Phenothiazine, owing to its ease of oxidation and modularity with respect to facile
functionalization, is an attractive central chemical unit from which to construct highly
reducing organic photoredox catalysts. While design improvements have been made in the
community, the yield of intersystem crossing (ΦISC), which determines access to the long-
lived triplet excited state, has yet to be systematically optimized. Herein, we explore the
impacts of N-aryl substituent variation on excited-state dynamics using picosecond to …

Phenothiazine compounds of Formula (I) are described herein. These compounds are
useful as highly reducing organic photoredox catalysts. Suitable substrates for use with the
compounds of Formula (I) include acrylates, styrene, acrylamides, acrylonitrile, vinyl
chloride, methylacrylonitrile, vinyl acetate, and acrylic acid.