Ultraviolet photoelectron spectroscopy of multiple atoms encapsulated fullerenes

Ultraviolet photoelectron spectra (UPS) of metallofullerenes with multiple atoms inside the cage, Ti2@C80, Ti2@C84 and Y2C2@C82, have been measured with a synchrotron orbital radiation light source. The spectra were compared with those of other metallofullerenes. Spectral onsets of these metallofullerenes are 0.7-0.8 eV, which is close to those of group II metal atom encapsulated metallofullerenes but much larger than those of other group III mono-metal atom encapsulated ones. The spectra are compared with molecular orbital calculation to estimate the amounts of transferred electrons and the cage structure.