Regulating Reversible Phase Transition Behaviors by Poly-H/F Substitution in Hybrid Perovskite-Like 2[CH2FCH2NH3]·[CdCl4]

• Published in: ACS omega Vol. 5; no. 12; pp. 6773 - 6780
• Main Authors: Song, Ning, Chen, Shao-Peng, Fan, Xiao-Wei, Tan, Yu-Hui, Wei, Wen-Juan, Tang, Yun-Zhi
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 31-03-2020
• ISSN: 2470-1343; 2470-1343
• DOI: 10.1021/acsomega.0c00113

The molecular design and regulation has shown bright future for constructing smart molecular materials such as ferroelectrics, dielectric switches, electro-optic effect, and so forth. Here, by poly-H/F substitution in a simple organic-inorganic hybrid 2­[CH2FCH2NH3]·[CdCl4], 1 (CH2FCH2NH3 = fluorine ethylamine cation), we obtained two novel hybrids, namely, 2­[CHF2CH2NH3]·[CdCl4], 2 (CHF2CH2NH3 = 2,2′-difluorine ethylamine cation) and 2­[CF3CH2NH3]·[CdCl4], 3 (CF3CH2NH3 = 2,2′,2″-trifluorine ethylamine cation). Further investigations show that compounds 1, 2, and 3 experience solid reversible phase transitions with temperatures at 294, 319, and 329 K respectively. These unique phase transitions were confirmed by their remarkable dielectric and heat anomalies around the phase transition temperatures. X-ray single-crystal diffraction analyses before and after the phase transitions show that the order–disorder motions of F atoms and the twist motions from the 2D [CdCl4]2– framework lead to these solid reversible phase transitions. Also, the Hirshfeld surface calculation of compounds 1, 2, and 3 suggests that the increasing ratio of the F···F interaction from the intermolecular interaction makes a major contribution for the substantial increase of their phase transition temperatures.