An Experimentally Observed Trimetallofullerene Sm₃@<i>I</i>_<i>h</i>‑C₈₀: Encapsulation of Three Metal Atoms in a Cage without a Nonmetallic Mediator

We report the synthesis, isolation, and characterizations of the novel trimetallofullerene Sm3@Ih-C80. Importantly, the experimental X-ray structure of Sm3@Ih-C80 verified for the first time that three metal atoms can be stabilized in a fullerene cage without a nonmetal mediator. Furthermore, computational studies demonstrated the electronic features of Sm3@Ih-C80, which are similar to that of theoretically studied Y3@Ih-C80. Electrochemical studies of Sm3@Ih-C80 showed a major difference from those of the well-studied isoelectronic species Sc3N@Ih-C80 and La2@Ih-C80.