Dielectric switching from a high temperature plastic phase transition in two organic salts with chiral features

Abstract

Organic ionic plastic crystals (OIPCs) with high-temperature reversible dielectric switching properties, single chiral characteristics, and the potential for various structural phase transformations provide more possibilities for obtaining different functional properties. Here, we successfully synthesized two organic ionic plastic crystals, namely [N(CH₂CH₃)₃(CH₂Cl)][ClO₄] (1) and [N(CH₂CH₃)₃(CH₂Cl)][BF₄] (2), which have two continuous reversible transitions triggered by the order and disorder of anions and ammonium ions. Interestingly, the dielectric constant of 2 is significantly higher than that of 1 under the same conditions. Impedance testing suggests that the arc radius of 2 is smaller than that of 1, indicating that 2 has a faster photogenerated charge carrier rate and greater conductivity. In addition, adopting the chiral space group P3₂21, 1 and 2 showed obvious CD signals. These two chiral compounds with high-temperature dielectric switching provide new ideas for the design of new phase transition compounds and for the exploration of ionic-crystal-based multifunctional organic materials.