Reversible phase transition and switchable dielectric behaviors triggered by rotation and order-disorder motions of crowns

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 47; no. 11; pp. 3851 - 3856
• Main Authors: Liu, Yi, Zhou, Hai-Tao, Chen, Shao-Peng, Tan, Yu-Hui, Wang, Chang-Feng, Yang, Chang-Shan, Wen, He-Rui, Tang, Yun-Zhi
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 2018
• Subjects: Benzene; Crown ethers; Dielectrics; Diffraction; Ethers; Ferroelectric materials; Ferroelectricity; Optical materials; Order disorder; Phase transitions; Single crystals; Switches
• ISSN: 1477-9226; 1477-9234; 1477-9234
• DOI: 10.1039/c8dt00003d

Solid-to solid-state reversible phase transitions are widely used in switchable dielectrics, ferroelectrics, piezoelectrics, and pyroelectric and non-linear optical materials. Herein we report a new crown ether clathrate, [Habf-(18-crown-6) 1.5 ] + [PF 6 ] − (Habf = p -ammonium benzene formamide) which shows an interesting reversible phase transition near room temperature (263 K). X-ray single crystal diffraction analysis shows that the synergetic rotation motion between the 18-crown-6 crown ethers and the order-disorder motions of both hexafluorophosphate guest anions and 18-crown-6 crown ether host molecules lead to the phase transition. This reversible phase transition is confirmed by an evident thermal anomaly behavior around 263 K. The apparent step-like dielectric change around the phase transition indicates that it has potential application in dielectric switches. Compound 1 shows apparent step-like dielectric changes near the phase transition, which are triggered by the synergetic rotation motion of 18-C-6 crown ether cycles and hexafluorophosphate anions.