Yttrium-containing endohedral metallofullerenes: Synthesis and extraction

Yttrium-containing endohedral metallofullerenes are synthesized in an RF arc discharge in the helium flow with embedded Y$_{2}$O$_{3}$. It is shown that the formation of the metallofullerenes depends on the helium pressure in a chamber; however, this dependence cannot be explained using the model of formation of conventional fullerenes without a guest atom in a molecule. The results of extraction of Y@C$_{82}$ by pyridine and carbon disulfide are reported. The pressure corresponding to the maximum yttrium-containing endohedral metallofullerene content is shown to be 60 kPa; under this pressure, extraction by carbon disulfide allows obtaining 27.1 wt % of the endohedral metallofullerene, while extraction by pyridine yields its amount of 17.3 wt%.