Photoinduced Reactions of Radical Ions via Charge Separation

Abstract

This article describes the recent development of photocatalytic reactions using a simple donor‐acceptor‐linked dyad, 9‐mesityl‐10‐methylacridinium ion (Acr + –Mes). The electron‐transfer state of Acr + –Mes (Acr · –Mes ·+ ), produced on visible light irradiation, acts as an efficient oxidant and reductant. The use of Acr + –Mes, which has an extremely long‐lived charge‐separated state, enables the construction of highly efficient photocatalytic systems such as oxygenation, bromination, and carbon‐carbon bond formation of aromatic compounds.

Competitive Desulfonylative Reduction and Oxidation of α-Sulfonylketones Promoted by Photoinduced Electron Transfer with 2-Hydroxyaryl-1,3-dimethylbenzimidazolines under Air

“…The earlier observations described above motivated us to carry out a detailed investigation of processes in which α-ketoalkyl radicals are generated under aerobic PET conditions using BIH-Ar or BIH-ArOH. In particular, we were interested in assessing the relevance of earlier suggestions that PET-generated carbonyl radical anions and radical cations of amines possessing α-hydrogens undergo proton transfer (PT) within contact (solvent-encased) radical ion pairs and that radical ions and radical intermediates are captured by molecular oxygen only after their dissociation from solvent cages . Specifically, we anticipated that BIH-Ar and BIH-ArOH promoted PET reactions of α-heterosubstituted ketones, which have appropriately tuned electron-accepting properties, would take place via pathways in which ketone radical anions or α-ketoalkyl radicals undergo proton or hydrogen atom abstraction (reduction pathway) from BIH-Ar •+ or BIH-ArOH •+ within contact radical ion pairs (CRIPs).…”