N-Methylpyrrolidinium hydrogen tartrate (NMPHT): an above-room-temperature order–disorder molecular switchable dielectric material $(document).ready(function() { if (!$("html").hasClass("ie8")) { $.ajax({ url: "https://crossmark-cdn.crossref.org/widget/v2.0/widget.js", dataType: "script", cache: true }).done(function() { $(".crossmark-button").addClass("visible"); }); } });

Abstract

A novel molecular switchable dielectric material N-methylpyrrolidinium hydrogen tartrate (NMPHT) has been synthesized, which undergoes above room temperature phase transition. Thermal measurements, e.g. differential scanning calorimetry and specific heat, confirm the presence of a phase transition around 317.5 K. The dielectric measurement displays a distinct step-like anomaly around T_c, showing two different dielectric states, which reveals that NMPHT is a switchable dielectric material. The single-crystal X-ray diffraction analyses at variable temperatures demonstrate that the phase transition emerges from the severe disordering of the N-methylpyrrolidinium (NMP) cation, and during the transition the symmetry of NMPHT is transformed from higher (C2/c) to lower (P2₁/n). These findings will provide a new horizon to design smart dielectric structural phase transition materials by incorporating a flexible NMP based scaffold.