A SPECTROSCOPIC STUDY OF M-AT-C-82 METALLOFULLERENES - RAMAN, FAR-INFRARED, AND NEUTRON-SCATTERING RESULTS

Polycrystalline samples of M@C-82 metallofullerenes have been studied at room temperature by Raman (for M = La, Y, Ce, Gd), far-infrared (FI R) (for M = La, Y, Ce), and inelastic neutron scattering (INS) (for M = La, Y) spectroscopy. Raman and FIR spectra suggest that these metall ofullerenes have a common dominant, if not a single, structure of the C-82 cage and a similar bonding of the encapsulated metal ion, i.e. th e bonding is primarily electrostatic and the metal atoms are in the sa me oxidation state (+3). The metal ion vibrations are located around 1 60 and 50 cm(-1). INS reveals no gap between internal vibrational and external vibrational and rotational modes in the range similar to 50-2 00 cm(-1) as is typically observed for other fullerides and also predi cted by our model calculations. Presumably this is due to strong inter molecular interactions between M@C-82 units in the bulk sample. The st udied metallofullerenes are air sensitive, and degradation in air coul d be followed by changes in the Raman spectra.