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A New Heteroleptic Ruthenium(II) Polypyridyl Complex with Long‐Wavelength Absorption and High Singlet‐Oxygen Quantum Yield
Author(s) -
Zhou QianXiong,
Lei WanHua,
Chen JingRong,
Li Chao,
Hou YuanJun,
Wang XueSong,
Zhang BaoWen
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200902563
Subject(s) - singlet oxygen , quantum yield , ruthenium , photochemistry , singlet state , ligand (biochemistry) , chemistry , absorption (acoustics) , excited state , absorption spectroscopy , ultrafast laser spectroscopy , yield (engineering) , oxygen , fluorescence , materials science , spectroscopy , atomic physics , physics , catalysis , organic chemistry , optics , metallurgy , composite material , biochemistry , receptor , quantum mechanics
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 ππ*(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).