Spin–orbit effects on the aromaticity of the Re3Cl9 and Re3Br9 clusters

Here, we report density functional calculations of the electronic structure and nuclear independent chemical shift (NICS) values of the Re3Cl9 and Re3Br9 clusters including scalar and spin–orbit relativistic effects (ADF + ZORA + SO). Our calculations have shown that both the clusters exhibit aromaticity and that spin–orbit effects decreases aromaticity due to the fact that the 5d3/2 spinors are mostly occupied and are more contracted than the scalar 5d orbitals.