Synthesis of new macrocyclic complexes of transition metals: Structural characterization and biological activity

Condensation reaction between benzildihydrazone and pyridine 2,3-dicarboxylic acid, pyridine 3,4-dicarboxylic acid or pyridine 2,4-dicarboxylic acid in methanol led to novel Schiff base macrocyclic ligands L-1, L-2, and L-3 respectively. Metal complexes of the type [MLCl2], [M = Co(II), Ni(II)], were synthesized by the reaction of a free macrocyclic ligand (L) with the corresponding metal salts in a 1 : 1 molar ratio. The complexes were characterized on the basis of analytical data, molar conductivity and magnetic susceptibility measurements, IR, H-1, and C-13 NMR, and electronic spectral data. Those demonstrated that all the complexes had octahedral arrangement around the metal ions. The ligand and its complexes were screened for their antibacterial, antifungal and DNA cleavage activities. The studies demonstrate that the complexes possessed antimicrobial and DNA cleavage activities.