Stereoisomeric Mixture of a Multigram-Synthesized Helicene Assembles Swiftly into Hierarchical Ribbons via Supramolecular Sheets

Abstract

Hierarchical supramolecular assembly is a hallmark of biological systems but remains difficult to emulate with synthetic tectons. The challenge increases with chiral tectons, particularly when they are not optically enriched. It follows that the most demanding scenario for hierarchical self-assembly arises from racemic mixtures of multiple diastereomers. Here, we report the rapid self-assembly of a mixture of six stereoisomers of a new helicene into hierarchical centimeters-long supramolecular ribbons. A structural analog of perylene-diimide, this helicene is accessible on a multigram scale (>10 g per batch). Microscopic, spectroscopic, and X-ray analyses suggest the helicene spontaneously forms homo-handed, single-molecule-thick sheets that associate into filaments. These filaments bundle into fibers, which entangle to form macroscopic ribbons—visible from the growth solution within seconds. This new helicene may be leveraged for the preparation of other hierarchical supramolecular assemblies, including those with stereochemically complex constituents.