Bisht KK, Patel P, Rachuri Y, Eringathodi S. Binary co-crystals of the active pharmaceutical ingredient 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene and camphoric acid.
ACTA CRYSTALLOGRAPHICA SECTION B, STRUCTURAL SCIENCE, CRYSTAL ENGINEERING AND MATERIALS 2014;
70:63-71. [PMID:
24441129 DOI:
10.1107/s2052520613031260]
[Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Accepted: 11/14/2013] [Indexed: 06/03/2023]
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.
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