Structural phase transitions coupled with prominent dielectric anomalies and dielectric relaxation in a one-dimensional organic-inorganic hybrid compound [C3H4NS][CdCl3]

A new one-dimensional chlorocadmate(II) compound containing linear chains of face-sharing CdCl6 octahedra, thiazolium trichlorocadmate(II) (1), exhibits one isostructural phase transition at 288 K and another symmetry-breaking phase transition at 215 K, accompanied by noteworthy dielectric anomalies and relaxation. Its phase transitions and dielectric responses were investigated by differential scanning calorimetry measurements, variable-temperature structural analyses, and dielectric measurements. The crystal structures determined at 328, 253, and 173 K were solved in Cmcm, Cmcm, and C2/m, respectively. The most distinct differences between these structures are the changes in the dynamics of thiazolium cations, which remain disordered in each structure. The isostructural transition can be ascribed to the slowing down of the molecular motions of thiazolium cations, while the symmetry-breaking one can be attributed to the reorientation of the cation. Two types of dielectric anomalies and one polydispersive dielectric relaxation process are clearly observed during the phase transitions. Such exceptional dielectric performances are also associated with the dynamic behaviors of the dipolar thiazolium cations.