Synthesis, spectral and antimicrobial studies of some Co(II), Ni(II) and Cu(II) Complexes containing 2-thiophenecarboxaldehyde moiety

Article abstract of DOI:10.1155/2012/585827

Some new Schiff base metal complexes of Co(II), Ni(II) and Cu(II) derived from 3-chloro-4-fluoroaniline (HL¹) and 4-fluoroaniline (HL ²) with 2-thiophenecarboxaldehyde have been synthesized and characterized by elemental analysis, FT

Full text of DOI:10.1155/2012/585827

ISSN: 0973-4945; CODEN ECJHAO
E-Journal of Chemistry
http://www.ejchem.net
2012, 9(3), 1113-1121
Synthesis, Spectral and Antimicrobial Studies of some
Co(II), Ni(II) and Cu(II) Complexes Containing 2-
Thiophenecarboxaldehyde Moiety
A. P. MISHRA, A. TIWARI, S. K. GUPTA, and RAJENDRA JAIN*
Synthetic Inorganic & Coordination Chemistry Laboratories
Department of Chemistry, Dr. H. S. Gour Central University, Sagar (M.P.)-470 003, India
jainrajchem@gmail.com
rajendrajain85@rediffmail.com
Received 26 September 2011; Accepted 8 November 2011
Abstract: Some new Schiff base metal complexes of Co(II), Ni(II) and Cu(II)
derived from 3-chloro-4-fluoroaniline (HL1) and 4-fluoroaniline (HL2) with 2-
thiophenecarboxaldehyde have been synthesized and characterized by
elemental analysis, FT-IR, FAB-mass, molar conductance, electronic spectra,
ESR and magnetic susceptibility. The complexes exhibit coordination number
4 or 6. The complexes are colored and stable in air. Analytical data revealed
that all the complexes exhibited 1:2 (metal: ligand) ratio. FAB-mass data show
degradation pattern of the complexes. The Schiff base and metal complexes
show a good activity against the bacteria; B. subtilis, E. coli and S. aureus and
fungi A. niger, A. flavus and C. albicans. The antimicrobial results also
indicate that the metal complexes are better antimicrobial agents as compared
to the Schiff bases.
Keywords: 2-Thiophenecarboxaldehyde, N, S donor, biological activity.
Introduction
Schiff base ligands have been widely studied in the field of coordination chemistry mainly
due to their facile syntheses, easily availability, electronic properties and good solubility in
common solvents. Transition metal complexes containing the Schiff base ligands have been
of interest for many years because the transition metal complexes play a central role in the
conduction of molecular materials, which display unusual conducting, magnetic, thermal
properties and find applicability in material chemistry and biochemistry1-3. A Transition
metal complexes which usually contain nitrogen, sulphur/or oxygen as ligand atoms are
becoming increasingly important because these Schiff base can bind with different metal
centers involving various coordination sites and allow successful synthesis of metallic

1114 RAJENDRA JAIN
complexes with interesting stereochemistry. Heterocyclic compounds are widely distributed
in the nature and essential to many biochemicals, analytical and industrial processes.
Compounds containing these heterocycles have important properties in the field of material
science and biological systems4-7.
Experimental
Melting points were taken in open glass capillaries and are uncorrected. Progress of reaction
was monitored by silica gel-G coated TLC plates using MeOH:CHCl3 system (1:9). The spot
was visualized by exposing dry plate at iodine vapours chamber. All the used chemicals and
solvents were of Anal R grade. All the reagents used for the preparation of the Schiff bases
were obtained from Sigma Aldrich. Metal salts were purchased from Loba Chemie.
Elemental analyses were performed on an Elemental Vario EL III Carlo Erba 1108 analyzer.
FAB-mass spectra were recorded on a JEOL SX 102/DA 6000 Mass Spectrometer using
argon/xenon (6 kV, 10 mA) as the FAB gas. The accelerating voltage was 10 kV and the
spectra were recorded at room temperature. Electronic spectra (in DMSO) were recorded on
Perkin Elmer Lambda-2B-spectrophotometer. Molar conductance measurements were
conducted using 10-3 M solutions of the complexes in DMSO on Elico-CM 82 Conductivity
Bridge at room temperature. Magnetic susceptibility measurements were carried out on a
Gouy balance at room temperature using mercuric tetrathiocyanatocobaltate(II) as the
calibrant. FT-IR spectra were recorded in KBr medium on a Perkin Elmer RX1
spectrophotometer in wave number region 4000-400 cm-1. X-band EPR spectra were
recorded on a Varian E-112 spectrometer using TCNE as the internal standard.
Synthesis of Schiff bases
The Schiff bases (HL1 and HL2) have been synthesized by adding the methanolic solution of
3-chloro-4-fluoroaniline and 4-fluoroaniline with methanolic solution of 2-
thiophenecarboxaldehyde in equimolar ratio. The reaction mixture was then refluxed on
water bath for about 4-6 hours. The condensation product was filtered, thoroughly washed
with ethanol and ether, recrystallized and dried in vacuo. The Purity of the synthesized
compound was monitored by TLC using silica gel G (Yield: HL1 - 78%; HL2 – 82%).
HL1
HL2
Preparation of Schiff Base Metal Complexes
The metal complexes have been prepared by mixing the methanolic solution of CoCl2.6H2O,
NiCl2.6H2O and CuCl2.2H2O to the methanolic solution of Schiff bases (HL1 and HL2) in

Synthesis, Spectral and Antimicrobial Studies of some Co(II), Ni(II) and Cu(II) 1115
1:2 molar ratio. The resulting mixture was then refluxed on water bath for about 5-8 hours.
A colored product appeared on standing and cooling the above solution. The complex was
filtered, washed with ether and dried under reduced pressure over anhydrous CaCl2 in a
desiccator. It was further dried in an electric oven at 50-70°C.
Biological activity
The in-vitro biological activity of the investigated Schiff base and its metal complexes was
tested against the bacteria B. subtilis, E. coli and S. aureus by disc diffusion method using
nutrient agar as medium and streptomycin as control. The antifungal activities of the
compounds were also tested by the Well diffusion method against the fungi A. niger, A.
flavus and C. albicans, on potato dextrose agar as the medium and Griseofulvin as control.
The stock solution was prepared by dissolving the compounds in DMSO. In a typical
procedure, a well was made on agar medium inoculated with microorganism. The well was
filled with the test solution using a micropipette and the plate was incubated 24 h for
bacteria at 37 °C and 72 h for fungi at 30 °C. During this period, the test solution diffused
and the growth of the inoculated microorganism was affected. The inhibition zone was
developed, at which the concentration was noted.
Results and Discussion
All the metal complexes are colored, solid and stable towards air and moisture at room
temperature. They decompose on heating at high temperature, more or less soluble in
common organic solvents. Analytical data of the compounds, together with their physical
properties are consistent with proposed molecular formula are given in Table 1. All the
metal chelates have 1:2 (metal:ligand) stoichiometry. The molar conductance in DMSO of
the complexes are 129.2, 49.5 and 56.2 Scm2mol-1 respectively, for Co(II), Ni(II) and Cu(II)
complexes of HL1. This indicates the Co(II) complex is electrolytic nature while Ni(II) and
Cu(II) complexes are non-electrolytic nature. The molar conductance values for Co(II),
Ni(II) and Cu(II) complexes of HL2 are 120.1, 39.6 and 46.5 Scm2mol-1 respectively. This
indicates the nature of Co(II) as electrolytic and Ni(II) and Cu(II) complex are non-
electrolytic.
FAB-mass spectrum
The FAB-mass spectra suggested that all the complexes have a monomeric nature. These
complexes show molecular ion peaks in good agreement with the empirical formula
suggested by elemental analyses.
The FAB mass spectrum gives additional information about the analyzed species. The
FAB mass spectrum of [Co(HL1)2]Cl2.3H2O shows a molecular ion peak (M+) at m/z 663
amu which suggests the monomeric nature of the complex thus confirming the proposed
formula. The spectrum of complex shows a series of peak at 643, 608, 542, 375, 279 and
105 corresponding to various fragments. The value of 105 corresponds to Co with N donor S
as ligand moiety. The FAB mass spectra of [Ni(HL1)2Cl2].2H2O shows a molecular ion peak
(M+) at m/z, 648 confirm the proposed formula. The spectrum of complex also shows a

1116 RAJENDRA JAIN
series of peak 611, 543, 470, 375, 278 and 107 corresponding to various fragments. Their
intensity gives an idea of stability of the fragments8, 9
.
Table 1. Analytical and Physical Data of Ligand and its Metal Complexes.
Molcular formula/
Mol. Wt./(Colour)
C11H7NClFS [HL1]
240 (Light Yellow)
[Co(C11H7NClFS)2]Cl2.3H2O
664 (Bitter almond)
[Ni(C11H7NClFS)2Cl2].2H2O
646 (Green)
Yield Elemental Analysis Found/Calcd. (%)
*Λm
(%)
78
C
H
N
M
54.54
2.89
5.78
-
-
(55.00) (2.91) (5.83)
39.81 3.01 4.02
(39.75) (3.01) (4.21)
40.74 3.04 4.32
8.88
65
63
68
82
68
72
70
129.2
49.5
56.2
-
(8.87)
9.03
(40.86) (3.09) (4..33) (9.06)
[Cu(C11H7NClFS)2Cl2]
614 (Black)
42.64
(42.99) (2.28) (4.56)
64.39 3.90 6.82
(64.42) (3.95) (6.88)
45.83 3.47 4.86
(45.75) (3.46) (4.85)
45.83 3.47 10.16
2.26
4.52
10.26
(10.34)
(C11H8NFS) [HL2]
205 (Black)
-
[Co(C11H8NFS)]Cl2.2H2O
576 (Green)
10.23
(10.21)
10.16
120.1
39.6
46.5
[Ni(C11H8NFS)Cl2].2H2O
576 (Green)
(45.75) (3.46) (10.14) (10.14)
[Cu(C11H8NFS)Cl2].2H2O
580 (Black)
45.50
3.41
4.79
6.22
(45.52) (3.45) (4.81)
(6.29)
*Conductance (Λm) = Scm2mol-1.
The FAB mass spectrum gives additional structural information about the analyzed species.
The FAB mass spectrum of [Cu(HL2)2Cl2].2H2O complex shows a molecular ion peak (M+)
m/z =580 amu, which suggest the monomeric nature of the complex. The spectrum of the
complex also shows a series of peaks corresponding to various fragments 541, 469, 434,
354, 280 and 107. Their intensity gives an idea about stability of the fragments8,9.

Synthesis, Spectral and Antimicrobial Studies of some Co(II), Ni(II) and Cu(II) 1117
IR spectra
The data of the IR spectra of Schiff base ligand and its metal complexes are listed in Table
2. The IR spectra of the complexes were compared with those of the free ligand in order to
determine the involvement of coordination sites in chelation. Characteristic peaks in the
spectra of the ligand and complexes were considered and compared.
The IR spectra of HL1 ligand exhibits a strong band at 1630 cm-1 due to ν(C=N)
azomethine group. This band shifts to lower energy region by 20-27 cm-1 in the complexes.
It suggests bonding through azomethine nitrogen. A strong band was observed at 848 cm-1,
assignable to ν(C-S-C) of thiophene. The band position of ν(C-S-C) has shifted to lower side
by 18-28 cm-1 in the complexes on coordination of metal ions with sulphur of thiophene.
The appearance of broad band around 3313, 3328 and 3350 cm-1 in the spectra of complexes
have been assigned to associated water molecule. In all complexes new bands at 490 ±8 cm-1
and 404±2 cm-1 are due to the formation of ν(M-N) and ν(M-S) bands respectively. The IR
spectrum of HL2 Schiff base shows a strong band at 1626 cm-1 due to ν(C=N) azomethine
group. On the chelation with metal ion, it has shifted down (11-38 cm-1) due to coordination
of the azomethine nitrogen to the central metal ion. Thiophene ring ν(C-S-C) shows
absorption band at 842 cm-1 in the Schiff base spectrum. This band shows lower shift by 24-
27 cm-1 in all complexes suggesting participation of thiophene ν(C-S-C) sulphur in
coordination. The appearance of broad band at 3397, 3387 and 3368 cm-1 in complexes have
been assigned to ν(OH) water molecules10-16
.
The IR data of both the Schiff base and its metal complexes show that the Schiff bases
(HL1 and HL2) is coordinated to the metal ion in bidentate manner with SN donor sites of
thiophene sulphur and azomethine nitrogen.
Electronic spectra and magnetic moment
The electronic spectral data of the metal complexes in DMSO solution are given in Table 3.
The nature of the ligand field around the metal ion has been deduced from the electronic
spectra.
The electronic spectrum of Co(II) complex of HL1 shows two bands of appreciable
intensity at 15503 cm-1 and 20125 cm-1 which have tentatively been assigned to 4A2→4T1(F)
(ν2) and 4A2→4T1(P) (ν3) transitions. The magnetic moment is 4.35 B.M. Thus the
tetrahedral geometry has been suggested for this complex. The electronic spectrum of Ni(II)
complex of HL1, shows three bands at 11070 cm-1, 18816 cm-1 and 24125 cm-1 corresponding
to transition 3A2g(F)→3T2g(F) (ν1), 3A2g(F)→3T1g(F) (ν2), 3A2g(F)→3T2g(P) (ν3) respectively. The
magnetic moment is 3.19 B.M. These findings are in favor of an octahedral geometry for the
Ni(II) complex. For Cu(II) complex of HL1, a single broad band at 13320 cm-1 has been
observed, this attributes to 2Eg→2T2g transition. Its magnetic moment is 1.85 B.M. Thus the
octahedral geometry has been suggested for complex. The electronic spectrum of Co(II)
complex of HL2 shows two bands of appreciable intensity at 12360 cm-1 and 19806 cm-1
which have tentatively been assigned to 4A2→4T1(F) (ν2) and 4A2→4T1(P) (ν3) transitions.
The magnetic moment is 4.67 B.M. Thus, the tetrahedral geometry has been suggested for
this complex. The electronic spectrum of Ni(II) complex of HL2 exhibits three bands at
11220 cm-1 and 20212 cm-1 and 23645 cm-1 which are assignable to 3A2g(F)→3T2g(F) (ν1),
3A2g(F)→3T1g(F) (ν2) and 3A2g(F)→3T1g(P) (ν3) transition respectively. The magnetic

1118 RAJENDRA JAIN
moment is 3.14 B.M. These findings are in favour of an octahedral geometry for the Ni(II)
complex. In the Cu(II) complex of HL2 a single broad band at 16750 cm-1 has been observed,
this attributes to 2Eg→2T2g transition. Its magnetic moment is 1.94 B.M. Thus the octahedral
geometry has been suggested for complex17-21
.
Table 2. IR bands of Schiff base ligands and their complexes.
Compound
υ(C=N)
1630
υ(C-S-C)
υ(H2O)
υ(M-N) υ(M-S)
[HL1]
848
-
-
-
[Co(HL1)2]Cl2.3H2O
1603
820
3350
486
402
[Ni(HL1)2Cl2].2H2O
[Cu(HL1)2Cl2]
1608
1610
830
825
3313
-
490
488
408
410
[HL2]
1626
1600
842
816
-
-
-
[Co(HL2)]Cl2.2H2O
3397
488
410
[Ni(HL2)Cl2].2H2O
[Cu(HL2)Cl2].2H2O
1598
1605
818
815
3387
3368
485
482
408
406
ESR spectra
The ESR spectra of Cu(II) provide information about the extent of the delocalization of
unpaired electron. The X-band ESR spectra of Cu(II) complexes were recorded in the solid
state at room temperature, their g║, g┴, Δg, gav, G have been calculated. The values of ESR
parameters g║, g┴, gav, Δg, G for Cu(II) complex of HL1 are 2.1775, 2.0977, 2.1030, 0.0526
and 1.83 respectively. Similarly, the corresponding values for Cu(II) complex of HL2 are
2.2454, 2.0665, 2.1048, 0.7254 and 3.77 respectively.
ESR spectra of the complexes revealed two g values (g║ and g┴). Since the g║ and g┴
values are closer to 2 and g║>g┴ suggesting a tetragonal distortion around the Cu(II) ion. The
2
trend g║ >g┴>ge(2.0023) shows that the unpaired electron is localized in dX -Y2 orbital in the
ground state of Cu(II), spectra are characteristic of axial symmetry. The g║>2.3 is
characteristic of an ionic environment and g║<2.3 indicates a covalent environment in metal
ligand bonding. The g║ values for these complexes are less than 2.3 suggesting the
environment is covalent. The exchange coupling interaction between two Cu(II) ions is
explained by Hathaway expression G = (g║-2.0023)/ (g┴-2.0023). According to Hathaway, if
the value G is greater than four (G>4.0), the exchange interaction is negligible; whereas
when the value of G is less than four (G<4) a considerable exchange coupling is present in
solid complex. The G values for these Cu(II) complexes are less than four indicate,
considerable exchange interaction in the complexes22,23
.

Synthesis, Spectral and Antimicrobial Studies of some Co(II), Ni(II) and Cu(II) 1119
Antimicrobial activities
The bactericidal and fungicidal investigation data of the compounds are summarized in
Tables 5 and 6. The results of the investigations account for the antipathogenic behavior of
the compounds and this efficacy is positively modified on complexation. Overtone’s
Concept and Chelation Theory explain well this drug action24-26
.
Table 3. In-vitro antibacterial activity of compounds and their inhibition zone (%).
Antibacterial activity Antifungal activity
B. subtilis
E. coli
S. aureus
A. niger
A. flavus
C.albicans
Compound
50 100 50 100 50 100 50 100 50 100 50 100
pp
m
pp
m
pp
m
pp
m
pp
m
pp
m
pp
m
pp
m
pp
m
pp
m
pp
m
pp
m
HL1
10
23
25
22
15
22
20
24
21
34
33
30
21
35
35
36
14
22
20
22
12
19
20
21
20
30
31
29
20
25
33
34
13
19
18
19
18
22
22
20
20
30
32
31
24
33
32
35
10
20
21
20
15
18
19
20
19
30
31
32
23
31
30
32
15
22
20
22
14
20
18
17
21
32
31
31
22
33
32
34
12
18
15
18
10
12
22
20
18
32
31
31
22
34
33
35
Co(II)
Ni(II)
Cu(II)
HL2
Co(II)
Ni(II)
Cu(II)
Streptomyc
in
28
-
37
-
26
-
34
-
27
-
35
-
-
-
-
-
-
-
Griseofulvi
n
22
32
20
35
24
36
Conclusion
In the present research studies, our successful efforts are synthesized of some newly
compounds. These synthesized compounds Characterized by various physicochemical and
spectral analyses. The synthesized Schiff base ligands bind with the metal ions in a bidentate
manner, with SN donor sites of thiophene-S and azomethine-N. FAB-mass shows

1120 RAJENDRA JAIN
degradation pattern of the complexes. The antimicrobial data show that the metal complexes
to be more biological active compared to those parent Schiff base ligand against all
phathogenic species. The compounds also inhibit the growth of fungi and bacteria to a
greater extent as the concentration is increased.
Acknowledgement
We are thankful to I.I.T. Mumbai for ESR analysis. We also acknowledge SAIF, CDRI
Lucknow for micro analysis and spectral analyses. Thanks are also due to the Head,
Department of Chemistry, Botany and Physics, Dr. Hari Singh Gour University, Sagar
(M.P.) for providing Laboratory facilities.
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