-band EPR spectra were
recorded on a Bruker ESP X-band EPR spectrometer using powdered samples at a microwave frequency of 9450
MHz. Magnetic susceptibilities were measured on an automagnetic susceptibility meter (MSB-Auto) at room
temperature. Melting points were determined using a melting point apparatus (Elico) and are uncorrected.
Conductivity measurements for the complexes were carried out on an Elico Conductivity Bridge and a dip
conductivity cell using dimethyl formamide as solvent. Fluorescence spectra were detected using a PerkinElmer
LS 45 spectrofluorometer.
3.1. Synthesis of Schiff-base ligand: E-4-(2-hydroxy-3-methoxybenzlideneamino)-N-(pyrimidin-2-
yl)benzenesulfonamide(L)
The Schiff base was prepared by the condensation of equimolar amounts of 2-sulphanilamidopyrimidine and
2-hydroxy-3-methoxy benzaldehyde in a minimal quantity of ethanol. The resulting mixture was then refluxed
on a water bath for 5 h. The pale orange coloured solid mass separated out on cooling was filtered, washed, and
dried over anhydrous CaCl2 in a desiccator. The purity of the ligand was checked by melting point, TLC, and
spectral data. The ligand is insoluble in some common organic solvents like acetone and benzene, and soluble
in polar solvents like DMF and DMSO.
3.2. Synthesis of metal complexes
Metal complexes were synthesised by mixing the hot solution of ligand (0.004 mol) in a minimal quantity of
dimethyl formamide and ethanolic solution of metal acetates (0.002 mol). The resulting mixture was then
refluxed in a water bath for 6 h. The complexes obtained in each case were cooled, filtered, and washed with
ethanol several times to remove any excess of the ligand. Finally the complexes were washed with anhydrous
diethylether and dried in a desiccator.
Acknowledgements
The authors express their gratitude to UGC-SERO, Hyderabad, for financial assistance. The authors express
their gratitude to the Secretary, Seethalakshmi Ramaswami College, for providing laboratory facilities and fac-
ulty members, PG and Research Department of Chemistry, Seethalakshmi Ramaswami College, Tiruchirappalli,
Tamilnadu, India.
References
1. Maurya, R. C.; Patel, P. Spectrosc. Lett. 1999, 32, 213–236.
2. Westcott, S. A. Transition Met. Chem. 2005, 30, 411–418.
3. Singh, H.; Srivastava, V. K.; Shukla, S. N.; Srivastava, M. K.; Upadhayay, M. K. Indian J. Chem. 1994, 33A,
350–351.
4. De Clercq, B.; Verpoort, F. Macromolecules 2002, 35, 8943–8949.
5. Goldstein, M.; Barton, J. K.; Goldberg, J. M.; Kumar, C. V.; Turro N. J. J. Am. Chem. Soc. 1986, 10, 2081–2088.
6. Mirkhani, V.; Moghadam, M.; Tangestanninejad S.; Baltork, M. P.; Rasouli N. Catal. Commun. 2008, 9, 219–223.
529

GOVINDARAJ and RAMANATHAN/Turk J Chem
7. Bera, P.; Saha, N.; Kumar, S.; Baneeja, D.; Bhattacharya, R. Transition Met. Chem. 1999, 24, 425–428.
8. Espinet, P.; Esteruelas, M. A.; Ore, L. A.; Sarrano, J. L.; Sola, E. Coord. Chem. Rev. 1992, 117, 215–220.
9. Spinu, C.; Kriza, A. Acta Chim. Slov. 2000, 47, 179–185.
10. Thakar, B. T.; Barvalia, R. S. J. Coord. Chem. 2000, 63, 1597–1610.
11. Valarmathy, G.; Subbalakshmi, R. Asian J. Chem. 2013, 25, 2077–2079.
12. Kumar, G.; Kumar, D.; Devi, S.; Johari, R.; Singh, C. P. Eur. J. Med. Chem. 2010, 45, 3056–3062.
13. Vanco, J.; Marek, J.; Travnicek, Z.; Racanska, E.; Muselik, J.; Svajlenova O. J. Inorg. Biochem. 2008, 102, 595–605.
14. Wermuth, C. G. J. Med. Chem. 2004, 47, 1303–1314.
15. Guo, Z.; Sadler, P. J. Angew Chem. Int. Edn. Engl. 1999, 39, 1512–1531.
16. Narang, K. K.; Pandey, J. P. Synth. React. Inorg. Met. Org. Chem. 1994, 21, 73–78.
17. Bult, A. Met. Ions Biol. Syst. 1982, 1, 261–265.
18. Geary, W. J. Coordin. Chem. Rev. 1971, 81.
19. Chinuusamy, V.; Natarjan, K. Synth. React. Inorg. Met.Org. Nanomet. Chem. 1993, 23, 889.
20. Maurya, R. C.; Misha, D. D.; Rathore, R.; Jain S. Synth. React. Inorg. Met. Org. Chem. 1994, 24, 427–437.
21. Sharda, L. N.; Ganokar, M. C. Indian J. Chem. 1988, 27A, 617–619.
22. Chattopadhyay, P.; Sinha, C. Indian J. Chem. 1995, 34A, 76–78.
23. Sahni, S. K. Transition Met. Chem. 1979, 4, 73–76.
24. Singh, H. R.; Agarwala, B. V. Transition Met. Chem. 1993, 18, 577–579.
25. Rao, T. R. Synth. React. Inorg. Met. Org. Chem. 1993, 32, 419–436.
26. Maurya, R. C.; Patel, P. Spectroscop. Lett. 1999, 32, 213–236.
27. Ghargava, B. P.; Bembi, R.; Tyagu, M. J. Indian Chem. Soc. 1983, 60, 214–217.
28. Lee, J. D. Concise Inorganic Chemistry; 5th Edition, Blackwell Science Publishers: Oxford, UK, 1999.
29. Singh, H. R.; Agarwala, B. V. J. Indian Chem. Soc. 1988, 65, 591–593.
30. Maurya, R. C.; Patel P. Spectroscop. Lett. 1999, 32, 213–236.
31. Lever, A. B. P. Inorganic Electronic Spectroscopy; Elsevier: Amsterdam, Netherlands, 1984.
32. Singh, H. R.; Agarwala, B. V. J. Indian Chem. Soc. 1988, 65, 591–593.
33. Agarwala, B. V.; Hingorani, S.; Puri, V.; Khetrapal, C. L.; Nagangowda, G. A. Transition Met. Chem. 1994, 19,
25–27.
34. Mabbot, G. A. J. Chem. Educ. 1983, 60, 697.
35. Vijayaraj, A.; Prabu, R.; Suresh, R.; Sangeetha Kumari, R.; Kaviyarasan, V.; Narayanan. V. Bull. Korean Chem.
Soc. 2012, 33, 3581–3588.
36. Ali, M. A.; Tan, A. L.; Mirza, A.; Santos, J. A.; Abdullah, A. H. Transition Met. Chem. 2012, 37, 651–659.
37. Karvembu, R.; Balasubramanian, K. P.; Chinnusamy, V.; Natarajan, K. Indian J. Chem. 2005, 44A, 2450–2454.
38. Rahman, A.; Choudhary, M. I.; Thomsen, W. J. Bioassay Techniques for Drug Development; Harwood Academic
Publishers: Amsterdam, Netherlands, 2001.
39. Indian Pharmacopoeia 1996, IIA, 105.
40. Gomathi, V.; Selvameena, R. Asian J. Chem. 2013, 25, 2083–2086.
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