Unravelling the Super-Reductive State of Iridium Photoredox Catalysts

21 June 2023, Version 1


Harnessing the excited state of reduced species has long posed a challenge in the field of photocatalysis. This study presents the isolation and characterization of 1-electron reduced iridium complexes commonly employed in photoredox catalysis. Stochiometric reactions unveiled an unprecedented super-reductant ability for the isolated complexes under light irradiation, reaching potentials below 3 V vs SCE. Notably, the reduced iridium complex can also be electrochemically generated in situ with analogous super-reductant ability, enabling electro(photo)catalysis. Experimental and computational studies reveal that photoreactivity rises from intrinsic excitation of the reduced (bpy●‒)* ligand within the iridium complex, while the metal center acts as a spectator. Corroborating this finding, the organic salt Li+bpy●‒ exhibited equivalent super-reducing reactivity under photochemical conditions. Our findings shed light on the access to the super-reductant states of iridium photoredox catalysts and other metalated bipyridines, opening new opportunities for electro(photo) synthetic methodologies.


Iridium Complexes
Excited State Reactivity
Electrochemical Photocatalysis
Photoinduced Electron Transfer Reactions
Organic Halide Reduction


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