Gd–LIII EXAFS study of structural and dynamic properties of Gd@C82 between 10 and 300 K Original Research Article

The location of endohedral Gd ions in Gd@C82 is studied by Gd–LIII X-ray absorption spectroscopy in the temperature range 10–300 K. The near-edge data point to a covalent bond of trivalent Gd ions with the carbon cage. The EXAFS data can be well fitted with a Gd position above a carbon hexagon with two neighbour shells of carbon at distances R1,2=2.49(3) and 2.95(5) Å, corresponding to a large off-center position of about 1.8 Å from the center of the C82 cage. The second cumulants of these distances are relatively large and weakly depending on temperature. This points to a considerable distribution in Gd–C1 and Gd–C2 distances and confirms the relatively strong binding of the Gd ion to the C82 cage. These results will be discussed together with previous EXAFS studies and theoretical calculations of Y@C82 and La@C82.