Relativistic effects on the aromaticity of the halogenated benzenes: C6X6, X = H, F, Cl, Br, I, At

Abstract

In this study we report about the relativistic effects on the aromaticity of the six hexahalogenated compounds (C₆H₆, C₆F₆, C₆Cl₆, C₆Br₆, C₆I₆ and C₆At₆), via a magnetically induced current density method. All-electron density functional theory (DFT) calculations were carried out using the four-component Dirac–Coulomb (DC) Hamiltonian, including scalar and spin–orbit (SO) relativistic effects. Fully relativistic values of the magnetically induced ring currents were obtained by numerical integration over the current flow. These values were compared to the spin-free (SO interaction switched off) and non-relativistic values, in order to assess the corresponding contributions to aromaticity. It was found that in C₆I₆ and C₆At₆ there is a strong SO influence, in line with the expected relativistic effects of the heavy elements, iodine and astatine.