N‐Heterocyclic Carbene‐Triarylamine Hybrids as Redox‐Tunable Organophotocatalysts for Radical Cross‐Coupling Reactions

ABSTRACT Visible‐light‐induced photoredox catalysis has emerged as a powerful platform for organic radical transformations under mild conditions. In this field, the development of efficient photocatalysts plays a crucial role. Conventional ruthenium and iridium polypyridyl photocatalysts are limited by the expense of these precious metals. From a sustainable perspective, organic photocatalysts represent cost‐effective and mild alternatives to photoredox catalysis; however, tuning their redox properties often requires complicated synthetic approach. Here we introduce N‐heterocyclic carbene‐triarylamine hybrids as novel donor–acceptor‐type organophotocatalysts. These hybrids feature with facile structural modification, broad intramolecular charge‐transfer absorption bands, and tunable redox potentials. Furthermore, these new photocatalysts have been successfully utilized for five distinct visible‐light‐induced redox‐neutral radical cross‐coupling reactions (94 examples, up to 99% yield). Mechanistic studies indicate that visible‐light irradiation of the photocatalyst generates a charge‐shifted excited state through photoinduced intramolecular electron transfer. This finding has a guiding significance for the design and development of new organophotocatalysts.