Photo-induced proton-transfer cycle of 2-naphthol in faujasite zeolitic nanocavities

Abstract

The excited-state deprotonation and ground-state reprotonation of a 2-naphthol molecule encapsulated in the zeolitic nanocavity of NaX have been studied by measuring static and time-resolved spectra of fluorescence and reflectance. The excited molecule undergoes enol dissociation within 300 ps to form an isolated ion pair, which undergoes geminate recombination in 1200 ps or separation to produce the anionic species of 2-naphtholate on the time scale of 2500 ps. Ground-state reprotonation, controlled by the diffusion rate of a proton, is then followed in 0.8 ms with an activation energy of 13 kJ mol⁻¹.