The electronic structure of (C59N)2 from high energy spectroscopy

We report the results of a detailed study of the occupied and unoccupied electronic structure of dimers of the new heterofullerene C59N by means of photoemission and electron energy-loss spectroscopy. A close similarity is found between the electronic structures of pristine (C59N)2 and C60 with an additional broadening of the spectra in the former due to the distortion of the fullerene cage caused both by dimerization and the chemical substitution. Both the occupied and unoccupied electronic states, as well as the interband transitions between them, attest to the high degree of molecular character retained in the solid state. Comparison of the shake-up structures in the C1s and N1s X-ray photo emission spectra confirm that the highest lying occupied states in the heterofullerene have a strong degree of N character, whereas the lowest lying unoccupied states have mainly C character. We also present the optical conductivity of the heterofullerene (derived from the loss function), which shows an optical gap of 1.4 eV, some 0.4 eV smaller than that of C60

Heterofullerenes

The state of the art in heterofullerene chemistry and physics is reviewed with emphasis on azafullerenes. The macroscopic synthetic methods that have been developed for aza[60] fullerene compounds since 1995 have led to a whole new and rich area in the science of fullerenes: cage modification chemistry. The synthetic routes towards aza[60]fullerene and its derivatives are reviewed in Sect. 2. The synthetic routes for aza[70]fullerene and its derivatives are summarized in Sect. 3. Section 4 comprises the theoretical and experimental work on the physicochemical properties of azafullerene compounds. Finally, in Sect. 5, the literature regarding heterofullerenes other than monoazafullerenes is reviewed