Ion-selective response of visible light photoswitchable indole-hemithioindigo: toward chemical sensing of fluoride and hydroxide

Abstract

The chemical sensing of hydrophilic anions such as F⁻ and OH⁻ is of significant importance but also presents considerable challenges. Herein, the thermal E to Z isomerization of a visible-light-responsive photoswitch (HTI-In) is utilized to address this challenge for the first time. The isomerization of HTI-In is dependent on the concentration of F⁻ and OH⁻, and exhibits excellent selectivity toward F⁻ and OH⁻ over other common anions and cations. Unlike irreversible chemodosimeters and other conventional fluorescent probes, the photodynamic sensing of F⁻ and OH⁻ (demonstrated in solvents and polyurethane hydrogels) is based on a non-equilibrium chemical kinetics and can be operated fully reversibly.