Switching between halogen- and hydrogen-bonding in stoichiometric variations of a cocrystal of a phosphine oxide

We describe a two-component cocrystal composition which appears in two stoichiometric variations exhibiting different supramolecular architectures: whereas one stoichiometric variation displays C-H center dot center dot center dot O hydrogen bonds, the second form exhibits short I center dot center dot center dot O halogen bonds alongside I center dot center dot center dot pi halogen-bonded contacts; the two forms are readily prepared mechanochemically by varying the relative amounts of starting materials in a liquid-assisted grinding process.