Multilevel chirality transfer and second harmonic generation in mesoscopic double helical supramolecular self-assemblies of fullerene enantiomers

Abstract

Inducing chirality in the highly symmetric fullerene C₆₀ is an effective approach that leads to chiroptical responses over a wide range. However, the optically active expression of C₆₀ is a challenging research topic and multiscale modulation of fullerene chirality is still in its infancy. Herein, we synthesized a pair of fulleropyrrolidine enantiomers named R/S-MBA-C₆₀ with a monoclinic P2₁ chiral space group in the solid-state. Rare mesoscopic double helical supramolecular self-assemblies with distinctly opposite chirality have been obtained. Substantial π–π stacking and non-covalent interactions realize the chirality transfer and amplification across different scales, from the chiral carbon atom to the mesoscopic helix. Such fullerene-based double helical structures exhibit intense CD responses over an extremely wide range, from the UV-visible region and even up to the NIR region, and a SHG effect due the non-centrosymmetric molecular structure. This research develops an efficient approach to precisely modulate fullerene chirality and highlights the potential of chirality-based applications in fullerene science.