A High-Valent Metal-Oxo Species Produced by Photoinduced One-Electron, Two-Proton Transfer Reactivity

Described herein is a photochemical approach to the generation of a high-valent metal-oxo species that utilizes a chromophore or “sensitizer”, a semiconducting electron acceptor, and a redox buffer that poises a catalyst’s initial protonation and oxidation state. The photoexcited sensitizer injects an electron into the semiconductor and then oxidizes the catalyst whose reactivity occurs in kinetic competition with back electron transfer. Core–shell SnO 2 /TiO 2 semiconductor nanocrystallites inhibited charge recombination relative to TiO 2 acceptors. With low sensitizer-catalyst surface coverages, a novel trapping process is exploited that enables catalysis reactivity to be quantified on time scales ranging from nanoseconds to minutes. A proof-of-principle example provides the demonstration of a light-initiated, (1e –, 2H + )-transfer reaction, with an inverse isotope effect of k H / k D = 0.63, to generate a Ru(IV) oxo species.