Room-temperature dielectric switching in a host–guest crown ether inclusion complex

Abstract

Host–guest compounds based on crown ether are promising candidates for switchable dielectric materials, holding great potential in the fields of sensing, information storage, and electronics. However, their phase transition temperature (T_p) is commonly found to be very low, seriously limiting their further development. Herein, using the “momentum matching theory”, we have successfully designed a room-temperature crown ether based switchable dielectric material, 3-methoxyanilinium-18-crown-6 bis(trifluoromethanesulfonyl)ammonium ([(3-methoxyanilinium)(18-crown-6)][TFSA]) (1). Compared with [C₇H₁₀NO-(18-crown-6)][PF₆] (T_p = 180 K), the introduction of the larger TFSA anion not only brings a new kind of C–H⋯O–S interaction between the host cations and ordered TFSA anions to affect the crystal stacking but also enhances the energy barrier of anionic movements, resulting in the occurrence of a phase transition at a higher temperature of about 308 K. Such a large T_p enhancement of 128 K has rarely been reported in a host–guest crown ether inclusion complex. The switchable dielectric behavior between high and low dielectric states suggests great potential for room-temperature bistable dielectric switches. This work paves the way towards the design of crown ether inclusion complex dielectric switches for a wide range of applications such as sensors and switches near room temperature.