Supramolecular assemblies of a nitrogen-embedded buckybowl dimer with C60

Abstract

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 C₆₀. In the presence of two equivalents of C₆₀, the azabuckybowl dimer formed crystals with a 1 : 2 stoichiometry. Conversely, in diluted solution, complexes with a 1 : 1 stoichiometry of the dimer and C₆₀ were detected predominantly, and these precipitated upon increasing the concentration of C₆₀. Scanning electron microscopy images of the precipitate showed fibre-like aggregates, indicating the formation of supramolecular assemblies with 1D chain structures. A variable-temperature ¹H NMR analysis revealed that the precipitate consists of the dimer and C₆₀ in a 1 : 1 ratio.