Intramolecular Electronic Coupling Enhances Lateral Electron Transfer across Semiconductor Interfaces

Abstract

The control of lateral electron-transfer reactions is important for many solar energy conversion strategies. Herein, four compounds with two redox-active groups, a bis(tridentate) cyclometalated RuII metal center and a substituted triphenylamine (TPA) donor separated by an organic bridge, were anchored to TiO2 surfaces to facilitate study of lateral intermolecular electron transfer. An important finding was that the TPA+/0 diffusion coefficients were about 1.6 times larger when the bridge promoted intramolecular electronic coupling between the Ru metal center and TPA. Under conditions where TPA+ was able to oxidize the RuII center or intramolecular electronic coupling was large, the RuIII/II electron transfer was facilitated by TPA+/0 transport. These findings indicate that synergistic interactions between redox-active groups can be tailored to control electron transfer at the molecular level across metal oxide surfaces.