A New Heteroleptic Ruthenium(II) Polypyridyl Complex with Long-Wavelength Absorption and High Singlet-Oxygen Quantum Yield
✍ Scribed by Qian-Xiong Zhou; Wan-Hua Lei; Jing-Rong Chen; Chao Li; Yuan-Jun Hou; Xue-Song Wang; Bao-Wen Zhang
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 301 KB
- Volume
- 16
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
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^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).