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

OVIEDO, PAOLA S.; BARALDO, LUIS M.; CADRANEL, ALEJANDRO

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA

NATL ACAD SCIENCES

Año: 2021 vol. 118

0027-8424

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 trajec- tories 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 ab- sorption prepares excited states of different wave function sym- metry. These states could be resolved using transient absorption spectroscopy, thanks to wave function symmetry-specific photoin- duced optical transitions. One of these excited states undergoes energy transfer to the acceptor, while another undertakes a back- electron transfer to restate the ground state. This differential be- havior 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.