Vol. 25, No. 2 (2013)
Synthesis and Spectroscopic Studies of Metal Complexes of Schiff Base 943
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the biological activity of the Schiff base and its metal
complexes with the standard bacteria, it reflects that the metal
complexes have moderate activity as compared to the standard,
but all the complexes are more active than ligand due to
chelation theory. Chelation tends to make the Schiff base to
act as more powerful and potent bacteriostatic agents, thus
inhibiting the growth of bacteria and fungi more than the parent
Schiff base. The enhancement in biocidal activity may be
understood on the basis of their structure that mainly possesses
azomethine linkage. Ligands with nitrogen and oxygen donor
system inhibit enzyme activity, since the enzymes which
require these groups for their activity appear to be especially
more susceptible to deactivation.Actually coordination reduces
the polarity of the metal ion mainly due to the partial sharing
of its positive charge with the donor group within the chelate
ring system formed during coordination. This process, in turn,
increases the biophilic character of the metal, which favours
its permeation more efficiently the lipid layer of the micro-
organism, thus destroying them more aggressively.
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TABLE-3
MINIMUM INHIBITING CONCENTRATION (MIC)
(µg/mL) OF THE COMPOUNDS
Compounds
PAQH
E. coli
40
S. aureus
55
86
75
65
[Co(PAQH)2(NH3)]
[Ni(PAQH)2(NH3)]
[Cu(PAQH)2(NH3)]
95
70
65
Conclusion
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Sinha, S.N. Vidyarathi and V. Singh, Asian J. Chem., 23, 4629 (2011);
B.K. Rai, V. Singh, S.N. Vidyarathi and P. Sinha, Asian J. Chem., 23,
4638 (2011); B.K. Rai and B. Kumar, Asian J. Chem., 23, 4635 (2011);
B.K. Rai and K.K. Sharma, Orient. J. Chem., 27, 143 (2011).
16. A.I. Vogel, Vogel's Text Book of Quantitative Chemical Analysis, Revised
by J. Mendham, R.C. Denny, J.D. Barnes and M. Thomas, Pearson
Education (2008).
The synthesized Schiff base, 2-phenyl-3-(p-aminophenyl)-
4-quinazolone hydrazone (PAQH) acts as uninegative bidentate
ligand. The metal ions are coordinated through the amine and
imine N atoms. The remaining coordination centres are satisfied
by neutral ligands such as ammonia, pyridine, α-picolin, β-
picolin and γ-picolin. All these observations put together lead
us to propose the complexes of Co(II) and Ni(II) to have octa-
hedral geometry whereas geometry of Cu(II) complexes is
proposed distorted octahedral geometry as shown in Fig. 1.
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New York (1963).
H
X
N
R
20. J.A.Wolmsley and S.V.Tyree, Inorg. Chem., 2, 312 (1963); O.N. Sathyanarayn
and C.C. Patel, Indian J. Chem., 5, 360 (1967).
NH2
N
N
21. C.J. Bollhausen, Introduction of Ligand Field Theory, McGraw Hill,
New York, p. 208 (1962).
N
C
N
N
C
M
X
N
NH2
22. C.C. Addison, N. Logan, S.C. Wallwork and D.C. Barner, Quart. Rev.
(1971).
R
N
H
23. A.B.P. Lever, Inorganic Electronics Spectroscopy, ElsevierAmsterdam,
p. 395 ( 1968).
M = Co(II), Ni(II) and Cu(II); X = NH3, C6H5,
α-picoline, β-picoline and γ-picoline; R = Phenyl
24. B.N. Figgis, Introduction to Ligand Field, Wiley Eastern Ltd., New
Delhi, p. 279 (1976).
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Metal Compounds, Springer Verlag, New York (1997).
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Microbiol., 35, 327 (1995).
Fig. 1. Proposed Structure of [M(PAQH)2X2]
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