Through-Linker Intramolecular Singlet Fission: General Mechanism and Designing Small Chromophores

We perform quantum chemistry calculations and quantum dynamics simulations to investigate the covalent linker’s through-bond effects in intramolecular singlet fission. A model molecule with two diazadiborine chromophore units and the para-phenylene linker is proposed. A general, step-by-step picture for the conversion from the single- to the multiexcitonic state through the linker is presented. On the basis of the picture, we discuss the triplet-pair delocalization into the linker and design two more chromophores with higher fission efficiency. All three designed chromophores have promising picosecond fission time scales and make good candidates for azaborine synthesis.