Carbo‐mer of Barrelene: A Rigid 3D‐Carbon‐Expanded Molecular Barrel.

After extensive studies of 1D and 2D skeletal carbo‐mers based on C8 π‐conjugating dialkynylbutatriene units (DABs: ∼C≡C−(R)C=C=C=C(R)−C≡C∼) bridging sp or sp2 centers in carbo‐butene, carbo‐xylylene or carbo‐benzene derivatives, 3D versions are envisaged through carbo‐barrelenes and partially reduced derivatives thereof where two or three DAB blades span a bridge between sp3 carbinol vertices or ether thereof. For R=Ph, stable representatives were synthesized through a pivotal [6]pericyclynedione, and extensively characterized by spectroscopic, electrochemical and crystallographic methods. Density functional theory calculations allow detailed analysis of structural and electronic features of the 7 Å high C26 barrel‐shaped molecules, and show that they can behave as cages for ionic species. Beyond aesthetical concerns, the results could open prospects of applications in host‐guest supramolecular chemistry and single molecule charge transport. [ABSTRACT FROM AUTHOR]