Synthesis, spectroscopic characterization, redox, and biological screening studies of some schiff base transition metal(II) complexes derived from salicylidene-4-aminoantipyrine and 2-aminophenol/2-aminothiophenol

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SYNTHESIS, SPECTROSCOPIC CHARACTERIZATION,
REDOX, AND BIOLOGICAL SCREENING STUDIES OF
SOME SCHIFF BASE TRANSITION METAL(II) COMPLEXES
DERIVED FROM SALICYLIDENE-4-AMINOANTIPYRINE AND
2-AMINOPHENOL/ 2-AMINOTHIOPHENOL
N. Raman a , A. Kulandaisamy a & K. Jeyasubramanian b
a Department of Chemistry, Virudhunagar Hindu Nadars', Senthikumara Nadar College,
Virudhunagar, 626001, India
b Department of Chemistry, Mepco Schlenk Engineering College, Sivakasi, 626005, India
Version of record first published: 15 Feb 2007.
To cite this article: N. Raman , A. Kulandaisamy & K. Jeyasubramanian (2001): SYNTHESIS, SPECTROSCOPIC
CHARACTERIZATION, REDOX, AND BIOLOGICAL SCREENING STUDIES OF SOME SCHIFF BASE TRANSITION METAL(II) COMPLEXES
DERIVED FROM SALICYLIDENE-4-AMINOANTIPYRINE AND 2-AMINOPHENOL/ 2-AMINOTHIOPHENOL, Synthesis and Reactivity in
Inorganic and Metal-Organic Chemistry, 31:7, 1249-1270
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SYNTH. REACT. INORG. MET.-ORG. CHEM., 31(7), 1249–1270 (2001)
SYNTHESIS, SPECTROSCOPIC
CHARACTERIZATION, REDOX,
AND BIOLOGICAL SCREENING STUDIES
OF SOME SCHIFF BASE TRANSITION
METAL(II) COMPLEXES DERIVED FROM
SALICYLIDENE-4-AMINOANTIPYRINE
AND 2-AMINOPHENOL=
2-AMINOTHIOPHENOL
N. Raman,*,1 A. Kulandaisamy,1 and
K. Jeyasubramanian2
1Department of Chemistry, Virudhunagar Hindu
Nadars’, Senthikumara Nadar College,
Virudhunagar-626 001, India
2Department of Chemistry, Mepco Schlenk Engineering
College, Sivakasi-626 005, India
ABSTRACT
Neutral complexes of Cu(II), Ni(II), Co(II), Mn(II), VO(IV)
and Zn(II) have been synthesised from the Schiff bases
derived from salicylidene-4-aminoantipyrine and 2-
aminophenol=2-aminothiophenol. The structural features
*Corresponding author. E-mail: ra man@123india.com
1249
Copyright # 2001 by Marcel Dekker, Inc.
www.dekker.com

1250
RAMAN, KULANDAISAMY, AND JEYASUBRAMANIAN
have been arrived at from their microanalytical, IR, UV-
1
Vis., H NMR and ESR spectral data. All of the complexes
exhibit square-planar geometry except the Mn(II) and
VO(IV) complexes. The Mn(II) chelates show an octahedral
environment and the VO(IV) chelates exist in a square-
pyramidal geometry. The non-electrolytic and monomeric
nature of the complexes are evidenced by their magnetic
susceptibility and low conductance data. The electro-
chemical behaviour of the Cu(II), Mn(II) and VO(IV)
complexes in DMSO at 300 ꢀK were studied. [CuL1] com-
plex shows an irreversible peak for the copper(II)=copper(I)
couple at Epc ¼ 0:16 V and Epa ¼ 0:53 V referenced to
1
Ag=AgCl. The cyclic voltammogram of the [CuL2] complex
in MeCN at 300 ꢀK shows a quasi-reversible peak for the
couples copper(II)=copper(III) at Epc ¼ 0:47 V and Epa ¼
0:61 V versus Ag=AgCl and two irreversible peaks for the
copper(II) ! copper(I) and copper(I) ! copper(0) reduc-
tion at Epc ¼ À0:63 V and À0:89 V, respectively. The
[MnL1] complex shows two irreversible couples, mangane-
se(II)=manganese(I) and manganese(I)=manganese(0) at
Epc ¼ À0:10 V and À0:84 V with the direct oxidation at
Epa ¼ À0:70 V and À0:04 V, respectively. X-band ESR
spectra of the Cu(II) and VO(IV) complexes in DMSO at
300 and 77 ꢀK were recorded and their salient features are
reported. The biological activities of the metal chelates
against the bacteria Staphylococcus aureus, Bacillus subtilis,
Klebsiella pneumoniae, Salmonella typhi, Pseudomonas aeru-
ginosa and Shigella flexneri and the fungi Aspergillus niger
and Rhizoctonia bataicola are also reported. Most of the
complexes have higher activities than those of the free
Schiff bases and the control.
INTRODUCTION
The Schiff bases of 4-aminoantipyrine and its complexes have a variety
of applications including in the biological, clinical, analytical and pharma-
cological areas177. Earlier work reported that some drugs showed increased
activity when administered as metal chelates rather than as organic com-
pounds. The coordinating property of 1-phenyl-2,3-dimethyl-4-aminopyr-
azol-5-one (4-aminoantipyrine) has been modified into a flexible ligand

SCHIFF BASE COMPLEXES
1251
Figure 1. Structures of the ligands.
system by condensation with a variety of reagents like aldehydes, ketones,
thiosemicarbazides, carbazides etc.8717 A search through the literature
reveals that no work has been done on the transition metal complexes of
Schiff bases formed by the condensation of salicylidene-4-aminoantipyrine
with 2-aminophenol=2-aminothiophenol. In the present context, we syn-
thesized new types of tetradendate ligand systems from salicylidene-4-
aminoantipyrine and 2-aminophenol=2-aminothiophenol. The synthesised
compounds are N2O2=N2OS donor types and their ligation behaviour with
different metal ions was studied. The proposed structure of the ligand
system is given in Fig. 1.
RESULTS AND DISCUSSION
The salicylidene-4-aminoantipyrine was prepared by using the repor-
ted method15. Its Schiff bases with 2-aminophenol=2-aminothiophenol were
prepared by the reaction in the equation shown below.

1252
RAMAN, KULANDAISAMY, AND JEYASUBRAMANIAN
The metal chelates were prepared as follows:
Ethanol
H2L þ MCl2 ÁxH2O À! ½MLŠ þ xH2O þ 2HCl
Reflux
Ethanol
H2L þ MnCl2 Á4H2O À!½MnLðH2OÞ2Š þ 2H2O þ 2HCl
Reflux
Ethanol
H2L þ VOSO4 ÁH2O À! ½VOLŠ þ H2O þ H2SO4
Reflux
where L ¼ L1 or L2 (M ¼ Cu(II), x ¼ 2; M ¼ Ni(II), x ¼ 6; M ¼ Co(II), x ¼
6; M ¼ Zn(II), x ¼ 0).
The analytical data of the ligands and complexes along with some phy-
sicalpropertiesaresummarisedinTableI.Theanalyticaldataofthecomplexes
correspond well with the general formula ML for M = Cu(II), Ni(II), Co(II),
Zn(II) and VO(IV) and L ¼ L1 or L2 while the manganese complexes have the
composition MnLÁ2H2O. The magnetic susceptibility values of the complexes
at room temperature are consistent with square-planar geometry around the
central metal ion except for the Mn(II) and VO(IV) complexes which show
octahedral geometry and square-pyramidal geometry, respectively. Thermal
analysis of the manganese complexes at 170 ꢀC indicates the presence of two
molecules of water coordinated to the central metal ion which is further con-
firmed by their characteristic IR spectra. The low conductance values of
the chelates support the non-electrolytic nature of the metal complexes.
1H NMR Spectra
1
The H NMR spectrum of H2L1 in DMSO-d6 shows the following
signals: C6H5 as multiplet at d 6.477.6, ›C-CH3 at d 2.7, -N-CH3 at d 3.2 to

1254
RAMAN, KULANDAISAMY, AND JEYASUBRAMANIAN
3.4 and azomethine proton at d 8.9. The peaks at d 9.7 and d 12.9 are
attributable to the phenolic OH group present in 2-aminophenol and the
OH group present in the salicylaldehyde moiety. The absence of these two
peaks noted for the zinc complex indicates the loss of the OH protons due to
complexation. The azomethine proton signal in the spectrum of the zinc
complex is shifted downfield compared to the free ligand, suggesting
deshielding of the azomethine proton due to coordination to the metal ion
through the azomethine nitrogen atom. There is no appreciable change in all
of the other signals of this complex (Table II).
Infrared Spectra
The IR spectrum of the ligand H2L1 shows a weak broad band in the
region 295073300 cmÀ1assignable to intramolecular hydrogen bonded OH
groups. The absence of this band, noted in the spectra of the complexes,
indicates the deprotonation of the intramolecular hydrogen bonded OH
groups on complexation. The IR spectrum of the ligand H2L2 shows a
strong broad band in the region 305073400 cmÀ1 and a weak band at
2580cm À1which are assigned to the OH and SH groups, respectively. The
disappearance of these two bands in the spectra of the complexes indicates the
deprotonation of the hydroxyl and thiol groups upon chelation. The spectra of
both ligands show the characteristic -C›N bands in the region
162071560cm À1, which are also shifted to lower frequencies in the spectra of
the complexes (160071530cm À1). The IR spectra of the metal chelates also
show some new bands in the region 4807450cm À1 and 4007350cm À1 which
are probably due to the formation of M-O and M-N bonds, respectively18. The
IRspectraofthe manganesecomplexesshowastrongbroadbandin theregion
320073600 cmÀ1 which confirms the presence of water molecules coordinated
to the metal ion19. In addition to the other bands, the vanadyl complexes show
an additional band at 9307910cm À1 attributed to the V›O frequency20.
Table II. 1H NMR Spectral Data of H2L1 and Its Zn(II) Complex (d, ppm) in
DMSO-d6 Solution
Phenolic
Phenolic
OH Group OH Group in
in Amino Salicylaldehyde
Benzene
Ring
Compound
¼C-CH3 -N-CH3 -N¼CH
Phenol
Moiety
H2L1
ZnL1
6.477.6
6.878.2
2.7
3.1
3.273.4
3.573.8
8.9
9.4
9.7
7
12.9
7

SCHIFF BASE COMPLEXES
1255
Table III. Electronic Absorption Spectral Data of the Compounds
Absorption
Compound Region (cmÀ1
Band
Assignment
)
e (cmÀ1, molÀ1
)
Geometry
H2L1
CuL1
42,016
28,011
43,860INCT
28,985
21,980
45,871
30,770
21,980
19,600
43,480INCT
28,910INCT
19,500
43,860INCT
28,730INCT
19,040
INCT
INCT
7
7
7
7
24
7
7
23
28
7
7
21
7
7
7
7
INCT
Square-planar
Square-planar
Square-planar
2B1g ! A1g
2
NiL1
INCT
INCT
1A1g ! A2g
1
1A1g ! B1g
1
CoL1
VOL1
1A1g ! B1g
1
1B2 ! A1
30Square-pyramidal
48
7
2
2
11,630
1B2 ! E
H2L2
CuL2
45,870INCT
28,985
40,486
24,814
18,657
46,948
34,965
24,096
16,233
48,076
32,680INCT
17,074
48,309
29,850INCT
22,675
12,180
INCT
INCT
INCT
7
7
7
24
7
7
23
28
7
7
21
7
7
7
Square-planar
2B1g ! A1g
2
NiL2
INCT
INCT
1A1g ! A2g
Square-planar
Square-planar
1
1A1g ! B1g
1
CoL2
VOL2
INCT
1A1g ! B1g
1
INCT
1B2 ! A1
30Square-pyramidal
48
2
1B2 ! E
2
e=Extinction coefficient, INCT=Intraligand charge transfer band.

1256
RAMAN, KULANDAISAMY, AND JEYASUBRAMANIAN
Electronic Absorption Spectra
The electronic absorption spectra of the Schiff bases and their Cu(II),
Ni(II), Co(II) and VO(IV) complexes were recorded at 300 ꢀK in DMSO
solution. The solvent, absorption regions, assignments, extinction coeffi-
cients and the proposed geometry of the complexes are given in Table III.
These values are comparable to those of other reported similar com-
plexes21725
.
Electrochemical Study
Cyclic voltammograms of CuL1, VOL1, MnL1 and CuL2 were recor-
ded in DMSO solution (tetramethylammonium perchlorate as supporting
electrotyte) at 300 ꢀK. The CuL1 complex exhibits an irreversible peak for
the copper(II)=copper(I) couple on the cathodic side at 0.16 V and on the
anodic side the direct oxidation takes place at 0.53 V. The MnL1 complex
shows two irreversible peaks in the cathodic direction, one at Epc ¼ À0:10 V
and another at À0:84 V which are due to the reduction of manganese(II) !
manganese(I) and manganese(I) ! manganese(0), respectively. In the anodic
direction, the direct oxidation takes place at Epa ¼ À0:70 V and À0:04 V,
respectively. The VOL1 complex in DMSO solution exhibits a cyclic vol-
tammogram typical of VO(IV) complexes. The peaks at Epa ¼ 0:62 V and
Epc ¼ 0:42 V are attributable to the V(IV)=V(III) couple. In the negative
region, it shows irreverisble peaks at Epa ¼ À0:62 V and Epc ¼ À0:74 V for
the couple V(III)=V(II).
The cyclic voltammogram of the CuL2 complex in MeCN was recor-
ded at room temperature (Fig. 2). It shows a quasi-reversible peak for the
copper(II) ! copper(III) couple at Epa ¼ 0:60 V with the direct cathodic
peak for copper(III) ! copper(II) at Epc ¼ 0:56 V. The complex also shows
two irreversible peaks characteristic for copper(II) ! copper(I) (Epc ¼
À0:64 V) and copper(I) ! copper(0) (Epc ¼ À0:98 V) reduction. In the
anodic side, the strong peak at Epa ¼ À0:32 V is assigned to the direct
oxidation of copper(0) ! copper(II).
Considering all of the above processes, the cyclic voltammogram of
the CuL2 complex may be described by the following equations for the range
1.2 to À1.2 V:
0:60V
*
½CuðIIފ
½CuðIIIފþe
)
0:56 V
À0:64V
½CuðIIފþeÀ À! ½CuðIފ

SCHIFF BASE COMPLEXES
1257
Figure 2. Cyclic voltammogram of the CuL2 complex in MeCN at 300 ꢀK (0.1 M
TMAP) scan rate 100 mVsÀ1
.
À0:98V
½CuðIފþeÀ À! ½Cuð0ފ
À0:32 V
½Cuð0ފ À!½CuðIIފ þ 2eÀ
varying the scan rates with peak potentials. The data are given in Table IV.
The quasi-reversibility of the Cu(II)=Cu(III) couple was checked by
ESR Spectra
The X-band ESR spectra of the Cu(II) complexes were recorded in
DMSO at 300 and 77 ꢀK. The typical ESR spectrum of CuL1 is shown in Fig. 3.
The spin Hamiltonian parameters of the complexes are given in Table V.
The g tensor values of this copper(II) complex can be used to derive
the ground state. In square-planar complexes, the unpaired electron lies in

1258
RAMAN, KULANDAISAMY, AND JEYASUBRAMANIAN
Table IV. Redox Potential for [CuL2] in MeCN Containing 0.1 M TMAP at 300 ꢀK
for the Cu(II)=Cu(III) Couple
Scan Rate
(m VsÀ1
)
Epc (V)
Epa (V)
DEp
Ipc(mA)
Ipa(mA)
Ipc=Ipa
50
100
150
200
0.58
0.57
0.56
0.55
0.61
0.61
0.62
0.62
0.03
0.04
0.04
0.07
15.23
15.61
16.74
17.25
À16.72
À17.53
À18.85
À18.92
0.91
0.89
0.88
0.89
2
the dx2Ày2 orbitals giving B1g as the ground state with gk > g?. From the
observed values it is clear that gk > g? which suggests that the complex is
square-planar. Further, this is also supported by the fact that the unpaired
electron lies predominantly in the dx2Ày2 orbital26728. The structure of the
Cu(II) complexes are given in Fig. 4.
The molecular orbital coefficients viz., in-plane p-bonding (b2) and in-
plane s-bonding (a2) were calculated by using the following expressions26, 29
a2 ¼ ÀðA =0:036Þ þ ðg À 2:0023Þ þ 3=7ðg À 2:0023Þ þ 0:04
.
k
k
?
b2 ¼ ðg À 2:0023ÞE=À8la2
k
In these equations l ¼ 828 cmÀ1 for the free ion and E is the electronic
transition energy of B1g ! A1g. From Table V, the a2 and b2 values
indicate that there is substantial interaction in the in-plane s-bonding
whereas the in-plane p-bonding is almost ionic. These results are anticipated
because there are no appropriate ligand orbitals to combine with the dxy
orbital of copper(II) ion.
2
2
The ESR spectra of the vanadyl complexes recorded in DMSO solu-
tion at 300 and 77 ꢀK show a typical eight-line and sixteen-line pattern,
respectively. The typical ESR spectra of [VOL2] are shown in Fig. 5. The
various parameters calculated from the spectra are given in Table V. The
observed parameters indicate that the molecule exists in a square-pyramidal
geometry which is characteristic for oxovanadium(II) chelates29732. The
molecular orbital coefficients a2 and b2 were also calculated for this complex
by using the following equations33
a2 ¼ ð2:0023 À g ÞE=8lb2
k
b2 ¼ 7=6ðÀA =p þ A =p þ g À 5=14g À 9=14geÞ
k
?
k
?
In these equations P ¼ 128 Â 10À4 cmÀ1, l ¼ 135 cmÀ1 and E is the
2
electronic transition energy of 2B2 ! E. The calculated in-plane p-bonding

SCHIFF BASE COMPLEXES
1259
Figure 3. The X-band ESR spectrum of the CuL1 complex in DMSO at 300 ꢀK (a)
and 77 ꢀK (b).
coefficient value (b2) does not deviate much from unity. For most of the
complexes, the in-plane p-bonding coefficient remains constant and spans
the region of 0.94 to 1.00. This is consistent with Kivelson’s conclusion33
which suggests that the d\rm xy orbital is essentially non-bonding while b2
remains constant. The proposed structure for the vanadyl complexes are
given in Fig. 6.

1260
RAMAN, KULANDAISAMY, AND JEYASUBRAMANIAN
Table V. The Spin Hamiltonian Parameters of Cu(II) and VO(IV) Complexes in
DMSO at 300 and 77 ꢀK
Hyperfine Constant Â10À4 cmÀ1
Complex
A
A
Aiso
g
k
g
?
giso
a2
b2
?
k
½CuL1Š
½CuL2Š
½VOL1Š
½VOL2Š
143
164
169
186
42
47
76
73
76
75
105
110
2.31
2.27
1.97
1.93
2.06
2.05
1.99
1.98
2.14
2.16
1.98
1.94
0.59
0.71
0.81
0.80
0.86
0.93
0.96
1.02
Figure 4. Structures of the Cu(II) complexes.

SCHIFF BASE COMPLEXES
1261
Figure 5. The X-band ESR spectrum of the VOL2 complex in DMSO at 300 ꢀK (a)
and 77 ꢀK (b).
Essentially, the delocalisation of electrons into the ligand may be
gauged from the in-plane s-bonding coefficient (a2) values. This follows the
s-donor strength of the ligand and it usually decreases as the covalent
bonding increases. From Table V it is clear that the in-plane s-bonding (a2)
is significant. The M.O. coefficients also show that the metal ion has some
covalent character in the ligand environment.

1262
RAMAN, KULANDAISAMY, AND JEYASUBRAMANIAN
Figure 6. Structures of the VO(VI) complexes.
Biological Screening Activity
The in vitro biological screening effects of the investigated compounds
were tested against six bacteria: Staphylococcus aureus, Bacillus subtilis,
Klebsiella pneumoniae, Salmonella typhi, Pseudomonas aeruginosa Shigella
flexneri and two fungi, namely Aspergillus niger and Rhizoctonia bataicola.
The zone of inhibition against the growth of microorganisms are reported in
Tables VI and VII which indicates that most of the complexes have higher
toxicity against the eight organisms. A comparative study of the ligands and
their complexes at the minimum inhibitory concentration (Table VI) indi-
cates that most of the metal chelates exhibit slightly higher antibacterial
activity than the free ligands. The increase in the antifungal activity of the
metal chelates with increase in concentration are due to the effect of metal
ion on the normal cell process.

SCHIFF BASE COMPLEXES
1263

1264
RAMAN, KULANDAISAMY, AND JEYASUBRAMANIAN
Table VII. The Zone of Inhibition Against the Growth of Fungi by the Well
Diffusion Method (mm)
Aspergillus niger
Rhizoctonia bataicola
No.
Compound
100
200
12
300 (mg)
100
18
1012
15
16
15
12
14
12
12
14
2027
12
14
200
300 (mg)
(1)
(2)
Amphotericin
H2L1
1012
7
1015
13
12
14
17
12
9
12
17
15
13
1013
14
18
18
12
11
26
17
20
16
(3)
(4)
(5)
(6)
(7)
(8)
[CuL1]
[NiL1]
18
19
18
23
17
13
15
23
21
17
24
25
23
29
21
18
21
3013
28
25
20
19
18
17
16
18
19
27
20
25
24
25
27
29
[CoL1]
[MnL1(H2O)2]
[ZnL1]
[VOL1]
(9)
H2L2
(10)
(11)
(12)
(13)
(14)
(15)
[CuL2]
[NiL2]
[CoL2]
17
20
22
29
[MnL2(H2OÞ2]
[ZnL2]
18
13
19
11
24
[VOL2]
19
27
16
22
Such increased activity of the metal chelates can be explained on the
basis of Overtone’s concept34 and the Tweedy’s chelation theory35,36
.
According to Overtone’s concept of cell permeability, the lipid membrane
that surrounds the cell favours the passage of only lipid-soluble materials
due to which liposolubility is an important factor which controls the
antimicrobial activity. On chelation, the polarity of the metal ion will be
reduced to a greater extent due to the overlap of the ligand orbital and
partial sharing of the positive charge of the metal ion with donor groups.
Further, it increases the delocalisation of p-electrons over the whole che-
late ring and enhances the lipophilicity of the complexes. This increased
lipophilicity enhances the penetration of the complexes into lipid mem-
branes and blocking of the metal binding sites in the enzymes of micro-
organisms. These complexes also disturb the respiration process of the cell
and thus block the synthesis of proteins which restricts further growth of
the organism. Furthermore, the mode of action of the compounds may
involve formation of a hydrogen bond through the azomethine group with
the active centres of cell constitutents, resulting in interference with the
normal cell process36.

SCHIFF BASE COMPLEXES
EXPERIMENTAL
1265
The carbon, hydrogen and nitrogen contents in each sample and the
1H NMR spectra were performed at the Regional Sophisticated Instru-
1
mentation Centre, Central Drug Research Institute, Lucknow. H NMR
spectra of the samples were recorded in DSMO-d6 solution in the range d
0715 ppm on a 400 MHz FT-NMR spectrophotometer. IR spectra using
KBr pellets were recorded on a Perkin-Elmer 783 spectrophotometer. UV-
Vis. spectra of the complexes in DMSO were recorded on a Perkin-Elmer
402 spectrophotometer. The X-band ESR spectra of the samples in DMSO
were obtained using a Varian E112 spectrophotometer, the field being
calibrated with diphenylpicrylhyrazyl (DPPH), at the Regional Sophisti-
cated Instrumentation Centre, Indian Institute of Technology, Chennai.
Electrochemical studies were carried out using a model BAS CV 50W Bio-
Analytical System Electrochemical Analyser. CV measurements were per-
formed using a glassy carbon working electrode, platinum wire auxillary
electrode and an Ag=AgCl reference electrode. [Me4N]ClO4 (TMAP) was
used as the supporting electrolyte. Unless otherwise mentioned, all the
potentials were referenced to Ag=AgCl. The magnetic susceptibility data of
the complexes in the solid state were obtained with a Guoy balance at room
temperature using copper sulfate as the calibrant. The molar conductance
values of the complexes in DMSO solution were measured using a type 305
Systronic conductivity bridge.
Synthesis of Schiff Bases
Salicylidene-4-aminoantipyrinyl-2-aminophenol (H2L1)
Salicylidene-4-aminoantipyrine (3.07 g, 10mmol) in 50mL of ethanol
was refluxed with 2-aminophenol (1.09 g, 10 mmol) for about 2 h. On
cooling, the orange red solid that separated (H2L1) was filtered and
recrystallized from ethanol; yield, 82%, 3.27 g.
Salicylidene-4-aminoantipyrinyl-2-aminothiophenol (H2L2)
An ethanolic solution (50mL) of salicylidene-4-aminoantipyrine
(3.07 g, 10 mmol) was refluxed with 2-aminothiophenol (1.25 g, 10 mmol) for
about 6 h. After refluxing, the volume of the solution was reduced to one
third. On cooling, a dark brown solid separated (H2L2) which was filtered
and recrystallized from ethanol; yield, 56%, 2.31 g.

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RAMAN, KULANDAISAMY, AND JEYASUBRAMANIAN
Synthesis of Complexes
A solution of H2L1 or H2L2 (5 mmol) in ethanol (20mL) was refluxed
with an ethanolic solution (10mL) of MCl 2 (5 mmol) for about 2 h. The
mixture was kept at 0 ꢀC for about 12 h. The solid product so formed was
separated by filtration and washed thoroughly with hot ethanol and then
dried in air.
Biological Screening Activity
Antibacterial Activity
The in vitro biological screening effects of the investigated compounds
were tested against two Gram-positive bacteria, Staphylococcus aureus and
Bacillus subtilis, and four Gram-negative bacteria, Klebsiella pneumoniae,
Salmonella typhi, Pseudomonas aeruginosa and Shigella flexneri, by the disc
diffusion method37,38 using agar nutrient as medium and utilising silver nitrate
as control. The stock solutions were prepared by dissolving the compounds in
acetonitrile and all the blank discs were moistened with the solvent. For disc
assays, paper (6 mm) containing the compounds were placed on the surface of
the nutrient agar plates previously spread with 0.1 ml of overnight cultures of
microorganisms. After 36 h of incubation at 37 ꢀC the diameter of the inhi-
bition zones were measured and are listed in Table VI.
Antifungal Activities
The antifungal activity of the compounds was evaluated by the well
diffusion method38 against the fungi Aspergillus niger and Rhizoctonia batai-
cola cultured on potato dextrose agar as medium. Acetonitrile was used as a
solvent and the drug Amphotericin as control. In a typical procedure a well
was made on the agar medium inoculated with microorganisms. The well was
filled with the test solutions using a micropipette and the plates were incubated
at 35 ꢀC for 72 h. During this period, the test solution was diffused and affected
the growth of the inoculated microorganisms. A zone was developed on the
plate and the inhibition zones were measured and are reported in Table VII.
ACKNOWLEDGMENTS
The authors express their sincere thanks to the University Grants
Commission, New Delhi, for financial support and to Prof. P. R. Athappan,

SCHIFF BASE COMPLEXES
1267
School of Chemistry, Madurai Kamaraj University, for CV facilities. The
authors also thank the Managing Board, Principal and Head of the
Department of Chemistry of Virudhunagar Hindu Nadars’Senthikumara
Nadar College for providing research facilities. K. J. thanks the Manage-
ment and Principal of Mepco Schlenk Engineering College for their support.
REFERENCES
1. Donia, A.M.; El-Saled, F.A. Complexes of Mn(II) and Ni(II) with the
Keto Form of Some Antipyrine Schiff Base Derivatives. Polyhedron
1988, 7, 214972153.
2. Joseph, M.; Nair, K.M.; Radhakrishnan, P.K. Complexes of
Yttrium and Lanthanide Bromides with 4-N-(20Hydroxybenzylidene)-
aminoantipyrine. Synth. React. Inorg. Met.-Org. Chem. 1995, 25 (8),
133171343.
3. Maurya, R.C.; Mishra, D.D.; Trivedi, P.K.; Mukherjee, S.;
Shrivastava, P.K. Synthesis and Characterisation of Some Novel
Penta-Coordinated Mixed-Ligand Derivatives of Zinc(II) Bis(acetyla-
cetone) and Bis(acetoacetanilide) Chelates with 2=3-Pyrazoline-5-one.
Synth. React. Inorg. Met.-Org. Chem. 1992, 22 (4), 4037414.
4. Agarwal, R.K.; Singh, G. Preparation, Spectral and Thermal Studies
of Some Oxovanadium(IV) Complexes of 4-Aminoantipyrine. Synth.
React. Inorg. Met.-Org. Chem. 1986, 16 (8), 118371196.
5. Chopra, J.R.; Uppal, D.; Arrora, U.S.; Gupta, S.K. Synthesis and
Spectral Studies of Cu(II) Complexes of 4[N-(2-Hydroxy-1-naphtha-
lidene)amino]antipyrine. Asian J. Chem. 2000, 12, 127771281.
6. Nair, M.L.H.; Prabhakaran, C.P. Synthesis and Spectral Studies of
Oxomolybdenum(V) and Dioxomolybdenum(VI) Complexes of 1,2-
Dihydro-1,5-dimethyl-2-phenyl-4-(2,4-dihydroxyphenylazo)-3H-pyra-
zol-3-one. Indian J. Chem. 2000, 39 A, 9897992.
7. Radhakrishnan, P.K.; Indrasenan, P.; Nair, C.G.R. Complexes of
Lanthanide Nitrates with 4N-(20-Hydroxybenzylidene)amino-anti-
pyrine. Polyhedron 1984, 3, 67770.
8. Radhakrishnan, P.K. Complexes of Lanthanide Perchlorates with
4-N-(20-Hydroxy-10-naphthylidene)aminoantipyrine. Polyhedron 1986,
5, 9957998.
9. Maurya, R.C.; Mishra, D.D.; Pandey, M.; Shukla, P.; Rathour, R.
Synthesis and Spectral Studies of Octa-Coordinated Dioxour-
anium(VI) Complexes with Some Schiff Bases Derived from 4-Acetyl-
2,3-dimethyl-1-(40-methylphenyl)-3-pyrazoline-5-one and Aromatic
Amines. Synth. React. Inorg. Met.-Org. Chem. 1992, 23 (1), 1617174.

1268
RAMAN, KULANDAISAMY, AND JEYASUBRAMANIAN
10. Ismail, K.Z.; El-Dissouky, A.; Shehada, A.Z. Spectroscopic and
Magnetic Studies on Some Copper(II) Complexes of Antipyrine Schiff
Base Derivatives. Polyhedron 1997 16, 290972916.
11. Agarwal, R.K.; Garg, P.; Agarwal, H.; Chandra, J. Synthesis,
Magneto-spectral and Thermal Studies of Co(II) and Ni(II) Com-
plexes of 4-[N-(N-(4-Dimethylaminobenzylidene)amino]antipyrine.
Synth. React. Inorg. Met.-Org. Chem. 1997, 27 (2) 2517268.
12. Singh, L.; Sharma, A.; Sindhu, S.K. Structure and Bonding of Some
Newly Synthesized Complexes of Lanthanide(III) Complexes of 4[N-p-
Dimethylaminobenzalidene)amino]antipyrine. Asian J. Chem. 1999,
11, 144571450.
13. Agarwal, R.K.; Prakash, J. Synthesis and Chatacterization of Thor-
ium(VI) and Dioxouranium(VI) Complexes of 4-[N(2-Hydroxy-1-
naphthalidene)amino]antipyrine. Polyhedron 1991, 10, 239972403.
14. Singh, L.; Tyagi, N.; Dhaka, N.P.; Sindhu, S.K. Synthesis, Spectral
and Thermal Studies of Some Lanthanide(III) Complexes of 4-[N-
(Benzalidene)amino]antipyrine-thiosemicarbazone. Asian J. Chem.
1999, 11, 50 37508.
15. Shankar, G.; Premkumer, R.R.; Ramalingam, S. K. 4-Aminoanti-
pyrine Schiff Base Complexes of Lanthanide and Uranyl Ions. Poly-
hedron 1986, 5, 991.
16. Kuncheria, B.; Indrasenan, P. Thorium(IV) Nitrate Complexes with
Some Schiff Bases of 4-Aminoantipyrine and Certain Carbonyl
Compounds. Polyhedron 1988, 7, 1437146.
17. Thomas, M.; Nair, K.M.; Radhakrishnan, P.K. Rare Earth Iodide
Complexes of 4-(20,40-Dihydroxyphenylazo)antipyrine. Synth. React.
Inorg. Met.-Org. Chem. 1995, 25 (3), 4717479.
18. Kriza, A.; Reiss, A.; Florea, S.; Caproiu, T. Studies on Complexes of
Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with Schiff Base Derived from
3-Aminodibenzofuran and Salicylaldehyde. J. Indian Chem. Soc. 2000,
77, 20 77208.
19. Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coordination
Compounds; 3rd Edn.; Wiley Interscience: New York, 1977; 2967346.
20. Zamian, J.R.; Dockal, E.R.; Castellano, G.; Oliva, G. Synthesis and
Characterisation of [N,N0-Ethylenebis(3-ethoxysalicylideneaminato]-
oxovanadium(IV). Polyhedron 1995, 14, 241172418.
21. Lever, A.B.P. Inorganic Electronic Spectroscopy; 2nd Edn.; Elsevier:
New York, 1968; 2567265, 3177361.
22. Sharada, L.N.; Ganorkar, M.C. Synthesis and Structural Studies of
VO(IV), Mn(II), Co(II), Ni(II) and Cu(II) Complexes with New Tri-
dentate Schiff Bases having ONO and ONN Donor Systems. Indian J.
Chem. 1988, 2 7 A, 6177621.

SCHIFF BASE COMPLEXES
1269
23. Warad, D.U.; Satish, C.D.; Kulkarni, V.H.; Bajgur, C.S. Synthesis,
Structure and Reactivity of Zr(IV), VO(IV), Co(II), Ni(II) and Cu(II)
Complexes Derived from Carbohydrazide Schiff Base Ligands. Indian
J. Chem. 2000, 39 A, 4157420.
24. Former, R.L.; Urbach, F.L. Stereochemistry and Electronic Structure
of Oxovanadium(IV) Chelates with Tetradentate Schiff Base Ligands
Derived from 1,3-Diamines. Inorg. Chem. 1974, 13, 5877591.
25. Xiu, R. Bu.; Mintz, F.L.; You, X.Z.; Wang, R.X.; Yue, Q.;
Meng, Q.J.; Lu, Y.J.; Derveer, D.V. Synthesis and Characterisation of
Vanadyl Complexes with Unsymmetrical Bis-Schiff Base Ligands
Containing a cis-N2O2 Coordinate Chromophore. Polyhedron 1996,
15, 458574591.
26. Ray, R.K.; Kauffman, G.R. EPR Spectra and Covalency of
Bis(amidinourea=o-alkyl-1-amidinourea)copper(II) Complexes; Part II.
2-
Properties of the CuN4 Chromophore. Inorg. Chim. Acta 1990, 173,
2077214.
27. Jeyasubramanian, K.; Samath, S.A.; Thambidurai, S.; Murugesan, R.;
Ramalingam, S.K. Cyclic Voltammetric and ESR Studies of a Tetraaza
14-Membered Macrocyclic Copper(II) Complex Derived from 3-Sali-
cylideneacetylacetone and o-Phenylenediamine; Stabilization and Acti-
vation of Unusual Oxidation States. Trans. Met. Chem. 1995, 20, 76780.
28. Babu, V.S.; Ramesh, A.; Raghuram, P.; Naidu, R.R. Electron Spin
Resonance Studies on Complexes of Copper(II) with o-Phenolic
Oximes. Polyhedron 1982, 1, 60 77610.
29. Duta, R.L.; Syamal, A. Elements of Magnetochemistry; 2nd Edn.;
East-West Press: New Delhi, 1992, 2067250.
30. Ravinder, V.; Swamy, S.J.; Srihari, S.; Lingaiah, P. Synthesis and
Spectral Studies of Copper(II) Complexes with Amide Group Ligands.
Polyhedron 1985, 4, 151171518.
31. Dodward, S.S.; Dhamnaskar, R.S.; Prabhu, P.S. Electron Spin
Resonance Spectral Studies of Vanadyl Complexes with Some Schiff
Bases. Polyhedron 1989, 8, 174871750.
32. Dutton, K.G.; Fallon, D.; Murray, K.S. Synthesis, Structure, ESR
Spectra and Redox Properties of [N,N0-Ethylenebis-(thiosalicylide-
neaminato)]oxovanadium(IV) and of Related fS; Ng Chelates of
Vanadium(IV). Inorg. Chem. 1988, 27, 34738.
33. Yen, T.F. Electron Spin Resonance of Metal Complexes; 1st Edn.
Plenum Press: New York, 1969; 1117133.
34. Anjaneyula, Y.; Rao, R.P. Preparation, Characterisation and Anti-
microbial Activity Studies on Some Ternary Complexes of Cu(II) with
Acetylacetone and Various Salicylic Acids. Synth. React. Inorg. Met.-
Org. Chem. 1986, 16 (2), 2577272.

1270
RAMAN, KULANDAISAMY, AND JEYASUBRAMANIAN
35. Malhota, R.; Kumar, S.; Dhindsa, K.S. Synthesis, Characterisation and
Microbiocidal Activity of Co(II), Ni(II), Cu(II) and Zn(II) Complexes of
Aryloxyacetic Acid Hydrazides. Indian J. Chem. 1993, 32A , 4577459.
36. Dharmaraj, N.; Viswanathamurthi, P.; Natarajan, K. Ruthenium(II)
Complexes Containing Bidentate Schiff Bases and Their Antifungal
Activity. Trans. Met. Chem. 2001, 26, 10 57109.
37. Pelczar, M.J.; Chan, E.C.S.; Krieg, N.R. Microbiology; 5th Edn.;
Blackwell Science: New York, 1998, 5357537.
38. Kannan, N. Laboratory Manual in General Microbiology; 1st Edn.;
Palani Paramount Publications: Palani, 1996, 1137117.
Received January 17, 2001
Accepted June 7, 2001
Referee I: L. J. Boucher
Referee II: S. M. Socol