Acta Crystallographica Section B

Structural Science, Crystal Engineering and Materials

Volume 70, Part 1 (February 2014)


crystal engineering



Acta Cryst. (2014). B70, 72-80    [ doi:10.1107/S2052520613033167 ]

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

N. Madusanka, M. D. Eddleston, M. Arhangelskis and W. Jones

Abstract: 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.

Keywords: co-crystals; polymorphism; solvates; hydrates.


rtvdisplay fileplot datadownload file

Rietveld powder data file (CIF format) (270.8 kbytes)
[ doi:10.1107/S2052520613033167/bi5010Form1sup2.rtv ]
Contains datablock Form1


rtvdisplay fileplot datadownload file

Rietveld powder data file (CIF format) (273.1 kbytes)
[ doi:10.1107/S2052520613033167/bi5010Form2sup3.rtv ]
Contains datablock Form2


rtvdisplay fileplot datadownload file

Rietveld powder data file (CIF format) (101.7 kbytes)
[ doi:10.1107/S2052520613033167/bi5010Bromobenzene_Hemisolvatesup5.rtv ]
Contains datablock Bromobenzene_Hemisolvate


rtvdisplay fileplot datadownload file

Rietveld powder data file (CIF format) (68.5 kbytes)
[ doi:10.1107/S2052520613033167/bi5010Toluene_Hemisolvatesup6.rtv ]
Contains datablock Toluene_Hemisolvate


rtvdisplay fileplot datadownload file

Rietveld powder data file (CIF format) (49.7 kbytes)
[ doi:10.1107/S2052520613033167/bi5010Theobromine_AAsup11.rtv ]
Contains datablock Theobromine_AA


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