Determination of the cage structure of Sc@C82 by synchrotron powder diffraction

Nishibori, Eiji; Takata, Masaki; Sakata, Makoto; Inakuma, M.; Shinohara, Hisanori

doi:10.1016/s0009-2614(98)01133-6

Cited by 157 publications

(101 citation statements)

References 18 publications

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“…2. This is in contrast to reported results for other metal atoms such as Sc, Y and La in 82, 8,28,29,30,31,32 where the metal atoms are found to be centered inside the fullerene cage on top of the C 2v axis six-membered ring. As discussed in Section II, the NPA charge partitioning tends to give better results; our Gd@82 calculations agree with this analysis, as the Mulliken charge analysis indicates charge transfer of 1.43 electrons from Gd atom to the C 82 cage, and NPA indicates a charge transfer of 2.43 electrons.…”

Section: B Structure Of Gd@82contrasting

confidence: 99%

Electronic Transport, Structure, and Energetics of Endohedral Gd@C₈₂ Metallofullerenes

2004

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Electronic structure and transport properties of the fullerene 82 and the metallofullerene Gd@82 are investigated with density functional theory and the Landauer-Buttiker formalism. The ground state structure of Gd@82 is found to have the Gd atom below the C-C bond on the C2 molecular axis of 82. Insertion of Gd into 82 deforms the carbon chain in the vicinity of the Gd atoms. Significant overlap of the electron distribution is found between Gd and the 82 cage, with the transferred Gd electron density localized mainly on the nearest carbon atoms. This charge localization reduces some of the conducting channels for the transport, causing a reduction in the conductivity of the Gd@82 species relative to the empty 82 molecule. The electron transport across the metallofullerene is found to be insensitive to the spin state of the Gd atom.

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Section: B Structure Of Gd@82contrasting

confidence: 99%

Electronic Transport, Structure, and Energetics of Endohedral Gd@C₈₂ Metallofullerenes

2004

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“…This lateral metal-cage mode in La@C 82 has also been identified using x-ray powder diffraction maximum entropy method (MEM) analysis [19], where a large charge density distribution was attributed to 'giant motion'. La would therefore be expected to give a significantly lower metal-cage frequency than from the tight distribution observed for Sc and Y in the C 82 cage [20,21], consistent with our results. It therefore appears that the lower frequency excited state (ν 1 ) may be due to metal-cage vibrational modes and that this is the dominant cause of T 1 relaxation in the system over the temperature range 15-60 K.…”

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confidence: 90%

“…These, along with x-ray diffraction measurements, have shown the metal atom to be off centre in the cage [19][20][21], with charge transfer to the cage dependent on the metal ion species [22]. These previous EPR studies have primarily used CW spectroscopy and few T 2 times have have been accurately extracted.…”

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confidence: 99%

Electron spin coherence in metallofullerenes: Y, Sc, andLa@C82

et al. 2010

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Endohedral fullerenes encapsulating a spin-active atom or ion within a carbon cage offer a route to self-assembled arrays such as spin chains. In the case of metallofullerenes the charge transfer between the atom and the fullerene cage has been thought to limit the electron spin phase coherence time (T2) to the order of a few microseconds. We study electron spin relaxation in several species of metallofullerene as a function of temperature and solvent environment, yielding a maximum T2 in deuterated o-terphenyl greater than 200µs for Y, Sc and La@C82. The mechanisms governing relaxation (T1, T2) arise from metal-cage vibrational modes, spin-orbit coupling and the nuclear spin environment. The T2 times are over 2 orders of magnitude longer than previously reported and consequently make metallofullerenes of interest in areas such as spin-labelling, spintronics and quantum computing.The possibility of encapsulating an atom inside a fullerene cage was discovered by Heath et al. [1] in 1985 and has led to widespread research into these novel materials. Encapsulation of a nitrogen atom within a C 60 cage (N@C 60 ) has been the subject of particular interest due to the remarkably long electron spin coherence times (T 2 ) reported from 80 to 250 µs [2,3]. Metallofullerenes, containing metal ions encased in a similar way, benefit from faster purification and higher production yields than N@C 60 . However, they have not shown particularly long coherence times (< 1.5 µs), attributed to much greater spin density on the fullerene cage [4,5].The prospect of exploiting the self-assembly of spinactive fullerene molecules into larger structures [6] has stimulated interest in spintronics [7] and quantum information processing (QIP) [8,9]. In particular, metallofullerenes can self-assemble within carbon nanotubes in a 'peapod' structure, creating a 1-D spin chain [6,[10][11][12]. For the potential of such structures to be fully realised, longer electron spin coherence times are required of the constituent metallofullerenes.Several electron paramagnetic resonance (EPR) studies have been conducted on the metallofullerenes Sc-, Y-and La@C 82 focusing on geometric and electronic properties of the molecules [4,5,[13][14][15][16][17][18]. These, along with x-ray diffraction measurements, have shown the metal atom to be off centre in the cage [19][20][21], with charge transfer to the cage dependent on the metal ion species [22]. These previous EPR studies have primarily used CW spectroscopy and few T 2 times have have been accurately extracted. Using pulsed EPR, Knorr et al. report a T 2 of 600 ns for Sc@C 82 (in trichlorobenzene solvent at 2.5 K) but a measured T 2 of 4.1 µs in a Y@C 82 sample was attributed to a 'background' signal [4]. Okabe et al. report a temperature and m I dependence of T 1 and T 2 for La@C 82 (in CS 2 ) arising from motional effects of anisotropic interactions and coherence times < 1.5 µs, in the range 183-283 K [5].In this letter we report pulsed EPR studies of spin relaxation times over a range of temperatures ...

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“…The location of metal atoms inside the fullerene cage and the metal-cage interaction are two central issues. Various diffraction, spectroscopy, and microscopy techniques have been used to characterize metallofullerenes [2][3][4][5][6][7]. Most of them require macroscopic quantities of metallofullerenes and give either ensemble averaged or spatially averaged results.…”

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Unveiling Metal-Cage Hybrid States in a Single Endohedral Metallofullerene

et al. 2003

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The local structural and electronic properties of individual metallofullerenes are studied using scanning tunneling microscopy, scanning tunneling spectroscopy, and theoretical simulations. The energy-resolved metal-cage hybrid states of a single endohedral metallofullerene Dy@C 82 isomer I have been spatially mapped, supporting a complex picture consisting of the orbital hybridization and charge transfer for the interaction between the cage and the metal atom. The relative position of the encapsulated Dy atom inside the cage and the molecular orientation on the surface have been inferred by comparing the experimental results with theoretical simulations. The combined technique provides promising applications in the fields of in situ characterization and diagnostics of metallofullerene-based nanodevices. DOI: 10.1103/PhysRevLett.91.185504 PACS numbers: 61.48.+c, 31.15.Ew, 68.37.Ef, 73.22.-f Endohedral metallofullerenes have been a subject of intensive investigation in recent years, not only because of their structural and electronic novelties but also because of their promising electronic, optical, and biomedical applications [1]. The location of metal atoms inside the fullerene cage and the metal-cage interaction are two central issues. Various diffraction, spectroscopy, and microscopy techniques have been used to characterize metallofullerenes [2][3][4][5][6][7]. Most of them require macroscopic quantities of metallofullerenes and give either ensemble averaged or spatially averaged results. It has been a challenging task to characterize the local properties of isolated metallofullerene molecules [8][9][10][11]. Here we show that scanning tunneling microscopy (STM) can be used to detect the encapsulated metal atom inside a fullerene cage. The energy-resolved metal-cage hybrid states of a single endohedral metallofullerene Dy@C 82 isomer I have been spatially mapped using scanning tunneling spectroscopy (STS). Compared with other states of the metallofullerene, these hybrid states provide unique information on the location of metal atoms inside the fullerene cage and the metal-cage interaction. The relative position of the encapsulated Dy atom inside the cage and the molecular orientation on the surface have been inferred by comparing the experiments with theoretical simulations.The Dy@C 82 isomer I is a metallofullerene in which the Dy atom lies along a C 2 axis on the six-membered ring of the C 2v -C 82 cage [6]. Details for the preparation and separation of Dy@C 82 isomer I were described elsewhere [12,13]. A small amount of solid powder of Dy@C 82 was obtained in a crucible by evaporation of solvent in a dry box. The experiments were conducted in an ultrahigh vacuum STM chamber with a base pressure of 3 10 ÿ11 Torr. We first evaporated one monolayer Ag onto a Si(111) surface to form a 3 p 3 p -Ag surface and then a submonolayer of Dy@C 82 molecules was deposited on the Ag surface. All STM and STS measurements were performed at 5 K using an OMICRON cryostat GmbH STM with W tips that had been subject to ca...

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Determination of the cage structure of Sc@C82 by synchrotron powder diffraction

Cited by 157 publications

References 18 publications

Electronic Transport, Structure, and Energetics of Endohedral Gd@C₈₂ Metallofullerenes

Electronic Transport, Structure, and Energetics of Endohedral Gd@C₈₂ Metallofullerenes

Electron spin coherence in metallofullerenes: Y, Sc, andLa@C82

Unveiling Metal-Cage Hybrid States in a Single Endohedral Metallofullerene

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Determination of the cage structure of Sc@C82 by synchrotron powder diffraction

Cited by 157 publications

References 18 publications

Electronic Transport, Structure, and Energetics of Endohedral Gd@C82 Metallofullerenes

Electronic Transport, Structure, and Energetics of Endohedral Gd@C82 Metallofullerenes

Electron spin coherence in metallofullerenes: Y, Sc, andLa@C82

Unveiling Metal-Cage Hybrid States in a Single Endohedral Metallofullerene

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Electronic Transport, Structure, and Energetics of Endohedral Gd@C₈₂ Metallofullerenes

Electronic Transport, Structure, and Energetics of Endohedral Gd@C₈₂ Metallofullerenes