Preparation of exTTF-(crown ether)2 receptors, which host C60, to understand the nature of the fullerene–crown ether interaction. A combination of experimental and in silico studies suggest that it results from the interplay of donor–acceptor, ð–ð , n–ð and CH•••ð interactions.

This work is dedicated to Professor Jean-Pierre Sauvage on the occasion of his 70 th birthday.Abstract: A fullerene-ammonium derivative has been combined with different metalloporphyrin-crown ether receptors to generate very stable supermolecules. The combination of fullerene-porphyrin and ammonium-crown ether interactions leads to a strong chelate effect as evidenced by a high effective molarity (3.16 M). The different parameters influencing the stability of the supramolecular ensembles, in particular the nature of the metal in the porphyrin moiety, have been rationalized with the help of theoretical calculations thus providing new insights into fullerene-porphyrin interactions.

Two new conjugated porphyrin-based systems (dimers 3 and 4) endowed with suitable crown ethers have been synthesized as receptors for a fullerene-ammonium salt derivative (1). Association constants in solution have been determined by UV–vis titration experiments in CH2Cl2 at room temperature. The designed hosts are able to associate up to two fullerene-based guest molecules and present association constants as high as ∼5 × 108 M–1. Calculation of the allosteric cooperative factor α for supramolecular complexes [3·12] and [4·12] showed a negative cooperative effect in both cases. The interactions accounting for the formation of the associates are based, first, on the complementary ammonium-crown ether interaction and, second, on the π–π interactions between the porphyrin rings and the C60 moieties. Theoretical calculations have evidenced a significant decrease of the electron density in the porphyrin dimers 3 and 4 upon complexation of the first C60 molecule, in good agreement with the negative cooperativity found in these systems. This negative effect is partially compensated by the stabilizing C60–C60 interactions that take place in the more stable syn-disposition of [4·12].