Atoms in carbon cages: the structure and properties of endohedral fullerenes

Bethune, Donald S.; Johnson, Robert D.; Salem, J.; Vries, Mattanjah S. de; Yannoni, C. S.

doi:10.1038/366123a0

Cited by 694 publications

(345 citation statements)

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“…The name 'metallo-fullerenes' has now become common to denote fullerenes with a metal atom inside. The first type of metallofullerene extracted from fullerene soot was lanthanum-fullerene La@C 82 [86][87][88][89] followed a short time later by scandium fullerene Sc@C 82 [90,91] and yttrium fullerene Y@C 82 [90,92].…”

Section: Intercalated Fullerenesmentioning

confidence: 99%

Solid State and Magnetic Properties of Pure, Intercalated and Superconducting Fullerenes

Buntar¹,

Sauerzopf²,

Weber³

1997

Aust. J. Phys.

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A review of some of the solid state and the magnetic properties of fullerenes is presented. We summarise and discuss experimental results on magnetism of pure C60, C70 and higher fullerenes. The main features of the structure and the magnetic properties of intercalated fullerenes, such as metallofullerenes, TDAE-C60 and polymeric A1C60, are presented. Attention is also paid to the mixed state properties of fullerene superconductors, especially to the evaluation of the critical fields and the characteristic lengths of these materials. Some new experimental results on this subject are also presented.

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Section: Intercalated Fullerenesmentioning

confidence: 99%

Solid State and Magnetic Properties of Pure, Intercalated and Superconducting Fullerenes

Buntar¹,

Sauerzopf²,

Weber³

1997

Aust. J. Phys.

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“…EPR measurements demonstrated that, for the case of La@C 82 , the La atom transfers three electrons to the fullerene cage and resides in the ϩ3 oxidation state. 4,5 Metal-to-cage transfer appears to be a common feature of transition metal-containing endohedral metallofullerenes. Meanwhile, nonlinear optical studies of empty-cage C 60 and C 70 have shown that these materials possess both large third order susceptibilities (3) (Ϫ 4 ; 1 , 2 , 3 ) 6-8 ͑ϳ10 Ϫ11 esu compared to a nonresonant value of 5ϫ10 Ϫ10 esu for a polydiacetylene polymer, 9 for example͒ and strong optical limiting behavior.…”

mentioning

confidence: 99%

“…One of the most intriguing fullerene classes is the endohedral fullerene in which the spheroidal molecular structure is employed to encapsulate a small number of atoms ͑one to four͒ internal to the cage. [3][4][5] Until recently, the difficult separation process of endohedral fullerenes had limited their availability to submilligram levels. Consequently, initial studies of these materials had primarily been restricted to electron paramagnetic resonance ͑EPR͒ and linear spectroscopy ͑UV-vis͒.…”

mentioning

confidence: 99%

Enhanced nonlinear optical response of an endohedral metallofullerene through metal-to-cage charge transfer

Heflin

Marciu

Figura

et al. 1998

Applied Physics Letters

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“…33.20.Wr, 02.20.Df Shortly after it was established that fullerenes are closed-cage structures of carbon, investigators speculated that atoms and clusters might be coaxed to occupy the space inside the cage. The existence of such endohedral fullerenes is now well-established by experiment [1]. Such endohedral doping of C 60 shows some promise as a technique to modify fullerene properties such as electric polarizibility, optical and infrared absorption, and magnetic susceptibility.…”

mentioning

confidence: 95%

“…The existence of such endohedral fullerenes is now well-established by experiment [1]. Such endohedral doping of C 60 shows some promise as a technique to modify fullerene properties such as electric polarizibility, optical and infrared absorption, and magnetic susceptibility.…”

mentioning

confidence: 95%

Theory of Spontaneous Polarization of Endohedral Fullerenes

Clougherty

Anderson

1998

Phys. Rev. Lett.

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A pseudo-Jahn-Teller model describing central atom distortions is proposed for endohedral fullerenes of the form A@C60 where A is either a rare gas or a metal atom. A critical (dimensionless) coupling gc is found, below which the symmetric configuration is stable and above which inversion symmetry is broken. Vibronic parameters are given for selected endohedral fullerenes. 33.20.Wr, 02.20.Df Shortly after it was established that fullerenes are closed-cage structures of carbon, investigators speculated that atoms and clusters might be coaxed to occupy the space inside the cage. The existence of such endohedral fullerenes is now well-established by experiment [1]. Such endohedral doping of C 60 shows some promise as a technique to modify fullerene properties such as electric polarizibility, optical and infrared absorption, and magnetic susceptibility.Several numerical studies [2][3][4][5][6] have concluded that for the case of metal endohedral dopants, such as Na@C 60 , Li@C 60 , and Ca@C 60 , the metal atom transfers its valence electrons to the C 60 cage, and establishes an offcenter equilibrium position, resulting in a net electric dipole moment for the molecule. For the case of rare gas dopants, however, the central atom sits at the cage center.A classical model was used by Erwin [7] to explain the two disparate cases; for metal dopants, the charge transferred to the cage occupies a highly delocalized t 1u orbital. Erwin treats the resulting negatively charged cage as a perfectly conducting sphere. The total energy of the metal cation and the conducting sphere is minimized by placing the cation off-center where electrostatic interaction between the cation and the cage can be made more attractive as the charge on the cage is polarized. The distortion is stabilized in Erwin's model by including a short-ranged repulsive interaction of Lennard-Jones form for the electron overlap between the cation and cage electrons. Such a classical model would predict that for the case of metal dopants, inversion symmetry is broken as the central atom is stabilized in an off-center equilibrium position; while for closed-shell rare gas atoms, there will be no charge transfer and, consequently, no central atom distortion. However, this classical model suffers from two serious problems. First, for the case of singly-ionized alkali atoms, such a classical model would again predict no charge transfer, as such an atom is isoelectronic to a rare gas atom. Thus, charged metallofullerenes such as Li + @C 60 would have the cation symmetrically positioned according to the classical model. This, however, contradicts electronic structure calculations [2,3]. Second, for the distortive case of metallofullerenes, the net dipole moment calculated from the classical model is zero, as the contributions from the cation and the polarized cage exactly cancel.The purpose of this work is two-fold: (1) to remedy the shortcomings of the classical model, and (2) to give insight into the physical mechanisms underlying previous numerical studies. We pre...

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Atoms in carbon cages: the structure and properties of endohedral fullerenes

Cited by 694 publications

References 121 publications

Solid State and Magnetic Properties of Pure, Intercalated and Superconducting Fullerenes

Solid State and Magnetic Properties of Pure, Intercalated and Superconducting Fullerenes

Enhanced nonlinear optical response of an endohedral metallofullerene through metal-to-cage charge transfer

Theory of Spontaneous Polarization of Endohedral Fullerenes

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