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.