title: A new heteroleptic ruthenium(II) polypyridyl complex with long-wavelength absorption and high singlet-oxygen quantum yield.
abstract: Ruthenium(II) polypyridyl complexes with long-wavelength absorption and high singlet-oxygen quantum yield exhibit attractive potential in photodynamic therapy. A new heteroleptic Ru(II) polypyridyl complex, [Ru(bpy)(dpb)(dppn)](2+) (bpy=2,2'-bipyridine, dpb=2,3-bis(2-pyridyl)benzoquinoxaline, dppn=4,5,9,16-tetraaza-dibenzo[a,c]naphthacene), is reported, which exhibits a (1)MLCT (MLCT: metal-to-ligand charge transfer) maximum as long as 548 nm and a singlet-oxygen quantum yield as high as 0.43. Steady/transient absorption/emission spectra indicate that the lowest-energy MLCT state localizes on the dpb ligand, whereas the high singlet-oxygen quantum yield results from the relatively long (3)MLCT(Ru-->dpb) lifetime, which in turn is the result of the equilibrium between nearly isoenergetic excited states of (3)MLCT(Ru-->dpb) and (3)pipi*(dppn). The dppn ligand also ensures a high binding affinity of the complex towards DNA. Thus, the combination of dpb and dppn gives the complex promising photodynamic activity, fully demonstrating the modularity and versatility of heteroleptic Ru(II) complexes. In contrast, [Ru(bpy)(2)(dpb)](2+) shows a long-wavelength (1)MLCT maximum (551 nm) but a very low singlet-oxygen quantum yield (0.22), and [Ru(bpy)(2)(dppn)](2+) shows a high singlet-oxygen quantum yield (0.79) but a very short wavelength (1)MLCT maximum (442 nm).
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.
authors.forename: Qian-Xiong
authors.initials: QX
authors.lastname: Zhou
authors.forename: Wan-Hua
authors.initials: WH
authors.lastname: Lei
authors.forename: Jing-Rong
authors.initials: JR
authors.lastname: Chen
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
authors.forename: Bao-Wen
authors.initials: BW
authors.lastname: Zhang
mesh_terms: D000042:Absorption; D018360:Crystallography, X-Ray; D008024:Ligands; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010777:Photochemistry; D011725:Pyridines / Q000737:chemistry*; D011789:Quantum Theory; D012428:Ruthenium / Q000737:chemistry*; D026082:Singlet Oxygen / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet
chemical_list: D008024:Ligands; D009942:Organometallic Compounds; D011725:Pyridines; D026082:Singlet Oxygen; D012428:Ruthenium