Suppression of Singlet Fission in a DPH dimer by a polar solvent

Singlet fission (SF), a multiexciton generation process in organic molecules, offers intriguing possibilities to overcome limitations in multielectron photocatalysis. For this approach to be viable, SF chromophores must combine sufficiently high triplet energies with efficient SF in the polar environments typically required for photocatalytic reactions. Herein, we present a detailed investigation of the excited-state dynamics of a covalently linked dimer based on diphenylhexatriene (DPH), a high-energy SF chromophore, in a polar solvent, benzonitrile (PhCN). While the dimer undergoes SF in toluene, SF is strongly suppressed in PhCN, where the excited-state dynamics instead favour symmetry-breaking charge separation (SBCS). These results highlight solvent polarity as an important consideration in the design of highly symmetric SF chromophores for photocatalytic applications