Pre-regulation of the planar chirality of pillar[5]arenes for preparing discrete chiral nanotubes.

Shixin Fa,Kouichi Egami,Kenichi Kato,Yuuya Nagata,Tomoki Ogoshi,Keisuke Adachi

doi:10.1039/d1sc00074h

Shixin Fa, Kouichi Egami + Show 4 more

Open Access

https://doi.org/10.1039/d1sc00074h

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Abstract

Regulating the chirality of macrocyclic host molecules and supramolecular assemblies is crucial because chirality often plays a role in governing the properties of these systems. Herein, we describe pillar[5]arene-based chiral nanotube formation via pre-regulation of the building blocks' chirality, which is different from frequently used post-regulation strategies. The planar chirality of rim-differentiated pillar[5]arenes is initially regulated by chiral awakening and further induction/inversion through stepwise achiral external stimuli. The pre-regulated chiral information is well stored in discrete nanotubes by interacting with a per-alkylamino-substituted pillar[5]arene. Such pre-regulation is more efficient than post-regulating the chirality of nanotubes.

Highlights

Chirality is widely observed in nature and critically important to living things and life processes;1 this property has been applied extensively in the eld of materials science.2 Research efforts have continuously focused on controlling the chirality of supramolecular assemblies3,4 or polymers5,6 because chirality o en has signi cant effects on the properties of these arti cial systems, as observed in biological systems and applications.7 Chiral control is o en obtained using post-regulation strategies, meaning that the chirality of the materials is regulated via external stimuli a er generating the desired supramolecular assemblies or polymers depending on the kinetic stability of these materials.4,6,8 Another useful strategy is pre-regulation, wherein the chirality of the building blocks is regulated, and the assemblies or polymers are constructed using those chiral building blocks
Chiral control of macrocycles,11 which are of critical importance in supramolecular chemistry as host molecules or building blocks of supramolecular assemblies, are rarely reported
We report a pillar[5]arene-based chirality control system, in which the planar chirality of building block molecules is governed by stepwise addition of external stimuli

Summary

Introduction

Chirality is widely observed in nature and critically important to living things and life processes;1 this property has been applied extensively in the eld of materials science.2 Research efforts have continuously focused on controlling the chirality of supramolecular assemblies3,4 or polymers5,6 because chirality o en has signi cant effects on the properties of these arti cial systems, as observed in biological systems and applications.7 Chiral control is o en obtained using post-regulation strategies, meaning that the chirality (e.g., helicity) of the materials is regulated via external stimuli a er generating the desired supramolecular assemblies or polymers depending on the kinetic stability of these materials.4,6,8 Another useful strategy is pre-regulation, wherein the chirality of the building blocks is regulated, and the assemblies or polymers are constructed using those chiral building blocks. When a shorter linear guest, 1,2-dichloroethane (DCE), was added to the chirality-awakened solution of 1, a weak pR induction was observed (blue line in Fig. 3a), signaling the conversion of the planar chirality of 1.

Results

Conclusion