Synthesis, structure, and phase transition of a novel proton transfer in a supramolecular cation with 2-nitroanilinium based on 18-crown-6

Abstract

One novel inorganic–organic hybrid supramolecular compound named (2-nitroanilinium)(18-crown-6)(IO4) (1) has been synthesized and characterized through single-crystal X-ray diffraction, elemental analysis, infrared analysis, thermogravimetric analysis, differential scanning calorimetry (DSC), and potential energy calculations. DSC measurements show a pair of reversible peaks at 260.5 (cooling) and 264.5 K (heating) with heat hysteresis of approximately 4 K. These characteristics indicate that this supramolecular compound undergoes a reversible phase transition, as confirmed by temperature-dependent dielectric measurements. Structural analysis and potential energy calculations demonstrate that dielectric anomaly and phase transition occur because of the intramolecular and intermolecular proton transfer of NH3+ in 2-nitroanilinium as a consequence of NO2 motion in the cation.