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

► We studied the [Re3(μ-Cl)3Cl9]3−, [Re3(μ-Br)3Br9]3−, [Re3(μ-I)3I9]3− clusters. ► The clusters exhibit aromaticity which is decreased by the SO effect. ► The [Re3(μ-I)3I9]3− is the most aromatic cluster. ► The TDDFT calculations corroborate the aromaticity.