Crystal structure and phase transition of 2-methoxyanilinium perchlorate-18-crown-6

A new phase transition compound, 2-methoxyanilinium perchlorate-18-crown-6 (1) {(o-CH3OC6H4NH3)+(18-crown-6)·ClO4−}, has been synthesized and separated as crystals. Differential scanning calorimetry (DSC) measurements show a pair of sharp peaks at 225 K (heating) and 210 K (cooling), indicating the phase transition is first-order. Dielectric anomalies observed at 225 K (heating) and 210 K (cooling) further confirm the phase transition. The crystal structures determined at 298 K and 123 K are both triclinic in P−1. The most distinct difference between room-temperature and low-temperature structures is the order–disorder transition of the host 18-crown-6 molecule, which is the driving force of the phase transition.

The most distinct difference between room-temperature and low-temperature structures is the order–disorder transition of the host 18-crown-6 molecule, which is the driving force of the phase transition.Figure optionsDownload as PowerPoint slide