Controlling intermolecular spin interactions of La@C82 in empty fullerene matrices

The ESR properties and crystal structures of solid-state La@C-82 in empty fullerene matrices were investigated by changing the concentration of La@C-82 and the species of an empty fullerene matrix: C-60, C-70, C-78(C-2v(3)), C-82(C-2) and C-84(D-2d(4)). The rotational correlation time of La@C-82 molecules tended to be shorter when La@C-82 is dispersed in larger fullerene matrices because large C-2n molecules provide more space for La@C-82 molecules for rotating. La@C-82 dispersed in a hcp-C-82 matrix showed the narrowest hyperfine structure (hfs) due to the ordered nature of La@C-82 molecules in the C-82 crystal. On the other hand, in a C-60 matrix, La@C-82 molecules formed clusters because of the large different solubility, which leads to the ESR spectra being broad sloping features due to strong dipole-dipole and exchange interactions.