Synthesis, crystal structure and anaerobic DNA photocleavage of ruthenium complexes [Ru(tpy)(dpoq)Cl](+) and [Ru(tpy)(dpoq)CH3CN](2.).

Two new Ru(II) complexes [Ru(tpy)(dpoq)Cl]+ 1 and [Ru(tpy)(dpoq)CH3CN]2+ 2 (tpy=2,2':6',2''-terpyridine; dpoq=dipyrido[1,2,5]oxadiazolo[3,4-b]quinoxaline) have been synthesized and characterized by elemental analysis, 1H NMR, electrospray ionization mass spectra (ESI-MS) and X-ray crystallographic study. The experimental results of spectra titration, thermal denaturation and viscosity measurements suggest that the two complexes intercalatively bind to DNA. When irradiated under light, the two complexes could efficiently photocleave DNA both under aerobic and anaerobic condition. The mechanism studies reveal that the photocleavage reaction functions through both oxygen-independent (photoinduced electron transfer, type III reaction) and oxygen-dependent (singlet oxygen generation, type II reaction) pathways and the oxygen-independent pathway is the major process. These complexes will be more promising photodynamic therapy (PDT) candidates used for treating hypoxic tumors.