Carbo-mer of barrelene: a rigid 3D-carbon-expanded molecular barrel†.

Abstract

After extensive studies of 1D and 2D skeletal\xa0carbo-mers based on C8π-conjugatingdialkynylbutatriene units(DABs:\xa0~C≡C-(R)C=C=C=C(R)-C≡C~) bridging\xa0spor\xa0sp2centers\xa0in\xa0carbo-butene, -xylylene or -benzene derivatives, 3D versions are envisaged through\xa0carbo-barrelenes and partially reduced derivatives thereofwhere two or three DAB blades span a bridge between\xa0sp3carbinol 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 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.