The close association of a fullerene and a porphyrin was first
recognized in the solid-state porphyrin-fullerene assembly of a
covalent fullerene-porphyrin conjugate.17 In the crystal structure
of this species, the 2.75 Å approach of a fullerene carbon atom
to center of a porphyrin plane was notably shorter than
separations of familiar π-π interactions. Graphite and typical
arene/arene separations are in the range 3.3-3.5 Å. Interfacial
porphyrin/porphyrin separations are >3.2 Å, fullerene/arene
approaches lie in the range 3.0-3.5 Å, and fullerene/fullerene
separations are typically ca. 3.2 Å.17 Two conclusions were
drawn.