Microwave Assisted Synthesis, characterization and biological studies of isonicotinoylhydrazones and their Manganese (II) complexes

Abstract

Among the most promising cleaner and energy efficient technologies, microwave-assisted technique has been popularly used for organic and inorganic synthesis. The use of microwave ovens in chemical synthesis has increasingly grown, due to its ability to dramatically reduce reaction times, improve yields, and simplified procedures. It is, therefore planned to synthesize some new Mn (II) Schiff base complexes using microwave irradiation technique. The Schiff base ligands 1-(2-furanyl) ethanone isonicotinoylhydrazone (L 5 H), 1-(2-thienyl) ethanone isonicotinoylhydrazone (L 6 H), 1-(2- pyridyl) ethanone isonicotinoylhydrazone (L 7 H), 1-(2-naphthyl) ethanone isonicotinoylhydrazone (L 8 H), were prepared by the condensation reaction of isonicotinic acid hydrazide with corresponding ethanons in 1:1 molar ratio, respectively, in ethanol under microwave exposure. The Mn (II) complexes have been prepared by mixing MnCl 2. 4H 2 O in 1:1 and 1:2 molar ratios with monofunctional bidentate ligands. The structure of the ligands and their transition metal complexes were confirmed by the elemental analysis, molecular weight determinations, IR, electronic and EPR spectral studies. On the basis of these studies it is clear that the ligands coordinated to the metal atom in a monobasic bidentate mode, by O ∩ N donor system. Thus a tetrahedral environment around the Mn (II) ionhas been proposed. The antimicrobial activity of Schiff base ligands and their respective Mn (II) complexes were tested against some of pathogenic bacterial and fungal strains. The results indicated that the complexes showed higher activity than the parent ligands.