Phase Transition Originating from Disorder–Order Transformation Coupled with Reorientation in the Organic–Inorganic Hybrid Compound (C4H14N2)[Cd2(H2O)6(SO4)3

Abstract

The organic–inorganic hybrid compound 1,4‐butyldiammonium hexaaquadicadmium(II) trisulfate (C4H14N2)[Cd2(H2O)6(SO4)3] (1) was synthesized by the reaction of 3CdSO4·8H2O with 1,4‐butanediamine in sulfuric acid aqueous solution. Differential scanning calorimetry measurements indicate that 1 undergoes a reversible phase transition at 243.4 K with a thermal hysteresis of 3.3 K. Single‐crystal X‐ray diffraction data disclose that the phase transition is from the room‐temperature phase with the space group C2/c to the low‐temperature phase with the space group P1 with the Aizu notation of 2/mF1. The structural phase transition of 1 is ascribed to the coupling of disorder–order transformations of the flexible 1,4‐butyldiammonium cation and a sulfate anion and reorientation of the cation. The temperature dependence of the dielectric permittivity demonstrates a step‐like change in the range 200–260 K, which makes (C4H14N2)[Cd2(H2O)6(SO4)3] a promising switchable dielectric material. The results could offer an avenue to design switchable dielectric materials through the synergistic effect of disorder–order transitions and reorientation motion.