Single-Crystal X‑ray Diffraction Study of Three Yb@C82 Isomers Cocrystallized with NiII(octaethylporphyrin)

Single crystals of three soluble Yb@C82 isomers, namely, Yb@C2(5)-C82, Yb@Cs(6)-C82, and Yb@C2v(9)-C82, cocrystallized with NiII(octaethylporphyrin), allowed accurate crystallographic elucidation of their molecular structures in terms of both cage symmetry and metal location. Multiple metal positions were found in all these isomers, but the major metal sites were found in some specific regions within these cages. Specifically, the Yb2+ ion prefers to reside close to a hexagonal ring in Yb@C2(5)-C82 and Yb@C2v(9)-C82 but a [5,6,6]-junction carbon atom in Yb@Cs(6)-C82. Theoretical calculations at the B3LYP level revealed that these metal positions all correspond to energy minima from the electrostatic potential maps and give rise to the most stable configurations of these Yb@C82 isomers. Furthermore, it is noteworthy that this is the first report on X-ray crystallographic studies of such metallofullerenes with the popular C2v(9)-C82 encapsulating a divalent metal ion, described as M2+@[C2v(9)-C82]2–.