Methane as a Selectivity Booster in the Arc‐Discharge Synthesis of Endohedral Fullerenes: Selective Synthesis of the Single‐Molecule Magnet Dy 2 TiC@C 80 and Its Congener Dy 2 TiC 2 @C 80

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 Dy 2 TiC@C 80 ‐I and its facile isolation in a single chromatographic step. A new type of cluster with an endohedral acetylide unit, M 2 TiC 2 @C 80 , is discovered along with the second isomer of M 2 TiC@C 80 . Dy 2 TiC@C 80 ‐(I,II) and Dy 2 TiC 2 @C 80 ‐I are shown to be single‐molecule magnets (SMM), but the presence of the second carbon atom in the cluster Dy 2 TiC 2 @C 80 leads to substantially poorer SMM properties.