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@I-h-C-80, Gd2ScN@I-h-C-80, and TbSC2@IhC80, have been obtained by single-crystal X-ray diffraction on GdSC2N@I-h-C-80 center dot Ni-II(OEP)center dot 2C(6)H(6), Gd2ScN@I-h-C-80 center dot Ni-II(OEP)center dot 2C(6)H(6), and TbSC2N @ I-h-C-80-Ni-II(OEP)center dot 2C(6)H(6). All three have I-h-C-80 cages and planar MM'N-2 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'N-2 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.