Time-Resolved Optical Spectroscopy of Heterosupramolecular Assemblies Based on Nanostructured TiO2 Films Modified by Chemisorption of Covalently Linked Ruthenium and Viologen Complex Components

Described is the preparation of transparent nanostructured TiO 2 (anatase) and Sb-doped SnO 2 films supported on F-doped conducting glass. Also described is the modification of these films by chemisorption of RV, bis(4,4‘-bis(phosphonomethyl)-2,2‘-bipyridine)(5-((1‘-ethyl-4,4‘-bipyridinediium-1-yl)butyl)-2,2‘-bipyridine)ruthenium(II) tetrakis(hexafluorophosphate), to form the covalent heterosupramolecular assemblies TiO 2 - RV and SnO 2 - RV, respectively. Visible light excitation of the ruthenium complex component, R, results in electron injection into the TiO 2 or SnO 2:Sb nanocrystal component (60%) and electron transfer to the viologen component (40%), V . In the case of TiO 2 - RV, however, long-lived formation of the radical cation of the V component, V • +, is observed. In the case of SnO 2 - RV, long-lived formation of V • + is not observed. These findings, based on a detailed study of the time-resolved optical spectroscopy of TiO 2 - RV and SnO 2:Sb- RV, are accounted for by proposing that long-lived V • + is formed by TiO 2 nanocrystal mediated electron transfer to the V component.