Thermal-responsive luminescence/dielectric responses with reversibly shifted light emissions

Abstract

Molecular-rotor-type crystals dominated by crown ethers have garnered significant attention for their applications in sensing, optoelectronics, information encryption and other diverse fields. However, the role of crown ethers in regulating photoluminescent properties has long been overlooked in such structural systems. Here, by inserting 18-crown-6 molecules into the ionic crystal (4-pyridinemethaneaminum)PF₆ (PP-1), we constructed a molecular-rotor-type crystal [(4-pyridinemethaneaminum)(18-crown-6)][PF₆] (PCP-1), exhibiting sensitively thermal-driven, unusual PL/dielectric responses. Notably, the introduction of the 18-crown-6 molecule changed the dynamic thermal motion and exerted a confinement effect through rich hydrogen bonding interactions, thereby inducing structural phase transitions and modulating energy transfer processes. These not only brought about switchable dielectric responses but also resulted in a comprehensive improvement of PL properties, encompassing extended lifetime, doubled quantum yield and temperature-controllable luminescent color. This study offers novel insights into the role of crown ethers in developing smart luminescent materials, holding promising prospects for intelligent recognition and information encryption.