Reversible phase transition driven by order–disorder transformations of metal-halide moieties in [(C6H14)NH2]2·CuBr4

Abstract

A novel phase transition has been discovered where the phase transition is primarily accomplished by the order–disorder transformation of metal-coordinated halogen atoms in an organic–inorganic hybrid material [(C₆H₁₄)NH₂]₂·CuBr₄ (1). Its phase transition behaviour was verified by specific heat capacity (C_p) and differential scanning calorimetry (DSC) measurements with a thermal hysteresis at 4.8 K. The dielectric measurements of 1 show a distinct step-like anomaly around T_c, demonstrating two states at two different phases, which enlightens that 1 can be conceived as a potential switchable dielectric material. Moreover, temperature-dependent single-crystal X-ray diffraction analyses of 1 disclose that disordering of metal-halides together with reorientations of the cations is the cause of this unique phase-transition material. All these results open a new way to design and assemble novel phase transition materials.