Exohedral adducts of La@C82

Akasaka, Takeshi; Kato, Tatsuhisa; Kobayashi, Kaoru; Nagase, Shigeru; Yamamoto, Kazunori; Funasaka, Hideyuki; Takahashi, Takeshi

doi:10.1038/374600a0

Cited by 177 publications

(155 citation statements)

References 10 publications

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“…A variety of ionization techniques, including fast-atom bombardment (FAB), electron ionization (EI), chemical ionization (CI), desorption EI (DEI), desorption CI (DCI), laser desorption (LD) and electrospray ionization have been used previously. [11][12][13][14] The characterization of C 60 derivatives is more difficult than that of C 60 itself, because many derivatives fragment easily under most ionization conditions. In the present paper, LD time-of-flight mass spectrometry was used for the characterization of water-soluble fullerenols.…”

mentioning

confidence: 99%

Unusual Polymerization Behavior of Water-soluble Fullerenols in Laser Desorption Ionization Time-of-flight Mass Spectrometry

Sun

Liu

Guo

et al. 1997

Rapid Commun. Mass Spectrom.

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confidence: 99%

Unusual Polymerization Behavior of Water-soluble Fullerenols in Laser Desorption Ionization Time-of-flight Mass Spectrometry

Sun

Liu

Guo

et al. 1997

Rapid Commun. Mass Spectrom.

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“…It is envisioned, therefore, that metallofullerenes could provide a unique alternative to chelating compounds because of their resistance to metabolism and their high kinetic stability. Additionally, the large carbon-based surface area of fullerenes and metallofullerenes (Ϸ200 Å 2 ) facilitates the development of tissue-targeting compounds by using established metallofullerene derivative chemistry (10)(11)(12)(13)(14)(15). Thus, the metallofullerenes may be useful as a new, more stable alternative for transporting radiometals in vivo.…”

mentioning

confidence: 99%

“…4), but comparatively little is known about endohedral metallofullerenes because of their low production yields, low solution solubilities, difficult purification, and air sensitivity (5)(6)(7)(8)(9). However, advances in HPLC purification procedures (5)(6)(7)(8)(9) and chemical derivatization (10)(11)(12)(13)(14)(15) of fullerenes have recently expanded research possibilities into applications for metallofullerenes when relatively small amounts of material are required.…”

mentioning

confidence: 99%

In vivo studies of fullerene-based materials using endohedral metallofullerene radiotracers

Cagle

Kennel²,

Mirzadeh³

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

288

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Biodistribution studies of a water-soluble radioactive metallofullerene compound have been conducted using BALB͞c mice. To this end, a sample containing Ho x @C 82 (x ‫؍‬ 1, 2) was purified and derivatized to prepare the watersoluble metallofullerol, Ho x @C 82 Since the discovery of fullerenes in 1985 (1) and the subsequent incorporation of metal atoms within their carbon cage (2), intense interest has focused on these unique molecules. Research efforts have greatly extended our knowledge of the chemical and biological properties of empty fullerenes (3; for review, see ref. 4), but comparatively little is known about endohedral metallofullerenes because of their low production yields, low solution solubilities, difficult purification, and air sensitivity (5-9). However, advances in HPLC purification procedures (5-9) and chemical derivatization (10-15) of fullerenes have recently expanded research possibilities into applications for metallofullerenes when relatively small amounts of material are required.One potential application for metallofullerenes is in the field of nuclear medicine. Current radiopharmaceuticals employ small quantities (nanograms to milligrams) of drugs containing specially chelated radioisotopes of metals for imaging or therapeutic applications. The chelating ligands prevent direct binding of the toxic metal ions with serum components and tissue by providing a thermodynamically stable molecular environment. A major concern with these drugs, however, is their in vivo kinetic instability, which can allow the release of small amounts of toxic radiometals (16). It is envisioned, therefore, that metallofullerenes could provide a unique alternative to chelating compounds because of their resistance to metabolism and their high kinetic stability. Additionally, the large carbon-based surface area of fullerenes and metallofullerenes (Ϸ200 Å 2 ) facilitates the development of tissue-targeting compounds by using established metallofullerene derivative chemistry (10-15). Thus, the metallofullerenes may be useful as a new, more stable alternative for transporting radiometals in vivo.Empty fullerenes have low cytotoxicity both in vitro (17-22) and in vivo (17,(23)(24)(25)(26), despite one report of a photosensitizing C 60 derivative (24). In addition, empty fullerenes and their derivatives have been tested for their biodistribution, and some C 60 derivatives have shown promise as anti-HIV (27-34) and anticancer (35-37) agents and as an agent to reduce reactive oxygen species (20,21). Dugan et al. (17,38) have also demonstrated the usefulness of fullerene derivatives as biological freeradical scavengers in vivo. Research involving the biodistribution of fullerenes in vivo is limited to studies on C 60 and La@C 82 suspensions (23, 25), and to three water-soluble C 60 derivatives (26,30,39). All of these studies indicate rapid localization and long-term residency in the liver (Ͻ1% clearance), and one of the studies demonstrated that fullerenes are not metabolized rapidly in vivo (39). To help opti...

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“…Evidence from ab initio and semiempirical calculations, and from cyclic voltammograms (CV) and differential pulse voltammograms (DPV), shows that the IP values of La@C 82 (6.19 eV), Ce@C 82 (6.46 eV) and Gd@C 82 (6.25 eV) are smaller than those of C 82 (6.96 eV), C 70 (7.64 eV) and C 60 (7.78 eV). 5,6,15 The Fig. 3(a).…”

Section: Ion/molecule Reactionsmentioning

confidence: 97%

“…Only recently have T. Akasaka et al published the chemical derivatization of isolated La@C 82 and Gd@C 82 by 1,1,2,2-tetramesityl-1,2-disilirane. 5,6 Mirroring studies in the condensed phase, mass spectrometry provides a powerful tool for chemical property research by virtue of its advantages, viz. small quantity sample requirements, convenience and speed.…”

mentioning

confidence: 99%

Gas phase derivatization of endohedral metallofullerenes R@C82 and R2@C80 (R = Nd, Ce)

Hao

Liu

Guo

et al. 1997

Rapid Commun. Mass Spectrom.

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1 The interest in these species is driven by the expectation that a whole new series of materials may be created, with properties tailored by altering the encapsulated atom.2 Researches on metallofullerenes developed slowly until the K-H method was used to prepare samples in bulk.3 Subsequently most of the rare-earth elements have been encapsulated in fullerene cages successfully, 4 and the isolation and characterization of these rare-earth metallofullerenes has been extensively studied.2 Up to now, however, their chemical properties have been little studied due to the low yields and separation difficulties. Only recently have T. Akasaka et al. published the chemical derivatization of isolated La@C 82 and Gd@C 82 by 1,1,2,2-tetramesityl-1,2-disilirane. 5,6 Mirroring studies in the condensed phase, mass spectrometry provides a powerful tool for chemical property research by virtue of its advantages, viz. small quantity sample requirements, convenience and speed. Reactions of singly, doubly and triply charged fullerene ions have been studied systematically, 7,8 and the Freiser group has embarked upon an extensive study of reactions of exohedrally bound MC 60 + ions by using the FTICRMS technique. 9,10 In our previous studies, the gas phase ion/molecule reactions of neutral C 60 with ions derived from small organic compounds have been investigated, and the two-fold reactivities of C 60 , 'superalkenity' and 'superaromaticity', have been confirmed intensively. 11-13Herein we report the first gas phase chemical derivatization of endohedral metallofullerenes by ion/molecule reactions with the plasma from self-chemical ionization of vinyl acetate. The strong electron-donating character of endohedral metallofullerenes, in contrast to the empty fullerenes is demonstrated directly from these reactions. EXPERIMENTAL MaterialsMetallofullerenes were prepared by using the K-H method, 3 arc burning under a 160 Torr He atmosphere. The 6 mm diameter graphite rods were cored by a 4 mm drill, and filled with a mixture of graphite and rare earth oxides. These R 2 O 3 /graphite composite rods (1.0R/100C, R = Ce, Nd) were baked for 4 hr at 2000 K, using a high-frequency generator under vacuum, before arc discharging. The resulting metallofullerene soots were extracted by using a toluene-pyridine two-step extraction method, 14 in which they were Soxhlet extracted (8 hr) with toluene to first remove the C 60 and C 70 and further extracted with pyridine in a sealed stainless steel autoclave under 20 atm at 523 K to dissolve most of the metallofullerenes from the soots.Vinyl acetate is commercially available with analytical grade purity, and was used without further purification. EI-MSElectron impact (EI) mass spectra were acquired using a QUATTRO triple-quadrupole mass spectrometer (Micromass, Manchester, UK). Spectra were recorded by using a direct exposure probe (DEP). The pyridine extract of metallofullerenes was dropped onto the wire at the end of the probe and the solvent was blown off before insertion into the ion source. 1400 mA c...

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Exohedral adducts of La@C82

Cited by 177 publications

References 10 publications

Unusual Polymerization Behavior of Water-soluble Fullerenols in Laser Desorption Ionization Time-of-flight Mass Spectrometry

Unusual Polymerization Behavior of Water-soluble Fullerenols in Laser Desorption Ionization Time-of-flight Mass Spectrometry

In vivo studies of fullerene-based materials using endohedral metallofullerene radiotracers

Gas phase derivatization of endohedral metallofullerenes R@C82 and R2@C80 (R = Nd, Ce)

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