Semitubular Aromatic Fragment of Schwarzite P192: A Conserved Structural Motif with Two Embedded Octagons

Molecular carbons with negative curvature constitute the foundation for the precise synthesis of schwarzite carbon. Herein, we report the successful synthesis of a distinctive semitubular molecule comprising two [8]circulene moieties, achieved through Scholl oxidation of a twisted bismacrocyclic precursor. Notably, the two octagonal motifs enforce a nearly 180° bend of the π-system. The highly warped structure of the semitube was revealed by X-ray crystallographic studies, and the flexibility of the π skeleton was illustrated by experimental and theoretical investigation. The structure exhibits an excellent match to the substructure of Schwarzite P192 confirmed by root-mean-square deviation (RMSD) analysis. Furthermore, the large negatively curved π-surface of the saddle allows interactions with multiple C₆₀ molecules, yielding a well-defined cocrystalline assembly. This study opens a promising avenue to the rational design and synthesis of negatively curved molecular carbon materials that combine π-conjugation with high porosity.