2026-10-13T13:11:20Z https://api.figshare.com/v2/oai

oai:figshare.com:article/34020473 2026-09-29T02:08:01Z category_1 category_915 category_24 category_272 category_873 category_39 category_734 portal_63 item_type_6 month_year_09_2026

Resolving Anomalous Cage Escape in Fe(III) Photosensitizers: A Marcus Theory Framework Sven Lempereur (25133771) Felix Glaser (7322096) Yoann Olivier (1337460) Benjamin Elias (136270) Ludovic Troian-Gautier (1891945) Biophysics Physical Sciences not elsewhere classified Evolutionary Biology Environmental Sciences not elsewhere classified Chemical Sciences not elsewhere classified Ecology Biological Sciences not elsewhere classified long remained unexplained geminate charge recombination even reaching unity complete data sets charge recombination becomes state electron transfer abundant photoredox catalysis smaller reorganization energy phtmeimb )< sub marcus theory framework ce </ sub cage escape yield systematically larger φ reorganization energy cage escape state quenching predictive framework photoredox transformations marcus parabola ∼ 0 results establish quantitatively accounts potential window polar solvents notoriously small key parameter inverted region empirical observation e ., driving force curated series 8 ev 17 nitrogen The cage escape yield (Φ_CE), i.e., the separation of the geminate radical pair formed upon bimolecular excited-state electron transfer, is a key parameter that governs the efficiency of photoredox transformations. For Fe(III) photosensitizers featuring doublet ligand-to-metal charge transfer excited states, Φ_CE are notoriously small in polar solvents such as acetonitrile yet increase markedly in dichloromethane, an empirical observation that has long remained unexplained. Herein, excited-state quenching and Φ_CE were quantified for the reaction between the prototypical [Fe(phtmeimb)₂]⁺ photosensitizer and a curated series of 17 nitrogen-based aromatic electron donors whose one-electron oxidation potentials span a potential window of ∼0.8 eV. We show that Φ_CE is dictated by the position of the geminate charge recombination on the Marcus parabola: as the driving force for charge recombination becomes more negative, Φ_CE increases from below 5% to 63% in acetonitrile. Because dichloromethane exhibits a smaller reorganization energy than acetonitrile, its inverted region is reached at less negative driving forces, which quantitatively accounts for the systematically larger Φ_CE measured in this solvent, even reaching unity. The complete data sets are reproduced by a single nonadiabatic Marcus model, providing a predictive framework for cage escape based solely on driving force and reorganization energy. These results establish that cage escape in open-shell Fe(III) photosensitizers obeys Marcus theory and deliver rational design guidelines for earth-abundant photoredox catalysis. 2026-09-28T00:00:00Z Text Journal contribution 10.1021/jacs.6c16361.s001 https://figshare.com/articles/journal_contribution/Resolving_Anomalous_Cage_Escape_in_Fe_III_Photosensitizers_A_Marcus_Theory_Framework/34020473 CC BY-NC 4.0