Alcohol‐Based Sensitizer–Semiconductor Linkages Towards Improved Interfacial Electron Transfer Kinetics

A series of four ruthenium complexes with alcohol binding groups of the general form [Ru(dtb)2(LL)](PF6)2 (where dtb is 4,4′‐(tert‐butyl)2‐2,2′‐bipyridine and LL is an alcohol‐containing ligand) were anchored to mesoporous TiO2 thin films. The complexes were found to sensitize light‐driven electron‐transfer reactivity of TiO2 to the visible region and the complexes were hence termed sensitizers. The kinetics and yields of interfacial electron transfer were quantified on the nanosecond and longer timescales. The stability under oxidizing and light excitation conditions was assessed by spectroscopic methods. Comparative analysis with the more commonly utilized dicarboxylic acid containing ligand revealed that the sensitizer bearing two terminal CH2OH groups was found to have more efficient electron injection and slower back electron transfer. Compare and contrast: Light‐driven interfacial electron transfer was investigated with a series of [Ru(dtb)2(LL)](PF6)2 compounds in which LL is a bipyridine ligand with either alcohol binding groups or carboxylic acid groups (as a reference). The sensitizer with two terminal CH2OH groups was found to exhibit more efficient electron injection and slower back electron transfer than the more commonly used dicarboxylic acid containing ligand.