In Situ Observation of Ferroelastic Domain and Phase Transition in a Three‐Dimensional Molecular Crystal

• Published in: Chemistry : a European journal 2021-12, Vol.27 (70), p.17655-17659
• Main Authors: Cheng, Sai‐Nan, Ding, Kun, Zhang, Tie, Zhang, Zhi‐Xu, Su, Chang‐Yuan, Ge, Jia‐Zhen, Zhang, Yi, Fu, Da‐Wei
• Format: Article
• Language: English
• Subjects: ferroelastics; fluorination effect; hybrid perovskite; multiple phase transitions; single crystal
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202103229

Massive efforts have been devoted to designing molecular ferroic materials by molecular modification. For molecular ferroelastic, previous work is focused on the temperature‐dependent ferroelastic domains, however, few are related to controlling the ferroelastic domain by the stress. Inspired by the “quasi‐spherical theory” and fluorination effect, we designed a more flexible (MedabcoF)2+ (MedabcoF=1‐fluoro‐4‐methyl‐1,4‐diazoniabicyclo[2.2.2]octane) cation by introducing a methyl group and a fluorine atom at the two symmetrical ends of the Dabco (1,4‐diazoniabicyclo[2.2.2]octane) and synthesized a hybrid 3D perovskite (MedabcoF)Rb(BF4)3 (1) which displays three reversible phase transitions accompanying dual ferroelastic behavior. Besides, it not only exhibits ferroelastic domains switching by the thermal stimulation, and the sensitive reaction of in situ domains under the stress of it is also realized. This work not only achieves a force‐controlled ferroelastic domain but develops a more profound comprehension of the relationship between the thermal motion behavior of guest cations and the intriguing properties of materials. The in situ observation of ferroelastic domain processing by the thermal and stress in hybrid molecular crystal and the compound shows four dielectric phase transitions caused by the order‐disorder transformation of the (MedabcoF)2+ cations and the Rb8(BF4)124‐ framework.