Synthesis, characterization and antimicrobial screening of Co(II), Ni(II), Cu(II), Mn(II) and Zn(II) complexes with schiff base derived from 2-sulphanilamidopyridine and 2-Hydroxy-3-methoxybenzaldehyde

Article abstract of DOI:10.14233/ajchem.2013.13322

The Schiff base derived from 2-sulphanilamidopyridine and 2-hydroxy-3-methoxy benzaldehyde and its metal complexes have been synthesized and characterised by IR, 1H NMR, UV, elemental analysis, molar conductance and magnetic susceptibility. The Schiff bas

Full text of DOI:10.14233/ajchem.2013.13322

Asian Journal of Chemistry; Vol. 25, No. 4 (2013), 2077-2079
http://dx.doi.org/10.14233/ajchem.2013.13322
Synthesis, Characterization and Antimicrobial Screening of Co(II), Ni(II),
Cu(II), Mn(II) and Zn(II) Complexes with Schiff Base Derived from
2-Sulphanilamidopyridine and 2-Hydroxy-3-methoxybenzaldehyde
*
G. VALARMATHY and R. SUBBALAKSHMI
Post Graduate and Research Department of Chemistry, Seethalakshmi Ramaswami College, Tiruchirappalli-620 002, India
*Corresponding author: E-mail: valarchola@gmail.com; subhavijay2008@g.mail.com
(Received: 23 December 2011;
Accepted: 12 October 2012)
AJC-12283
The Schiff base derived from 2-sulphanilamidopyridine and 2-hydroxy-3-methoxy benzaldehyde and its metal complexes have been
synthesized and characterised by IR, 1H NMR, UV, elemental analysis, molar conductance and magnetic susceptibility. The Schiff base
ligand and the metal complexes were screened for antimicrobial activity by disc diffusion technique. From the analytical and spectral data,
the stoichiometry has been found to be 1:2 for all the metal complexes. An octahedral structure has been proposed. All these metal
complexes were found to be active against bacteria and fungi.
Key Words: Schiff base, 2-Sulphanilamidopyridine, 2-Hydroxy-3-methoxybenzaldehyde, Metal complexes, Biological activity.
synthesis of homo and hetero metallic complexes with varied
stereochemistry11.
INTRODUCTION
Sulpha drugs are chemotherapeutic agents whose molecular
structures contain a sulfanilamide (4-amino benzenesulfonamide)
moiety. The antibacterial activity of these drugs is believed
from the structural resemblance between sulfanilamide group
and p-aminobenzoic acid where the sulpha drug mimics this
metabolite and blocks folic acid synthesis in bacteria, there
by causing cell death1. The direct use of transition metal salts
as antimicrobial agents cannot be recommended as they are
very toxic to host animals. It has been reported that the biolo-
gically active compounds show greater activity when adminis-
tered as metal complexes than as free organic compound2.
Transition metal complexes containing oxygen and nitrogen
donor Schiff base ligands have been of research interest for
many years3 because of the versatility of their steric and
electronic properties. Schiff bases and their metal complexes
exhibited biological activity as antibiotics4, antiviral5 and
antitumour agents6 because of their specific moiety7. The
presence of -SO2NH moiety in sulpha drugs has toxophoric
function8. Sulphur containing Schiff base ligands are the
important components of biological transition metal complexes
which are used in the preparations of diuretic, antiglaucoma
or antiepileptic drugs9. The azomethine ( >C=N) linkage in
Schiff bases imparts an idea in elucidating the mechanism of
transamination and resamination reactions in biological
system10. Schiff bases can accomodate different metal centers
involving various co-ordination modes allowing successful
The present paper records the synthesis and characteri-
zation of Co(II), Ni(II), Cu(II), Mn(II) and Zn(II) complexes
of Schiff base (Fig. 1) derived from 2-sulphanilamidopyridine
and 2-hydroxy-3-methoxy benzaldehyde. The structures of the
ligand and its metal complexes were characterized by elemental
analysis, IR, 1H NMR, UV, molar conductance and magnetic
susceptibility measurements.
CH
N
NH
SO
2
N
OH
CH
3
Fig. 1. Structure of the ligand
EXPERIMENTAL
All the chemicals used were of analytical reagent grade
(AR) and of 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 Perkin Elmer
RX1 FT-IR Spectrophotometer in the 4000-400 cm-1 range.
The electronic spectra were recorded in DMF on a Perkin
Elmer Lambda 35 spectrophotometer in the 190-1100 nm
1
range. The H NMR spectra were recorded on a Bruker 400

2078 Valarmathy et al.
Asian J. Chem.
RESULTS AND DISCUSSION
MHz FT-PMR spectrometer (DMSO-d6) at the microanalytical
centre, Bharathidasan University. The analysis of carbon,
hydrogen and nitrogen were performed at the Indian Institute
of Technology, Chennai, India. Magnetic susceptibilities were
measured on aAutomagnetic Susceptibility meter (MSB-Auto)
at room temperature. Melting points were determined using
melting point apparatus (Elico) and are uncorrected. Conduc-
tivity measurements for the complexes were carried out on
Elico conductivity bridge and a dip conducitivity cell using
dimethyl formamide as solvent.
The Schiff base ligand is synthesized by using equimolar
quantities of 2-sulphanilamidopyridine and 2-hydroxy-3-
methoxy benzaldehyde and the complexes using metal
acetates. The metal complexes derived vary in their colour.
All the complexes are stable, non-hygroscopic and coloured
solids. The low molar conductance values in the range of 2.9-
16.7 ohm-1 cm2 mol-1 in Co(II), Ni(II), Cu(II), Mn(II) and Zn(II)
chelates indicate that they are non-electrolytic in nature12. The
low conductance values may be attributed to the large cations13.
Infrared spectra: The infrared spectral data of the Schiff
base and its metal complexes are recorded in Table-2. Schiff
base showed a strong absorption band at 1618 cm-1 charac-
teristic of ν(C=N) whereas the broad band at 3426 cm-1 is
characteristic of hydrogen bonded ν(O-H) stretching vibration14.
The azomethine ν( >C=N) band at 1618 cm-1 in Schiff base is
shifted to lower frequency in Co(II), Ni(II), Cu(II), Mn(II)
and Zn(II) by 21, 25, 16, 07 and 26 cm-1, respectively which
indicated the co-ordination of azomethine nitrogen in comp-
lexation15. The disappearance of phenolic (OH) at 3426 cm-1
in all the complexes suggests the coordination of phenolic
oxygen after deprotonation16. The linkage with oxygen atom
is further supported by the appearance of a band in the region
around 450 cm-1 which may be assigned to ν(M-O)17. The
bands at 1374 and 1130 cm-1 are assigned to νas(SO2) and
νs(SO2), respectively in schiff base ligand. These bands also
show no significant change in all the complexes and thereby
indicating the non-participation of sulfonamide oxygen in the
bonding. The coordination of water molecule is indicated by
Synthesis of Schiff base ligand: (L) The Schiff base
was prepared by the condensation of equimolar amounts of
2-sulphanilamidopyridine and 2-hydroxy-3-methoxy benzal-
dehyde in minimum quantity of ethanol. The resulting mixture
was then refluxed on a water bath for 5 h. An 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 viz.,
acetone, benzene and soluble in polar solvents viz., DMF,
DMSO.
Synthesis of metal complexes: Metal complexes were
synthesized by mixing the hot solution of ligand (0.004 mol)
in minimum quantity of dimethyl formamide and ethanolic
solution of corresponding 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 complexes were washed with anhydrous
diethylether and dried in a desiccator.
the presence of band in the region 3350-3200 cm-1 18
.
The microanalytical data, melting point, colour and other
physical properties of the ligand and metal complexes are given
in Table-1. The probable structure of complexes proposed in
the present work is given in Fig. 2.
Electronic spectra: Electronic spectrum of the ligand
showed two high intensity bands at 31,347 and 39,524 cm-1
indicates n → n* and π → π* transitions, respectively of the
ligand moiety19. The electronic spectra of Co(II) complex
shows bands at 35398, 32130, 27392 and 23,415 cm-1. The
first two high intensity peaks are due to L → M charge transfer
CH
N
NH
SO
2
N
4
3
spectra and the other two correspond to T1g(F) → A2g(F),
4
4T1g(F) → T1g(P) suggesting octahedral geometry for this
CH O
3
O
complex. Ni(II) complex showed absorption bands at 39122-
36626 cm-1. The high intensity band at 39122 cm-1 is relatively
attributed to L → M charge transfer transitions20 whereas at
36626 cm-1 may be due to 3A2g → 3T1g transition. The Cu(II)
complex displays three bands at 38022, 37460 and 36523 cm-1.
The first two bands are due to intraligand transitions21. The
third band at 36, 523 cm-1 is due to 2E(g) → 2T2g transition. The
electronic spectrum of the Mn(II) complex shows three
bands at 38759, 36496 and band at 29525 cm-1 assignable to
M → L charge transfer transitions and the 29525 cm-1 is due
OH
2
M
H O
2
O
OCH
3
N
N
CH
NH
SO
2
Fig. 2. Structure of the complex
TABLE-1
PHYSICAL CHARACTERISTICS AND MICROANALYTICAL DATA OF SCHIFF BASE LIGAND AND THEIR COMPLEXES
Λm (ohm-1
m2 mol-1)
Elemental analysis (%) calcd. (found.)
Ligand/
complexes
m.p. Yield
(ºC) (%)
µEff
(BM)
Colour
m.f.
CN
C
H
N
L
Red orange
C19H17O4N3S
180
235
220
221
160
150
80
60
65
70
55
55
59.38 (59.48) 4.42 (4.01) 10.93 (10.94)
–
6
6
6
6
6
–
–
[CoL2(H2O)2] Dark green
[NiL2(H2O)2] Green
C38H36N6O10S2Co
C38H36N6O10S2Ni
53.08 53.20)
4.19 (4.01)
9.77 (9.55)
9.78 (9.62)
9.72 (9.22)
9.82 (9.86)
9.70 (9.63)
4.45
3.4
16.7
3.44
6.0
53.10 (53.30) 4.19 (4.07)
52.80 (52.62) 4.16 (4.15)
53.33 (53.41) 4.21 (4.09)
52.69 (52.51) 4.15 (4.10)
[CuL2(H2O)2] Yellow brown C38H36N6O10S2Cu
[MnL2(H2O)2] Yellow orange C38H36N6O10S2Mn
1.96
5.2
7.86
2.9
[ZnL2(H2O)2]
Pale yellow
C38H36N6O10S2Zn
Dia

Vol. 25, No. 4 (2013)
Ligand/complexes
Synthesis of Co(II), Ni(II), Cu(II), Mn(II) and Zn(II) Complexes with Schiff Base 2079
TABLE -2
IR AND ELECTRONIC SPECTRAL DATA
IR spectral data (cm-1)
Electronic spectral data (cm-1)
γ(O-H)
3426
3420
3416
3436
3411
3409
γ(C=N)
1618
1597
1593
1602
1594
1611
γ(M-N)
–
γ(M-O)
–
L
31347, 39, 524
[CoL2(H2O)2]
[NiL2(H2O)2]
[CuL2(H2O)2]
[MnL2(H2O)2]
[ZnL2(H2O)2]
568
554
574
560
564
460
480
440
460
450
35398, 32130, 27392, 23, 415
39122, 36626
38022, 37460, 36523
38759, 36496, 29525
38461, 35211
TABLE-3
ANTIMICROBIAL ACTIVITY OF SCHIFF BASE LIGAND AND COMPLEXES
Antimicrobial activity of
the ligand and complexes
Staphylococcus aureus
Pseudomonas aeruginosa
Candida albicans
Aspergillus niger
Ligand (L)
[CoL2(H2O)2]
[NiL2(H2O)2]
[CuL2(H2O)2]
[MnL2(H2O)2]
[ZnL2(H2O)2]
++
++
++
++
++
+++
+++
+++
+++
+++
+++
+++
+++
+++
+++
+++
+++
+++
+++
+++
++
+++
+++
++
Standard = ciprofloxacin 5 µg/disc for bacteria; Nystatin = 100 units/disc for fungi. Highly active = +++ (inhibition zone > 15 mm); moderatively
active = ++ (inhibition zone > 10mm); slightly active = + (inhibition zone > 5 mm); Inactive = -- (inhibition zone < 5 mm).
to 6A1g → 4Eg(D)22. Zn(II) complex displays absorption bands at
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ACKNOWLEDGEMENTS
The authors express their gratitude to UGC-SERO,
Hyderabad for financial assistance.