Preparation and Extraction of Ca@C60

Kubozono, Yoshihiro; Ohta, Takayoshi; Hayashibara, Tosiyuki; Maeda, Hironobu; Ishida, Hiroyuki; Kashino, Setsuo; Oshima, Kokichi; Yamazaki, Hitoshi; Ukita, Sigeyuki; Sogabe, T.

doi:10.1246/cl.1995.457

Cited by 44 publications

(22 citation statements)

References 6 publications

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“…It has been difficult to extract the most abundant M@C 60 and M@C 70 metallofullerenes due to their insolubility in regular fullerene solvents ,, such as toluene and CS 2 . Even though several metallofullerenes with cages as small as C 60 have been extracted by solvents such as pyridine and aniline, − it has become a large challenge to separate the M@C 60 fraction since pyridine and aniline solvents are not suitable for high-performance liquid chromatography (HPLC) . Only recently, La@C 70 and Y@C 2 n with 2 n ≥ 60, functionalized by CF 3 radicals, have been separated using toluene and CS 2 as solvents. , In this new strategy, the function of trifluoromethyl radicals was to further separate the metallofullerene cages and to chemically stabilize their unstable open-shell electronic configuration .…”

Section: Resultsmentioning

confidence: 99%

Can CF₃-Functionalized La@C₆₀ Be Isolated Experimentally and Become Superconducting?

Guan

Tománek

2017

Nano Lett.

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Superconducting behavior even under harsh ambient conditions is expected to occur in La@C if it could be isolated from the primary metallofullerene soot when functionalized by CF radicals. We use ab initio density functional theory calculations to compare the stability and electronic structure of C and the La@C endohedral metallofullerene to their counterparts functionalized by CF. We found that CF radicals favor binding to C and La@C and have identified the most stable isomers. Structures with an even number m of radicals are energetically preferred for C and structures with odd m for La@C due to the extra charge on the fullerene. This is consistent with a wide HOMO-LUMO gap in La@C(CF) with odd m, causing extra stabilization in the closed-shell electronic configuration. CF radicals are both stabilizing agents and molecular separators in a metallic crystal, which could increase the critical temperature for superconductivity.

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Section: Resultsmentioning

confidence: 99%

Can CF₃-Functionalized La@C₆₀ Be Isolated Experimentally and Become Superconducting?

Guan

Tománek

2017

Nano Lett.

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“…103 Furthermore, N-containing solvents such as N,N-dimethylformamide (DMF) and pyridine were found to be particularly affinitive to mono-EMFs, most probably by forming some unclear complexes. 102,[104][105][106][107] However, after evaporation of these solvents, the complexes decomposed and some of the EMF species, such as M@C 60 , remained insoluble in other non-polar solvents, which impedes further purification and characterization.…”

Section: Extractionmentioning

confidence: 99%

Current status and future developments of endohedral metallofullerenes

et al. 2012

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Endohedral metallofullerenes (EMFs), a new class of hybrid molecules formed by encapsulation of metallic species inside fullerene cages, exhibit unique properties that differ distinctly from those of empty fullerenes because of the presence of metals and their hybridization effects via electron transfer. This critical review provides a balanced but not an exhaustive summary regarding almost all aspects of EMFs, including the history, the classification, current progress in the synthesis, extraction, isolation, and characterization of EMFs, as well as their physiochemical properties and applications in fields such as electronics, photovoltaics, biomedicine, and materials science. Emphasis is assigned to experimentally obtained results, especially the X-ray crystallographic characterizations of EMFs and their derivatives, rather than theoretical calculations, although the latter has indeed enhanced our knowledge of metal-cage interactions. Finally, perspectives related to future developments and challenges in the research of EMFs are proposed. (381 references).

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“…The inability to extract and purify M@C 60 is due to their very small highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps predicted, which lead to high chemical reactivity toward surrounding soot, air, moisture, and various organic solvents. There have been, however, several attempts 12 – 15 to try and extract and purify M@C 60 by, for example, vacuum sublimation from soot followed by liquid chromatographic separation 13 , 14 . Unfortunately, none of these efforts led to the final macroscopic preparation of pure and isolated M@C 60 .…”

Section: Introductionmentioning

confidence: 99%

Crystalline functionalized endohedral C60 metallofullerides

et al. 2018

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Endohedral metallofullerenes have been extensively studied since the first experimental observation of La@C60 in a laser-vaporized supersonic beam in 1985. However, most of these studies have focused on metallofullerenes larger than C60 such as (metal)@C82, and there are no reported purified C60-based monomeric metallofullerenes, except for [Li@C60]+(SbCl6)− salt. Pure (metal)@C60 compounds have not been obtained because of their extremely high chemical reactivity. One route to their stabilization is through chemical functionalization. Here we report the isolation, structural determination and electromagnetic properties of functionalized crystalline C60-based metallofullerenes Gd@C60(CF3)5 and La@C60(CF3)5. Synchrotron X-ray single-crystal diffraction reveals that La and Gd atoms are indeed encapsulated in the Ih-C60 fullerene. The HOMO-LUMO gaps of Gd@C60 and La@C60 are significantly widened by an order of magnitude with addition of CF3 groups. Magnetic measurements show the presence of a weak antiferromagnetic coupling in Gd@C60(CF3)3 crystals at low temperatures.

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Preparation and Extraction of Ca@C60

Cited by 44 publications

References 6 publications

Can CF₃-Functionalized La@C₆₀ Be Isolated Experimentally and Become Superconducting?

Can CF₃-Functionalized La@C₆₀ Be Isolated Experimentally and Become Superconducting?

Current status and future developments of endohedral metallofullerenes

Crystalline functionalized endohedral C60 metallofullerides

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Preparation and Extraction of Ca@C60

Cited by 44 publications

References 6 publications

Can CF3-Functionalized La@C60 Be Isolated Experimentally and Become Superconducting?

Can CF3-Functionalized La@C60 Be Isolated Experimentally and Become Superconducting?

Current status and future developments of endohedral metallofullerenes

Crystalline functionalized endohedral C60 metallofullerides

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Can CF₃-Functionalized La@C₆₀ Be Isolated Experimentally and Become Superconducting?

Can CF₃-Functionalized La@C₆₀ Be Isolated Experimentally and Become Superconducting?