Described is the preparation of transparent nanostructured TiO2 (anatase) and Sb-doped SnO2 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 TiO2-RV and SnO2-RV, respectively. Visible light excitation of the ruthenium complex component, R, results in electron injection into the TiO2 or SnO2:Sb nanocrystal component (60%) and electron transfer to the viologen component (40%), V. In the case of TiO2-RV, however, long-lived formation of the radical cation of the V component, V.+, is observed. In the case of SnO2-RV, long-lived formation of V.+ is not observed. These findings, based on a detailed study of the time-resolved optical spectroscopy of TiO2-RV and SnO2:Sb-RV, are accounted for by proposing that long-lived V.+ is formed by TiO2 nanocrystal mediated electron transfer to the V component.