Isolation of CeLu2 N@Ih -C80 through a Non-Chromatographic, Two-Step Chemical Process and Crystallographic Characterization of the Pyramidalized CeLu2 N within the Icosahedral Cage

Abstract

By combining two chemical methods of purification, 4 mg of purified CeLu2 N@C80 was readily isolated from 500 mg of carbon soot extract without the use of recycling HPLC, a method which has previously been necessary to obtain pure samples of endohedral fullerenes. In stage 1, CeLu2 N@C80 was selectively precipitated by virtue of its low first oxidation potential (+0.01 V) and the judicious choice of MgCl2 as the Lewis acid precipitant. For stage 2, we used a stir and filter approach (SAFA), which employed the electron-rich NH2 groups immobilized on silica gel to selectively bind residual endohedrals and higher cage fullerenes that were contaminants from stage 1. Crystallographic analysis of CeLu2 N@C80 in the co-crystal CeLu2 N@Ih -C80 ⋅Ni(octaethylporphyrin)⋅2(toluene) reveals that the Ih -C80 cage is present with a pyramidalized CeLu2 N unit inside.

Keywords: cerium; endohedral fullerene; lutetium; purification; structure elucidation.