Temperature-induced reversible isostructural phase transition in N-isopropylbenzylammonium trifluoromethanesulfonate

A novel organic molecular phase transition material, N-isopropylbenzylamine trifluoromethanesulfonate (1), which displays the reversible tunable dielectric behavior, has been successfully assembled by the intermolecular hydrogen-bonds. It undergoes a first-order solid-to-solid state phase transition at 189.7 K (Tc), being confirmed by thermal analyses including differential scanning calorimetry (DSC), specific heat (Cp) and dielectric measurements. The dielectric constant and dielectric loss of 1 exhibit obvious anomalies and slight tunabilities triggered by heating when the temperature increases approaching to Tc. Variable-temperature single crystal X-ray diffraction demonstrates that the origin of its phase transition may be ascribed to the order–disorder transformation of trifluoromethanesulfonate anions, together with the slight twisting motions of the isopropyl groups in N-isopropylbenzylammonium cation. All the findings make us believe that 1 might be a potential phase transition material.