High-Resolution Analysis of (Sc 3 C 2 )@C 80 Metallofullerene by Third Generation Synchrotron Radiation X-ray Powder Diffraction
ABSTRACT The X-ray structure of Sc(3)C(82) is redetermined by the MEM/Rietveld method by using synchrotron radiation powder data at SPring-8, where the C(2) encapsulated structure available to discuss the Sc-Sc interatomic distances has been determined. The encapsulated three scandium atoms form a triangle shape. A spherical charge distribution originating from the C(2) molecule is located at the center of the triangle. Interatomic distances between Sc and Sc are 3.61(3) A in the triangle. The distance between Sc and the center of the C(2) molecule is 2.07(1) A.
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ABSTRACT: The isolated pentagon rule (IPR) is now widely accepted as a general rule for determining the stability of all-carbon fullerene cages composed of hexagons and pentagons. Fullerenes that violate this rule have been deemed too reactive to be synthesized. The stabilization of non-IPR endohedral fullerenes depends on charge transfer from the encapsulated metal clusters (endoclusters) to fullerene cages, the electronic properties of empty all-carbon cages, the matching size and geometries of fullerene and endocluster, as well as the strong coordination of the metal ions to fused pentagons. The stability of non-IPR exohedral fullerenes can be rationalized primarily by both the 'strain-relief' and 'local-aromaticity' principles. This Review focuses on recent work on stabilization of non-IPR fullerenes, including theoretical and empirical principles, experimental methods, and molecular structures of fused-pentagon fullerenes characterized so far. The special chemical properties of non-IPR fullerenes that distinguish them from IPR-satisfying ones are also emphasized. NNSFC 20525103,20531050,20721001 973 Program 2007CB815301
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ABSTRACT: A systematic powder X-ray structure study for (Sc2C2)@C82(isomer III) and (Y2C2)@C82(III) is carried out by the MEM/Rietveld method by using high resolution synchrotron radiation powder data. In both fullerene materials, two carbon atoms are encapsulated in the cage and a M2C2 bent cluster is most likely formed in the cage. The obtained cage structure of Sc2C84(III) is C82–C3V(8), which is the same as those of (Y2C2)@C82(III) and Y2@C82(III). The charge density of C2 is located at the center of fullerene cage. Two scandium atoms show the rotational disorder, indicating the presence of a rapid hopping motion inside C82–C3V(8) cage. The inter-atomic distances between metal and carbon atoms on fullerene cage are 2.29Å for (Sc2C2)@C82(III), which is 0.2Å smaller than that of (Y2C2)@C82(III).Chemical Physics Letters 12/2006; 433(1):120-124. DOI:10.1016/j.cplett.2006.11.008 · 1.99 Impact Factor
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ABSTRACT: Materials containing disordered moieties and/or amorphous or liquid-like phases or showing surface-or defect-related phenomena constitute a problem with respect to their characterization using X-ray powder diffraction (XRPD), and in many cases Raman spectroscopy can provide useful complementary information. A novel experimental setup has been designed and realized for simultaneous in situ Raman/high-resolution XRPD experiments, to take full advantage of the complementarities of the two techniques in investigating solid-state transformations under non-ambient conditions. The added value of the proposed experiment is the perfect synchronization of the two probes with the reaction coordinate and the elimination of possible bias caused by different sample holders and conditioning modes used in 'in situ but separate' approaches. The setup was tested on three solid-state transformations: (i) the kinetics of the fluorene–TCNQ solid-state synthesis, (ii) the thermal swelling and degradation of stearate–hydrotalcite, and (iii) the photoinduced (2 + 2)-cyclization of (E)-furylidenoxindole. These experiments demonstrated that, even though the simultaneous Raman/XRPD experiment is more challenging than separate procedures, high-resolution XRPD and Raman data can be collected. A gas blower allows studies from room temperature to 700 K, and 100 K can be reached using a nitrogen cryostream. The flexibility of the experimental setup allows the addition of ancillary devices, such as a UV lamp used to study photoreactivity.Journal of Applied Crystallography 08/2007; 40(4):684-693. DOI:10.1107/S0021889807025113 · 3.95 Impact Factor