Visualizing back electron transfer in eosin Y photoredox catalysis

Abstract

Back electron transfer (BET) in eosin Y (EY) photoredox catalysis was visualized via the fluorescence of single EYs. BET between the radical ion pair formed in photoinduced electron transfer (PET) induced photoblinking of single EYs under constant photoexcitation. Commonly used quenchers, alkyl bromides and a tertiary amine, were studied. BET was observed in alkyl bromides, but not in the tertiary amine. The findings helped explain the mechanism of EY-catalyzed photoinduced atom transfer radical polymerizations. The method can be applied to studying BET on photo-emissive catalysts.