Exploiting π-type halogen bonds as a means to achieve mixed co-crystals: crystallographic and computational evidence of a Cl⋯π halogen bond in the organic solid state

Abstract

The formation of a pair of mixed co-crystals based upon 1,4-diiodoperchlorobenzene and iodoperchlorobenzene as π-type halogen-bond donors is reported. These molecular solids are held together by the combination of I⋯π and Cl⋯π halogen bonds to the aromatic ring on both benzoic acid and benzamide. As expected, the π-type halogen bonds behave as an ancillary force that is essential in the formation of the mixed co-crystal without disrupting the stronger acid or amide dimer. The binding energies for these π-type halogen bonds were quantified by a series of density functional theory calculations.