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Author: Rosenkranz, Marco × Publisher: Hoboken, NJ : Wiley ×

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    Methane as a selectivity booster in the arc-discharge synthesis of endohedral fullerenes: Selective synthesis of the single-molecule magnet Dy2TiC@C80and Its Congener Dy2TiC2@C80
    (Hoboken, NJ : Wiley, 2015) Junghans, Katrin; Schlesier, Christin; Kostanyan, Aram; Samoylova, Nataliya A.; Deng, Qingming; Rosenkranz, Marco; Schiemenz, Sandra; Westerström, Rasmus; Greber, Thomas; Büchner, Bernd; Greber, Thomas; Popov, Alexey A.
    The use of methane as a reactive gas dramatically increases the selectivity of the arc‐discharge synthesis of M‐Ti‐carbide clusterfullerenes (M=Y, Nd, Gd, Dy, Er, Lu). Optimization of the process parameters allows the synthesis of Dy2TiC@C80‐I and its facile isolation in a single chromatographic step. A new type of cluster with an endohedral acetylide unit, M2TiC2@C80, is discovered along with the second isomer of M2TiC@C80. Dy2TiC@C80‐(I,II) and Dy2TiC2@C80‐I are shown to be single‐molecule magnets (SMM), but the presence of the second carbon atom in the cluster Dy2TiC2@C80 leads to substantially poorer SMM properties.
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    Synthesis and isolation of the titanium–scandium endohedral fullerenes—Sc2TiC@Ih‐C80, Sc2TiC@D5h‐C80 and Sc2TiC2@Ih‐C80: Metal size tuning of the TiIV/TiIII redox potentials
    (Hoboken, NJ : Wiley, 2016) Junghans, Katrin; Ghiassi, Kamran B.; Samoylova, Nataliya A.; Deng, Qingming; Rosenkranz, Marco; Olmstead, Marylin M.; Balch, Alan L.; Popov, Alexey A.
    The formation of endohedral metallofullerenes (EMFs) in an electric arc is reported for the mixed‐metal Sc–Ti system utilizing methane as a reactive gas. Comparison of these results with those from the Sc/CH4 and Ti/CH4 systems as well as syntheses without methane revealed a strong mutual influence of all key components on the product distribution. Whereas a methane atmosphere alone suppresses the formation of empty cage fullerenes, the Ti/CH4 system forms mainly empty cage fullerenes. In contrast, the main fullerene products in the Sc/CH4 system are Sc4C2@C80 (the most abundant EMF from this synthesis), Sc3C2@C80, isomers of Sc2C2@C82, and the family Sc2C2 n (2 n=74, 76, 82, 86, 90, etc.), as well as Sc3CH@C80. The Sc–Ti/CH4 system produces the mixed‐metal Sc2TiC@C2 n (2 n=68, 78, 80) and Sc2TiC2@C2 n (2 n=80) clusterfullerene families. The molecular structures of the new, transition‐metal‐containing endohedral fullerenes, Sc2TiC@Ih‐C80, Sc2TiC@D5h‐C80, and Sc2TiC2@Ih‐C80, were characterized by NMR spectroscopy. The structure of Sc2TiC@Ih‐C80 was also determined by single‐crystal X‐ray diffraction, which demonstrated the presence of a short Ti=C double bond. Both Sc2TiC‐ and Sc2TiC2‐containing clusterfullerenes have Ti‐localized LUMOs. Encapsulation of the redox‐active Ti ion inside the fullerene cage enables analysis of the cluster–cage strain in the endohedral fullerenes through electrochemical measurements.