A Chiral Saddle‐Shaped Nanographene With Two Heptagon‐Embedded [4]Helicenes

Abstract

ABSTRACT Chiral non‐benzenoid nanographenes (NGs) remain highly appealing, yet underexplored synthetic targets due to the lack of feasible synthetic strategies to simultaneously construct non‐hexagonal rings and stable chirality. Herein, we demonstrate a novel synthetic strategy to construct a chiral saddle‐shaped nanographene ( cSNG ) via stepwise oxidation of an anthracene‐containing oligophenylene precursor. Scholl‐type oxidation first yields a key intermediate featuring sp 3 ‐defect heptagons, and subsequent oxidative dehydrogenation furnishes target cSNG incorporating two heptagon‐embedded [4]helicenes. The structure of cSNG is unambiguously confirmed by single‐crystal analysis, demonstrating its saddle‐shaped geometry with intrinsic chirality. Remarkably, due to the heptagon‐embedded [4]helicene subunits, cSNG exists as configurationally stable enantiomers which enable chiral resolution, leading to pronounced chiroptical responses and enhanced dissymmetry factors, compared with its sp 3 ‐defect precursor. Moreover, profiting from chiral saddle geometry with shape‐adaptive character, cSNG presents strong host–guest interactions with fullerenes, with association constants up to 2.3 × 10 4  M −1 for C 60 and 8.7 × 10 4  M −1 for C 70 , which are among the highest values reported for negatively curved nanographenes. Crystallographic analysis of cocrystals of cSNG with C 60 further revealed a distinct 1:3 binding mode for supramolecular complexation, featuring two fullerenes accommodated within the saddle cavity and two additional fullerenes externally shared between neighboring saddle units.