Anion radicals of isomeric [5,6] and [6,6] benzoadducts of Sc3N@C80: remarkable differences in endohedral cluster spin density and dynamics.

The anion radicals of isomeric [5,6] and [6,6] Sc3N@C80 benzoadducts were studied by electron spin resonance spectroscopy, density functional theory computations, and molecular dynamics. In both compounds the rotation of the Sc3N cluster is frozen and the spin density distribution of the cluster is highly anisotropic, with hyperfine coupling constants of 9.1 and 2 × 33.3 G for the [5,6] adduct and ∼0.6 and 2 × 47.9 G for the [6,6] adduct. Remarkably, the subtle variation of the position of the exohedral group on the surface of the cage results in very pronounced changes in the spin density distribution and the dynamics of the encapsulated Sc3N cluster.