Activated Type I and Type II Process for Two-Photon Promoted ROS Generation: The Coordinated Zn Matters

The construction of novel classes of photosensitizers for efficient reactive oxygen species (ROS) generation is of great interest, yet it is a challenge. In this work, a bis(terpyridine)zinc(II) complex (namely, ZnL1) with two-photon absorption activity as an efficient ROS photogenerator was synthesized. Benefiting from the coordinated Zn, the decreased singlet–triplet energy gap favors the intersystem crossing process facilitating the singlet oxygen (1O2) generation via energy transfer. In addition, it makes the superoxide radical (O2·–) generation easier. This is an extremely rare study on two-photon excited ROS generation by activating type I and type II processes based on a cheaper and bioaccessible Zn complex.