Synthesis, characterization of metal complexes of schiff base derived from pyrrole-2-carbaldehyde and 4-methoxy aniline and their biological studies

Article abstract of DOI:10.14233/ajchem.2020.22874

The metal complexes of Fe(II), Co(II) and Ni(II) have been synthesized from N-((1H-pyrrol-2-yl)methylene)-4-methoxyaniline. The synthesized Schiff base and its metal complexes were structurally characterized based on IR, NMR, UV-vis spectroscopic techniqu

Full text of DOI:10.14233/ajchem.2020.22874

Asian Journal of Chemistry; Vol. 32, No. 12 (2020), 3012-3018
A
SIAN
J
OURNAL OF HEMISTRY
C
https://doi.org/10.14233/ajchem.2020.22874
Synthesis, Characterization of Metal Complexes of Schiff Base derived from
Pyrrole-2-carbaldehyde and 4-Methoxy Aniline and their Biological Studies
1
2,
3,*
A. CHARLES , R. KRISHNAVENI and K. SIVARAJ
1Research and Development Centre, Bharathiar University, Coimbatore-641046, India
2Saveetha School of Engineering, Saveetha Institute of Medical and Technical Sciences, Thandalam-602105, India
3Department of Chemistry, Tamilavel Umamahesuwaranar Karanthai Arts College, Thanjavur-613002, India
*Corresponding author: E-mail: sivaa25@gmail.com
Received: 27 June 2020;
Accepted: 24 August 2020;
Published online: 7 December 2020;
AJC-20132
The metal complexes of Fe(II), Co(II) and Ni(II) have been synthesized from N-((1H-pyrrol-2-yl)methylene)-4-methoxyaniline. The
synthesized Schiff base and its metal complexes were structurally characterized based on IR, NMR, UV-vis spectroscopic techniques. The
presence of coordinated water molecules were confirmed by thermal studies. All the synthesized compounds were screened for their
antibacterial (Escherichia coli, Bacillus substilis, Salmonella typhi, Staphylococcus epidermis) and antifungal (Aspergillus flavus) and
DNA cleavage activity.
Keywords: Antibacterial, Antifungal, DNA cleavage, Schiff base, Metal complexes, Pyrrole-2-carbaldehyde.
base have also been reported. Such metal complexes are widely
used as a model antibacterial agent due to their growth inhib-
iting activity towards bacteria and fungi [5]. Such heteronuclear
Schiff base complexes have found tremendous applications in
the field of bio-engineering [6]. Organoiron(III) complexes
and copper(II) complexes are widely reported for their enhanced
selectivity and enabled photo-toxicity [7]. In particular, the
coordination chemistry of Schiff base complexes of carbal-
dehyde have attained much attention during the last decade
[8]. Samarium(II) complexes of symmetrical N4 tetradendate
Schiff base ligands are found to be highly stable due to the
introduction of pyrrole ring has been reported [9]. Based on
these findings, this study aims to synthesize and characterize
novel inorganic complexes obtained by the reaction of Fe(II),
Co(II) and Ni(II) salts with N-((1H-pyrrol-2-yl)-methylene)-
4-methoxyaniline. Additionally, antimicrobial and biological
studies were also carried out. With the choice of the metals here,
an effective photophysical investigation of the complexes is
anticipated in future owing to their emitting characteristics [10].
INTRODUCTION
Schiff bases are regarded as “privileged ligands” due to
their capability to form metal complexes with a wide range of
transition metal ions yielding stable and intensely coloured
metal complexes [1]. New materials with interesting properties
like specific sensors, magnetic and optical devices and
molecular wires can be obtained by successful formulation of
compounds with distinctly different metal ion binding sites
within the same ligand [2]. Schiff base metal complexes attract
considerable interest and an important role in the development
of such new materials. The reason is attributed to the chemistry
of chelate systems of Schiff bases, especially those with N2O2
or N4 tetra-dentate ligands, which closely resemble
metalloproteins [3]. Synchronized applications of a wide
variety of Schiff bases with different metal complexes having
such tetradentate donor atoms around the metal ion have been
reported to catalyse reactions such as epoxidation,
hydroformylation, hydroge-nation, electrochemical
investigation and biological studies of proteins as well [4].
Amalgamation of Schiff bases with metallo-elements
(transition metals) enhancing the stability, formation constants
and enhancing the biological activity of synthesized Schiff
EXPERIMENTAL
All the chemicals and reagents used were of analytical grade
and procured from Sisco Research Laboratories, India. Metal
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Vol. 32, No. 12 (2020)
Synthesis, Characterization of Metal Complexes of Schiff Base and their Biological Studies 3013
salts were purchased from E. Merck (India) Ltd. and used as
received. The solvent used were either spectroscopic pure or
purified by the recommended methods.All the apparatus used
during the experimental work were fitted with quick fit inter-
changeable standard ground joints. Melting points were mea-
sured using a capillary melting point apparatus. Shimadzu FT-IR
spectrophotometer and JASCO UV-Vis spectrophotometer were
used for IR and absorption recordings respectively. Emission
studies were done using Perkin-Elmer spectrophotometer.
Thermogravimetry measurements were done with TGA instru-
ment with horizontal balance and furnace temperature was
maintained at 1200 ºC with a heating rate of 5 to 20 ºC/min.
1H NMR spectrometric measurements were done with Bruker
EXT40178, 400 MHz NMR spectrometer using deuterated
acetone as solvent. Mass spectral analysis were done using a
Perkin-Elmer GC-MS mass spectrophotometer. A Vario (EL
III) analyzer was used for elemental analysis.
Synthesis of Schiff base ligand: N-((1H-Pyrrol-2-yl)-
methylene)-4-methoxyaniline (PMMA) was synthesized acco-
rding to reported method [11] (Scheme-I). Condensation of
pyrrole-2-carbaldehyde and 4-methoxy aniline was carried out
in ethanol. The reaction mixture was refluxed for 3-4 h and
allowed to cool. The products were filtered, washed and recry-
stallized from the same solvent and dried. The compound
appeared yellowish brown in colour and had a glittering texture.
The purity of the product was checked by TLC method, yield:
64%, m.p. 239 ºC, m.f. C12H12N2O and m.w. 200.24 (calcd).
The consigned molecular formula and mass were arrived based
on mass spectral analysis in which the molecular ion peaks,
[M+] appeared at m/z = 200.2031 with intensity 80% and [M+1]
peak appeared at 201.2462 with intensity 10%, confirming the
stoichiometry of the ligand.
Synthesis of metal-Schiff base complexes: Fe(II), Co(II)
and Ni(II) complexes with the Schiff base ligand were prepared
by adding of equimolar solution of corresponding metal(II)
salt and the ligand using alcohol as the solvent. The mixture
was maintained under refluxing condition for 4-5 h. On cooling
solid complexes were precipitated, filtered, washed with cold
ethanol and dried in a vacuum desiccator over fused CaCl2. The
yield of the metal complexes was 56, 72 and 64%, respectively.
RESULTS AND DISCUSSION
The reaction of Schiff base ligand (PMMA) with Fe(II),
Co(II) and Ni(II), ions in an equimolar ratio resulted in
[M(PMMA)2(Cl)2] complexes. There was a good agreement
observed between the physical and analytical data with the
proposed composition of Schiff base ligand and its metal(II)
complexes. The newly synthesized complexes were found to
be insoluble in water and organic solvents like DMSO and
DMF, but was very stable in air. They all appeared coloured
and amorphous in nature. The elemental analysis of ligand
and its metal(II) complexes are given in Table-1.
IR studies: FTIR spectrum of the ligand was recorded to
confirm the formation of the ligand moiety. The absence of
any peak around 3200 cm-1 (-NH2) indicated the absence of
any residual starting material methoxy aniline in the compound
[12]. The band due to (C=N) group, which was the link between
the aldehyde and amine molecules appeared at 1616 cm-1, thus
establishing the confirmation of the formation of Schiff base
ligand. The other important observations from IR spectrum
were the peaks at 1029 and 1439 cm-1, which were attributed
to the ν(C-O-C) and ν(Ar-N), respectively.
H C
3
O
Electronic spectroscopic studies: The absorption
spectrum of the ligand synthesized was recorded which evid-
enced the successful formation of the ligand moiety through
the characteristic maximum absorption at 321 nm which is
attributed to π-π* transition of the C=N link.
H C
3
O
O
NMR characterization: The NMR recordings further
confirmed the linkage between the starting materials and proved
the preservence of the structural moiety of the proposed ligand.
The 1H NMR spectrum of the ligand (Fig. 1) showed the signals
of the aromatic protons of aniline between δ 6.6 to 7.2 (double
triplets, 6H), methoxy protons at δ 3.762 ppm (s, 3H), the
new link C-C=N at δ 8.313 (s,1 H) and pyrrole N at δ 11.663
(s, 1H).
-H O
2
NH
N
+
Ethanol
2-3 h reflux
Pyrrole-2-carbaldehyde
NH
2
NH
4-methoxyaniline
N
-((1H
-pyrrol-2-yl)-
methylene)-4-methoxyaniline
(PMMA)
This was strongly supported by the 2D COSY NMR
spectrum (Fig. 2) which shows no cross-coupling of this proton
Scheme-I: Synthesis of PMMA ligand
TABLE-1
ELEMENTAL ANALYSIS OF THE PMMA LIGAND AND ITS METAL COMPLEXES WITH Fe(II), Co(II) AND Ni(II)
Elemental analysis (%): Found (calcd.)
Compound
*PMMA
[Fe(PMMA)2Cl2]·4H2O
[Co(PMMA)2Cl2]·6H2O
[Ni(PMMA)2Cl2]·6H2O
Colour
Yield (%)
m.w.
M
–
C
H
N
Yellowish brown
Reddish brown
Black
64
56
72
64
200.24
527.23
530.32
530.08
71.98 (72.04)
6.04 (6.09)
4.59 (4.61)
4.56 (4.59)
4.56 (4.54)
13.99 (13.92)
10.63 (10.69)
10.57 (10.59)
10.57 (10.54)
10.59 (10.54) 54.68 (54.65)
11.11 (11.06) 54.36 (54.39)
11.07 (11.09) 54.38 (54.40)
Black
*PMMA refers to the ligand-(C12H12N2O).

3014 Charles et al.
Asian J. Chem.
15 14 13 12 11 10
4
3
8.5 8.4 8.3 8.2 8.1 8.0 7.9 7.8 7.7 7.6 7.5 7.4 7.3 7.2 7.1 7.0 6.9 6.8 6.7 6.6 6.5 6.4 6.3 6.2 6.1
ppm
Fig. 1. 1H NMR spectrum of ligand (PMMA). Insets show the signals corresponding to aromatic and methoxy protons
thermic peaks at 95.39 °C and 239.05 °C in the thermal analysis,
which are indicative of dehydration reactions and melting of
the compound respectively and no net chemical reaction occurs
on heating the sample (Table-2). Also the TGA curve shows
the thermal stability of the ligand shows a massive stability as
a solid even at high temperatures (Fig. 3).
ppm
5.5
6.0
6.5
7.0
7.5
8.0
8.5
Electronic spectroscopic studies: The UV-vis spectrum
of Fe(PMMA)2 complex showed three characteristic absorption
maxima as observed at 316, 398 and 645 nm. The peak at 316
nm is the signature peak of the PMMA ligand and the broader
peaks at longer wavelengths are assigned to the n→π*, C-T
transition and d-d transition of the metal, respectively.
The UV-vis absorption spectrum of Co(PMMA)2 complex
also showed a similar behaviour with the peaks occurring at
321, 439 and 651 nm. While in the case of Fe(PMMA)2 Schiff
base complex, here again the peaks were assigned to the π→π*
of the ligand, n→π* charge transfer and d-d transitions of
the metal based complex respectively. Similar peaks correspon-
ding to these transitions were observed at 324,358 and 692
nm for Ni(PMMA)2 complex. The broad band observed at
longer wavelengths for all the three metal complexes are in
accor-dance with crystal field stabilization energy requirements
for an octahedral geometry of metal(II) complexes [13] viz.,
15100, 14534, 14450 cm-1. Thus, octahedral geometry for the
complexes was first designated by the electronic spectra of
the metal complexes which were further supported by present
thermal analyses.
9.0
8.5
8.0
7.5
7.0
6.5
6.0
5.5
ppm
Fig. 2. 2D COSY NMR spectrum of ligand (PMMA)
at C1. The aromatic protons obtained as two triplets at 6.9 and
7.1 δ ppm are attributed to the cross coupling of the two protons
at C2 and C3 positions of the benzene ring as established by
the 2D NMR spectrum.
Thermal analysis: The physical and chemical stability
of the ligand was also checked with DTA and TGA studies,
respectively. The DTA curve of the ligand shows two endo-
TABLE-2
TGA DATA OF M (PMMA)2 SCHIFF BASE COMPLEXES
Mass loss (%)
Calculated
Decomposition
temperature (°C)
Compound
Dissociation stages
Assignment
4H2O, OCH3
C7H8O
C6H6O
Residue
6H2O, C2H5OH, CH3
C6H6O
Residue
OCH3
C12H12N2
C6H7NO
Residue
Found
15.97
15.99
13.92
52.68
24.3
13.86
59.93
4.56
Stage I
Stage II
Stage III
Stage IV
Stage I
Stage II
Stage III
Stage I
100-250
250-540
540-780
Above 780
80-300
300-780
Above 780
60-140
16.52
16.84
13.96
52.73
25.68
14.24
60.11
4.69
[Fe(PMMA)2Cl2]·4H2O
[Co(PMMA)2Cl2]·6H2O
[Ni(PMMA)2Cl2]·6H2O
Stage II
Stage III
Stage IV
140-400
400-780
Above 780
27.13
16.07
52.59
27.95
16.2
51.14

Vol. 32, No. 12 (2020)
Synthesis, Characterization of Metal Complexes of Schiff Base and their Biological Studies 3015
1.0
120
(a)
(b)
100
80
60
40
20
0
239.05 °C
0.1765 °C min/mg
0.8
95.39 °C
0.1857 °C min/mg
265.31 °C
0.6
0.4
99.18%
(1.841 mg)
99.88 °C
0
50
100
150
200
250
300
350
0
50
100
150
200
250
300
350
Exo up
Temperature (°C)
Temperature (°C)
Fig. 3. Thermal analysis of ligand (PMMA) (a) DTA and (b) TGA spectrum
IR studies: The IR absorption spectra of the Schiff base
metal complexes were recorded in order to confirm the func-
tional groups. The peak positions of the prominent functional
groups and links were compared with the peaks of the ligand
and the shifts were also compared as collated in Table-3.
The above comparison emphasizes a negative shift of the
peaks and their change in intensities. This observation is
attributed to the difference in binding modes of the complexes
with reference to the free ligand. Hence, the phenomenon
chelation is predicted in the metal complexes which also may
involve the coordination of donor atoms of the ligand with the
metal ions.
Escherichia coli MTCC 433, Bacillus substilis MTCC 441,
Salmonella typhi MTCC 3224 and Staphylococcus epidermis
ATCC 12228. The procedure followed for carrying out the
biological studies as described earlier [14]. Mueller-Hinton
agar media were used for antibacterial studies. The pure
dehydrated Mueller-Hilton agar (38 g) dissolved in 1000mL
of distilled water. The pure cultures of the bacterial strains E.
coli, B. substilis, S. typhi and S. epidermis were subcultured
by inoculating in the nutrient broth and were incubated at 37
ºC for about 12 h [15]. The above media was used to prepare
the agar plates and wells were dug with a sterile metallic cork
borer 6 mm in diameter. Then 0.1 mL of fresh inoculum
(containing around 1-2 × 106 CFU/mL as per McFarland
standards) was spread onto the surface of sterile Mueller Hinton
agar plates using a sterilized spreader. Then discs impregnated
with crude extract of the complexes (1 mg/disc) and solvent
controls were placed on plates with the help of a sterilized
forceps and the plates were incubated aerobically at 37 ºC.
Similarly a negative solvent control (DMSO) disc were placed
on each pathogen inoculated plates. The entire microbial assay
was carried out under strict aseptic conditions. The zone of
inhibition (mm) of the different metals was examined after
12-18 h. The experiments were done in triplicate and the
average values were calculated for antibacterial activity.
As illustrated, the ligand by itself does not show any
antibacterial activity. But the metal complexes of PMMA were
found to show optimal zones of inhibition. Though the Fe(II)
complex of the ligand was found active only against E. coli
bacteria, the Co(II) complex showed positive results against
all the species tested (Table-4). The activity of the metal
complexes as good antibacterial agents can be explained based
on the chelation theory [16]. The antibacterial action is
1
NMR studies: The H NMR spectrum recorded for the
Fe(PMMA)2 complex (Fig. 4a) revealed the retainment of all
the signals of the ligand except a slight shift in their chemical
shift positions. This is attributed to change in the geometry of
the structure which is expected to complexation with a metal.
The peaks are assigned as methoxy protons at δ 3.824 ppm (s,
3H), aromatic protons between δ 6.6 and 7.4 (m, 6H), Ar-
CH=N at δ 8.55 (s, 1H) and pyrrole N-H at δ 9.5 (s, 1H) ppm.
Similar behaviour was also observed with Co(PMMA)2
complex (Fig. 4b). The peak assignments were methoxy protons
at δ 3.83 (s, 3H), aromatic protons between δ 6.27 and 7.6 ppm
(m, 6H), Ar-CH=N at δ 8.597 (s, 1H) and pyrrole N-H at δ
9.569 (s, 1H) ppm. The 1H NMR spectrum of Ni(PMMA)2 is
as shown in Fig. 4c.The peaks obtained were assigned as methoxy
protons at δ 3.833 (s, 3H), aromatic protons between δ 6.32
and 7.45 ppm (m, 6H),Ar-CH=N at δ 8.601 (s, 1H) and pyrrole
N-H at δ 9.55 (s, 1H) ppm.
Antibacterial activity: The in vitro antimicrobial activity
of the synthesized Schiff base ligand PMMA and its metal(II)
complexes were assayed with bacterial pathogens namely
TABLE-3
IR FREQUENCIES OF THE SCHIFF BASE (PMMA) AND ITS METAL COMPLEXES
Compound
ν(C=N)
1616
1597
1602
1597
ν(C–O–C)
1029
1028
1026
1026
ν(Ar–N)
1439
1465
1504
1506
ν(para sub.arene)
ν(M–N)
_
543
527
545
PMMA
829
823
827
827
[Fe(PMMA)2Cl2]·6H2O
[Co(PMMA)2Cl2]·6H2O
[Ni(PMMA)2Cl2]·6H2O

3016 Charles et al.
Asian J. Chem.
TABLE-4
ANTIBACTERIAL ACTIVITY SCHIFF BASE (PMMA) AND ITS METAL COMPLEXES AGAINST HUMAN PATHOGENIC BACTERIA
Pathogens
[Fe(PMMA)2]Cl2·4H2O
[Co(PMMA)2]Cl2·6H2O
[Ni(PMMA)2]Cl2·6H2O
PMMA
E. coli
Bacillus subtilis
Staphylococcus epidermis
Salmonella typhi
0.6
–
–
0.9
3.0
2.5
2.0
1.1
–
–
–
–
–
–
–
–
Values are (Mean S.D); Zone of Inhibition in mm
attributed to the principle that the positive charge of the metal
is shared with the donor atoms of the ligand. This kind of
sharing becomes possible due to the chelate structure formed
between the ligand having a C=N bond and a metal possessing
d-electrons which results in an overall delocalization of π-
electrons over the entire chelate [17]. Such an electron delocali-
zation eventually enhances the lipophilic nature of the metal
chelate and favours its permeation through the lipid layer of
the bacterial membranes hence acting as promising bactericides.
The studies revealed that Fe(II) complexes are more active as
antifungal agents than Co(II) and Ni(II) complexes.
(a)
Antifungal activity: For the synthesized PMMA ligand
and its metal(II) complexes, minimum inhibitory concentration
was determined in nutrient agar plate by micro dilution method,
procedures followed being in accordance to the National
Committee for Clinical Laboratory Standards [18]. The stand-
ardized suspension of test organisms (0.1 mL, 106 cfu/mL)
and synthesized Schiff base ligand (PMMA) and its metal(II)
complexes in different dilutions were taken with Aspergillus
flavus as positive control for bacterial and fungal strains,
respectively. The bacterial tubes were incubated at 37 ºC for
18 h and fungal tubes were incubated at 32 ºC for 48 h.
Among the synthesized metal(II) complexes, it is found
that Co(II) complex are more active in antibacterial activities
while Fe(II) complex in antifungal activities (Table-5). The
difference in antimicrobial functions of the individual metal
complexes with respect to various biological samples may be
attributed to the difference in solubility, environmental condi-
tions, nature of the species, etc.
15 14 13 12 11 10 9
8 7 6 5 4 3 2 1 0 -1 -2
ppm
(b)
9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5
TABLE-5
ASSAY OF ANTIFUNGAL ACTIVITY (Aspergillus flavus)
Zone of inhibition
(mm in diameter)
Sample
Schiff base (PMMA)
–
16
–
–
14
–
[Fe(PMMA)2]Cl2·4H2O
[Co(PMMA)2]Cl2·2H2O
[Ni(PMMA)2]Cl2·2H2O
Amphotericin B (100 Units/Discs) (Std.)
Control
(c)
DNA cleavage activity: The method of electrophoresis
in a gel medium is used to carry out the study. The DNA cleavage
of super coiled pBR322 DNA promoted by the synthesized
metal(II) complexes was analyzed using agarose gel electro-
phoresis method [19,20]. The interaction of supercoiled plasmid
DNA (pBR322 DNA) with the newly synthesized ligand PMMA
and its metal(II) complexes are shown in Fig. 5. Ethidium
bromide was used as the stock solution. The forms I, II, III
15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
Fig. 4. 1H NMR spectrum of (a) Fe(PMMA)2 (b) Co(PMMA)2 (c) Ni(PMMA)2
Schiff base complexes

Vol. 32, No. 12 (2020)
Synthesis, Characterization of Metal Complexes of Schiff Base and their Biological Studies 3017
1
2
3
4
1
2
3
4
(a)
(b)
Form II
Form III
Form II
Form III
Form I
Form I
Lane 1 – PUC18 DNA – Control
Lane 2 – DNA + H2O2 (1 mM)
Lane 3 – DNA + H2O2 (1 mM) + Fe (30 µM)
Lane 4 – DNA + H2O2 (1 mM) + Fe (40 µM)
Lane 1 – PUC18 DNA – Control
Lane 2 – DNA + H2O2 (1 mM)
Lane 3 – DNA + H2O2 (1 mM) + SB (30 µM)
Lane 4 – DNA + H2O2 (1 mM) + SB (40 µM)
1
2
3
4
1
2
3
4
(d)
(c)
Form II
Form III
Form II
Form III
Form I
Form I
Lane 1 – PUC18 DNA – Control
Lane 2 – DNA + H2O2 (1 mM)
Lane 1 – PUC18 DNA – Control
Lane 2 – DNA + H2O2 (1 mM)
Lane 3 – DNA + H2O2 (1 mM) + Co (30 µM)
Lane 4 – DNA + H2O2 (1 mM) + Co (40 µM)
Lane 3 – DNA + H2O2 (1 mM) + Ni (30 µM)
Lane 4 – DNA + H2O2 (1 mM) + Ni (40 µM)
Fig. 5. DNA cleavage on plasmid pBR322: (a) PMMA (b) Fe(PMMA)2 (c) Co(PMMA)2 (d) Ni(PMMA)2 complex
observed in the photoactivated image reveals the cleavage of
the pBR322 DNA supercoiled strand. This is observed in the
presence of PMMA ligand and all the synthesized metal(II)
complexes. This indicates that the ligand and its metal(II)
complexes have acted on DNA because of a difference in mole-
cular weight between the control and the treated DNA samples.
This reveals the influence of the newly synthesized complexes
as good pathogenic microorganism inhibitor.
antibacterial material. The complexes also showed an optimal
efficiency for DNA cleavage function. Hence, the complexes
studies are expected to have a profound scope towards anti-
cancer studies.
CONFLICT OF INTEREST
The authors declare that there is no conflict of interests
regarding the publication of this article.
Conclusion
REFERENCES
The present work focuses on the synthesis, characteriza-
tion and biological studies of Schiff base complexes of Fe(II),
Co(II) and Ni(II) the synthesized complexes were characterized
by UV-vis, IR, NMR, mass spectroscopic techniques. Thermal
analyses were also carried out to ensure the composition of
the metal complexes. The ligand and its metal complexes were
tested for their antimicrobial functions and found to be
successful. The antimicrobial function of the complexes against
pathogenic organisms (Escherichia coli, Bacillus substilis,
Salmonella typhi, Staphylococcus and Aspergillus flavus) by
measuring the zones of inhibition indicated the enhanced
antimicrobial activity of the complexes over the controls used.
A comparison of antimicrobial sensitivity of the complexes
revealed that Fe(II) complex was found to be more active as
an antifungal whereas Co(II) complex was more active as an
1. S. Chandra, S. Parmar andY. Kumar, Bioinorg Chem. Appl., 2009, 851316
(2009);
https://doi.org/10.1155/2009/851316
2. H.M. Parekh and M.N. Patel, Russ. J. Coord. Chem., 32, 431 (2006);
https://doi.org/10.1134/S1070328406060066
3. Z.H.A. El-Wahab and M.R. El-Sarrag, Spectrochim. Acta A Mol.
Biomol. Spectrosc., 60, 271 (2004);
https://doi.org/10.1016/S1386-1425(03)00216-6
4. F. Firdaus, K. Fatma, M. Azam and M. Shakir, J. Coord. Chem., 63,
3956 (2010);
https://doi.org/10.1080/00958972.2010.526707
5. H. Keypour, M. Shayesteh, M. Rezaeivala, F. Chalabian, Y. Elerman
and O. Buyukgungor, J. Mol. Struct., 1032, 62 (2013);
https://doi.org/10.1016/j.molstruc.2012.07.056
6. E. Abele, Main Group Met. Chem., 28, 45 (2005);
https://doi.org/10.1515/MGMC.2005.28.2.45

3018 Charles et al.
Asian J. Chem.
7. U. Basu, I. Pant, A. Hussain, P. Kondaiah and A.R. Chakravarty, Inorg.
Chem., 54, 3748 (2015);
15. N.G. Yernale and M.B. Hire Mathada, Bioinorg. Chem. Appl., 2014,
314963 (2014);
https://doi.org/10.1021/ic5027625
https://doi.org/10.1155/2014/314963
8. C.M. Alvarez, R. Garcia-Rodriguez and D. Miguel, Dalton Trans., 32,
3546 (2007);
16. A.K. Sharma and S. Chandra, Spectrochim. Acta A Mol. Biomol.
Spectrosc., 78, 337 (2011);
https://doi.org/10.1039/b702418e
https://doi.org/10.1016/j.saa.2010.10.017
9. C.D. Berube, S. Gambarotta, G.P.A.Yap and P.G. Cozzi, Organometallics,
22, 434 (2003);
17. Z.H. Chohan, M. Arif, M.A. Akhtar and C.T. Supuran, Bioinorg. Chem.
Appl., 2006, 83131 (2006);
https://doi.org/10.1021/om020773r
https://doi.org/10.1155/BCA/2006/83131
10. T. Kawamoto, M. Nishiwaki, Y. Tsunekawa, K. Nozaki and T. Konno,
Inorg. Chem., 47, 3095 (2008);
18. R.L. Londonkar, U. Madire Kattegouga, K. Shivsharanappa and J.V.
Hanchinalmath, J. Pharm. Res., 6, 280 (2013);
https://doi.org/10.1016/j.jopr.2013.02.010
https://doi.org/10.1021/ic7020758
11. S. Chandra and P. Ballabh, Int. J. Pharm. Sci. Res., 4, 2393 (2013);
https://doi.org/10.13040/IJPSR.0975-8232.4(6).2393-99
12. R.B. Xu, N. Zhang, H.Y. Zhou, S.P. Yang, Y.Y. Li, D.H. Shi, W.X. Ma
and X.X. Xu, J. Chem. Crystallogr., 42, 928 (2012);
https://doi.org/10.1007/s10870-012-0338-1
19. NCCLS (National Committee for Clinical Laboratory Standards),
Performance Standards for Antimicrobial Disc Susceptibility Test,
Approved Standard M2-A6, NCCLS, Wayne, PA, USA, edn 6 (1997).
20. A. Sitlani, E.C. Long, A.M. Pyle and J.K. Barton, J. Am. Chem. Soc.,
114, 2303 (1992);
13. B. Lakshmi, K.N. Shivananda, G.A. Prakash, K.R.K. Rama and K.N.
Mahendra, Bull. Korean Chem. Soc., 32, 1613 (2011);
https://doi.org/10.5012/bkcs.2011.32.5.1613
https://doi.org/10.1021/ja00033a003
14. A.W. Bauer, W.M.M. Kirby, J.C. Sherris and M. Turck, Am. J. Clin.
Pathol., 45(4_ts), 493 (1966);
https://doi.org/10.1093/ajcp/45.4_ts.493