Synthesis, characterization and antimicrobial studies on transition ...

S. Sunitha <strong>and</strong> K.K. Aravindakshan, Int J Pharm Biomed Sci 2011, 2(4), 103-113
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2. MATERIALS AND METHODS
All chemicals used in the present work viz.,aniline,
benzoylchloride, ethylacetoacetate, phenylhydrazine,
isoniazid, metal salts, solvents etc., were of AR grade. (BDH,
Sarabhai, Qualigens, E. Merck, Loba Chemie or Glaxo).
Carbon, hydrogen <strong>and</strong> nitrogen analyses were carried out
by using VarioEL III CHNS analyser at SAIF, CUSAT,
Kochi. The anions present in the complexes were estimated
by st<strong>and</strong>ard methods. The 1 H NMR spectrum of the lig<strong>and</strong>
was recorded on Advance III 500 MHz Bruker spectrometer
using DMSO-d 6 as solvent. Infrared spectra were measured in
the range 4000-400 cm -1 as KBr pellets on a Perkin-Elmer
spectrophotometer. The solid-state electronic spectra of the
complexes were recorded on a JASCO UV-Visible
spectrophotometer. The magnetic measurements were made
at room temperature by Evans method using Hg[Co(CNS) 4 ]
as calibrant.
2.1 <strong>Synthesis</strong> of the compounds
The synthesis of the lig<strong>and</strong> consisted of three stages. The
first stage which involves the preparation of 3-methyl-1-
phenyl-5-pyrazolone[5] <strong>and</strong> the second stage which involves
the benzoylation of the above to 4-benzoyl-3-methyl-1-
phenyl-5-pyrazolone were carried out using Jensen’s
procedure [6]. The third stage involved the condensation of
4-benzoyl-3-methyl-1-phenyl-5-pyrazolone with distilled
aniline to prepare the Schiff base lig<strong>and</strong>. Added an ethanolic
solution of aniline (0.0109 mol, 1mL) to a hot refluxing
solution of 4-benzoyl-3-methyl-1-phenyl-5-pyrazolone(0.01
mol, 2.7840 g) in ethanol <strong>and</strong> refluxed for 3 h .The lemon
yellow coloured crystals obtained on cooling were filtered at
the pump, washed with ethanol <strong>and</strong> dried (yield= 65.8%).
Complexes of Co(II) with this lig<strong>and</strong> were synthesized
using iodide <strong>and</strong> nitrate salts of the metal. Complexes of
Ni(II) with this lig<strong>and</strong> were synthesized using acetate salt of
the metal. Complexes of Cu(II) of this lig<strong>and</strong> were
synthesized using acetate, chloride, nitrate <strong>and</strong> sulphate salts
of the metal. Solutions of the lig<strong>and</strong> <strong>and</strong> iodide <strong>and</strong> nitrate
salts of Co(II) salts in methanol (2:1 molar ratio) were
refluxed for 0.5h. Acetate of Ni(II)salt, nitrate <strong>and</strong> sulphate
salts of Cu(II) were dissolved in water <strong>and</strong> added to the
refluxing solution of the lig<strong>and</strong> in methanol (1:2 molar ratio)
<strong>and</strong> refluxed for 2h. Acetate of Cu(II) was dissolved in
ethanol <strong>and</strong> added to a refluxing solution of methanol(1:2
molar ratio) <strong>and</strong> refluxed for 15 min. The chloride of Cu(II)
was dissolved in methanol <strong>and</strong> added to refluxing solution of
the lig<strong>and</strong> in methanol (1:2 molar ratio) <strong>and</strong> refluxed for 7.5h.
The complexes formed on cooling were filtered off, washed
with the respective solvents <strong>and</strong> dried except the complex
synthesized using the chloride of Cu(II) in which case the
volume was reduced to half by evaporating off the solvent.
The solid which separated was filtered off, washed with the
solvent <strong>and</strong> dried.
3. RESULTS AND DISCUSSION
3.1 Characterization of the lig<strong>and</strong>
The lig<strong>and</strong> was characterized by m.p., elemental
analysis, 1 H NMR <strong>and</strong> IR spectral data. The 1 H NMR
spectrum of the lig<strong>and</strong> was recorded in DMSO-d 6 <strong>and</strong> it
showed a number of characteristic signals of the compound
[7,8]. The singlet observed at 1.4 ∂ was assigned to the
methyl group at 3 position of the pyrazolone ring. The
multiplet observed in the range 7.0-7.5 ∂ was assigned to the
aromatic protons. The singlet at 8.0 ∂ was assigned to the
proton at 4 position of the pyrazolone ring. Singlets at 2.4 ∂
<strong>and</strong> 3.4 ∂ are due to DMSO-d 6 <strong>and</strong> H 2 O. The IR spectrum of
the lig<strong>and</strong> showed a number of absorption b<strong>and</strong>s which were
characteristic of the different groups present in it [7,8]. The
b<strong>and</strong>s present at 1628 cm -1 <strong>and</strong> at 1226 cm -1 have been
assigned to >C=N <strong>and</strong> C-N stretching vibrations,
respectively. The characteristic frequency due to the
stretching of the aromatic keto group, at 1650 cm -1 was not
present in the spectrum, which indicated that condensation
between 4-benzoyl-3-methyl-1-phenyl-5-pyrazolone <strong>and</strong>
aniline was complete. The b<strong>and</strong> at 1500 cm -1 has been
assigned to >C=O group of the pyrazolone ring. The b<strong>and</strong>s
due to the in plane bending of the aromatic C-H stretching
are usually found in the range 1250-950 cm -1 . The b<strong>and</strong>s at
1138 cm -1 , 1007 cm -1 <strong>and</strong> 906 cm -1 have been assigned to
these modes of vibrations. The most characteristic
frequencies of aromatic groups were found below 900 cm -1 ,
usually in the range 600-900cm -1 , due to the out-of-plane
bending vibration of the aromatic C-H. The b<strong>and</strong>s at 770cm -1 ,
760 cm -1 <strong>and</strong> 698 cm -1 have been assigned to these modes of
vibrations. The elemental analysis <strong>and</strong> spectral data for L are
consistent with the formula C 23 H 19 N 3 O.
3.2 Formulae <strong>and</strong> general properties of complexes
The reaction of the lig<strong>and</strong> (L) with different salts of
Co(II), Ni(II) <strong>and</strong> Cu(II) ions in 2:1 molar ratios gave metal
complexes of the given formulae, as evidenced by the microanalytical
<strong>and</strong> spectral data.
1. [ML 2 X 2 ]where M=Co(II), Ni(II) or Cu(II) <strong>and</strong>
X=CH 3 COO - , I - or NO 3
-
2. [Cu(L) 2 SO 4 ]
Suggested structure for [ML 2 X 2 ] <strong>and</strong> [Cu(L) 2 SO 4 ] are
shown in Fig.3 <strong>and</strong> Fig.4, respectively. The colours, magnetic
susceptibilities, molar conductivities <strong>and</strong> melting points <strong>and</strong>
the micro-analytical data of the complexes are listed in
Table 1. These air-stable metal complexes were nonhygroscopic,
partially soluble in most of the organic solvents
but freely soluble in DMF <strong>and</strong> DMSO. The molar
conductivities in DMF/DMSO (10 -3 M) showed that all the
complexes behaved as non-electrolytes, indicating the
coordinated nature of the anions.
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