ESR studies on Sc-3@C-82 in dependence on the temperature and of the used s
olvent have led to a new behaviour of the scandium cluster stabilization in
side the carbon cages. A 22 line spectrum, which can be measured down to 20
0 K, is well known from the literature. In the region from 300 K to 200 K t
he coupling constant of the scandium splitting increases reversibly with de
creasing temperature. At 240 K a superposition of the 22 line spectrum and
a single line appears. In the temperature range of 180 K and 150 K the obse
rved single line forms the main part of the ESR spectrum. This effect is co
mpletely reversible.
This behaviour at low temperatures is explained by a model including the ch
ance of the metal cluster position inside the C-82 cage below 200 K and the
chemical pressure of the frozen solvent.