Deuteration triggered downward shift of dielectric phase transition temperature in a hydrogen-bonded molecular crystal

• Published in: Chinese chemical letters 2022-03, Vol.33 (3), p.1422-1424
• Main Authors: Liang, Bei-Dou, Jin, Tong, Miao, Le-Ping, Chai, Chao-Yang, Fan, Chang-Chun, Han, Xiang-Bin, Zhang, Wen
• Format: Article
• Language: English
• Subjects: Deuteration; Dielectric phase transition; Downward shift of transition temperature; Geometric isotope effect; Stimulus responsive material
• ISSN: 1001-8417; 1878-5964
• DOI: 10.1016/j.cclet.2021.08.032

Deuteration of hydrogen-bonded phase transition crystals can increase the transition temperatures due to the isotope effect. But rare examples show the opposite trend that originates from the structural changes of the hydrogen bond, known as the geometric H/D isotope effect. Herein, we report an organic crystal, diethylammonium hydrogen 1,4-terephthalate, exhibits a reversible structural phase transition and dielectric switching. Structural study shows the cations reside in channels formed by one-dimensional hydrogen-bonded anionic chains and undergo an order-disorder transition at around 206 K. The deuterated counterpart shows an elongation of the O···O hydrogen bond by about 0.005 Å. This geometric isotope effect releases the internal pressure of the anionic host on the cation guests and results in a downward shift of the phase transition temperature by 10 K. [Display omitted]