Annelated N-heterocyclic carbene-derived organic redox system for consecutive visible-light photocatalysis.

Electron transfer is a fundamental process ubiquitous in both natural and artificial systems. The construction of organic redox systems serves as an ideal platform to explore this mechanism. The interconversion between different electronic structures endows them with unique photoelectric properties, enabling their promising applications in fields such as photocatalysis, organic batteries and electrochromic materials. Herein, we present an organic redox system derived from bis(imino)acenaphthene-supported N-heterocyclic carbene, which exhibits two reversible and well-separated redox processes. The different oxidation states could be isolated and fully characterized, including X-ray diffraction. Moreover, the radical cation exhibits strong absorption in the visible-light region and can be easily generated through photoinduction, fulfilling the prerequisites for consecutive photoinduced electron transfer. Therefore, organic redox system can function as a photocatalyst in the reduction of aryl halides. This strategy expands the variety of organic redox systems and provides a novel approach to the development of photocatalysts.