pH-dependent electron transfer from re-bipyridyl complexes to metal oxide

The dependence of Re(L(sub p))(CO)3Cl (or ReClP) [Lp = 2,2'-bipyridine-4,4'-bis-CH2PO(OH)2] and Re(LA)(CO)3Cl (or ReClA) [L(sub A)=2,2'-bipyridine-4,4'-bis-CH2COOH] sensitized TiO2 and ReClP sensitized SnO2 nanocrystalline thin films is examined. Results suggests that the observed pH-dependent electron transfer rate can be qualitatively accounted for by considering the change of density of electron-accepting states caused by the pH-dependent conduction band edge position.