Bis(2,2′-bipyridine)cobalt(III) complexes containing asymmetric ligands: Synthesis, DNA-binding and photocleavage studies

Abstract

Three new CoIII complexes: [Co(bpy)2(pdtb)]3+ (1), [Co(bpy)2(pdta)]3+ (2) and [Co(bpy)2(pdtp)]3+ (3) have been synthesized and characterized. The DNA binding behavior of the CoIII complexes has been investigated by spectroscopic methods and viscosity measurements. The results indicate that the size and shape of the intercalated ligand have a marked effect on the binding affinity of complexes involving CT-DNA. Complexes (2) and (3) have been found to promote cleavage of plasmid pBR 322 DNA from the supercoiled form I to the open circular form II upon irradiation. Photocleavage mechanisms are proposed.