Dynamic mirror-symmetry breaking in bicontinuous cubic phases.
Dynamic mirror-symmetry breaking in bicontinuous cubic phases.
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DOI：
10.1002/anie.201406907
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发表时间：
2014-11-24
期刊：
影响因子：
--
通讯作者：
Tschierske C
中科院分区：
文献类型：
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作者：
Dressel C;Liu F;Prehm M;Zeng X;Ungar G;Tschierske C
自巴斯德以来，非手性分子的对映异构体或手性构象异构体在有序晶体超结构中自组装过程中的手性分离一直吸引着化学家。本文报道了非手性多链端联苯-2，2 ′-联噻吩形成的立方相的自发镜像对称破缺。结果表明，随机对称性破缺是非手性棒状化合物双连续立方液晶相的普遍现象。在所有研究的化合物中，${{\it Im}\bar 3 m}$立方相总是手性的，而${Ia\bar 3d}$相是非手性的。这些有趣的观察解释了传播的同手性螺旋扭曲在整个网络通过螺旋匹配在网络连接。在${Ia\bar 3d}$阶段中，两个网络的相反手征性抵消，但在三个网络${{\it Im}\bar 3 m}$阶段中并非如此。${{\it Im}\bar 3 m}$相的高扭曲解释了它以前未被认识的手性，以及这种复杂结构的起源和不同立方相之间的转变。
Chiral segregation of enantiomers or chiral conformers of achiral molecules during self-assembly in well-ordered crystalline superstructures has fascinated chemists since Pasteur. Here we report spontaneous mirror-symmetry breaking in cubic phases formed by achiral multichain-terminated diphenyl-2,2′-bithiophenes. It was found that stochastic symmetry breaking is a general phenomenon observed in bicontinuous cubic liquid crystal phases of achiral rod-like compounds. In all compounds studied the ${{\it Im}\bar 3m}$ cubic phase is always chiral, while the ${Ia\bar 3d}$ phase is achiral. These intriguing observations are explained by propagation of homochiral helical twist across the entire networks through helix matching at network junctions. In the ${Ia\bar 3d}$ phase the opposing chiralities of the two networks cancel, but not so in the three-networks ${{\it Im}\bar 3m}$ phase. The high twist in the ${{\it Im}\bar 3m}$ phase explains its previously unrecognized chirality, as well as the origin of this complex structure and the transitions between the different cubic phases.