Mechanism of a Luminescent Dicopper System That Facilitates Electrophotochemical Coupling of Benzyl Chlorides via a Strongly Reducing Excited State

Photochemical radical generation has become a modern staple in chemical synthesis and methodology. Herein, we detail the photochemistry of a highly reducing, highly luminescent dicopper system [Cu-2] (Eox* approximate to -2.7 V vs SCE; tau(0) approximate to 10 mu s) within the context of a model reaction: single-electron reduction of benzyl chlorides. The dicopper system is mechanistically well defined. As we show, it is the [Cu-2]* excited state that serves as the outer-sphere photoreductant of benzyl chloride substrates; the ground-state oxidized byproduct, [Cu-2](+), is electrochemically recycled, demonstrating a catalytic electrophotochemical C-C coupling process.