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

While the trimetallic nitrides of Sc, Y and the lanthanides between Gd and Lu preferentially template C-80 cages, M3N@C-80, and while those of Ce, Pr and Nd preferentially template the C-88 cage, M3N@C-88, we show herein that the largest metallic nitride cluster, La3N, preferentially leads to the formation of La3N@C-96 and to a lesser extent the La3N@C-88. This is the first time that La3N is successfully encapsulated inside fullerene cages. La3N@C-2n, metallofullerenes were synthesized by arcing packed graphite rods in a modified Kratschmer-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@C-88, La3N@C-92, and La3N@C-96, were characterized by UV/Vis-NIR and cyclic voltammetry. Unlike other trimetallic nitride metallofullerenes of the same carbon cage size, La3N@C-88 exhibits a higher HOMO-LUMO gap and irreversible reduction and oxidation steps.