Lanthanum Nitride Endohedral Fullerenes La3N@C2n (43≤n≤55): Preferential Formation of La3N@C96

• Published in: Chemistry : a European journal 2008-09, Vol.14 (27), p.8213-8219
• Main Authors: Chaur, Manuel N., Melin, Frederic, Ashby, Jarryd, Elliott, Bevan, Kumbhar, Amar, Rao, Apparao M., Echegoyen, Luis
• Format: Article
• Language: English
• Subjects: absorption; electrochemistry; fullerenes; HOMO-LUMO gaps; metallofullerenes
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200800881

While the trimetallic nitrides of Sc, Y and the lanthanides between Gd and Lu preferentially template C80 cages, M3N@C80, and while those of Ce, Pr and Nd preferentially template the C88 cage, M3N@C88, we show herein that the largest metallic nitride cluster, La3N, preferentially leads to the formation of La3N@C96 and to a lesser extent the La3N@C88. This is the first time that La3N is successfully encapsulated inside fullerene cages. La3N@C2n metallofullerenes were synthesized by arcing packed graphite rods in a modified Krätschmer–Huffman arc reactor, extracted from the collected soot and identified by mass spectroscopy. They were isolated and purified by high performance liquid chromatography (HPLC). Different arcing conditions were studied to maximize fullerene production, and results showed that yields have a high La2O3/C dependence. Relatively high yields were obtained when a 1:5 ratio was used. Three main fractions, La3N@C88, La3N@C92, and La3N@C96, were characterized by UV/Vis‐NIR and cyclic voltammetry. Unlike other trimetallic nitride metallofullerenes of the same carbon cage size, La3N@C88 exhibits a higher HOMO–LUMO gap and irreversible reduction and oxidation steps. Size matters! The La3N cluster is the largest metallic nitride encapsulated in fullerene cages with a preference for the C96 cage. The redox properties of La3N@C88 are very different from those observed for other metallic nitride endohedral fullerenes with the same carbon cage (see figure).