Structural and magnetic characterisation of Ce@C-82

We report the structural and magnetic properties of the endohedral metallof ullerene Ce@C-82. A hexagonal close packing phase [P6(3)/mmc [a = 11.1544 A ngstrom, c = 18.2256 Angstrom] is formed exclusively after vacuum annealing of the solvent precipitated compound. In contrast, sublimed Ce@C82 was fou nd to be dominantly face-centred cubic close packed [Fm-3m; a = 15.7668 Ang strom]. X-ray powder profile calculations revealed that the endohedral ceri um atom lies close to 1.8 Angstrom, from the C-82 cage centre in both phase s. Hexagonal Ce@C-82 has been investigated by magnetic susceptibility measu rements. Paramagnetic behaviour is maintained down to 2K attributable to Ce 3+ ions. Towards lower temperatures, the observed paramagnetic moment falls from the free ion Ce3+(mu(eff) = 2.54 mu B) value, monotonically approachi ng 1 mu B at 2K.