Internal and external factors in the structural organization in cocrystals of the mixed-metal endohedrals (GdSc2N@Ih-C80, Gd2ScN@Ih-C80, and TbSc2N@Ih-C80) and nickel(II) octaethylporphyrin.

Structural characterizations of three new mixed-metal endohedrals, GdSc 2N@ I h -C80, Gd 2ScN@ I h -C80, and TbSc 2@ I h -C80, have been obtained by single-crystal X-ray diffraction on GdSc 2N@ I h -C80 x Ni (II)(OEP) x 2C 6H 6, Gd 2ScN@ I h -C 80 x Ni(II)(OEP) x 2C6H6, and TbSc 2N@ I h -C80 x Ni (II)(OEP) x 2C6H6. All three have I h -C 80 cages and planar MM' 2N units. The central nitride ion is positioned further from the larger Gd3+ or Tb3+ ions and closer to the smaller Sc3+ ions. The MM' 2N units show a remarkable degree of orientational order in these and related compounds in which the endohedral fullerene is cocrystallized with a metalloporphyrin. The MM' 2N units are oriented perpendicularly to the porphyrin plane and aligned along one of the N-Ni-N axes of the porphyrin. The smaller Sc3+ ions show a marked preference to lie near the porphyrin plane. The larger Gd3+ or Tb3+ ions assume positions further from the plane of the porphyrin. The roles of dipole forces and electrostatic forces in ordering these cocrystals of endohedral fullerenes and metalloporphyrins are considered.