Search for a Small Chromophore with Efficient Singlet Fission: Biradicaloid Heterocycles

Abstract
Of the five small biradicaloid heterocycles whose S1, S2, T1, and T2 adiabatic excitation energies were examined by the CASPT2/ANO-L-VTZP method, two have been found to meet the state energy criterion for efficient singlet fission and are recommended to the attention of synthetic chemists and photophysicists.