Excited State Bond\nHomolysis of Vanadium(V) Photocatalysts\nfor Alkoxy Radical Generation

Advancements in photocatalysis have\ntransformed synthetic\norganic\nchemistry, using light as a powerful tool to drive selective chemical\ntransformations. Recent approaches have focused on metal-halide ligand-to-metal\ncharge transfer (LMCT) photoactivated bond homolysis reactions leveraged\nby earth-abundant elements to generate valuable synthons for radical-mediated\ncross-coupling reactions. Of recent utility, oxovanadium(V) LMCT photocatalysts\nexhibit selective alkoxy radical generation from aliphatic alcohols\nupon blue light (UVA) irradiation under mild conditions. The selective\nphotochemical liberation of alkoxy radicals is valuable for applying\nlate-stage fragmentation approaches in organic synthesis and depolymerization\nstrategies for nonbiodegradable polymers. Steady-state and time-resolved\nspectroscopy were used to assign the electronic structure of three\nwell-defined V(V) photocatalysts in their ground and excited states.\nWe assign the excited state for this transformation at earth-abundant\nvanadium(V), interrogating the electronic structure using static UV–visible\nabsorption, ultrafast transient absorption, and electron paramagnetic\nresonance spectroscopy coupled to computational approaches. These\nfindings afford assignments of the short-lived excited state intermediates\nthat dictate selective homolytic bond cleavage in metal alkoxides,\nillustrating the valuable insight gleaned from fundamental investigations\nof the molecular photochemistry responsible for light-escalated chemical\ntransformations.