Spin-orbite effects on the aromaticity of the Re₃X ₉^2- (X = CI, Br) cluster ions

In our recent article (Chem. Phys. Lett. 2008, 467, 94-96), we reported the aromaticity via NICS calculations of the neutral Re₃Cl₉ and Re₃Br₉ clusters. Spin-orbit effects decrease their aromaticity due to the fact that the 5d_3/2 spinors are mostly occupied and are more contracted than the scalar 5d orbitals. Here, we report that the title anions are also aromatic but, oppositely, spin-orbit effects increase the clusters' aromaticity due to the fact that the 5d_3/2 spinors are now being populated and are more expanded than the scalar 5d orbital. All the clusters discussed here have larger induced diatropic ring currents than benzene.