Supramolecular assemblies of a nitrogen-embedded buckybowl dimer with C60

A directly connected azabuckybowl dimer was synthesized via a palladium-catalysed C-H/C-Br coupling. The electron-donating nature of the pyrrolic nitrogen atoms of the azabuckybowl enabled a strong complexation with pristine C-60. In the presence of two equivalents of C-60, the azabuckybowl dimer formed crystals with a 1 : 2 stoichiometry. Conversely, in diluted solution, complexes with a 1 : 1 stoichiometry of the dimer and C-60 were detected predominantly, and these precipitated upon increasing the concentration of C-60. Scanning electron microscopy images of the precipitate showed fibre-like aggregates, indicating the formation of supramolecular assemblies with 1D chain structures. A variable-temperature H-1 NMR analysis revealed that the precipitate consists of the dimer and C-60 in a 1 : 1 ratio.