Solid-state phase transition induced by ordering of flexible chain alkylamine in N-ethyl-n-butylammonium 3, 5-dinitrobenzoate monohydrate

Abstract

A new molecule-based compound, N-ethyl-n-butylammonium 3, 5-dinitrobenzoate monohydrate, which undergoes a reversible solid-state phase transition at 197K (Tc), has been successfully constructed based on long-chain alkylamine. Specific heat capacity and differential scanning calorimetry (DSC) measurements confirm that it is first-order phase transition with a 5K thermal hysteresis between heating and cooling scans. Dielectric constants exhibit distinct anomalies around Tc accompanied with step-like responses between low and high dielectric states, which further confirm the phase transition. Variable-temperature single-crystal X-ray diffraction analyses illustrate that the phase transition was elucidated from ordering of the flexible N-ethyl-n-butylammonium cations coupled with reorientational motion of the alkylamine chain.