title: Substituent effect and wavelength dependence of the photoinduced Ru-O homolysis in the [Ru(bpy)2(py-SO3)](+)-type complexes.
abstract: [Ru(bpy)2(py-SO3)](+) (3, bpy = 2,2'-bipyridine, py-SO3 = pyridine-2-sulfonate) was recently found to undergo py-SO3 ligand dissociation and py-SO3˙ radical generation under hypoxic conditions upon irradiation (Chem. Commun., 2015, 51, 428). To explore the substituent effect on the Ru-O homolysis by which the py-SO3˙ radical may be produced, [Ru(4,4'-(R)2-bpy)(py-SO3)](+), where R = OCH3 (1), CH3 (2), COOCH3 (4), were synthesized and their photochemical properties were investigated. The py-SO3˙ radical generation efficiencies followed the order of 4 > 3 > 2 > 1, and the radical generation efficiencies are wavelength dependent. As a result, 3 and 4 may lead to DNA covalent binding and DNA cleavage upon 355 nm irradiation, but merely DNA covalent binding upon 470 nm irradiation. In contrast, 1 and 2 can serve as DNA photo-binding agents only due to their less efficient Ru-O homolysis. The Ru-O homolysis via the (3)σ(Ru-O)π*(R-bpy) state is proposed to rationalize the substituent effect and the wavelength dependence, which is supported by TD-DFT calculations. This work gave insights into the mechanism of the Ru-O homolysis and provided guidelines for developing new [Ru(bpy)2(py-SO3)](+)-type complexes with higher Ru-O homolysis efficiency. Such complexes have dual activities of photoactivated chemotherapy (PACT) and photodynamic therapy (PDT) under hypoxic conditions and are therefore promising as a new class of antitumor drugs.
authors.affiliation: Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China. xswang@mail.ipc.ac.cn zhouqianxiong@mail.ipc.ac.cn.
authors.forename: Yue
authors.initials: Y
authors.lastname: Zheng
authors.forename: Qian-Xiong
authors.initials: QX
authors.lastname: Zhou
authors.forename: Yang-Yang
authors.initials: YY
authors.lastname: Zhang
authors.forename: Chao
authors.initials: C
authors.lastname: Li
authors.forename: Yuan-Jun
authors.initials: YJ
authors.lastname: Hou
authors.forename: Xue-Song
authors.initials: XS
authors.lastname: Wang
mesh_terms: D015082:2,2'-Dipyridyl / Q000737:chemistry*; D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D004247:DNA / Q000737:chemistry; D053837:DNA Cleavage / Q000187:drug effects; D055808:Drug Discovery; D004735:Energy Transfer; D005609:Free Radicals / Q000737:chemistry; D008027:Light; D015394:Molecular Structure; D010782:Photolysis; D017319:Photosensitizing Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D012428:Ruthenium / Q000737:chemistry*; D013451:Sulfonic Acids / Q000737:chemistry*
chemical_list: D000970:Antineoplastic Agents; D056831:Coordination Complexes; D005609:Free Radicals; D017319:Photosensitizing Agents; D013451:Sulfonic Acids; D015082:2,2'-Dipyridyl; D012428:Ruthenium; D004247:DNA