Structural and Electrochemical Property Correlations of Metallic Nitride Endohedral Metallofullerenes

Structural and electrochemical property correlations of metallic nitride endohedral metallofullerenes (MN EMFs) were studied in detail. The electrochemical properties of these compounds are strongly dependent on the symmetry of the carbon cage and, except for the Sc3N cluster, are independent of the nature of the metallic cluster due to the localization of the HOMO and LUMO on the carbon cage. The X-ray structure of Gd3N@C-86 shows that the cage obeys the isolated pentagon rule and uses a cage with D-3 symmetry, in agreement with previously published data for Tb3N@C-86, the only other structurally characterized C-86 MN EMF. The electrochemical properties of different MN EMFs are used to probe the structural features of these compounds. Electrochemistry was used to determine the relative abundances of the D-5h and I-h isomers of M3N@C-80 compounds, whereas HPLC allowed the analysis of larger MN EMFs. The binding energies (BEs) were computed for different MN EMFs, and a strong correlation between the BE (of the cluster and fullerene cage) and the corresponding abundance of the given MN EMF was obtained. The results account for the different template stages and for the relative abundances observed for MN EMFs.