Remote Interfacial Electron Transfer from Supramolecular Sensitizers

The sensitizers [(4,4‘-(CO2H)2bpy)ReI(CO)3−CN−RuII(bpy)2(CN)](PF6) and [(4,4‘-(CO2H)2bpy)ReI(CO)3−NC−RuII(bpy)2(CN)](PF6), where bpy is 2,2‘-bipyridine, have been prepared, characterized, and anchored to porous nanocrystalline TiO2 surfaces for light-to-electrical energy conversion. The facial geometry about the ReI center orientates the RuII center proximate to the TiO2 surface. Long wavelength excitation is absorbed exclusively by the −RuII(bpy)2 group. Photoelectrochemical and time-resolved absorption measurements demonstrate rapid and efficient interfacial electron transfer even though the sensitizer is remote to the semiconductor-bound ligand.