Vibrational structure of endohedral fullerene Sc3N@C78 (D3h′):: Evidence for a strong coupling between the Sc3N cluster and C78 cage

The vibrational structure of the endohedral cluster fullerene Sc3N"C-78 is studied by FTIR spectroscopy, Raman spectroscopy and DFT-based quantum chemical calculations. Remarkably good agreement between experimental and calculated spectra is achieved and a full assignment of the ScN3-based vibrational modes is given. Significant differences in the vibrational structure of the endohedral cluster fullerene Sc3N@C-78 and the empty, charged C-78(6-): 5(D-3h') are rationalized by the strong coupling between the Sc3N cluster and the fullerene cage. This coupling has its origin in a significant overlap of the Sc3N and C-78 molecular orbitals, and causes atomic-charge and bond-length redistributions compared to the neutral C-78 and the C-78(6-) anion. An ionic model is not sufficient to describe the electronic, geometric and vibrational structure of the Sc3N@C-78 nitride cluster fullerene.