Bifurcation of excited state trajectories toward energy transfer or electron transfer directed by wave function symmetry

This work explores the concept that differential wave function overlap between excited states can be engineered within a molecular chromophore. The aim is to control excited state wave function symmetries, so that symmetry matches or mismatches result in differential orbital overlap and define low-energy trajectories or kinetic barriers within the excited state surface, that drive excited state population toward different reaction pathways. Two donor-acceptor assemblies were explored, where visible light absorption prepares excited states of different wave function symmetry. These states could be resolved using transient absorption spectroscopy, thanks to wave function symmetry-specific photoinduced optical transitions. One of these excited states undergoes energy transfer to the acceptor, while another undertakes a backelectron transfer to restate the ground state. This differential behavior is possible thanks to the presence of kinetic barriers that prevent excited state equilibration. This strategy can be exploited to avoid energy dissipation in energy conversion or photoredox catalytic schemes.

Automated summary

This work investigates the concept of engineering differential wave function overlap between excited states within a molecular chromophore to control excited state wave function symmetries, which leads to differential orbital overlap and low-energy trajectories within the excited state surface. By exploring two donor-acceptor assemblies, it was found that visible light absorption can prepare excited states with different wave function symmetry, allowing for energy transfer and backelectron transfer. The presence of kinetic barriers prevents excited state equilibration, providing a strategy to avoid energy dissipation in energy conversion or photoredox catalytic schemes.