A C82 Carbon Cage Stable toward Two Different Oxidation States of Endohedral Metal Atoms

The effect of transmutation of a metallic element encaged in C 82 through EC radioactive decay was studied for the 146 Gd → 146 Eu → 146 Sm decay series. The metallofullerene containing the EC decay progeny 146 Eu was found chemically stable and eluted in a HPLC separation at a retention time which corresponded to the retention time of one of the minor isomers of Eu@C 82 (3). As the oxidation state of the metal atom in Gd@C 82 and Eu@C 82 is known to be +3 and +2, this result suggests that the C 82 cage which forms a chemically stable metallofullerene with the metal atom at the +3 oxidation state can also form a stable metallofullerene with a metal atom at the +2 oxidation state.