Acta Cryst. (2009). E65, o532-o533 [ doi:10.1107/S1600536809004607 ]
Abstract: The combination of 2-hydroxypropane-1,2,3-tricarboxylic acid (H3hypta, also called citric acid) and 4,4'-bipyridine (4,4'-bipy) in a 1:1.5 molar ratio leads to the formation of the title molecular cocrystal, 1.5C10H8N2·C6H8O7. The asymmetric unit contains one and a half 4,4'-bipy units, with one lying across a centre of inversion, and one H3hypta molecule. The significant differences in the C-O bond distances support the existence of the un-ionized acid molecule and confirm the formation of a cocrystal. There are - and C-H stacking interactions between the aromatic rings of 4,4'-bipy [with interplanar distances of 3.7739 (8) and 3.7970 (8) Å] and between CH groups of H3hypta [with an H distance of 2.63 Å]. In the crystal structure, intermolecular O-HN hydrogen bonds occur and an O-HO hydrogen bond occurs within the citric acid moiety.
Online 18 February 2009
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