This study establishes that hydrogen-, halogen- and chalcogen-bonding intermolecular and non-covalent intramolecular interactions are driven by a face-to-face orientation of electrophilic (charge-depleted) and nucleophilic (charge-concentrated) regions, which is the origin of the specific geometries found in synthons and supramolecular motifs.

The ability to control the yield for a [2+2] cyclo­addition photoreaction by using a mixed cocrystal approach is reported. The two isosteric halogen-bond donors allow for the formation of the cocrystal solid solution and as a result influences the extent of the photoreaction based upon their initial molar ratios.

The role of secondary noncovalent inter­actions in the structures of a series of 2:1 cocrystals of ditopic halogen-bond donors and 4-(di­methyl­amino)­pyridine is analyzed.

The packing of the title solvate features hetero-halogen⋯halogen (Cl⋯F), and chalcogen (S⋯O) bonding, as well as non-standard offset π–π stacking.

4,4′-Disulfanediyldipyridinium chloride triiodide (1) was synthesized. The structural characterization of 1 by SC-XRD analysis was supported by elemental analysis, FT–IR, and FT–Raman spectroscopic measurements.