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 [Cu2] (Eox* ≈ −2.7 V vs SCE;
τ0 ≈ 10 μs) 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 [Cu2]* excited state that serves as the outer-sphere
photoreductant of benzyl chloride substrates; the ground-state oxidized
byproduct, [Cu2]+, is electrochemically recycled,
demonstrating a catalytic electrophotochemical C–C coupling
process.