Long-Range Electron Transfer across Molecule-Nanocrystalline Semiconductor Interfaces Using Tripodal Sensitizers
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- 作者：Elena Galoppini ; Wenzhuo Guo ; Wei Zhang ; Paul G. Hoertz ; Ping Qu ; and Gerald J. Meyer
- 刊名：Journal of the American Chemical Society
- 出版年：2002
- 出版时间：July 3, 2002
- 年：2002
- 卷：124
- 期：26
- 页码：7801 - 7811
- 全文大小：193K
- 年卷期：v.124,no.26(July 3, 2002)
- ISSN：1520-5126
文摘
Four tripodal sensitizers, Ru(bpy)2(Ad-tripod-phen)2+ (1), Ru(bpy)2(Ad-tripod-bpy)2+ (2), Ru(bpy)2(C-tripod-phen)2+ (3), and Ru(bpy)2(C-tripod-bpy)2+ (4) (where bpy is 2,2'-bipyridine, phen is 1,10-phenanthroline, and Ad-tripod-bpy (phen) and C-tripod-bpy (phen) are tripod-shaped bpy (phen) ligandsbased on 1,3,5,7-tetraphenyladamantane and tetraphenylmethane, respectively), have been synthesizedand characterized. The tripodal sensitizers consist of a rigid-rod arm linked to a RuII-polypyridine complexat one end and three COOR groups on the other end that bind to metal oxide nanoparticle surfaces. Theexcited-state and redox properties of solvated and surface-bound 1-4 have been studied at roomtemperature. The absorption spectra, emission spectra, and electrochemical properties of 1-4 in acetonitrilesolution are preserved when 1-4 are bound to nanocrystalline (anatase) TiO2 or colloidal ZrO2 mesoporousfilms. This behavior is indicative of weak electronic coupling between TiO2 and the sensitizer. The kineticsfor excited-state decay are exponential for 1-4 in solution and are nonexponential when 1-4 are boundto ZrO2 or TiO2. Efficient and rapid (kcs > 108 s-1) excited-state electron injection is observed for 1-4/TiO2.The recombination of the injected electron with the oxidized RuIII center is well described by a second-order kinetic model with rate constants that are independent of the sensitizer. The sensitizers bound toTiO2 were reversibly oxidized electrochemically with an apparent diffusion coefficient ~1 × 10-11 cm2 s-1.