Shigeru Nagase

Structures and electronic states of M@C82 (M=Sc, Y, La and lanthanides)

Abstract Ab initio molecular orbital and nonlocal density functional calculations show that the C2v endohedral structure is most stable for M@C82 (M=Sc, Y, La and lanthanides), in which M is strongly bonded to a hexagonal ring in C82 by electrostatic interactions. The structural features are consistent with experimental data. The electronic states depend strongly on the encapsulated M atoms.

A theoretical study of C80 and La2@C80

Abstract The structures, energies and electronic properties of seven C 80 fullerene isomers and of La 2 @C 80 are investigated by means of semi-empirical and ab initio calculations. Unlike recent theoretical studies, it is found that the most stable C 80 isomers have D 2 and D 5 symmetries while the I h isomer is most unstable. Upon endohedral doping by two La atoms, however, the I h isomer is most highly stabilized thermodynamically and kinetically with an electronic structure of (La 3+ ) 2 C 80 6− . The I h cage structure and electronic properties predicted for La 2 @C 80 agree with experimental data.

Endohedral dimetallofullerenes Sc2@C84 and La2@C80. Are the metal atoms still inside the fullerence cages?

Abstract In order to provide insight into the motion of metal atoms in endohedral dimetallofullerenes, Sc 2 @C 84 and La 2 @C 80 are investigated as typical examples by use of ab initio molecular orbital and nonlocal density functional methods. It is suggested that the two Sc atoms can oscillate with considerable amplitude while the two La atoms can circulate inside the fullerene cage with small barriers of ≈ 5 cal/mol. It is expected that such metal motions will lead to interesting electronic and magnetic properties.

Isolation and characterization of two Pr@C82 isomers

Abstract The second isomer of Pr@C 82 (Pr@C 82 -II) has been isolated by a two-step HPLC method, separately from the known major isomer (Pr@C 82 -I). Visible and near-IR absorption spectra, as well as cyclic and differential pulse voltammograms show that the characteristic features of Pr@C 82 -II are significantly different from those of Pr@C 82 -I. The absorption peaks of Pr@C 82 -II have blue-shifts and the redox potentials have negative shifts, relative to those of Pr@C 82 -I. Chemical derivatization of both isomers with disilirane have also been achieved.

Unconventional cage structures of endohedral metallofullerenes

Abstract New structures are reported for endohedral metallofullerenes. Through theoretical calculations of Ca@C 72 , Ca@C 74 , and Sc 2 @C 74 , it is found that unconventional cage structures are significantly stabilized by endohedral metal-doping, which violate the isolated pentagon rule or contain heptagonal rings. It is expected that these unconventional structures will extend and enrich the research area of endohedral metallofullerenes. Also reported is a new endohedral metallofullerene La 2 @C 79 N with a heteroatom incorporated in the cage.

Structures and electronic states of endohedral dimetallofullerenes: M2@C80 (M = Sc, Y, La, Ce, Pr, Eu, Gd, Yb and Lu)

Abstract Encapsulation of group 3 and lanthanide metals inside C 80 isomers is investigated using ab initio molecular orbital and non-local density functional methods. The stability and structures depend on the properties of the metal. It is suggested that an energetically stable structure (with a large HOMO-LUMO gap) is most abundantly produced.

Theoretical study of endohedral metallofullerenes: Sc3−nLanN@C80 (n=0–3)

To provide theoretical insight into the structures and properties of Sc3N@C80, which has been isolated in high yield and purity as a new stable endohedral metallofullerene, density functional calculations are carried out for the Sc3−nLanN@C80 (n=0–3) series. Because of electron transfer from Sc3N to C80, the electronic structure of Sc3N@C80 is formally described as (Sc3N)6+Cdocumentclass{article}pagestyle{empty}begin{document}

Structures of the Ca@C82 isomers: a theoretical prediction

_{80}^{6-}

Synthesis and crystal structure of a stable S-nitrosothiol bearing a novel steric protection group and of the corresponding S-nitrothiol

end{document}. The encapsulated Sc3N cluster takes a planar structure with long Sc–Sc distances and is highly stabilized inside the Ih cage of C80, which rotates rapidly. As the number of La atoms increases, the Sc3−nLanN cluster is forced to maintain a pyramidal structure in Sc3−nLanN@C80. In addition, the C80 cage takes an open‐shell electronic structure due to an increase in the number of electrons transferring from Sc3−nLanN. These make the endohedral structure less stable and more reactive.

Strong metal-cage hybridization in endohedral La@C82, Y@C82 and Sc@C82

Abstract Ab initio molecular orbital and nonlocal density functional calculations of Ca@C 82 have been carried out to disclose in which cage isomers of C 82 the Ca atom is encapsulated. Encapsulations inside the C 2v , C s , C 2 and C 3v cages are the most stable and close in energy. This agrees with the fact that four isomers have been isolated and purified for Ca@C 82 . It is suggested that the endohedral structures are determined during the annealing process.