Synthesis, characterization and antimicrobial analysis of Schiff bases of o-phenylenediamine and 2-aminopyridine-3-carboxylic acid with ofloxacin and their metal (II) complexes

Abstract

The increasing multi-drug resistance of microbes to the existing anti-biotic drugs has been of great concern to medical scientists and challenge has directly concerned pharmacologists, inorganic chemists, molecular microbiologists etc. This work attempted modifying a second generation fluoroquinolone (ofloxacin) toward attaining more improved activity. Schiff base Ligands HL¹ and HL² were obtained from separate condensation of o-phenylenediamine and 2-aminopyridine-3-carboxylic acid with ofloxacin in 2:1 and 1:1 mole ratio respectively. These ligands were complexed with chloride salts of Ni (II), Mn (II) and Zn (II) to afford their metal complexes. The new compounds were characterized on the basis of physicochemical properties, IR spectroscopy, UV-visible spectroscopy, Molar conductance and metal analysis. The IR spectra revealed that the metal ions coordinated with the ligands through azomethine nitrogen and carboxylato oxygen depicting tetradentate character with the formular type ML and ML₂ for HL¹ and HL² metal complexes respectively. The antimicrobial evaluation of the ligands and their respective complexes in Staphylococcus aureus, Bacillus subtilis, Salmonella typhi, Escherichia coli, Aspergellus niger and Aspergellus fumigatus presented a promising to excellent activity except for A. niger which showed no activity in all the tested compounds.

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Keywords: Schiff base, metal complexes, ofloxacin, o-phenylenediamine, 2-aminopyridine-3-carboxylic acid, antimicrobial activity