La₂@C₇₂: Metal-mediated stabilization of a carbon cage

Abstract

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 metalmediated 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.