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

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 angstrom(3), reveals to have the right size for the inclusion of large molecules such as fullerenes. Cage I 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 H-1 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 dockin. simulations.