Exploiting π-type halogen bonds as a means to achieve mixed cocrystals: 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.