A ferroelastic molecular rotor crystal showing inverse temperature symmetry breaking

Functional dynamic molecular crystals have drawn increasing interest in exploring next-generation flexible and smart materials. Molecular rotors, as a typical type of dynamic material, are good candidates that can exhibit bulk properties and functionalities. Herein, we report a molecular rotor cryst...

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Bibliographic Details
Published in:Inorganic chemistry frontiers 2021-06, Vol.8 (11), p.2809-2816
Main Authors: Le-Ping, Miao, Lin-Lin, Chu, Xiang-Bin, Han, Bei-Dou Liang, Chao-Yang, Chai, Chang-Chun, Fan, Xiao-Xu, Wang, Ye-Feng, Yao, Zhang, Wen
Format: Article
Language:English
Subjects:
Broken symmetry
Crystal structure
Crystallography
Ferroelasticity
Functional materials
High temperature
Inorganic chemistry
Low temperature
NMR spectroscopy
Phase transitions
Rotors
Smart materials
Structural analysis
Symmetry
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Summary:Functional dynamic molecular crystals have drawn increasing interest in exploring next-generation flexible and smart materials. Molecular rotors, as a typical type of dynamic material, are good candidates that can exhibit bulk properties and functionalities. Herein, we report a molecular rotor crystal as a model system to show a unique structural phase transition-related ferroelasticity. The molecular rotor is dumbbell shaped containing a freely rotating axial rotator and multiple peripheral tert-butyl groups on the two plates with restricted motions. The crystal undergoes a ferroelastic structural phase transition at 263 K with unconventional inverse temperature symmetry breaking (ITSB), i.e., a higher-symmetric low-temperature paraelectric phase (point group mmm) vs. a lower-symmetric high-temperature ferroelastic phase (point group 2/m). Combined crystallographic and NMR spectroscopy studies reveal that unequal motions of the peripheral tert-butyl rotators and anisotropic steric repulsion among the molecules are the key cooperative intermolecular interactions to drive a concerted molecular movement to result in the unique ferroelastic phase transition with ITSB. Our study may open avenues for designing and exploring new types of dynamic functional materials.
ISSN:2052-1545
2052-1553
DOI:10.1039/d1qi00309g