Temperature dependent metal cluster position inside a C82 cage:: Sc3@C82

ESR studies on Sc-3@C-82 in dependence on the temperature and of the used solvent have led to a new behaviour of the scandium cluster stabilization inside the carbon cages. A 22 line spectrum, which can be measured down to 200 K, is well known from the literature. In the region from 300 K to 200 K the coupling constant of the scandium splitting increases reversibly with decreasing 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 observed single line forms the main part of the ESR spectrum. This effect is completely reversible. This behaviour at low temperatures is explained by a model including the chance of the metal cluster position inside the C-82 cage below 200 K and the chemical pressure of the frozen solvent.