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, GdSc2N@Ih -C80, Gd2ScN@Ih -C80, and TbSc2@Ih -C80, have been obtained by single-crystal X-ray diffraction on GdSc2N@Ih -C80·NiII(OEP)·2C6H6, Gd2ScN@Ih -C80·NiII(OEP)·2C6H6, and TbSc2N@Ih -C80·NiII(OEP)·2C6H6. All three have Ih -C80 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.