title: Gate effect of vacancy-type defect of fullerene cages on metal-atom migrations in metallofullerenes.
abstract: Metal-atom migration outside from a defective fullerene cage of a metallofullerene Gd@C(82) (Ca@C(82)), where the Gd(3+) (Ca(2+)) ion is incorporated inside the C(2)(v)()-C(82) cage, is discussed in detail at the B3LYP DFT level of theory. The metal-atom migrations are initiated by the formation of vacancy-type defects involving two coordinatively unsaturated C atoms. This step, which is assumed to proceed due to energy-particle irradiation, leads to the formation of antibonding orbitals between the two C atoms. Since the antibonding orbitals can interact with vacant d-orbitals of the Gd(3)(+)() ion in an in-phase fashion, the attractive interactions allow the Gd ion to insert into the two C atoms in the defect. As a result, the metal ion passes through the defect under energy-particle irradiation. In contrast, the Ca(2+) ion with the vacant s-orbitals does not have such orbital interactions, and thus, a C-C bond is reformed between the two C atoms, which prohibits the Ca ion from penetrating the defected C(82) cage. DFT calculations nicely demonstrate that the orbital interactions control metal-atom migration around the defect site using their orbital symmetries, and therefore, the vacancy-type defect acts as a "gate" that permits a specific atom to go out from a defected fullerene cage.
authors.affiliation: Research Center for Advanced Carbon Materials, National Institute of Advanced Industrial Science and Technology (AIST) Tsukuba, Japan. t-yumura@aist.go.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Yumura
authors.forename: Yuta
authors.initials: Y
authors.lastname: Sato
authors.forename: Kazutomo
authors.initials: K
authors.lastname: Suenaga
authors.forename: Koki
authors.initials: K
authors.lastname: Urita
authors.forename: Sumio
authors.initials: S
authors.lastname: Iijima
mesh_terms: D002118:Calcium / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry*; D037741:Fullerenes / Q000737:chemistry*; D005682:Gadolinium / Q000737:chemistry*; D008956:Models, Chemical; D011789:Quantum Theory
chemical_list: D037741:Fullerenes; D002244:Carbon; D005682:Gadolinium; D002118:Calcium