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Polymorphs, hydrates and solvates of a co‐crystal of caffeine with anthranilic acid
Author(s) -
Madusanka Nadeesh,
Eddleston Mark D.,
Arhangelskis Mihails,
Jones William
Publication year - 2014
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520613033167
Subject(s) - isostructural , anthranilic acid , crystallography , crystallization , hydrogen bond , chemistry , crystal structure , molecule , crystal (programming language) , theobromine , monoclinic crystal system , stereochemistry , caffeine , organic chemistry , computer science , programming language , endocrinology , medicine
A polymorph screen on a new 1:1 co‐crystal of caffeine, C 8 H 10 N 4 O 2 , with anthranilic acid, C 7 H 7 NO 2 , 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, C 7 H 8 N 4 O 2 , and anthranilic acid resulted in the formation of only one 1:1 co‐crystal form.