A novel supramolecular complex with C60 in a porphyrin box has been computer-modeled using a docking program. The same complex has been experimentally studied by means of time-resolved spectroscopy and compared with another porphyrin box characterized by a different geometry. The results show that rapid singlet energy transfer occurs in toluene — the product of a very effective intermolecular interaction — only when the geometry allows C60 to fit into the box, whereas no interaction was detected when access to the box was physically denied.