H NMR spectroscopic host-guest titrations and mass spectrometric experiments were carried out and revealed a 1:3 binding with pyrene. Density functional calculations further proved the 1:3 binding stoichiometry of the adducts, consistent with the symmetry of the cages. The corresponding binding constants decrease with expanding cage size, and therefore decreasing the packing coefficient, providing an example for Rebek's rule of 55%.
Seib et al. (Tue,) studied this question.