Endohedral nitride cluster fullerenes: Formation and spectroscopic analysis of L3−xMxN@C2n (0≤x≤3; N=39,40) Original Research Article

The class of endohedral fullerenes is demonstrated in its large variety by the new type of nitride cluster fullerenes. These endohedral fullerenes were obtained as the most abundant fullerenes in the soot extract. This is reached by the concept of reactive gas atmosphere in arc burning fullerene production. The chemical reactions in the gas atmosphere during the production are described. Different nitride cluster fullerenes were produced with selectivity up to 90% by using reactive gas addition to the cooling gas of the arc burning process. Fullerenes prepared by this method are Sc3N@C80, Sc3−xErxN@C80 (x=1,2,3), Sc3N@C78, Y3N@C80, Ho3N@C80 and Tb3N@C80. By studying Vis/NIR spectra, it is demonstrated that nitride cluster fullerenes are generally large band-gap endohedrals. Therefore, the M3N@C80 structures are very stable and suitable for applications. This stability is caused by a charge transfer from the cluster to the carbon cage and the formation of a M3N–carbon cage bond as well as covalent metal–nitrogen bonds. Infrared spectroscopy of M3N@C80 was used to study the metal and cage size influence on the structure of the nitride cluster.