Mononuclear copper (II) salicylate complexes with 1,2-dimethylimidazole and 2-methylimidazole: Synthesis, spectroscopic and crystal structure characterization and their superoxide scavenging activities

The complexes cis-bis (1,2-dimethylimidazole) bis (salicylato) copper (II) (1) and tris (2-methylimidazole) (salicylato) copper (II) (2) have been prepared by the reaction of appropriate methylimidazole derivative with binuclear copper (II) aspirinate. Spectral and X-ray structural studies for complex 1 showed that the copper ion is coordinated in a cis arrangement to two imidazole nitrogen atoms and two carboxylate oxygen atoms from the salicylate mono-anion ligands. The second carboxylate oxygen atoms form weak axial interactions with the copper ion. Spectral, magnetic and analytical data for complex 2 showed that the copper ion is bonded to three 2-methylimidazole nitrogen atoms and one doubly deprotonated salicylate di-anion, which is chelated to Cu (II) ion through one of its carboxylate oxygen atoms and the deprotonated hydroxyl oxygen atom to form distorted square-pyramidal geometry having CuN3O + O chromophore. The superoxide dismutase (SOD) mimetic activities (IC50) of the complexes 1, 2 and the structurally known mixture complexes Cu (imidazole)n(salicylato)2(3) (where n = 2, 5 and 6) were determined using the xanthine–xanthine oxidase assay and compared with those reported for other copper (II) complexes with anti-inflammatory drugs. The results obtained indicated that complexes 1–3 have high SOD-like activities, which may act as good mimics for native Cu, Zn–SOD enzyme.