Coerulein B: a water-soluble and water-compatible near-infrared photoredox catalyst.

The recent expansion of photoredox catalysis into chemical biology has underscored the importance of photochemistry, attracting the attention of many researchers. On the other hand, as conventional photoredox catalysts were developed for organic synthesis, there is a necessity to develop biocompatible photoredox catalysts. Here, we show a water-soluble and water-compatible near-infrared (NIR) photoredox catalyst, coerulein B (CB). CB is a water-soluble molecule with a slightly twisted molecular structure, and its anionic species (CB-) exhibits NIR absorption and emission. We demonstrated that CB works as a water-compatible photoredox catalyst in the coupling reaction of pyridine hydrochloride and aryldiazonium salt. These results indicate that CB is one of the promising candidates for photocatalysts used in biological reactions.