Uniform Helical 3D Microflowers from Single-Component Hierarchical Assembly.

Abstract

This study demonstrates the template-free preparation of uniform macroscopic helical flower-like structures from a solution of a single axially chiral compound via simple annealing. To achieve a balance between structural flexibility and rigidity while introducing hydrogen-bonding sites, the molecular design connects the binaphthalene-azobenzene core to the terminal benzoic acid groups via flexible alkyl chains. The synthesized microflower displays a highly ordered, "windmill-like" spiral architecture, exhibiting unambiguous handedness. This structure achieves a clear macroscopic manifestation of chirality. Morphological analysis traces the macroscopic chirality to screw dislocation formation and progressive twist accumulation within the lamellae. Crystallographic and spectroscopic evidence reveals that these defects originate from solvent-hydrogen-bond-directed interlayer slip and precise axial chirality transfer through helical molecular chain formation. This work provides a straightforward route to macroscopically chiral structures with elegant and intricate morphologies, providing a new paradigm for the expression and amplification of molecular axial chirality at the macroscopic scale.