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

The ESR properties and crystal structures of solid-state La@C₈₂ in empty fullerene matrices were investigated by changing the concentration of La@C₈₂ and the species of an empty fullerene matrix: C₆₀, C₇₀, C₇₈(C_2v(3)), C₈₂(C₂) and C₈₄(D_2d(4)). The rotational correlation time of La@C₈₂ molecules tended to be shorter when La@C₈₂ is dispersed in larger fullerene matrices because large C_2n molecules provide more space for La@C₈₂ molecules for rotating. La@C₈₂ dispersed in a hcp-C₈₂ matrix showed the narrowest hyperfine structure (hfs) due to the ordered nature of La@C₈₂ molecules in the C₈₂ crystal. On the other hand, in a C₆₀ matrix, La@C₈₂ 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.