Preparation characterization and antibacterial studies of chelates of schiff base derived from 4-aminoantipyrine, furfural and o-phenylenediamine

Article abstract of DOI:10.1155/2011/254018

A new series of transition metal complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) were synthesized from the Schiff base ligand derived from 4-aminoantipyrine, furfural and o-phenylenediamine. The structural features were derived from their elemental

Full text of DOI:10.1155/2011/254018

ISSN: 0973-4945; CODEN ECJHAO
E-Journal of Chemistry
http://www.e-journals.net
2011, 8(3), 1408-1416
Preparation Characterization and Antibacterial
Studies of Chelates of Schiff Base Derived from
-Aminoantipyrine, Furfural and o-Phenylenediamine
4
*
M.S.SURESH and V.PRAKASH
Department of Chemistry
Government Arts College, Ooty-643002, India
vprakasharmy@yahoo.co.in
Received 1 October 2010; Accepted 18 December 2010
Abstract: A new series of transition metal complexes of Mn(II), Co(II), Ni(II),
Cu(II) and Zn(II) were synthesized from the Schiff base ligand derived from
4
-aminoantipyrine, furfural and o-phenylenediamine. The structural features
were derived from their elemental analyses, infrared, UV-visible spectroscopy,
NMR spectroscopy, thermal gravimetric analyses, ESR spectral analyses and
conductivity measurements. The data of the complexes suggested square
planar geometry for the metals with primary valency two. Antimicrobial
screening tests were performed against bacteria. The comparative study of the
MIC values of the Schiff base and its metal complexes indicate that the metal
complexes exhibit greater antibacterial activity than the free ligand.
Keywords: Schiff base, 4-Aminoantipyrine, Furfural, o-Phenylenediamine.
Introduction
Metal complexes with Schiff base ligands have been studied for their application in
1
biological, clinical, analytical and pharmacological areas . Studies of new kinds of
2,3
chemotherapeutic Schiff bases are now attracting the attention of biochemists Earlier
.
work reported that some drugs showed greater activity, as metal complexes when compared
3
to the organic compounds . The coordinating properties of 4-aminoantipyrine have been
modified to give new ligands formed by the reaction with aldehydes, ketones, thiocarbazides
4
and carbazides etc. . Several works have been carried out on the transition metal complexes
of 4-aminoantipyrine derivatives. Very less work is done on the chemistry of transition
metal complexes and biological behavior involving the amino group of 4-aminoantipyrine. It
is found from literature that very less work is done on the synthesis of Schiff base and its
transition metal complexes involving the carbonyl group 4-aminoantipyrine. In this paper
efforts were taken for the synthesis, characterization and antimicrobial studies of transition
metal complexes containing tetra dentate Schiff base derived from furfural, 4-amino-
antipyrine and o-phenylenediamine.

1
409
V.PRAKASH et al.
Experimental
All the chemicals and solvents were of AR grade. Metal salts were purchased from Merck
and Loba chemie Mumbai, India. Vanillin and anthranilic acid were purchases from Loba
chemie, Mumbai, India. Ethanol, methanol and the solvents were dried by the standard
4,5
procedures . The elemental analyses were performed at central electro chemical research
institute (CECRI) India using vario EL elemental analyzer. IR spectroscopy analyses were
-
1
recorded on Schimadzu FTIR 8400S spectrometer in 4000-200 cm range using KBr pellet.
The UV visible spectra were recorded on a Schimadzu UV spectrometer in the wavelength
range 200-800 nm. The thermal analyses were recorded on universal V4.3A TA instrument
from CECRI, India. The ESR spectral analyses were recorded on Bruker instrument at 300
1
13
and 77 K from CECRI. The H NMR and C NMR were recorded on a Bruker DPX-300
spectrometer using EtOD as solvent and TMS as internal standard. The molar conductance
was measured on ELICO-CM180 using DMSO as the solvent at room temperature. The
antibacterial activity was determined with the disc diffusion method. Stock solutions were
prepared by dissolving the compounds DMSO and serial dilutions of the compounds were
prepared in sterile distilled water to determine the minimum inhibition concentration (MIC).
Synthesis of Schiff base
An ethanolic solution (20 mL) of 1-phenyl 2, 3-dimethyl-4-aminopyrazol-5-one (2.03 g, 0.01 mol)
(4-aminoantipyrene) was added to an ethanolic solution of furfural (1.52 g, 0.01 mol). The
solution was stirred vigorously. The solution was refluxed for 5 h and allowed to cool. The
resulting solution was poured in crushed ice when crystals formed. The yellow crystals were
filtered and recrystallized from ethanol. The solid intermediate (3.373 g, 0.01 mol) was
added to an ethanolic solution (20 mL) of o-phenylenediamine (0.541 g, 0.005 mol). The
mixture was refluxed for calculated 30 h. The reaction was followed using TLC. The
contents were poured in to crushed ice. The brown solid (L) product was separated. It was
filtered and recrystallized from ethanol. The scheme of the experiment is given below. Yield:
6
2%: m.p: 160 °C.
Step I
O
NH2
O
O
N
N
H
O
O
+
N
N
H C
3
CH
3
N
H C
3
CH
3
Step II
H
3
C
CH3
N
3
H C
CH
3
N
N
N
H
N
O
N
H
O
O
NH
2
N
N
+
NH
2
O
H
O
O
N
N
N
N
H
N
N
CH
3
3
H C
H C
CH
3
3
Scheme 1

Preparation Characterization and Antibacterial Studies
1410
Synthesis of Schiff base complexes
The Schiff base ligand (0.002 mol 1.493 g) is dissolved in 50 mL hot ethanol. The hot
ethanolic solution of the ligand was slowly added to a hot 1:1 aqueous ethanolic solution of
the metal salts. The resulting solution was refluxed on a water bath for 5 h. The solution was
+
2
+2
+2
reduced to one third on a water bath and cooled. The (Mn -brown, Co -pink, Ni -maroon,
+2
+2
Cu -brown, Zn -brown) colored precipitate was separated by filtration. The solid was
washed several times with distilled water and hot ethanol.
Antibacterial activity
The antibacterial activity was determined with the disc diffusion method. Stock solutions
were prepared by dissolving the compounds DMSO and serial dilutions of the compounds
were prepared in sterile distilled water to determine the minimum inhibition concentration
(
MIC). The nutrient agar medium was poured into petri plates. A suspension of the tested
microorganism (0.5 mL) was spread over the solid nutrient agar plates with the help of a
spreader. Fifty microlitres of the stock solutions was applied on the 10 mm diameter sterile
disc. After evaporating the solvent, the discs were placed on the inoculated plates. The Petri
plates were placed at low temperature for two hours to allow the diffusion of the chemical
o
and then incubated at a suitable optimum temperature (29±2 C) for 30-36 hours. The
diameter of the inhibition zones was measured in millimeters.
Results and Discussion
The formation of square planar complexes with (D h symmetry) is confirmed with the help of the
4
analyses done on the complexes. The 3d transition metals in the first row have been selected for
the analyses. The ligand acts as a tetra dentate chelating agent which participates in the formation
of coordinate bonding with the central metal atom. The elemental analysis confirms (Table 1) the
empirical and molecular formula for the synthesized complexes. The presence of 1:1 and 1:2
electrolytic natures of complexes are confirmed by the conductivity measurements.
Table 1. Physical characterization, analytical and molar conductance data of the complexes
-
1
Compd.
m.p., Yield,
Found (Calc.) %
N
Λm, Ω
mol
-1
(
Colour)
°C
%
C
H
S
0
0
M
-
-
C H N O = L
70.939
5.247
18.951
38
34
8
2
1
60
87
47
52
57
51
62
(
Brown)
+2
(71.831) (5.356) (17.643)
[
Mn (L)]SO
58.426
(58.25)
61.92
(62.98)
57.082
4.238
14.268
3.962
6.782
4
1
1
1
1
1
72
70
50
60
63
108
120
92
(
Brown)
(4.343) (14.307) (4.087) (6.642)
+
2
[
Co (L)]Cl
4.022
(4.188) (13.797)
4.096 14.083
13.192
0.0
(0)
3.968
7.503
(7.259)
6.498
2
(
Pink)
+2
[
Ni (L)]SO
4
(
Brown)
(57.757) (4.306) (14.186) (4.053) (7.434)
55.826 3.968 13.863 4.125 7.903
(56.132) (4.432) (13.787) (3.939) (7.822)
+
2
[
Cu (L)]SO
4
108
108
(
Brown)
+
2
[
Zn (L)]SO
59.092
4.208
14.386
0.03
(0)
8.853
(8.479)
4
(
Brown)
(59.135) (4.409) (14.524)
IR analyses
The IR analyses proves the formation of bonds between the metal and the ligand through the
azomethine (C=N) group. The Table 2 gives the important frequencies observed for the
ligand and the complexes.

1
411
V.PRAKASH et al.
-1
Table 2. Characteristic infrared absorption frequencies in (cm ) of ligand and complexes
-
1
-1
No
1
2
3
4
Compound
C H N O
4
ν C=N cm
ν M-N cm
-
1
-1
1650 cm to 1565 cm
1627.26 cm and 1583.25 cm
1620.16 cm and 1582.15 cm
1559.15 cm
1625.16 cm and 1523.15 cm
1625.16 cm and 1583.20 cm
44
+2
42
8
-1
-1
-1
[Mn (L)]SO
445.57
445.57
505.37
445.57
445.57
4
+
2
-1
[Co (L)]Cl
2
+2
-1
[Ni (L)]SO
4
+2
-1
-1
5
6
[Cu (L)]SO
4
+2
-1
-1
[Zn (L)]Cl
2
UV Visible analyses
The electronic spectral data was used to study the geometry of the synthesized complexes.
Based on the UV Visible spectrum the complexes were shown to have a square planar
geometry. Table 3 gives the information on the various electronic spectral absorption
regions for the ligand and their metal complexes.
-1
Table 3. Characteristic infrared absorption frequencies in (cm ) of ligand and complexes
-
1
Compound
Solvent Absorption, cm
Ethanol 262 and 319
Band assignment
Geometry
*
*
C H N O =L
π→π , n- π transitions.
and ν are INCT, Square
4
4
42
8
4
+
2
28735, 31646 and
1367
ν
1
2
1
[
[
[
Co (L)]Cl
Ethanol
Ethanol
Ethanol
1
2
2
ν = A → B g
planar
Square
planar
3
1g
1
ν and ν are INCT
1
2
+2
28169, 31645,
5873 and 19417
1
1
1
Ni (L)]SO
ν3= A g→ A g
1 2
1
4
1
ν = A g→ B g
4
3
1
1
+2
30303, 27932 and
5797
ν
1
and ν
2
are INCT
Square
planar
Cu (L)]SO
2
2
4
1
ν3= B → A g
1 1
Thermal analyses
The thermal analyses data provides the information on the number of water molecules coordinated
to the metal in the coordination sphere, the water of hydration and the residue gives information on
the type of molecular formula. Based on the TGA it is confirmed that there are no water molecules
present in the coordination sphere. Table 4 gives the data on the TGA for the complexes. The
complexes of manganese and zinc donot give absorptions in the UV- visible region.
Table 4. Thermogravimetric analyses of complexes
Temp.
Weight loss, %
S. No
Compound
Stage
Range, ºC
Above 614
Above 598
Above 579
Found
Calculated
11.09
+2
1
2
3
[Mn (L)]SO
I
I
I
10.16
9.262
8.389
4
+2
[Ni (L)]SO
8.262
4
+2
[Cu (L)]SO
8.39
4
Stage-I
+
2
[
[
[
Mn (C H N O )] SO
→ MnO (Residue)
→ NiO (Residue)
→ CuO (Residue)
(1)
(2)
(3)
38
34
8
2
4
2
+2
Ni (C H N O )] SO
4
38
34
8
2
+
2
Cu (C H N O )] SO
38 34 8 2 4
NMR analyses
13
The spectral information (Figure 1) was obtained from the proton NMR and C NMR spectrum of the
ligand (Figure 2) with respect to TMS. Multiplet around δ 7.52 shows the presence of benzylidenium
CH group. The peak for the benzene appears as multiplet at δ 7.44, the peaks for C-CH and N-CH3
3

Preparation Characterization and Antibacterial Studies
1412
appears in the region δ 3.11 and δ 2.44 respectively. The peaks for the benzylidenium
13
hydrogen appear at δ 7.82 and δ 7.75. The C NMR spectral analyses shows corresponding
peaks at δ152.6 for imines, the peak at δ 140.5 corresponds to –N=C bonded to benzene ring
through nitrogen. The peak at δ 129.2 corresponds to the benzene carbon atoms. The peak at
δ 56.1 and δ 35.2 corresponds to the –CH group present in the ring.
3
Chemical Shift, ppm
1
Figure 1. H NMR spectrum of the ligand
NONAME01
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
200
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
Chemical Shift, ppm
13
Figure 2. C NMR spectrum of the ligand

1
413
V. PRAKASH et al.
NMR studies of zinc complex
The azomethine proton signal in the spectrum (Figure 3) of the zinc complex is shifted
downfield. Thus the peak at δ 7.52 found in the ligand is shifted to δ 7.84 and the rest of the
peaks, C-CH and N-CH appear in the same region δ 3.11, δ 2.44 respectively. The peaks
3
3
for the benzylidenium hydrogen appear at low field δ 8.68 and δ 8.27.There is no
appreciable change in all the signals of the complex except –CH=N. This shows the
+2
formation of coordinate bond between the Zn metal and the four azomethine groups.
Chemical Shift, ppm
Figure 3. NMR spectrum of Zn complex
The ESR analysis was used for the study of type of bonding and geometry of the
complexes. The ESR study confirms the presence of covalent character in the bond present
+2
between the ligand, azomethine (C=N) group and the central Cu metal. The presence of a
+2
square planar geometry is confirmed with the help of ESR study on Cu complex.
Antibacterial activity
The antibacterial study for the complexes was performed on Staphylococcus aureus,
Escherichia coli, Bacillus subtilis and Pseudomonos aeruginosa. The results are given in the
Table 5. The toxicity of the complexes was found to be better than the ligand owing to the
theory of Tweedy.
Table 5. Antibacterial activity data for the ligand and their metal complexes
Inference anti
bacterial activity
Compound
C H N O
S.aureus
E.coli
B.subtilis
P.aeruginosa
7
8
7
8
12
13
6
10
6
9
13
15
5
9
5
8
13
12
4
9
4
9
14
12
+
++
+
++
+++
+++
3
8
34
8
2
+
2
[
[
[
[
[
Mn (L)]SO
4
+2
Co (L)]Cl
2
+2
Ni (L)]SO
4
+2
Cu (L)]SO
4
+2
Zn (L)]SO
4

Preparation Characterization and Antibacterial Studies
1414
Elemental analyses (cf. Table 1) reveals the presence of 1:1 coordination of the metal
with the ligands in the case of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). The molar
conductance of the complexes reveals the presence of chloride and sulphate ions outside the
coordination sphere in the complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II).
IR Studies
The IR spectra provide valuable information regarding the nature of the functional group
6
attached to the metal atom . The frequency corresponding to νC=N nitrogen in the complex
7
participates in coordination to the metal ion . Coordination to the metal through the nitrogen
atom is expected to reduce the electron density in the azomethine link and lowers the νC=N.
-
1
-1
The spectrum of the ligand shows two νC=N bands in the region 1650 cm to 1565 cm
-
1
-1
which is shifted to lower frequencies 1610 cm and 1597 cm in the spectrum of the
7
complex, showing the participation of –C=N nitrogen in the coordination to the metal ion .
The ligand acts as a tetra dentate chelating agent, bonded to the metal ion via the four
-
1
nitrogen –C=N atoms of the Schiff base. The appearance of medium band at 445.57 cm
confirms the presence of M-N coordination in the complex.
UV Studies
-
1
The UV spectrum of cobalt(II) complex shows three peaks at 348 nm (28735 cm ), 316 nm
-
1
-1
-1
(
3
31646 cm ) and 468 nm (21367 cm ) respectively. The peak at 348 nm (28735 cm ),
-1
16 nm (31646 cm ) are the bands corresponding to the inter-nuclear charge transfer band.
The band at 468 nm (21367 cm ) is for the A → B g transition . The transitions suggests
the presence of square planar geometry for cobalt complex. Nickel(II) has a (d )
-1
1
1
1
1
g
1
8
-
1
-1
configuration giving peaks, found at 355 nm (28169 cm ), 316 nm (31645 cm ), 630 nm
-
1
-1
(
15873 cm ) and 515 nm (19417 cm ) respectively for the nickel complex. The first and
-
1
-1
second peaks at 355 nm (28169 cm ) and 316 nm (31645 cm ) are assigned for the
-
1
inter-nuclear charge transfer bands. The third peak at 630 nm (15873 cm ) is assigned for
1
1
-1
the A g→ A g excitation and the fourth peak at 515 nm (19417 cm ) is assigned for the
1
1
2
1
A g→ B g excitations respectively. This confirms the presence of an square planar
geometry for the nickel complex . Copper(II) has a (d ) configuration giving peaks, found at
30 nm (30303 cm ), 358 nm (27932 cm ) and 633 nm (15797 cm ) respectively for the
1
1
1
9
-1
-1
-1
3
-
1
copper complex. The first peak at 330 nm (30303 cm ) and second peaks at 358 nm
-
1
(
(
27932 cm ) are assigned for the inter-nuclear charge transfer bands. The third peak at 633 nm
-
1
2
2
15797 cm ) is assigned for the B → A g excitation respectively. This confirms the
1
1
1
presence of an square planar geometry for the copper complex .
Thermal studies
Thermogravimetric analyses of the complex was used to get the (i) information on water of
hydration if present in the coordination sphere of the central metal ion. (ii) scheme of thermal
decomposition of the complexes and (iii) to find thermal stability of the complex. From the
thermogram, it was observed that this compound is thermally stable up to 150-190 ºC. The
complexes decompose with the formation residue which is close to the theoretical value.
ESR analyses
+2
ESR spectra of [Cu (C H N O )]SO recorded in DMSO solution at 300 and 77 K the
38
34
8
2
4
spectrum of the Cu complex at 300 K shows one intense absorption band in the high field
region and is isotropic due to the tumbling motion of the molecules. However, this complex
in the frozen state at 77 K, four well-resolved peaks of low intensities in the low field region

1
415
V.PRAKASH et al.
was observed in the spectrum ruling out any Cu–Cu interaction. The g tensor values of
Cu(II) complex can be used to derive the ground state. In tetragonal and square planar
complexes, the unpaired electron lies in the dx2–y2 orbital giving 2B1g as the ground state
with the g|| > g⊥. From the observed values, it is clear that g|| > g⊥ (2⋅2895 > 2⋅0478), which
8-10
suggests that the complex is square planar . Also it is supported by the fact that the
unpaired electron lies predominantly in the dx2–y2 orbital for the copper complex,
g|| = 2⋅2895, which is between 2⋅
3–2⋅4 and thus in conformity with the presence of copper–
2
nitrogen bonds in these chelates. Molecular orbital coefficients, α (covalent in-plane s-
2
Bonding) and β (covalent in-plane π-bonding), were calculated by using the following
equations.
2
α Cu = – (A||/0⋅
036) + (g|| – 2⋅
0023) + 3/7(g⊥

(4)
(5)
2
2
β Cu = (g|| – 2⋅0023) E/ –8λ α
Where, E is the electronic transition energy of 2B1g →
β =0.9345 value for the complex supports its covalent nature of the bonding. Hathway
2
9
pointed out that for the pure σ – bonding K
ꢀ
> K ≈ 0.77 and for in-plane π- bonding K
ꢀ
< K┴,
┴
while for the out-of-plane π- bonding K < K
ꢀ
the following simplified expressions were
┴
used to calculate K
ꢀ
and K┴.
= (g
K = (g - 2.0023 / 2 x λ ) x d – d transition
K
ꢀ
ꢀ
- 2.0023 / 8 x λ ) x d – d transition
(6)
(7)
0
┴
┴
0
ꢀ
┴
The observed K (0.6849) > K (0.434) relation indicates the absence of significant
in- plane π- bonding. The molar conductance of the complexes reveals the presence of
chloride ions outside the coordination sphere in chromium and iron complexes. In the
+
2
+2
+2
+2
+2
complexes of Mn , Co , Ni , Cu and Zn the primary valency of the metals are
satisfied within the coordination sphere due to the coordination with the carboxylate
groups of the ligand.
Antibacterial activity
+2
The antibacterial property of the ligands was compared to the complexes. The Zn
complexes show good antibacterial activity against the strain of bacteria taken under study
when compared to the ligand and other metal complexes taken for study.
Conclusion
A new series of transition metal complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) were
synthesized from the Schiff base ligand derived from 4-aminoantipyrine, furfural and o-
phenylenediamine. The structural features were derived from their elemental analyses,
infrared, UV-visible spectroscopy, NMR spectroscopy, thermal gravimetric analyses,
ESR spectral analyses and conductivity measurements. The data of the complexes
suggested, square planar geometry for the metals with primary valency two.
Antimicrobial screening tests were performed against bacteria. The comparative study
of the MIC values of the Schiff base and its metal complexes indicate that the metal
complexes exhibit greater antibacterial activity than the free ligand. The Schiff base
coordinates through its four azomethine nitrogen. The Schiff base behaves as a tetra
dentate ligand. The molar conductance measurements suggest the presence of anion
+2
+2
+2
+2
+2
outside the coordination sphere for Mn , Co , Ni , Cu and Zn as shown in Figure 4.
The metals, forms 1:1 complexes with the Schiff base ligand.

Preparation Characterization and Antibacterial Studies
1416
3
H C
C H
3
H
N
N
N
O
O
N
M
N
N
N
N
H
C H
3
3
H C
Figure 4. Structure of the metal complex
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2
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.
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Journal of
International Journal of
Journal of
Theoretical Chemistry
Catalysts
Research International
Chemistry
Spectroscopy
Hindawi Publishing Corporation
http://www.hindawi.com
Hindawi Publishing Corporation
http://www.hindawi.com
Hindawi Publishing Corporation
http://www.hindawi.com
Hindawi Publishing Corporation
http://www.hindawi.com
Hindawi Publishing Corporation
http://www.hindawi.com
Volume 2014
Volume 2014
Volume 2014
Volume 2014
Volume 2014