Time-resolved resonance Raman spectroscopic studies of the photosensitization of colloidal titanium dioxide

Resonance Raman and time-resolved resonance Raman spectroscopies have been used to study the surface interactions of substituted bipyridyl complexes of ruthenium(II) as sensitizers with the colloidal semiconductor TiO{sub 2}. It has been shown that the adsorption of ruthenium(II) tris((2,2{prime}-bipyridyl)-4,4{prime}-dicarboxylate) (RB4H) onto a colloidal TiO{sub 2} surface is through the solvation layer, whereas cis-diaquaruthenium(II) bis((2,2{prime}-bipyridyl)-4,4{prime}-dicarboxylate) (RBDA) adsorption is via the water ligands of the complex. The transient Raman spectrum of the metal-ligand charge-transfer triplet excited state of the ethyl ester of RB4H is reported. Analysis of the spectrum provides conclusive evidence for the excited electron being localized on one of the ligands. The photosensitization of TiO{sub 2} by RB4H and RBDA has also been studied by using time-resolved resonance Raman spectroscopy.