Self-assembled M\xf6bius strips with controlled helicity

Guanghui Ouyang,Frank Würthner,Lukang Ji,Minghua Liu,Yuqian Jiang

doi:10.1038/s41467-020-19683-z

Abstract

Different from molecular level topology, the development of supramolecular topology has been limited due to a lack of reliable synthetic methods. Here we describe a supramolecular strategy of accessing Möbius strip, a fascinating topological object featured with only a single edge and single side. Through bending and cyclization of twisted nanofibers self-assembled from chiral glutamate amphiphiles, supramolecular nano-toroids with various twist numbers were obtained. Electron microscopic techniques could clearly identify the formation of Möbius strips when twist numbers on the toroidal fibers are odd ones. Spectroscopic and morphological analysis indicates that the helicity of the Möbius strips and nano-toroids stems from the molecular chirality of glutamate molecules. Therefore, M- and P-helical Möbius strips could be formed from L- and D-amphiphiles, respectively. Our experimental results and theoretical simulations may advance the prospect of creating chiral topologically complex structures via supramolecular approach.

Highlights

Different from molecular level topology, the development of supramolecular topology has been limited due to a lack of reliable synthetic methods
As a continuation of our ongoing endeavor in developing self-assembled chiral structures from supramolecular gels[32], we hypothesized that glutamic acid amphiphiles functionalized with aromatic moieties (Fig. 1a) could form chiral twisted nanostructures derived from bilayer stacking (Fig. 1b)
When the twist numbers on toroid fibers are odd ones, this should prevail in the form of multiple-twisted Möbius strip (Fig. 1d, upper images)

Summary

Introduction

Different from molecular level topology, the development of supramolecular topology has been limited due to a lack of reliable synthetic methods. Through bending and cyclization of twisted nanofibers self-assembled from chiral glutamate amphiphiles, supramolecular nano-toroids with various twist numbers were obtained. While several kinds of important topologically complex molecular structures such as rotaxane[8], knot[9], and catenane[10], have been fabricated via organic synthesis, their supramolecular analogous nanostructures through self-assembly approach are still considered as rather scarce[11,12]. Several self-assembled circular structures were successfully constructed[15,16], toroidal nanostructures with controlled chirality characteristics have been rarely reported. As a special topological circular structure, a physical Möbius strip can be prepared via half-twisting a band any odd number of times and fixing the ends together, leading to a topology that has only a single edge and a single side[17]. Some pioneering reports described Möbius strips from (bio-)macromolecules[12,30] and a NbSe3 inorganic conductor[31], utilizing self-assembly approach, supramolecular

Methods

Results

Conclusion