Acta Crystallographica Section B

Structural Science, Crystal Engineering and Materials

Volume 70, Part 1 (February 2014)


crystal engineering



Acta Cryst. (2014). B70, 63-71    [ doi:10.1107/S2052520613031260 ]

Binary co-crystals of the active pharmaceutical ingredient 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene and camphoric acid

K. K. Bisht, P. Patel, Y. Rachuri and S. Eringathodi

Abstract: Co-crystals comprising the active pharmaceutical ingredient 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, C12H10N4, and the chiral co-formers (+)-, (-)- and (rac)-camphoric acid (cam), C10H16O4, have been synthesized. Two different stoichiometries of the API and co-former are obtained, namely 1:1 and 3:2. Crystallization experiments suggest that the 3:2 co-crystal is kinetically favoured over the 1:1 co-crystal. Single-crystal X-ray diffraction analysis of the co-crystals reveals N-H...O hydrogen bonding as the primary driving force for crystallization of the supramolecular structures. The 1:1 co-crystal contains undulating hydrogen-bonded ribbons, in which the chiral cam molecules impart a helical twist. The 3:2 co-crystal contains discrete Z-shaped motifs comprising three molecules of the API and two molecules of cam. The 3:2 co-crystals with (+)-cam, (-)-cam (space group P21) and (rac)-cam (space group P21/n) are isostructural. The enantiomeric co-crystals contain pseudo-symmetry consistent with space group P21/n, and the co-crystal with (rac)-cam represents a solid solution between the co-crystals containing (+)-cam and (-)-cam.

Keywords: co-crystal; molecular adduct; camphoric acid; active pharmaceutical ingredient; crystal engineering.


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[ doi:10.1107/S2052520613031260/bi5004sup5.pdf ]
Synthesis, spectroscopic and thermal characterization


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