Bicyclic 2-Pyridone, with Fused Heterocyclic Rings, a Facile Core for Pure Type I Photosensitizers

Effectively improving the ability of electron transfer is the cornerstone of designing pure type I photosensitizers (PSs). At present, the bright strategies are to introduce the electron-rich structures to promote electron transfer capacity. Herein, we developed a novel core with fused heterocyclic ring (bicyclic 2-pyridone, BCP) based on which a series of excellent pure type I PSs can subsequently be constructed. BCP, with the fused heterocyclic rings, can act as an “electronic pool” for forming electron-rich environment. Electrochemical experiments and theoretical calculations prove that BCP has a more significant electron transfer phenomenon compared to the non-conjugated one. Based on BCP, the pure type I PSs core, triphenylamine (electron donor, D) was introduced to produce a molecule (BCP-TPA) with near infrared emission and high type I PDT efficiency by the typical D-π-D structure. BCP-TPA showed superior ability to produce pure type I ROS, which effectively inhibited tumor growth in in vivo experiments. This work provides a new core to synthesize pure type I PSs, combining fused heterocyclic rings to form electron-rich environment.