Knapp Claus, Weiden Norbert, Dinse Klaus-Peter
Phys. Chem. III, Chemistry Department, Darmstadt University of Technology, Petersenstrasse 20, D-64287 Darmstadt, Germany.
Magn Reson Chem. 2005 Nov;43 Spec no.:S199-204. doi: 10.1002/mrc.1661.
A comparative study of C60-based endohedral fullerenes was performed. From an analysis of spin relaxation times of the recently characterized Cu@C60 metallo-endofullerene, it could be shown that the encased ion occupies a well-defined off-centre position even at room temperature. Localization on the timescale of an EPR experiment is combined with charge transfer of approximately two electrons, resulting in the EPR signature of a 3d9 copper ion. This is in contrast to N@C60, for which a nearly complete decoupling from the cage is found. An upper limit for the variance of collision-induced modulation of the anisotropic nitrogen hfi is determined as (A(eff)2)(1/2) < 500 kHz by an analysis of cross peak intensities in a 2D EPR experiment. Pulsed 95 GHZ ENDOR experiments have been performed to confirm that deformation-induced hyperfine anisotropies are expected to be very small in N@C60.
