Self-Assembled Molecular Capsules for C₇₀ Separation

Significance

Reaction of imidazolide 1 with tris(ethylamino) cyclotriveratrylene (CTV) 2 in dichloromethane at 50 °C provided compound 3 in 92-94% yield. The combination of the concave CTV molecule with the strongly quadruple hydrogen-bonding ureidopyrimidinone unit led to the formation of a novel, well-defined dimeric hydrogen-bonded assembly. Such host complex can encapsulate a fullerene molecule within its large cavity. The system displays a high selectivity for the encapsulation of C₇₀ over C₆₀. By simple ­solid-liquid extractions, C₇₀ could be obtained with a purity of 97% from fullerite after two runs. Addition of trifluoroacetic acid to the THF solutions of the complexes caused the hydrogen-bonded network to break and the encapsulated fullerenes were released from the capsules.