An asymmetric thiazolo-thiazole derivative as a solvatochromic, reversible and self-color recovery acid–base molecular switch

Abstract

Hydrogen chloride is extensively used in industry and its accidental discharge into the environment is deleterious to various life-forms. Development of minimally sophisticated sensors for the detection of acid vapours is thus of significance for a safe environment and human health. Herein, we report a new asymmetric optical probe, (4-(5-(pyridin-2-yl)thiazolo[5,4-d]thiazol-2-yl)-N,N-bis(pyridin-2-ylmethyl)aniline (1)), which exhibits a rapid, but reversible, visual colour change as well as red-shifted fluorescence (∼650 nm) upon exposure to acid vapours. The mechanism of action is elucidated as a change in conductivity of the material induced as a result of protonation. An electronic prototype for acid sensing is demonstrated by using a thin film wherein 1 is embedded into the polymer polyvinyl alcohol. The prototype functions as a cost-effective and reusable sensor for HCl, with a response time of 1 minute over 4 cycles.