La2@C72: Metal-Mediated Stabilization of a Carbon Cage

In this study, we report production, isolation, and characterization for the relatively small endohedral metallofullerene, La2@C72. As described, La2@C72 is readily isolated from conventional electric-arc-generated carbon/metal soot. This new species was purified by HPLC chromatography and characterized by laser desorption mass spectrometry and UV-vis spectroscopy. The mass spectrum also demonstrates the presence of the monometal species, La@C72, but the absence of empty-cage C72. Since empty-cage C72 has not been successfully isolated to date, the results of the present study are in agreement with the argument for metal-mediated stabilization of the C72 carbon cage by lanthanum ions. The chromatographic retention data suggest that the electronic structure of La2@C72 is consistent with a (La3+)2@C726- species and the prediction of a relatively small dipole moment