Discrete chiral organic nanotubes by stacking pillar[5]arenes using covalent linkages

Abstract

Owing to their unique one-dimensional hollow structures, organic nanotubes have been widely explored in recent years. Covalent organic nanotubes (CONs) can be prepared by stacking building blocks, such as macrocycles, through covalent linkages. However, because of the mismatched covalent connections, controllable synthesis of the discrete CONs with clear structures, such as sidewall and chirality, is a challenging target. In this work, by coupling two pillar[5]arenes through dynamic covalent bonds, thermodynamically stable discrete CONs with 5-fold symmetry are successfully prepared. Three different chiral CONs are separated, including homo-CONs, consisting of two enantiomers (pR, pR and pS, pS), and hetero-CON, consisting of the meso form (pR, pS). These CONs show negative allosteric binding affinities toward guest molecules, which are not observed in individual pillar[5]arenes.