Impact of metal on the DNA photo-induced cleavage activity of a family of Phterpy complexes.

A family of Phterpy complexes, [Mn(Phterpy)2][N(CN)2]2·0.5H2O (1), [Fe(Phterpy)2](NO3)2 (2), [Ni(Phterpy)2](NO3)2 (3), [Ni(Phterpy)2]Cl2·10H2O (4), [Cd(Phterpy)2](NO3)2·2H2O (5) and [Zn(Phterpy)Cl2] (6) (Phterpy=4'-phenyl-2,2':6',2″-terpyridine), have been synthesized and structurally characterized, and their DNA binding and photo-induced DNA cleavage activities have been investigated. These complexes display binding propensity to the CT-DNA giving a relative order: 1>4>3, 5, 2, 6. Under dark or ambient lighting conditions, all complexes show no efficient DNA cleavage activity to pBR322 DNA. While on irradiation with UV-A light of 365nm, complexes of 1, 3 and 4 exhibit significant cleavage activities. In the presence of H2O2 as a revulsant or an activator, the cleavage ability of complex 2 is obviously enhanced. Complexes 5 and 6 do not exhibit any apparent chemical nuclease activities under irradiation conditions or with the addition of H2O2. The DNA photo-induced cleavage activities are consistent with the number of single-electron in the central metal ion of complexes and singlet oxygen and hydroxyl radical are found as the reactive oxygen species.