Novel fullerene receptors based on calixarene-porphyrin conjugates

Several different synthetic approaches enabling a direct covalent connection between the meso-position of porphyrin and the upper rim of calix4]arene have been studied. The best results were obtained via condensation of an excess of pyrrole and p-methylbenzaldehyde with calix4]arene-5,17-dialdehyde under BF₃·Et₂O catalysis in CHCl₃. Subsequent oxidation of the intermediate porphyrinogen gave the corresponding bis-porphyrin-calixarene conjugate in 15% overall yield. The ¹H NMR complexation study revealed the pronounced selectivity of the bis-porphyrin derivative towards C₇₀ fullerene.