Visible Light Photoredox Catalysts Useful for Chemical Modifications

Iridium(III) phenylpyridyl complex (1) and its derivatives (2 and 3) work as photoredox catalysts under irradiation of visible light.^1,2) A photocatalyst working for both one-electron oxidation and reduction under visible light irradiation, the so-called “visible light photoredox catalyst”, receives much attention, because there is the possibility for use as a solar energy source.³⁾ A reaction mediated by a photoredox catalyst particularly works simply, whereas a thermal reaction under coexistence of oxidizing and reducing reagents is normally hard to make work. These transition metal complexes (1-3) are useful photocatalysts, because they can form a long-lived triplet-excited state under photoirradiation, and the visible light induced trifluoromethylation of alkynes using 1 is reported as an application.²⁾