Isolation and spectroscopic characterization of Sm-containing metallofullerenes

We report the first isolation of a series of Sm-containing metallofullerenes, Sm@C74, Sm@C76(I, II), Sm@C78, Sm@C80, Sm@C82(I, II, III) and Sm@C84(I, II, III), and their characterization by UV–VIS–NIR absorption spectroscopy and electron energy-loss spectroscopy (EELS). The UV–VIS–NIR absorption spectra of Sm@C74, Sm@C80, Sm@C82(I, II, III) and Sm@C84(I, II) are quite similar to those of the corresponding Ca-, Sr-, Ba-, Eu-, Tm-, Yb-based metallofullerenes. In contrast, the absorption spectra of Sm@C76(I, II), Sm@C78 and Sm@C84(III) show a novel feature: the onset for Sm@C78 is observed ∼2600 nm, which corresponds to a small band gap (∼0.5 eV). Furthermore, the oxidation state of Sm atom in Sm@C82(II) is investigated by EELS, which reveals that the Sm atom takes +2 oxidation state in this fullerene cage.