Synthesis, DNA-binding and photocleavage studies of cobalt(III) mixed-ligand complexes

Two novel complex ions [Co(bpy)(2)IP](3+) and [Co(bpy)(2)PIP](3+), have been prepared and characterized by EA, mass spectra, u.v.-vis., and cyclic voltammetry. The binding behavior of both complexes to calf thymus DNA (CT-DNA) has been investigated by spectroscopic methods, cyclic voltammetry, and viscosity measurements. The results suggest that both complexes bind to DNA by intercalation. Both promote cleavage of plasmid pBR 322 DNA from the supercoiled Form I to the open circular Form II upon irradiation. Mechanisms for photocleavage are proposed.