Structure of endohedral fullerene Eu@C74.

Structure determination of endohedral fullerenes in the absence of X-ray data is difficult and often controversial. Here we show that the structure of endohedral fullerene Eu@C(74) may be determined by density functional theory aided interpretation of its electronic, infrared and Raman spectra. The use of recently developed analytical polarizability gradient methods to simulate resonance-enhanced Raman spectra is crucial for this approach and allows for a nearly complete assignment of the experimental spectra. Eu@C(74) is assigned a pear-shaped C(2v) symmetric structure and shows strong ionic interaction between the encapsulated metal and the fullerene pi system.