Construction of Self-Assembled Catenanes by Supramolecular Polymers: Unprecedented Mesoscale Molecular Assemblies That Can Be Spontaneously Organized through a Simple Method

Abstract

Catenanes, a class of interlocked compounds wherein cyclic molecules are interlaced through mechanical bonds, have garnered considerable interest as nanomaterials, owing to their distinctive properties arising from the considerable mobility of constituent rings. Efficient synthesis of catenanes is achievable through the "template synthesis method," where precursors of cyclic molecules are arranged via specific noncovalent interactions. In contrast, our research group has pioneered the development of "nanocatenanes," wherein the constituent ring comprises not a single molecule, but an assemblage of several hundred molecules (nanoring). We have successfully visualized chain-like mesoscale structures of nanocatenanes utilizing atomic force microscopy. The construction of nanocatenanes is facilitated by secondary nucleation, a process in which the nucleation of subsequent nanoring is accelerated on the surface of existing nanorings. This article presents an overview of our exploration of nanocatenanes including details of the experimental verification of secondary nucleation and the control over the degree of nanocatenation by constricting the inner diameter of the nanorings through molecular design. Our studies demonstrate the feasibility of structural control within the mesoscale regime, bridging the gap between nanoscale and microscale, an achievement previously unattainable with traditional nanotechnological approaches.

graphical abstract