Bicyclic 2-pyridone, with fused heterocyclic rings, a facile core for pure type I photosensitizers

Abstract

Effectively improving the ability of electron transfer is the cornerstone of designing pure type I photosensitizers (PSs). At present, the attractive strategy is to introduce electron-rich structures to promote electron transfer capacity. Herein, we developed a novel core with fused heterocyclic rings (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 an electron-rich environment. Electrochemical experiments and theoretical calculations prove that BCP exhibits a more significant electron transfer phenomenon compared to the non-conjugated case. Based on BCP, a pure type I PS core, triphenylamine (electron donor, D) was introduced to produce a molecule (BCP-TPA) with near infrared emission and high type I PDT efficiency using 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 an electron-rich environment.