X-ray Crystallographic Characterization of New Soluble Endohedral Fullerenes Utilizing the Popular C82 Bucky Cage. Isolation and Structural Characterization of Sm@C3v(7)-C82, Sm@Cs(6)-C82, and Sm@C2(5)-C82

Three isomers of Sm@C-82 that are soluble in organic solvents were obtained from the carbon soot produced by vaporization of hollow carbon rods doped with Sm2O3/graphite powder in an electric arc. These isomers were numbered as Sm@C-82(I), Sm@C-82(II), and Sm@C-82(III) in order of their elution times from HPLC chromatography on a Buckyprep column with toluene as the eluent. The identities of isomers, Sm@C-82(I) as Sm@C-s(6)-C-82, Sm@C-82(II) as Sm@C-3v(7)-C-82, and Sm@C-82(III) as Sm@C-2(5)-C-82, were determined by single-crystal X-ray diffraction on cocrystals formed with Ni(octaethylporphyrin). For endohedral fullerenes like La@C-82, which have three electrons transferred to the cage to produce the M3+@(C-82)(3-) electronic distribution, generally only two soluble isomers (e.g., La@C-2v(9)-C-82 (major) and La@C-s(6)-C-82 (minor)) are observed. In contrast, with samarium, which generates the M2+@(C-82)(2-) electronic distribution, five soluble isomers of Sm@C-82 have been detected, three in this study, the other two in two related prior studies. The structures of the four Sm@C-82 isomers that are currently established are Sm@C-2(5)-C-82, Sm@C-s(6)-C-82, Sm@C-3v(7)-C-82, and Sm@C-2v(9)-C-82. All of these isomers obey the isolated pentagon rule (IPR) and are sequentially interconvertable through Stone-Wales transformations.