Quantitative Sequential Photoenergy Conversion Process from Singlet Fission to Intermolecular Two-Electron Transfers Utilizing Tetracene Dimer

Singlet fission (SF) theoretically enables the performance of the sequential photoenergy conversion process starting from the singlet state and leading to electron transfer (ET) with the radical ion pair quantum yield approaching 200%. Additionally, the long lifetime of the triplet state opens the possibility for an intermolecular ET process in a diffusion-limited reaction. However, the quantitative two-electron transfer process through SF has yet to be reported. Herein we demonstrate the quantitative sequential process involving SF and leading to intermolecular two-electron transfers using 2,2′-biphenyl-bridged tetracene dimer (Tet-BP-Tet: SF and electron donor) and chloranil (Ch: electron acceptor). The high-yield and long-lived individual triplet excited states of Tet-BP-Tet by SF (φ_T = 175 ± 5% and τ_T = 0.29 ms) resulted in the quantitative two-electron transfer process (φ_ET = 173 ± 5%) with Ch in benzonitrile.