Inclusion of methano[60]fullerene derivatives in cavitand-based coordination cages

Abstract

The X-ray study of self-assembled coordination cage 1, constituted of two tetrapyridyl-substituted resorcin[4]arene cavitands coupled through four square-planar palladium complexes is reported. The coordination cage, embracing an internal cavity of ca. 840 Å³, reveals to have the right size for the inclusion of large molecules such as fullerenes. Cage 1 forms 1:1 complexes with methano[60]fullerene derivatives 3 and 4 bearing a dimethyl and a diethyl malonate addend, respectively. Evidence for inclusion complexation was provided by ¹H NMR spectroscopic studies and ESI-MS investigations, which unambiguously showed the formation of 1:1 fullerene–cage complexes. The association constants (K_a) were experimentally determined to be ca. 150 M⁻¹ at 298 K in CD₂Cl₂. In both complexes 1·3 and 1·4, the malonate residue is threaded through one of the four lateral portals, as clearly shown by docking simulations.