title: Sc2@C66 revisited: an endohedral fullerene with scandium ions nestled within two unsaturated linear triquinanes.
abstract: The geometries of fullerenes are governed by the isolated pentagon rule (IPR), which states that stable fullerenes have each of their 12 pentagons surrounded by five hexagons. At the dawn of fullerene science, it was widely believed that the IPR would also be applicable for endohedral fullerenes. In 2000, that idea was altered by the discovery of the first non-IPR fullerenes, Sc2@C66 and Sc3N@C68. The structural data for Sc2@C66 were interpreted to indicate the presence of a pair of doubly fused pentagons. However, that structure has remained a long-standing mystery, since it is thermodynamically unfavorable. Here, we demonstrate definitively that Sc2@C66 does not have the structure that was long believed to be but a brand new type. 2D NMR spectroscopic and single-crystal X-ray analyses disclose that Sc2@C66 has a C2v(4059)-C66 cage containing two sets of unsaturated linear triquinanes (ULTs), in which three pentagons abut one another and two scandium ions are located within the folds of each of the ULT units.
authors.affiliation: Department of Chemistry, Tokyo Gakugei University , Tokyo 184-8501, Japan.
authors.forename: Michio
authors.initials: M
authors.lastname: Yamada
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kurihara
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Suzuki
authors.forename: Jing Dong
authors.initials: JD
authors.lastname: Guo
authors.forename: Markus
authors.initials: M
authors.lastname: Waelchli
authors.forename: Marilyn M
authors.initials: MM
authors.lastname: Olmstead
authors.forename: Alan L
authors.initials: AL
authors.lastname: Balch
authors.forename: Shigeru
authors.initials: S
authors.lastname: Nagase
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Maeda
authors.forename: Tadashi
authors.initials: T
authors.lastname: Hasegawa
authors.forename: Xing
authors.initials: X
authors.lastname: Lu
authors.forename: Takeshi
authors.initials: T
authors.lastname: Akasaka
mesh_terms: D018360:Crystallography, X-Ray; D037741:Fullerenes / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure
chemical_list: D037741:Fullerenes