The aromaticity of the [Re3(μ-X)3X9]3− clusters, X = Cl, Br, I

The results of this Letter reveals that the [Re3(μ-Cl)3Cl9]3−, [Re3(μ-Br)3Br9]3−, [Re3(μ-I)3I9]3− clusters exhibit aromaticity and that spin–orbit effect decreases the aromaticity due to the fact that the 5d3/2 spinors are more contracted than the scalar 5d orbitals. The [Re3(μ-I)3I9]3− and [Re3(μ-Br)3Br9]3− clusters are the most aromatic clusters. This can be explained by the np1/2 and np3/2 spinors radial expectation (〈r〉) values which follows the Cl < Br < I sequence. Thus, the most extended spinors correspond to I and Br ligands, as indicated in the ELF plots. Furthermore we carried out TDDFT calculations which agrees with the fact that [Re3(μ-I)3I9]3− should show the highest value of aromaticity.