Facile Synthesis of a Fully Fused, Three-Dimensional π-Conjugated Archimedean Cage with Magnetically Shielded Cavity

The synthesis of molecular cages consisting of fully fused, pi-conjugated rings is rare due to synthetic challenges including preorganization, large strain, and poor solubility. Herein, we report such an example in which a tris-2-aminobenzophenone precursor undergoes acid-mediated self-condensation to form a truncated tetrahedron, one of the 13 Archimedean solids. Formation of eight-membered [1,5]diazocine rings provides preorganization and releases the strain while still maintains weak pi-conjugation of the backbone. Thorough characterizations were performed by X-ray, NMR, and UV-vis analysis, assisted by theoretical calculations. The cage exhibits a rigid backbone structure with a well-defined cavity that confines a magnetically shielded environment. The solvent molecule, o-dichlorobenzene, is precisely encapsulated in the cavity at a 1:1 ratio with multiple pi center dot center dot center dot pi, C-H center dot center dot center dot pi, and halogen center dot center dot center dot pi interactions with the cage skeleton, implying its template effect for the cage closing reaction. Our synthetic strategy opens the opportunity to access more complex, fully fused, three-dimensional pi-conjugated cages.

Automated summary

The study reports the synthesis of molecular cages consisting of fully fused, pi-conjugated rings, where a self-condensation process forms a cage with a defined cavity structure and preorganization provided by eight-membered rings. The synthetic strategy opens opportunities for accessing more complex three-dimensional pi-conjugated cages.