Abstract
Interest in co-crystals formation has been constantly growing since their discovery, almost a century ago. Such success is due to the ability to tune the physical-chemical properties of the components in solid state by avoiding a change in their molecular structure. The properties influenced by the co-crystals formation range from an improvement of mechanical features and chemical stability to different solubility. In the scientific research area, the pharmacological field is undoubtedly one of those in which an expansion of the co-crystal knowledge can offer wide benefits. In this work, we described the crystalline structure of hexamethylenetetramine co-crystallized with the isophthalic acid, and we compared it with another co-crystal, showing the same components but different stoichiometry. To give a wider overview on the nature of the interactions behind the observed crystal packing and to rationalize the reasons of its formation, a computational analysis on such structures was carried out.
Highlights
One of the main limits in the development of highly efficient drug molecules regards their low aqueous solubility with the consequent limitation of the bioavailability
We examine and attempt to provide some rationalization to a new co-crystal structure of a hexamethylenetetramine (HMTA) and isophthalic acid (IPA) containing a water molecule linked through hydrogen bonds to the crystal lattice
The asymmetric unit (AU) of the supramolecular complex is constituted by half a molecule of water, IPA and HMTA
Summary
One of the main limits in the development of highly efficient drug molecules regards their low aqueous solubility with the consequent limitation of the bioavailability. It is nowadays well known that the arrangement adopted by species in their solid form brings a change of their physical-chemical properties and can have profound effects on the dissolution rate [5,6], stability, and bioavailability of that species Such properties and the possibility to predict them led to an increased economic interest by pharmaceutical companies on the study of the basic principles that can influence co-crystals, polymorphs and pseudo-polymorphs formation. By taking advantage of computational chemistry, it is possible to evaluate the thermodynamic stability of many possible structures, and among them, select the most thermodynamically plausible ones In this general framework, we examine and attempt to provide some rationalization to a new co-crystal structure of a hexamethylenetetramine (HMTA) and isophthalic acid (IPA) containing a water molecule linked through hydrogen bonds to the crystal lattice.
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