Coronene Bisimide as a Visible-Light-Mediated Triplet-Triplet Energy Transfer Catalyst

Photosensitization has emerged as a versatile tool to facilitate access to excited states under mild conditions, allowing for efficient and selective photochemical transformations. Herein, we report a very simple molecule, coronene bisimide (CBI), as a potent visible-light photosensitizer featuring a high extinction coefficient with a broadband absorption spanning from ultraviolet to green region of the visible spectrum, along with a long-lived triplet state generated via efficient intersystem crossing (ISC). Utilizing the triplet-triplet energy transfer (TTEnT) strategy, CBI catalyzes diverse reactions under green light irradiation. Through this, we propose CBIs as a new class of heavy-atom-free visible-light sensitizers overcoming the limitations of conventional sensitizers, such as low extinction coefficient in the visible regime, short triplet-state lifetimes, and high toxicity, by relying on heavy atoms.