Proof for trivalent Sc ions in Sc-2 @ C-84 from high-energy spectroscopy

The electronic structure and the valency of the Sc ions in the endohedral d imetallofullerene Sc-2 @ C-84 with D-2d symmetry are probed using high-ener gy spectroscopy. Comparison of the Sc 2p --> 3d x-ray-absorption spectrum w ith calculated ionic multiplet spectra shows that the Sc ions are trivalent . Detailed multiplet calculations including covalency indicate that the eff ective valency of the Sc(III) ions can be described by a formal charge tran sfer to the fullerene cage of 2.6 +/- 0.1. This illustrates that a purely i onic picture is not valid for the electronic structure of Sc-2 @ C-84, and that a more complex picture including finite hybridization between the Sc a nd the fullerene cage has to be applied.