Double-Helix Supramolecular Nanofibers Assembled from Negatively Curved Nanographenes

Abstract

The layered structures of graphite and related nanographene molecules play key roles in their physical and electronic functions. However, the stacking modes of negatively curved nanographenes remains unclear, owing to the lack of suitable nanographene molecules. Herein we report the synthesis and one-dimensional supramolecular self-assembly of negatively curved nanographenes without any assembly-assisting substituents. This curved nanographene self-assembles in various organic solvents and acts as an efficient gelator. The formation of nanofibers was confirmed by microscopic measurements, and an unprecedented double-helix assembly by continuous π-π stacking was uncovered by three-dimensional electron crystallography. This work not only reports the discovery of an all-sp<sup>2</sup>-carbon supramolecular π-organogelator with negative curvature, but also demonstrates the power of three-dimensional electron crystallography for the structural determination of submicrometer-sized molecular alignment.

Negatively Curved Octagon‐Incorporated Aza‐nanographene and its Assembly with Fullerenes

“…[1] Unlike their positively curved counterparts with bowl-like structures, negatively curved NGs show saddleshaped geometries that can serve as models for elusive three-dimensional carbon allotropes such as Mackay crystals and toroidal carbon nanotubes. [2] In addition to the intriguing structures and esthetic appeal, the emergent properties arising from the negative curvature such as conformational dynamics, [3] mechanochromism, [4] chiroptical responses, [4a,5] and supramolecular assembly, [6] have also captivated the scientific community. Moreover, such negatively curved NGs have been further utilized as bioimaging probes, [7] organic semiconductors, [8] and anode materials in lithiumion batteries.…”

π‐Extended Diaza[7]helicenes with Dual Negatively Curved Heptagons: Extensive Synthesis and Spontaneous Resolution into Strippable Homochiral Lamellae with Helical Symmetry

“…[1e,11] It endows helicenes with negative curvatures and hence interesting supramolecular stacking behaviors. [12] Despite of these advances, the synthetic routes for these heptagon-containing helicenes are so far generally limited in full-carbon systems, [13] and the conjugated fusion of more than one heteroatom-doped heptagonal rings remains challenging. This has substantially impeded the comprehensive structural and functional exploration of the helicene family.…”