Traversing the Tightrope between Halogen and Chalcogen Bonds Using Structural Chemistry and Theory

Adjusting the physical and chemical properties of crystalline materials by controlling their structures is highly desirable in solid-state and materials chemistry. Such control can be achieved by carefully exploiting and fine-tuning the interactions between molecules. In this work, functionalized benzochalcogena-diazole molecules capable of forming two different sigma-hole interactions (halogen and chalcogen bonds) are used as building blocks to assemble crystals with distinctly different structural features. Ab initio calculations are performed in order to rationalize the crystal structures obtained and to quantify the intermolecular interactions. It is found that the structural features and the balance between different interactions, as well as the relative strength of the sigma-hole interactions, are highly sensitive to the identity of the halogen and chalcogen atoms in the molecules. Both electrostatic/polarization and dispersion forces play an important role in defining the energetics of the chalcogen-bonded and halogen-bonded isomers, and by a control of the balance between these components, it is possible to precisely control the point at which one type of supramolecular architecture is favored over another.