Photoredox catalysis constitutes a very powerful tool in
organic synthesis, due to its versatility, efficiency, and the mild conditions
required by photoinduced transformations. In this paper, we present an
efficient and selective photocatalytic procedure for the aerobic oxidative
dehydrogenation of partially saturated N-heterocycles to afford the respective
N-heteroarenes (indoles, quinolines, acridines, and quinoxalines). The
protocol involves the use of new Ir(III) biscyclometalated photocatalysts
of the general formula [Ir(C^N)2(N^N′)]Cl, where the C^N ligand is 2-
(2,4-difluorophenyl)pyridinate, and N^N′ are different ligands based on the
2-(2′-pyridyl)benzimidazole scaffold. In-depth electrochemical and photophysical studies as well as DFT calculations have allowed us to establish
structure−activity relationships, which provide insights for the rational design
of efficient metal-based dyes in photocatalytic oxidation reactions. In
addition, we have formulated a dual mechanism, mediated by the radical
anion superoxide, for the above-mentioned transformations.
