Synthesis, characterisation and antimicrobial studies on transition metal complexes of n-[phenyl(methylphenyl-5-pyrazolyl)methylidene] pyridine-4-carbohydrazide

The novel Schiff base N′-[phenyl(methylphenyl-5-pyrazolyl)methylidene] pyridine-4-carbohydrazide was synthesised in three stages. Ethylacetoacetate and phenylhydrazine were allowed to react together to form 3-methyl-1-phenyl-5-pyrazolone. This was benzoylated at the 4- position to get 4-benzoyl-3-methyl-1-phenyl-5-pyrazolone. This was condensed with isonicotinic acid hydrazide to get the novel Schiff base. Though there are four potential ligating sites, only two of the ligating sites are involved in coordination. The ligand was characterised by elemental analysis and IR spectrum. Co(II), Ni(II) and Cu(II) complexes of the neutral bidentate chelating Schiff base ligand were synthesized using acetates, chlorides and nitrates of the metals. They were characterised by elemental analysis, conductance and magnetic susceptibility measurements, UV, VIS and IR spectra. The ligand exhibited tautomerism and the complexes were found to have octahedral geometry. The in vitro antibacterial activity against Escherichia coli and in vitro antifungal activity against Aspergillus niger of the ligand and the complexes were investigated using nutrient agar medium.