A New Heteroleptic Ruthenium(II) Polypyridyl Complex with Long‐Wavelength Absorption and High Singlet‐Oxygen Quantum Yield |
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Authors: | Qian‐Xiong Zhou Dr Wan‐Hua Lei Jing‐Rong Chen Chao Li Yuan‐Jun Hou Xue‐Song Wang Prof Bao‐Wen Zhang |
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Institution: | 1. Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (P.R. China), Fax: (+86)?106‐487‐9375;2. Graduate School of Chinese Academy of Sciences, Beijing 100049 (P.R. China) |
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Abstract: | Ruthenium(II) polypyridyl complexes with long‐wavelength absorption and high singlet‐oxygen quantum yield exhibit attractive potential in photodynamic therapy. A new heteroleptic RuII polypyridyl complex, Ru(bpy)(dpb)(dppn)]2+ (bpy=2,2′‐bipyridine, dpb=2,3‐bis(2‐pyridyl)benzoquinoxaline, dppn=4,5,9,16‐tetraaza‐dibenzoa,c]naphthacene), is reported, which exhibits a 1MLCT (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 3MLCT(Ru→dpb) lifetime, which in turn is the result of the equilibrium between nearly isoenergetic excited states of 3MLCT(Ru→dpb) and 3ππ*(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 RuII complexes. In contrast, Ru(bpy)2(dpb)]2+ shows a long‐wavelength 1MLCT 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 1MLCT maximum (442 nm). |
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Keywords: | antitumor agents bioinorganic chemistry DNA cleavage ligand design ruthenium |
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