Breaking Kasha's Rule to Enable Higher Reactivity in Photoredox Catalysis.

ABSTRACT: Nearly all photochemical transformations known to date follow Kasha's rule, implying that reactions occur only from the lowest electronically excited state of a given spin multiplicity due to the fast relaxation of higher-energy states. We challenge this foundational principle by demonstrating with time-resolved laser spectroscopy that the 4,4″-dicyano-p-terphenyl radical anion can undergo photoinduced electron transfer directly from a higher-energy excited state, enabling reactivity inaccessible to the lowest excited state with the same spin multiplicity. Preassociation with the substrate and driving-force optimization are critical for overcoming the kinetic barrier to subnanosecond electron transfer, enabling bimolecular anti-Kasha reactivity. This advance establishes a general an

SUBMITTER: Pfund B 

PROVIDER: S-EPMC12314908 | biostudies-literature | 2025 Jul

REPOSITORIES: biostudies-literature