Polymorphs, hydrates and solvates of a co-crystal of caffeine with anthranilic acid

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...

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Published inActa crystallographica Section B, Structural science, crystal engineering and materials Vol. 70; no. Pt 1; p. 72
Main Authors Madusanka, Nadeesh, Eddleston, Mark D, Arhangelskis, Mihails, Jones, William
Format Journal Article
LanguageEnglish
Published England Blackwell Publishing Ltd 01.02.2014
Subjects
Bromobenzenes - chemistry
Caffeine - chemistry
Calorimetry, Differential Scanning
Central Nervous System Stimulants
Chlorobenzenes - chemistry
Crystal structure
Crystallization
Crystallography
Crystallography, X-Ray
Hydrogen Bonding
Magnetic Resonance Spectroscopy
Models, Molecular
Molecular Conformation
ortho-Aminobenzoates - chemistry
Powder Diffraction
Single crystals
Solvents - chemistry
Thermogravimetry
Toluene - chemistry
Xylenes - chemistry
polymorphism
hydrates
solvates
co-crystals
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Summary: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.
ISSN:2052-5192
2052-5206
DOI:10.1107/S2052520613033167