Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, 637371 Singapore.
Division of Theoretical Chemistry and Biology, School of Biotechnology, KTH Royal Institute of Technology , SE-10691 Stockholm, Sweden.
ACS Nano. 2017 Dec 26;11(12):11880-11889. doi: 10.1021/acsnano.7b06097. Epub 2017 Nov 20.
Probing the supramolecular chirality of assemblies and controlling their handedness are closely related to the origin of chirality at the supramolecular level and the development of smart materials with desired handedness. However, it remains unclear how achiral residues covalently bonded to chiral amino acids can function in the chirality inversion of supramolecular assemblies. Herein, we report macroscopic chirality and dynamic manipulation of chiroptical activity of hydrogels self-assembled from phenylalanine derivatives, together with the inversion of their handedness achieved solely by exchanging achiral substituents between oligo(ethylene glycol) and carboxylic acid groups. This helicity inversion is mainly induced by distinct stacking mode of the self-assembled building blocks, as collectively confirmed by scanning electron microscopy, circular dichroism, crystallography, and molecular dynamics calculations. Through this straightforward approach, we were able to invert the handedness of helical assemblies by merely exchanging achiral substituents at the terminal of chiral gelators. This work not only presents a feasible strategy to achieve the handedness inversion of helical nanostructures for better understanding of chiral self-assembly process in supramolecular chemistry but also facilities the development of smart materials with controllable handedness in materials science.
探究超分子组装体的手性以及控制其手性，与超分子水平手性的起源以及具有所需手性的智能材料的发展密切相关。然而，目前尚不清楚与手性氨基酸共价键合的非手性残基如何在手性超分子组装体的反转中发挥作用。本文报道了由苯丙氨酸衍生物自组装而成的水凝胶的宏观手性和圆二色活性的动态操控，以及通过在聚（乙二醇）和羧酸基团之间交换非手性取代基，仅实现其手性的反转。这种螺旋反转主要是由自组装结构单元的不同堆积模式引起的，这一点通过扫描电子显微镜、圆二色性、晶体学和分子动力学计算得到了共同证实。通过这种简单的方法，我们仅通过在手性凝胶剂末端交换非手性取代基，就能够反转螺旋组装体的手性。这项工作不仅为更好地理解超分子化学中手性自组装过程提供了实现螺旋纳米结构手性反转的可行策略，而且还为材料科学中具有可控手性的智能材料的发展提供了便利。
