Heterofullerenes are classes of fullerenes, at least one carbon atom is replaced by another element.[1][2] Based on spectroscopy, substitutions have been reported with boron (borafullerenes),[3][4] nitrogen (azafullerenes),[5][6] oxygen,[7] arsenic, germanium,[8] phosphorus,[9] silicon,[10][11] iron, copper, nickel, rhodium[11][12] and iridium.[11] Reports on isolated heterofullerenes are limited to those based on nitrogen [13][14][15][16][17] and oxygen.[18]