Electron spin-controlled charge transfer and the resulting long-lived charge transfer state: from transition metal complexes to organic compounds

The generation of long-lived charge transfer (CT) states in electron donor/acceptor dyads upon photoexcitation is crucial for artificial photosynthesis, photocatalysis and photovoltaics. Electron spin control is a novel strategy to prolong the CT state lifetime via generation of the (CT)-C-3 triplet state, instead of the traditional short-lived (CT)-C-1 state. This method involves a local triplet excited state ((LE)-L-3) as the precursor of charge separation (CS), and the electron forbidden feature of the charge recombination (CR) of (CT)-C-3 -> S-0 vs. the electron spin allowed (CT)-C-1 -> S-0 prolongs the CT state lifetime. In this article, we summarized the recent developments and challenges in this emerging fascinating area.