Efficient Photochemical Reduction of Quinone into Hydroquinone Promoted by Imidazolyl N-H Proton

Photochemical reductions of imidazole-conjugated quinones in acetonitrile solutions containing [Ru(bpy)(3)](2+) (bpy: 2.2'-bipyridine) as a photosensitizer and triethanolamine as an electron donor selectively afforded the corresponding hydroquinones. These conversions were accelerated by the presence of an imidazolyl N-H proton, suggesting that the proton-coupled electron transfer retards the back-electron transfer.