Giant motion of La atom inside C82 cage

Nishibori, Eiji; Takata, Masaki; Sakata, Makoto; Tanaka, Hiroshi; Hasegawa, Masaki; Shinohara, Hisanori

doi:10.1016/s0009-2614(00)01079-4

Cited by 132 publications

(121 citation statements)

References 21 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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“…Similar experimental data on La@C 82 is less conclusive, with a broader mode centered at ∼45-50 cm −1 for La@C 82 [29], though theoretical studies have predicted 'lateral' La-cage modes at 27 and 30 cm −1 [32], slightly higher than our extracted value. 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.…”

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confidence: 82%

“…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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“…[14][15][16][17][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] Since the first X-ray structural determination of Y@C 82 , [19] the molecular structures of various monometallofullerenes M@C 82 have been determined by 13 C NMR [5][6][7]13] and X-ray analyses. [21,23,32,33] In particular, Gd@C 82 [32] and Eu@C 82 [33] have an anomalous structure, in which the metal atom having 7 electrons in f orbital is located on the C 2 axis but is adjacent to the CÀC double bond. This is the opposite position along the molecular axis to that of other monometallofullerenes with C 2v symmetry of the C 82 cage so far reported.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Properties and Crystal Structure of Solvent‐Free Sc@C₈₂ Metallofullerene Microcrystals

et al. 2007

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Magnetic properties of solvent-free crystals of the endohedral Sc@C82 are investigated by SQUID and X-ray powder diffraction. We find that the crystal is a paramagnet and the magnetic susceptibility decreases from 150 K with evidence of antiferromagnetic-like interactions by slow cooling. X-ray crystal analysis reveals the presence of a phase transition at 150 K, which is attributed to an orientational ordering transition of the fullerene molecules. At low temperatures we find a magnetic metastable state that can be controlled by the cooling rate. The metastable state can be formed by rapid cooling. The direction of Sc@C82 molecular axis in the crystals is disordered in the metastable state, and the susceptibility is higher than that in the slow cooling case at low temperature.

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Giant motion of La atom inside C82 cage

Cited by 132 publications

References 21 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

Magnetic Properties and Crystal Structure of Solvent‐Free Sc@C₈₂ Metallofullerene Microcrystals

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Giant motion of La atom inside C82 cage

Cited by 132 publications

References 21 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

Magnetic Properties and Crystal Structure of Solvent‐Free Sc@C82 Metallofullerene Microcrystals

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

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

Magnetic Properties and Crystal Structure of Solvent‐Free Sc@C₈₂ Metallofullerene Microcrystals