Selective Generation of Singlet Oxygen in Chloride Accelerated Copper Fenton Chemistry

Singlet oxygen (1O2), a widely used reactive oxygen species (ROS) in industry and biomedical applications, plays a fundamental role throughout nature. We report a novel method to generate 1O2selectively and efficiently through copper-based Fenton chemistry under circumneutral conditions enhanced by chloride as co-catalyst, with reactivity completely different than that observed in classical iron-based Fenton chemistry. The mechanism of its formation was elucidated through the kinetic studies of orthogonally reactive reporter molecules, i.e., singlet oxygen sensor green, 4-hydroxy-2,2,6,6-tetramethylpiperidine, and phenol, and selective ROS quenchers. This method selectively generates 1O2in situneither relying on photosensitization nor resulting in side reactions, and together with the mechanistic understanding of the Cu-Fenton reaction, not only opens new possibilities in many industries, such as organic synthesis and antimicrobial treatments, but also provides insight into Cu and H2O2containing chemical, environmental, and biological systems.