Substituent Effect on Molecular Motions of m-Halogenated Anilinium/Dibenzo[18]crown-6 Supramolecular Cations in [Ni(dmit)2]- Crystals
Substituent Effect on Molecular Motions of m-Halogenated Anilinium/Dibenzo[18]crown-6 Supramolecular Cations in [Ni(dmit)2]- Crystals
复制标题
DOI：
10.1021/acs.cgd.0c01739
复制
发表时间：
2021-03-30
影响因子：
3.8
通讯作者：
Nakamura, Takayoshi
中科院分区：
文献类型：
--
作者：
Kubo, Kazuya;Takahashi, Kiyonori;Nakamura, Takayoshi
晶体内部的分子运动对晶体的介电性能和功能有显著影响。晶体(m-XAni (+)) (DB [18] crown-6) (Ni (dmit) 2) (-) (m-XAni (+) = m-halogenated anilinium (X = F (1), (X = Cl, 2), (X = Br, 3),和(X =我,4);DB[18]冠-6 =二苯并[18]冠-6；合成了dmit(2-) = 2-thioxio-1,3- dithiolol -4,5-dithiolate)，并从晶体结构、介电响应和分子运动方面讨论了晶体2-4的取代基效应，并与晶体1进行了比较，晶体1由于m-FAni（+）阳离子的触发器运动而表现出铁电转变。虽然由于卤素原子的尺寸较大，晶体2-4没有表现出芳基的旋转无序性，但观察到了面内和面外摆运动。温度依赖晶体学分析表明，晶体2在293 K时从P2(1)/m空间群对称性降低到93 K时的P2(1)空间群，m- clani（+）上的镜面消失与面外摆运动停止有关。对于晶体3和晶体4，提出了小摆角的面内摆运动，势能计算进一步支持了这一观点。由于晶体的半导体性质，这些钟摆运动不能通过电介质测量来检测。
Molecular motion within crystals can significantly affect their dielectric properties and functionalities. Crystals of (m-XAni(+)) (DB[18]crown-6) [Ni(dmit)2](-) (m-XAni(+) = m-halogenated anilinium (X = F, 1), (X = Cl, 2), (X = Br, 3), and (X = I, 4); DB[18]crown-6 = dibenzo[18]crown-6; dmit(2-) = 2-thioxio-1,3-dithiol-4,5-dithiolate) were synthesized, and the substituent effects of crystals 2-4 were discussed in terms of crystal structure, dielectric response, and molecular motion compared with crystal 1, which exhibited a ferroelectric transition due to the flip-flop motion of the m-FAni(+) cation. Although crystals 2-4 did not show rotational disorder of the aryl groups due to the larger size of the halogen atoms, in- and out-of-plane pendulum motions were observed. Temperature-dependent crystallographic analysis revealed that crystal 2 underwent a symmetry reduction from space group P2(1)/m at 293 K to P2(1) at 93 K with the disappearance of the mirror plane on m-ClAni(+) associated with the stopping of the out-of-plane pendulum motion. In the case of crystals 3 and 4, an in-plane pendulum motion at small swing angles was suggested, which was further supported by potential energy calculations. Owing to the semiconducting nature of the crystals, these pendulum motions could not be detected by dielectric measurements.