Spin-orbit effects on the aromaticity of the Re3X9(2-) (X = Cl, Br) cluster ions.

In our recent article (Chem. Phys. Lett. 2008, 467, 94-96), we reported the aromaticity via NICS calculations of the neutral Re(3)Cl(9) and Re(3)Br(9) 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(5/2) 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.