Synthesis and characterization of manganese(II),
cobalt(II), nickel(II), copper(II), and zinc(II) mixed ligand complexes with
[(1-phenyl-3- methyl-5- hydroxopyrazol-4-yl) methylimino] 2',3' dimethylaniline
and 2- hydroxy-1-naphthaldehyde
Sheela M. Valecha*
Department of Chemistry, K.C. College, Churchgate, Mumbai-400020. India
*Corresponding Author
E-mail:
ABSTRACT:
Mixed ligand complexes of the type [MLL']
where M=Mn(II), Co(II), Ni(II), Cu(II), Zn(II)
HL=[(1-phenyl-3-methyl-5-hydroxopyrazol-4-yl)methylimino]2, 3 dimethylaniline;
(HPMPZM)dma. HL'=2-hydroxy-1-naphaldehyde;(HNA), have been synthesized and characterized
on the basis of elemental analysis, conductivity measurements, magnetic,
electronic and infra red spectral studies. The complexes confirm to 1:1:1
stoichiometry and are non electrolytes. The Schiff base HL act as a monovalent
bidentate ligand co-ordinating through azomethine nitrogen and phenolic oxygen.
On the basis of electronic spectra, IR spectra and magnetic moment
measurements; six coordinated octahedral structures have been proposed for the
complexes. Thermal studies revealed the presence of two co-ordinated water
molecules. The Schiff base and mixed ligand complexes have been tested for
their antibacterial activity against the Escherichia coli, Bacillus substilis,
staphylococcus aureus.
KEYWORDS:
1-phenyl-3-methyl-
5-pyrazolone (PMP) has different biological effects as antipyrine metabolic and
is a good biologically active molecule.1-3 In recent years several
pyrazolone derivatives have been synthesized such as 4-acyl- pyrazolones.4
It has been observed from literature survey that these 4-substituted pyrazolone
derivatives mainly exhibit bidentate co-ordinate behaviour in which keto-enol
tautomerism plays an important role in the chelate formation with numerous
metal ions. The acyl pyrazolones in turn are utilized in the synthesis of
schiff base pyrazolone, 5-7 which act as either tridentate or
tetradentate ligands.
In view
of growing interest in the biological properties of Schiff base complexes, the
present study is carried out with the synthesis, characterization and
biological study of mixed ligand complexes of general formula [MLL'].
where M=Mn(II), Co(II), Ni(II), Cu(II), Zn(II)
HL=[(1-phenyl-3-methyl-5-hydroxopyrazol-4-yl)methylimino]2, 3 dimethylaniline;
(HPMPZM)dma. HL'=2-hydroxy-1-napthaldehyde;(HNA),
All the
reagents used were of analytical grade. Solvents were purified and dried
according to standard procedures.
Synthesis
of Schiff base (HPMPZM)dma:-
1-phenyl-3-methyl-4-benzoyl-5
pyrazolone was synthesized by reported method,8 and recrystallized
from ethyl alcohol.
The
pure crystals of 1-phenyl-3-methyl-4-acetyl-5-pyrazolone and 2, 3 dimethylaniline
were taken in round bottom flask in 1:1 stoichiometric proportion. The mixture
was dissolved in about 20-25ml of alcohol. The resulting solution was refluxed
in presence of 2ml of concentrated hydrochloric acid for 4-5 hours. On cooling
the crystals of Schiff base i.e (HPMPZM)dma separated out which were filtered
under suction.
An
appropriate quantity of the Schiff base (HPMPZM)dma was weighed and mixed with
an equimolar quantity of ligand (HNA).The mixture of Schiff base and ligand was
dissolved in minimum quantity of alcohol. An equimolar quantity of bivalent
transition metal chloride was dissolved in minimum quantity of water. Alcoholic
solution of ligands was added to an aqueous solution of metal chloride with
constant stirring. The pH of the solution was raised to 7.5-8.0 by adding 0.1N
sodium hydroxide. The resulting reaction mixture was stirred on a magnetic
stirrer for 1-1.5 hours. The solid complex was separated out, filtered, washed
with water and air dried. This is the general method of synthesis of ternery
complex of (HPMPZM)dma and (HNA) with bivalent transition metal chlorides. The
metal to schiff base to ligand ratio is 1:1:1, i.e schiff base, metal and
ligand are in 1:1:1 stoichiometric proportion. Elemental analysis was carried
out in micro analytical laboratory of IIT (Powai).
The
metal contents in the complexes were determined by standard complexometric
titrations.9 IR spectra of the schiff base and the complexes were
recorded on Perkin Elmer Spectrophotometer. UV-visible spectra of the complexes
were recorded on Shimadzu UV-160 spectrophotometer. Magnetic moments were
measured by Gouy method using Hg[Co(SCN)4] as a calibrant.
Conductivity measurements were made Elico CM-180 conductometer using DMSO as a
solvent. Thermogravimetric analysis of complexes was carried out in Mettler
TA40000 system. The ESR spectra of copper complex at room temperature was
recorded on Varian-E line ESR spectrophotometer at IIT (Powai) using TCNE as
the ' g ' marker.
Analytical data presented in (Table 1)
indicates that Metal:Ligand: Schiff Base stoichiometry is (1:1:1) i.e the
probable general formulae of the complexes is [(MLL')(H2O)2].
All
the complexes decompose in the 220ΊC-290ΊC temprature
range. The complexes are insoluble in water and poorly soluble in common
organic solvents, but fairly soluble in DMSO and DMF. The molar conductance
values lie in the range of 14.30-17.2 ohm-1cm2mol-1.
Low molar conductance values of 10-3M solutions in DMSO showed them
to be non electrolytes. Insufficient solubility of these complexes in suitable
solvent precluded the determination of molecular weights.
The IR
spectra of uncomplexed ligand i.e the schiff base shows the broad band at
3448cm-1(HL) which can be assigned to symmetric and antisymmetric
vibrations νOH. The free ν OH is generally
observed between 3500 and 3600cm-1.The observed low value is due to
intermolecular or intramolecular hydrogen bonding.7 A peak at around
1200 cm-1 for δOH is absent. It shows a weak band at
1364cm-1 which can be assigned to νC-O phenolic. The
spectra also show the sharp bands at 1592cm-1 and 1631cm-1
due to νC=N of pyrazolone nucleus and νC=N of
azomethine group respectively. The ligand HL shows a band at 1246cm-1due
to δO-H. The spectra also show the sharp band at 1367cm-1
and 1646cm-1 which can be assigned to νC-O phenolic
and νC=O carbonyl group respectively. All the complexes exhibit
an identical pattern suggesting them to be isostructural. Metal complexes show
bands in the region 3368cm-1 - 3500cm-1. The bands are
rather diffused and broadened. Broadening may be caused by the participation of
oxygen from OH group in complexation, and appearance of νO-H of
co ordinated water molecules. A new band appears in the spectra of all
complexes in the range 818cm-1 --876cm-1 which is characteristic
of δO-H of co ordinated water molecules10.
In all
the complexes a sharp and strong band appears in the range of 1604cm-1
---1620cm-1 and 1589cm-1 --1593cm-1 which are characteristic
of νC=N azomethine group
and νC=N pyrazolone nucleus respectively. The shift in νC=N
azomethine by 1217cm-1indicates that co-ordination of schiff
base with metal ion takes place through nitrogen11.It is expected
that co-ordination of the nitrogen atom of the ligand to the metal ion would
reduce the electron density from ligand to metal ions, which in turn reduce the
electron density in the azomethine link, thereby reducing the νC=N frequency.
The νC=N of pyrazolone nucleus has not shifted appreciably
suggesting the non involvement of nitrogen of pyrazolone nucleus in the co
ordination to metal ion. The frequency νC-O phenolic in the
complexes is shifted to higher frequency and is in the range of 1305 --1352cm-1.
This indicates that the other co ordination of schiff base is through phenolic
oxygen in all the complexes12. The lower frequency region of spectra
also confirm the participation of nitrogen of azomethine group and oxygen of
phenolic group in the co-ordination to metal ion by showing the weak bands in
the region 494 ---650cm-1 and 450 ---467cm-1
respectively.
In both
ligands the sharp and strong bands, characteristic of δO-H vibration are observed
(HL =1260cm-1, HL =1246cm-1). In the spectra
of complexes, band from HL becomes a very band at a slightly lower frequency
and from ligand HL it disappears indicating the deprotanation of
the phenolic protons prior to co ordination. The shift is also observed for the
strong band due to νC=O (carbonyl) from ligand HL
by 8---10cm-1 suggesting the involvement of oxygen from aldehyde
group in the complex formation.
The
schiff base is expected to exist in tautomeric forms as depicted below. These
structures show keto enol tautomers along with hydrogen bond.
The UV
spectra of schiff base (HPMPZM)dma show the bands at 27, 777cm-1 and
35, 714cm-1
The
ligand (HNA) show two bands at 34, 483cm-1 and 25, 974cm-1.
These bands are attributed to intra ligand transitions. In the complexes the
bands show the blue shift in their positions. Mn (II) complex has magnetic
moment value of 5.50B.M suggesting octahedral environment The electronic
spectra of Mn (II) complex registers weak band at 17, 391cm-1
which can be assigned to 6A1g→4T1g
(G) transitions of Mn(II) ion in a spin free d5 configuration
confirming to octahedral arrangement.
The
Co(II) complex registers an intense band at 18, 181cm-1 and a weak
one at 9, 523cm-1 These bands may be assigned to 4T1g(F)
→ 4T1g(P) (ν3 ) and 4T1g
(F) → 4T2g (F) (ν2) transitions; characteristic
of an octahedrally co-ordinated Co (II) ion. The magnetic moment of 5.0 B. M
supports octahedral environment around Co(II) ion. The other parameters for
Co(II) ion are Dq=1064cm-1, B=645 β =0.664 β=23.14
% suggesting the appreciable covalent character in the complex. The ν3/ν1
ratio (1.90) is in accordance with expected (1.92-2.95) value for an octahedral
Co(II) complex.
The Ni
(II) complex registers an intense band at 22, 988cm-1, broad one at
16, 129cm-1 and a weak one at 9, 523cm-1.These bands may
be assigned respectively to 3A2g (F)→ 3T1g
(P)(ν3), 3A2g (F) → 3T1g
(F) (ν2), 3A2g (F) → 3T2g
(F) (ν1). The ν2/ν1 equals
to1.69, Dq =952 B=703, β =0.., β =27.4%.For
Ni(II) complex the magnetic moment is 3.20B.M suggesting distorted octahedral
geometry. The μ eff value higher than expected for 2e-
may be due to ferromagnetic nature Ni(II) complex or due to incomplete
quenching of orbital angular momentum by ligands13, 14.The high
value can also be due to mixing of multiple excited state in which spin orbit
coupling is appreciable.15 The visible spectra of Cu complex show a
broad band spanning at 14, 814cm-1. This band appears due to 2Eg
→ 2Tg transition in an octahedral field. The
copper complex has magnetic moment of 1.79B.M which is usually observed for
octahedral Cu (II) complex. The ESR spectra exhibit a single broad signal
resulting from the interaction of unpaired electron. The analysis gave g//
=2.14, g┴=2.073.The observed value g‼ for the
Cu complex is less than 2.3 in agreement with the covalent character of the
metal ligand bond. The trend g ∕∕ > g ┴
> 2.073 observed for the complex indicate that the unpaired electron is
localized in dx²-y² orbital of the Cu(II) ion and the spectral
features are characteristic of axial symmetry. Tetragonally elongated structure
may be assumed for Cu(II) complex. The zinc complex is found to be diamagnetic
in nature.
TGA
Studies:- The existence of co-ordinated water molecules in the complexes is
confirmed by TGA studies. The representative complex [Ni(LL)(H2O)2]
is stable upto the temperature of 120°C and there after it registers
a mass loss of 5.9% (calculated 6.16%) which corresponds loss of two water
molecules. The above mentioned mass loss takes place in temperature range of
120°C--240°C.After 200°C the anhydrous complex
starts decomposing. Total mass loss upto 580°C is found to be 89%
which corresponds to the loss of two ligands. Finally the residue left is10.2% hence
from TGA, it is clear that the complexes under study contain two water
molecules co-ordinated to metal ion.16, 17, 18
TABLE1. Physical
properties of Ligands and their Mixed ligand complexes
|
Compound |
Molecular formula (formula wt) |
Colour |
M.P°C |
μ eff |
ΛM |
|
|
|
B.M |
ohm-1cm2mol-1 x
10-3 |
||||
|
1) |
HL =
(HPMPZM)dma |
C20H21N3O
(319) |
Whitish
yellow |
145°C |
------- |
---------- |
|
2) |
HL=(HNA) |
C11H8O2
(172) |
Yellow |
|
------ |
---------- |
|
3) |
[Mn(LL)(H2O)2] |
C31H31N3O5Mn
(580) |
Mud
brown |
235°C |
5.50 |
4.3 |
|
4) |
[Co(LL)(H2O)2] |
C31H31N3O5Co
(583.9) |
Yellowish
green |
220°C |
5.0 |
16.8 |
|
5) |
[Ni(LL)(H2O)2] |
C31H31N3O5Ni
(583.8) |
Greenish
yellow |
240°C |
3.2 |
13.9 |
|
6) |
[Cu(LL)(H2O)2] |
C31H31N3O5Cu
(588.5) |
Dull
light brown |
240°C |
1.79 |
16.9 |
|
7) |
[Zn(LL)(H2O)2] |
C31H31N3O5Zn
(590.5) |
Light
yellow |
290°C |
Diamagnetic |
17.2 |
TABLE:2. Elemental Analysis of ligands and Mixed ligand
complexes
|
Compound |
Elemental Analysis |
||||
|
|
|
%C cal (found) |
%H cal (found) |
% N cal (found) |
% M cal(found) |
|
1) |
HL =
(HPMPZP)dma |
75.3
(74.91) |
6.56
(6.41) |
13.17 (12.2) |
|
|
2) |
HL=(HNA) |
76.75 |
4.65 |
---- |
|
|
3) |
[Mn(LL)(H2O)2] |
64.1 (64.24) |
5.345 (5.18) |
7.24
(7.12) |
9.48
(9.25) |
|
4) |
[Co(LL)(H2O)2] |
63.7 (64.3) |
5.309
(5.11) |
7.19
(6.98) |
10.08
(10.31) |
|
5) |
[Ni(LL)(H2O)2] |
63.72
(63.91) |
5.31
(5.12) |
7.19
(6.98) |
10.07
(10.18) |
|
6) |
[Cu(LL)(H2O)2] |
63.2
(62.89) |
5.26
(5.30) |
7.13
(7.22) |
10.8(11.08) |
|
7) |
[Zn(LL)(H2O)2] |
62.99
(63.18) |
5.25(5.30) |
7.11(7.20) |
11.09(10.91) |
Antimicrobial activity:
The
Schiff base, ligand along with the mixed ligand complexes were tested for their
anti-microbial activity Gram positive (Staphylococcus aureus and Bacillus
subtilis) and Gram negative (Escherichia Coli and Salmonella typhi) by
paper disc diffusion method.. Streptomycin was used as a standard.The ligand
and Schiff base show moderate against all organisms except S-typhi. Mn(II),
Co(II), Ni(II) complexes show moderate activity with E-Coli, S-aureus and
B-subtilis. Copper and Zinc complexes do not posses any activity. It has been
observed from these results that some metal complexes exhibit slightly higher
activity than free ligands against the same microorganism and under the
identical conditions. The mode of action of the complexes may involve the formation
of hydrogen bonds involving the azomethine group with microbials or ribosomes
of microbial cells resulting in interference with normal cell processes.
On the
basis of above discussion the mixed ligand complexes [M(LL)(H2O)2]
may be assigned The following structure;-
2.
Lida S, Hamada K, Kurata N, Ueda t, Nishimara Y, Uchida
E, Kobayashi S and Yasuthara H. Asia Pac J Pharmacal, 6 (1991)235.
3.
Offiah Veronia N, Nimeijer Sandra M, Van Duin Cock T.M,
Witkamp Renger F and Van Miert Adelbert
S JPAM, Am.J Vet Res, 53(1992) 1354.
Received on 20.10.2015 Modified on 12.11.2015
Accepted on 19.11.2015 © AJRC All right reserved
Asian J. Research
Chem. 8(11): November 2015; Page 693-696
DOI: 10.5958/0974-4150.2015.00111.X