Light controlled liquefactions of non-photoresponsive crystals

Abstract The design and construction of photoresponsive compounds with solid-liquid transitions has been one of the central challenges in chemistry. Particularly, challenges remain for non-photoresponsive compounds. Herein, we show that a tiny dope of azobenzene (Azo) in conventional imidazolium-based ionic crystals could demonstrate light-switchable solid-liquid transitions with a rapid responsive speed. The mechanism is based on ordering structure changes of non-photoresponsive ionic crystals induced by photoisomerization of Azo. Imidazolium ionic regions facilitated Azo isomerization while Azo isomerization altered the molecular ordering of ionic crystals, with a result of solid-liquid transitions. The sharp solid-liquid transitions distinctively switched ionic conduction from insulator and conductor, applied in lightcontrolled capacitance and UV sensor. The supramolecular assembly of Azo in imidazolium-based ionic crystals provides a strategy into design of non-photoresponsive materials with photoliquefactions and successfully delivered responsiveness from molecules to macroscopic materials.