Electrochemical and photophysical properties of DNA metallo-intercalators containing the ruthenium(II) tris(1-pyrazolyl)methane unit

Three new ruthenium(II) complexes containing the tris(1-pyrazolyl) methane (tpm) ligand have been prepared: [Ru( tpm)(L)(dppn)](n+) (where n = 1; L = Cl ( 5), n = 2; L = MeCN ( 6) and pyridine ( 7); dppn = benzo[i] dipyrido[ 3,2- a: 2', 3'-c] phenazine). Complex 6 was structurally characterized by single-crystal X-ray diffraction. Binding parameters of these complexes with calf thymus DNA are reported and compared to those obtained for a previously reported monocation, [RuCl(tpm)(dppz)](+). Binding studies with the dications and the synthetic oligonucleotides poly( dA).poly( dT) and poly(dG).poly(dC) have also been determined. Photophysical and electrochemical properties of 5 - 7 have been investigated and compared with their dipyridophenazine ( dppz) analogues.