Switchover from singlet oxygen to superoxide radical through a photoinduced two-step sequential energy transfer process

Abstract

The competitive nature of type II photosensitizers in the transfer of excitation energy for the generation of singlet oxygen (¹O₂) presents significant challenges in the design of type I photosensitizers to produce the superoxide anion radical (O₂^˙−). In this study, we present an efficient method for the direct transformation of type II photosensitizers into type I photosensitizers through the implementation of an artificial light-harvesting system (ALHSs) involving a two-step sequential energy transfer process. The designed supramolecular complex (DNPY-SBE-β-CD) not only has the ability to generate ¹O₂ as type II photosensitizers, but also demonstrates remarkable fluorescence properties in aqueous solution, which renders it an efficient energy donor for the development of type I photosensitizers ALHSs, thereby enabling the efficient generation of O₂^˙−. Meanwhile, to ascertain the capability and practicality of this method, two organic reactions were conducted, namely the photooxidation reaction of thioanisole and oxidative hydroxylation of arylboronic acids, both of which display a high level of efficiency and exhibit significant catalytic performance. This work provides an efficient method for turning type II photosensitizers into type I photosensitizers by a two-step sequential energy transfer procedure.