Dibenzylammonium trichloroacetate: an above-room-temperature order–disorder switchable dielectric material

Abstract

Solid-state phase transition materials with a controllable dielectric response are of great interest owing to their technological importance. In the present work, a new molecular electric-ordered compound, dibenzylammonium trichloroacetate (compound 1), showing switchable and tunable dielectric properties, has been successfully synthesized and grown as bulk crystals. It is found that 1 undergoes a reversible solid-to-solid phase transition at 329 K (T_c), which was confirmed by differential scanning calorimetry (DSC), dielectric measurements and variable-temperature powder X-ray diffraction. Structural analyses reveal that intermolecular N–H⋯O hydrogen bonds connect the functional groups together and form a chain-like supramolecular architecture along the a-axis. Further, variable-temperature single-crystal X-ray diffraction discloses the order–disorder feature of its structural change, which is mainly induced by the disordering of trichloroacetate anions upon gradual heating. Moreover, the dielectric constants of 1 display a step-like anomaly around T_c, suggesting that its dielectric responses could be switched or even tuned by external temperature. It is believed that this finding might provide a possible candidate with controllable dielectric performance for potential application.