Polymorphs, hydrates and solvates of a co‐crystal of caffeine with anthranilic acid. Issue 1 (1st February 2014)

• Record Type: Journal Article
• Authors: Madusanka, Nadeesh; Eddleston, Mark D.; Arhangelskis, Mihails; Jones, William
• Is Part Of: Acta crystallographica. Volume 70:Issue 1(2014:Feb.)
• Page Start: 72
• Page End: 80
• Publication Date: 2014-02-01
• DOI: 10.1107/S2052520613033167
• Languages: English
• ISSNs: 2052-5206

Abstract

<abstract abstract-type="main" xml:lang="en"> <title> <x xml:space="preserve">Abstract</x> </title> <p>A polymorph screen on a new 1:1 co‐crystal of caffeine, C₈H₁₀N₄O₂, with anthranilic acid, C₇H₇NO₂, has revealed a rich diversity of crystal forms (two polymorphs, two hydrates and seven solvates, including two sets of isostructural solvates). These forms were prepared by liquid‐assisted grinding and solution crystallization, and the crystal structures of nine of these forms have been solved using either single‐crystal or powder X‐ray data. The structures contain O—H...N and N—H...O hydrogen bonds through which caffeine and anthranilic acid molecules assemble to form zigzag‐type chains. These chains can interact in an anti‐parallel and offset manner to form cage‐ or channel‐type skeletons within which solvent molecules can be located, giving rise to the diversity of forms observed for this co‐crystal. In contrast, an equivalent series of liquid‐assisted grinding and solution crystallization experiments with the closely related system of theobromine, C₇H₈N₄O₂, and anthranilic acid resulted in the formation of only one 1:1 co‐crystal form.</p> </abstract>