Straightforward metal-free synthesis of an azacalix[6]arene forming a host–guest complex with fullerene C60

Abstract

Contrasting with the well mastered azacalix[4]arene, the synthesis and characterization of azacalix[6]arene derivatives remain a challenge for chemists. In this framework, bulky n-octylamino groups appended on 1,3-meta-diaminobenzene 2b can lead to the concomitant and straightforward one-pot formation of azacalix[6]arene 4b and of the thermodynamically favoured azacalix[4]arene 3b through simple consecutive nucleophilic aromatic substitutions. The conformations of 3b and 4b were studied in solution and in the solid state using their X-ray molecular structures, their NMR and UV-Visible spectra combined with first principles TD-DFT calculations. Preliminary solution experiments show that 4b can form a 1 : 1 host–guest complex with C₆₀.