Facile\nSynthesis of a Fully Fused, Three-Dimensional\nπ‑Conjugated Archimedean Cage with Magnetically Shielded\nCavity

Abstract

The synthesis of molecular cages\nconsisting of fully fused, π-conjugated\nrings is rare due to synthetic challenges including preorganization,\nlarge strain, and poor solubility. Herein, we report such an example\nin which a tris-2-aminobenzophenone precursor undergoes acid-mediated\nself-condensation to form a truncated tetrahedron, one of the 13 Archimedean\nsolids. Formation of eight-membered [1,5]­diazocine rings provides\npreorganization and releases the strain while still maintains weak\nπ-conjugation of the backbone. Thorough characterizations were\nperformed by X-ray, NMR, and UV–vis analysis, assisted by theoretical\ncalculations. The cage exhibits a rigid backbone structure with a\nwell-defined cavity that confines a magnetically shielded environment.\nThe solvent molecule, <i>o</i>-dichlorobenzene, is precisely\nencapsulated in the cavity at a 1:1 ratio with multiple π···π,\nC–H···π, and halogen···π\ninteractions with the cage skeleton, implying its template effect\nfor the cage closing reaction. Our synthetic strategy opens the opportunity\nto access more complex, fully fused, three-dimensional π-conjugated\ncages.