Identification of a Stable ZnII–Oxyl Species Produced in an MFI Zeolite and Its Reversible Reactivity with O2 at Room Temperature

Abstract

AbstractAlthough a terminal oxyl species bound to certain metal ions is believed to be the intermediate for various oxidation reactions, such as O−O bond generation in photosystem II (PSII), such systems have not been characterized. Herein, we report a stable ZnII–oxyl species induced by an MFI‐type zeolite lattice and its reversible reactivity with O2 at room temperature. Its intriguing characteristics were confirmed by in situ spectroscopic studies in combination with quantum‐chemical calculations, namely analyses of the vibronic Franck–Condon progressions and the ESR signal features of both ZnII–oxyl and ZnII–ozonide species formed during this reversible process. Molecular orbital analyses revealed that the reversible reaction between a ZnII–oxyl species and an O2 molecule proceeds via a radical O–O coupling–decoupling mechanism; the unpaired electron of the oxyl species plays a pivotal role in the O−O bond generation process.