Structural organization and molecular self-assembly of a new class of polar and non-polar four-ring based bent-core molecules
Structural organization and molecular self-assembly of a new class of polar and non-polar four-ring based bent-core molecules
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DOI：
10.1016/j.molliq.2019.111687
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发表时间：
2019-12-01
影响因子：
6
通讯作者：
Pal, Santanu Kumar
中科院分区：
文献类型：
--
作者：
Kaur, Supreet;Mohiuddin, Golam;Pal, Santanu Kumar
本文研究了两个新系列的极性和非极性四环基非手性双核分子，它们在分子短臂末端分别含有-CN和-OCH_3基团，并研究了它们在晶态和液晶态下的分子自组装。晶体结构分析表明，这些化合物的分子几何构型发生了沿着151 °的弯曲，并伴随着极性分子的反平行排列、分子间氢键、不同类型的π-π相互作用以及分子在三维空间中的缠结/螺旋排列等基本的分子间相互作用。由于二聚体的反平行分子排列，系列1-n（1-8，1-10）的极性化合物的低级同系物表现出长距离的反相，并具有cybotactic群集（N-cyb）。然而，系列2-n（2-6，2-8）的非极性化合物的低级同系物不形成任何类型的簇，其表现出正常的反相。化合物1-8的介电光谱研究和X-射线衍射测量证实了该化合物具有非对称性。因此，在α-核分子的α-相中形成团簇不仅是由于潜在的近晶相，而且是由于分子结构参数，包括弯曲角，分子偶极矩及其空间排列的综合作用。在整个拉伸范围内观察到负弯曲-张开（K-33-K-11）弹性常数行为。(C)2019爱思唯尔B. V.保留所有权利。
We have studied two new series of polar and non-polar four-ring based achiral bent-core molecules containing -CN and -OCH3 moiety respectively at the tip of the molecular short arm and their molecular self-assembly in crystal and liquid crystal state. Crystal structure analysis revealed the bent molecular geometry of the compounds with bent angle 151 degrees along with fundamental intermolecular interactions such as antiparallel arrangement of the polar molecules, intermolecular hydrogen bonding, different types of pi-pi interactions and entangled/helical molecular arrangement in 3D space. Due to the dimeric antiparallel molecular arrangement, lower homologues of the polar compounds of series 1-n (1-8, 1-10) exhibited long range nematic phase with cybotactic clustering (N-cyb). However, the lower homologues of non-polar compounds of series 2-n (2-6, 2-8) did not form any type of clustering exhibiting normal nematic phase. Dielectric spectroscopic investigations and X-ray diffraction measurements of compound 1-8 confirmed the presence of nematic cybotacticity. Thus, the formation of clusters in nematic phase of bent-core molecules was not only due to an underlying smectic phase but also due to the combined effect of the molecular structural parameters including bent angle, molecular dipole moment and its spatial arrangement. Negative bend-splay (K-33-K-11) elastic constant behavior was observed in the entire nematic range. (C) 2019 Elsevier B.V. All rights reserved.