Solid State Molecular Dynamic Investigation of An Inclusion Ferroelectric: [(2,6-Diisopropylanilinium)([18]crown-6)]BF4
Solid State Molecular Dynamic Investigation of An Inclusion Ferroelectric: [(2,6-Diisopropylanilinium)([18]crown-6)]BF4
复制标题
铁电体夹杂物的固态分子动力学研究：[(2,6-二异丙基苯胺)([18]crown-6)]BF4
DOI：
10.1021/ja503344b
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发表时间：
2014-07-16
影响因子：
15
通讯作者：
Xiong, Ren-Gen
中科院分区：
文献类型：
--
作者：
Ye, Heng-Yun;Li, Shen-Hui;Xiong, Ren-Gen
分子基铁电体中的许多有序无序型相变都与分子动力学的变化有关。如果分子运动不涉及偶极矩的重新取向，则它们的有序化不能直接促成自发电极化。为了理解这些系统中的铁电机制，重要的是要澄清这样的分子动力学的变化如何诱导结构上的破坏性相变，从而自发电极化的外观。系统表征了[18]冠-6基主客体包合物[（DIPA）（[18]冠-6）] BF 4（DIPA = 2，6-二异丙基苯胺），发现它是一种具有大介电异常、显著热释电性、倍频响应和矩形极化电场磁滞回线的优良铁电体。通过变温单晶结构测定和固体核磁共振观察，发现[18]冠-6分子转动的减慢和BF 4阴离子的翻滚导致了对称性破缺，而自发极化则是由正负离子亚晶格之间的相对位移引起的.这一研究将有助于更深入地理解新兴的分子铁电体的结构和性能之间的关系。
Many order disorder-type phase transitions in molecule-based ferroelectrics are related to changes of molecular dynamics. If the molecular motions do not involve reorientations of dipole moments, their ordering fails to contribute directly to spontaneous electric polarization. For understanding ferroelectric mechanisms in these systems, it is important to clarify how such molecular dynamics changes induce structurally symmetry-breaking phase transitions and thus the appearance of spontaneous electric polarization. Systematic characterization of an [18]crown-6 based host guest inclusion compound, [(DIPA) ([18] crown-6)]BF4 (DIPA = 2,6-diisopropylanilinium), shows it is an excellent ferroelectric with a large dielectric anomaly, significant pyroelectricity, and SHG response, and rectangular polarizaiton electric field hysterisis loops. By the combination of variable-temperature single-crystal structural determination and solid-state NMR observation, it is found that the slowing down of the rotation of the [18]crown-6 molecule and the tumbling of the BF4 anion causes the symmetry breaking, while the spontaneous polarization is induced by the relative displacement between the cationic and anionic sublattices. This investigation will contribute to a deeper understanding of the structure property relationship in the emerging molecular ferroelectrics.