Fig. 1: Photoinduced electron transfer between metal complexes and tertiary amines.
From: Cage escape governs photoredox reaction rates and quantum yields
a, Catalytic cycle of a photocatalyst (PC) reacting with an electron donor (D) via a so-called reductive quenching mechanism (oxidative quenching mechanisms are also common but are not considered here)7. Following excitation of the photocatalyst, photoinduced electron transfer leads to the reduced photocatalyst and the oxidized donor embedded in a solvent cage. Escape from this solvent cage competes with unproductive thermal reverse electron transfer (charge recombination). Only successful cage escape can lead to productive photoredox chemistry, here electron transfer to the substrate (S), which reacts onwards to the desired product (P) in subsequent (light-independent) elementary reaction steps. b, Molecular structures of the investigated photocatalysts [Ru(bpz)3]2+ and [Cr(dqp)2]3+ showing the pertinent microstates of the photoactive 3MLCT excited state and the 2E and 2T1 spin-flip excited states, respectively. c, Molecular structures of the investigated electron donors 1–12. PEG, polyethylene glycol.
