Studies on DNA-binding and plasmid-cleavage of cobalt (III) mixed ligand complexes

Mixed ligand cobalt (III) complexes of [Co(phen)(2)nip](3+), [Co(phen)(2)apip](3+), [Co(bpy)(2)nip](3+), [Co(bpy)(2)apip](3+) where [apip = 2(4-aminophenyl)imidazo[4,5f][1,10] [phenanthroline], [nip = 2(2-napthyl)14-midazo[4,5-f][1,10]phenanthroline] have been synthesized and characterized. The interaction of these complexes with calf thymus DNA was investigated by absorption (UV/Vis), emission spectroscopy, viscosity measurements, and DNA melting. The results suggest that the complexes bind to DNA via the intercalative mode with complexes 1 > 2 > 3 > 4 binding more strongly to CT DNA. Moreover, these complexes have been found to promote the photocleavage of plasmid DNA pBR322.