Molecular Conformation of Bent-Core Molecules Affected by Chiral Side Chains Dictates Polymorphism and Chirality in Organic Nano- and Microfilaments
Molecular Conformation of Bent-Core Molecules Affected by Chiral Side Chains Dictates Polymorphism and Chirality in Organic Nano- and Microfilaments
复制标题
手性侧链影响下的弯曲核分子的分子构象决定了有机纳米及微丝的多态性和手性
DOI：
10.1021/acsnano.1c00527
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发表时间：
2021-03-18
期刊：
影响因子：
17.1
通讯作者：
Hegmann, Torsten
中科院分区：
文献类型：
--
作者：
Liu, Jiao;Shadpour, Sasan;Hegmann, Torsten
分子构象和手性之间的耦合是构建不同长度尺度的小分子超分子螺旋结构的基石。受生物系统的启发，人工螺旋分子、聚合物和聚集体的构象预选和控制在光学、光子学和手性分离等领域有着广泛的应用，这些应用通常基于通过模板和自组装等过程进行的固有手性放大。由一些弯曲形状的分子形成的所谓的B4纳米或微丝相是这种手性放大的跨长度尺度的典型案例，最好地说明了由分子构象控制的独特的纳米或微观手性形态的形成。在脂肪族侧链中引入一个或多个手性中心导致了同手性螺旋纳米丝、螺旋微丝和螺旋层状纳米柱的形态的发现。在这里，我们展示了如何使用手性侧链影响的分子构象的先验计算来设计弯曲形状的分子，这些分子自组装成手性纳米和微丝以及纳米环状聚集体，尽管分子具有同手性。此外，手性中心的移位导致了螺旋状和扁平状纳米带的形成。来自偏振光学以及扫描和透射电子显微镜、薄膜和溶液圆二色光谱偏振以及基于同步加速器的X射线衍射实验的自洽数据集支持由手性侧链的结构变化控制的渐进和可预测的形态变化。根据分子手性的影响随着链长的增加或手性中心从核-链连接处移开而减弱的情况，讨论了这些形态的形成。生成的纳米或微丝的相类型(B1柱状或B4)和形态可进一步通过样品处理条件来控制，例如通过各向同性熔体的冷却速度或通过在随后的胶体分散体中存在有机溶剂。我们发现，这些纳米尺度的形态可以组织成丰富的二维和三维形状和结构，范围从鲜花到由相交的平面纳米带形成的纤维垫。
The coupling between molecular conformation and chirality is a cornerstone in the construction of supra-molecular helical structures of small molecules across various length scales. Inspired by biological systems, conformational preselection and control in artificial helical molecules, polymers, and aggregates has guided various applications in optics, photonics, and chiral sorting among others, which are frequently based on an inherent chirality amplification through processes such as templating and self-assembly. The so-called B4 nano- or microfilament phase formed by some bent-shaped molecules is an exemplary case for such chirality amplification across length scales, best illustrated by the formation of distinct nano- or microscopic chiral morphologies controlled by molecular conformation. Introduction of one or more chiral centers in the aliphatic side chains led to the discovery of homochiral helical nanofilament, helical microfilament, and heliconical-layered nanocylinder morphologies. Herein, we demonstrate how a priori calculations of the molecular conformation affected by chiral side chains are used to design bent-shaped molecules that self-assemble into chiral nano- and microfilament as well as nanocylinder conglomerates despite the homochiral nature of the molecules. Furthermore, relocation of the chiral center leads to formation of helical as well as flat nanoribbons. Self-consistent data sets from polarized optical as well as scanning and transmission electron microscopy, thin-film and solution circular dichroism spectropolarimetry, and synchrotron-based X-ray diffraction experiments support the progressive and predictable change in morphology controlled by structural changes in the chiral side chains. The formation of these morphologies is discussed in light of the diminishing effects of molecular chirality as the chain length increases or as the chiral center is moved away from the core-chain juncture. The type of phase (B1-columnar or B4) and morphology of the nano- or microfilaments generated can further be controlled by sample treatment conditions such as by the cooling rate from the isotropic melt or by the presence of an organic solvent in the ensuing colloidal dispersions. We show that these nanoscale morphologies can then organize into a wealth of two- and three-dimensional shapes and structures ranging from flower blossoms to fiber mats formed by intersecting flat nanoribbons.