Isolation of three isomers of Sm@C84 and X-ray crystallographic characterization of Sm@D(3d)(19)-C84 and Sm@C2(13)-C84.

Three isomers with the composition Sm@C(84) were isolated from carbon soot obtained by electric arc vaporization of carbon rods doped with Sm(2)O(3). These isomers were labeled Sm@C(84)(I), Sm@C(84)(II), and Sm@C(84)(III) in order of their elution times during chromatography on a Buckyprep column with toluene as the eluent. Analysis of the structures by single-crystal X-ray diffraction on cocrystals formed with Ni(II)(octaethylporphyrin) reveals the identities of two of the isomers: Sm@C(84)(I) is Sm@C(2)(13)-C(84), and Sm@C(84)(III) is Sm@ D(3d)(19)-C(84). Sm@C(84)(II) can be identified as Sm@C(2)(11)-C(84) on the basis of the similarity of its UV/vis/NIR spectrum with that of Yb@C(2)(11)-C(84), whose carbon cage has been characterized by (13)C NMR spectroscopy. Comparison of the three Sm@C(84) isomers identified in this project with two prior reports of the preparation and isolation of isomers of Sm@C(84) indicate that five different Sm@C(84) isomers have been found and that the source of samarium used for the generation of fullerene soot is important in determining which of these isomers form.