Chemical Insights to the Electron Transfer from the Triplet Pair State in Singlet Fission Dimers

Photocatalytic production of H2 or hydrocarbons requires multiple electrons, necessitating the absorption of multiple photons and accumulation of photoexcited charges. Alternatively, multiexciton generation (MEG) could loosen this requirement. Despite intense studies of the MEG process singlet fission (SF) for solar cells, its use in photocatalysis has only recently been demonstrated. Here we provide chemical insights to the nature of the SF generated triplet pair state (1TT) with implications for electron transfer reactions from SF materials. We demonstrate that electron transfer from the 1TT state in a tetracene dimer can occur through two different mechanisms, depending on the energetically allowed pathways for electron transfer. This finding is crucial for designing SF dimers for solar cells and photoredox catalysis, as it emphasizes the importance of considering acceptor/donor redox potentials relative to the T1 energy.