A In (III)-based organic-inorganic hybrid compound: (C4H7N2)4[InBr6][InBr4]·2H2O with a two-step phase transition and switchable dielectric property

Abstract

Organic–inorganic hybrid phase transition compounds with dielectric switchable property have attracted great attention, which can be used in data storage, sensor, NLO materials. Herein, a new organic–inorganic hybrid phase transition compound (C4H7N2)4[InBr6][InBr4]·2H2O(1) is synthesized by In2O3 and 4-methylimidazole in excess HBr. Two pairs of thermal anomaly peaks at 242/236 K (T1) and 253/249 K (T2) are presented in the DSC curves, the small heat hysteresis (6 K and 4 K) and shape of the peaks indicating the second-order type of phase transition. Distinct dielectric anomaly are detected around the phase transition temperature, the value of dielectric constant in room temperature is four times higher than that in low temperature. Crystal structure analysis demonstrates that the order–disorder transition of 4-methylimidazole cations and change of the disorder degree in [InBr4]− anions collectively induce the phase transition. This finding broadens the horizon on designing new In-based organic–inorganic hybrid compounds with dielectric property.