Intermolecular hydrogen transfer and solubility tuning in multi-component molecular crystals of the API piroxicam

A series of twelve multi-component molecular crystals of the active pharmaceutical ingredient (API) piroxicam (PX) have been synthesised and their structures analysed with respect to their supramolecular motifs and degree of intermolecular hydrogen transfer observed on formation of the various complexes. The multi-component crystals of PX formed with a series of basic N-heterocycles are contrasted with those formed with strong haloanilic acids, with PX found to adopt different ionisation states. The effect of the formation of these multi-component molecular crystals on the physical property of solubility, often crucial in API formulation, has been investigated and these solubility determinations are compared with those of the parent PX material. Enhanced solubility is evident in some of the multi-component crystals formed.