Cobalt(III), nickel(II) and ruthenium(II) complexes of 1,10-phenanthrolinefamily of ligands: DNA binding and photocleavage studies

DNA binding and photocleavage characteristics of a series of mixed-ligand c omplexes of the type [M(phen)(2)LL](n+) (where M = Co(III), Ni(II) or Ru(II ), LL = I,10-phenanthroline (phen), phenanthroline-dione (phen-dione) or di pyridophenazine (dppz) and n = 3 or 2) have been investigated in detail. Va rious physico-chemical and biochemical techniques including UV/Visible, flu orescence and viscometric titration, thermal denaturation, and differential pulse voltammetry have been employed to probe the details of DNA binding b y these complexes; intrinsic binding constants (K-b) have been estimated un der a similar set of experimental conditions. Analysis of the results sugge sts that intercalative ability of the coordinated ligands varies as dppz > phen > phen-dione in this series of complexes. While the Co(II) and Ru(II) complexes investigated in this study effect photocleavage of the supercoile d pBR 322 DNA, the corresponding Ni(II) complexes are found to be inactive under similar experimental conditions. Results of detailed investigations c arried out inquiring into the mechanistic aspects of DNA photocleavage by [ Co(phen)(2)(dppz)](3+) have also been reported.