Extraction and Chromatographic Elution Behavior of Endohedral Metallofullerenes:  Inferences Regarding Effective Dipole Moments

Fuchs, D.; Rietschel, H.; Michel, R. H.; Fischer, Achim; Weis, Patrick; Kappes, Manfred M.

doi:10.1021/jp951537f

Cited by 64 publications

(75 citation statements)

References 39 publications

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“…It should be pointed out that the results we obtained for La@C 82 , Ce@C 82 , and Gd@C 82 are consistent with the published results in retention time. 9 In addition, we verified the above retention time sequence in separate preparations of the 14 lanthanide metallofullerenes by using one metal at a time. The results of HPLC measurements are given in Table 1.…”

Section: Resultssupporting

confidence: 53%

Relative Yields of Endohedral Lanthanide Metallofullerenes by Arc Synthesis and Their Correlation with the Elution Behavior

Huang

Yang

1998

J. Phys. Chem. B

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Fourteen endohedral lanthanide metallofullerenes were synthesized using the arc-discharge method under identical conditions, and their relative yields and elution behavior have been studied by mass spectrometry and HPLC. The eluate around the M@C 82 peak (M ) lanthanide metal) was collected in two fractions of equal amount. The DCI negative ion mass spectrum of each metallofullerene in each collected fraction was well resolved on the basis of the characteristic isotopic distribution. The relative yield of these metallofullerenes was found to be in the following order: Ce > Pr > Tb > Gd > Nd > La ∼ Er > Ho > Dy > Lu . Tm ∼ Sm ∼ Eu ∼ Yb. The order of their retention times (Tb > Gd > Pr > Ce > Er ∼ Lu > La ∼ Ho > Nd > Dy . Tm ∼ Sm ∼ Eu ∼ Yb) was also obtained by comparing the mass peak intensities of each metallofullerene from the two HPLC fractions. A fairly good correlation between these two sequences is identified and discussed.

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Section: Resultssupporting

confidence: 53%

Relative Yields of Endohedral Lanthanide Metallofullerenes by Arc Synthesis and Their Correlation with the Elution Behavior

Huang

Yang

1998

J. Phys. Chem. B

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“…[8][9][10][11][12][13] This results from a most annoying limiting factor in HPLC separa-tion of endohedral metallofullerenes that in various fullerene solvent extracts empty fullerenes (mainly C 60 and C 70 ) are usually above 2 orders of magnitude more abundant than the endohedral metallofullerenes. 1-3 With the increasing availability of endohedral metallofullerene samples accompanying the advance of metallofullerene separation techniques more and more properties of the various endohedral metallofullerenes have been characterized.…”

Section: Intrductionmentioning

confidence: 99%

Efficient N,N-Dimethylformamide Extraction of Endohedral Metallofullerenes for HPLC Purification

Ding

Yang

1996

Chem. Mater.

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A new and efficient extraction method using DMF (N,N-dimethylformamide) was developed to concentrate endohedral metallofullerenes. This single-step extraction method obtained a solution containing 5-15% endohedral metallofullerenes and strongly discriminated against the dominant C 60 , C 70 , and higher empty fullerenes in raw soot. This highly selective extraction procedure substantially reduced sample loading in the HPLC isolation for a given volume of sample injection. The efficiency of our separation method is demonstrated by the isolation of the endohedral metallofullerene Ce@C 82 . IntrductionDuring the past three years there has been a surge of research activity in the isolation and characterization of endohedral metallofullerenes. 1-3 With the increasing availability of endohedral metallofullerene samples accompanying the advance of metallofullerene separation techniques more and more properties of the various endohedral metallofullerenes have been characterized. 1-3 The most recent developments include the revelation of the monoclinic structure of Y@C 82 by X-ray diffraction, 4 exohedral derivatization of La@C 82 , 5 electrochemistry of the less common metallofullerene La 2 @C 80 , 6 and the FT-EPR of La@C 82 . 7 However, the preparation of milligram amounts of endohedral metallofullerenes (∼95% purity) is still very time consuming and solvent consuming and involves multistep chromatographic procedures. [8][9][10][11][12][13] This results from a most annoying limiting factor in HPLC separa-tion of endohedral metallofullerenes that in various fullerene solvent extracts empty fullerenes (mainly C 60 and C 70 ) are usually above 2 orders of magnitude more abundant than the endohedral metallofullerenes. One way to circumvent this problem is to improve the HPLC column for higher loading capacity while maintaining a reasonable selectivity. 14 Another solution, which is perhaps more convenient and cost-effective, is to raise the extraction selectivity toward the metallofullerenes. High-pressure toluene extraction succeeded to some extent in this regard but did not attract widespread use. 15 Kappes et al. reported an enhancement of extraction efficiency of metallofullerenes by mixing the dipolar solvent CH 3 OH into CS 2 . 13 In our efforts to separate endohedral metallofullerenes we have also noted a prominent difference in dipole moment between empty fullerenes and endohedral metallofullerenes. By exploiting the dipole moment difference, we have successfully developed an efficient extraction scheme to separate endohedral metallofullerenes.In this work we report this new and efficient extraction scheme which uses DMF to concentrate endohedral metallofullerenes. A simple one-step extraction obtained a solution containing 5-10% endohedral metallofullerenes and strongly discriminated against the dominant C 60 , C 70 , and higher empty fullerenes in the raw soot. This highly selective extraction procedure reduced the sample loading in the HPLC isolation by at least an order of magnitude in comparison with other e...

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“…Lin and co-workers reported the Nd-C 82 cluster reconfiguration on a C 60 film with the tip. 8 The result indicates that Lu-C 82 molecules have a larger dipole moment than that of Nd-C 82 molecules. This was attributed to the interaction between the strong electric field at the apex of the tip and the dipole moment of the endohedral metallofullerene molecules.…”

Section: Resultsmentioning

confidence: 95%

Scanning tunneling microscopy of endohedral metallofullerene Lu–C82 on C60 film

Shi¹,

Wang²,

Huang³

et al. 2002

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Articles you may be interested inThermal stability of surface freezing films in Ga-based alloys: An x-ray photoelectron spectroscopy and scanning tunneling microscopy study Wurtzite GaN surface structures studied by scanning tunneling microscopy and reflection high energy electron diffraction J.Endohedral metallofullerene Lu-C 82 molecules adsorbed on C 60 film have been investigated by an ultra-high-vacuum scanning tunneling microscopy. The C 60 film was obtained by depositing 2-3 ML of C 60 molecules on a highly oriented pyrolytic graphite surface. The as-deposited Lu-C 82 molecules were observed to form various structures on the C 60 film. The nucleation behavior of Lu-C 82 was compared with that of Nd-C 82 and Tb-C 82 on the C 60 film. These structures were explained based on the interactions of Lu-C 82 -C 60 , Lu-C 82 -Lu-C 82 , and Lu-C 82 scanning tunneling microscopy tip.

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Extraction and Chromatographic Elution Behavior of Endohedral Metallofullerenes: Inferences Regarding Effective Dipole Moments

Cited by 64 publications

References 39 publications

Relative Yields of Endohedral Lanthanide Metallofullerenes by Arc Synthesis and Their Correlation with the Elution Behavior

Relative Yields of Endohedral Lanthanide Metallofullerenes by Arc Synthesis and Their Correlation with the Elution Behavior

Efficient N,N-Dimethylformamide Extraction of Endohedral Metallofullerenes for HPLC Purification

Scanning tunneling microscopy of endohedral metallofullerene Lu–C82 on C60 film

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