Electronic structure of pristine and intercalatedSc3N@C80metallofullerene

We report a study of the electronic structure and charge transfer in the metallofullerene ${\mathrm{Sc}}_3\mathrm{N}@{\mathrm{C}}_{80}$ using photoemission and x-ray absorption spectroscopy. Through a comparison of the x-ray absorption spectrum of ${\mathrm{Sc}}_3\mathrm{N}@{\mathrm{C}}_{80}$ at the Sc $L_{2,3}$ edge with atomic multiplet calculations, the $\mathrm{Sc}3d$ electron count is determined to be 0.6, thus giving an effective Sc valency of 2.4. With the N atom gaining a full electronic shell by means of covalent bonding with the Sc (also involving the $\mathrm{Sc}3d$ electron density observed in the x-ray absorption experiments), the remaining six valence electrons of the ${\mathrm{Sc}}_3\mathrm{N}$ cluster are then transferred to the carbon cage which stabilizes the ${\mathrm{C}}_{80}$ cage structure with $I_h$ symmetry, a structure which is not energetically favored in neutral ${\mathrm{C}}_{80}.$ The presence of the highly symmetric $I_h$ cage structure is further supported by the observation of distinct fine structure in the valence band photoemission spectra of the endohedral, which results from the high degree of effective degeneracy of the electronic states in the molecule. Finally, the results of investigations of K-doped ${\mathrm{Sc}}_3\mathrm{N}@{\mathrm{C}}_{80}$ using photoemission give insight into the ${\mathrm{K}}_x{\mathrm{Sc}}_3\mathrm{N}@{\mathrm{C}}_{80}$ phases that are formed upon intercalation.