Intramolecular Singlet Fission: Insights from Quantum Dynamical Simulations

We
investigate the dynamics of intramolecular singlet fission in
a dimer consisting of two pentacene-based chromophores covalently
bonded to a phenylene spacer using an approach that combines high-level ab initio multireference perturbation theory methods and
quantum dynamical simulations. The results show that the population
of the multiexcitonic state, corresponding to the first step of singlet
fission, is facilitated by the existence of higher-lying doubly excited
and charge transfer states that participate in a superexchange-like
way. The important role played by high-frequency ring-breathing molecular
vibrations in the process is also discussed.