Redetermination of the crystal structure of the 3:1 urea-benzene-1,3,5-tri-carb-oxy-lic acid co-crystal by powder diffraction data.

The crystal structure of the 3:1 urea-benzene-1,3,5-tri-carb-oxy-lic acid (trimesic acid) co-crystal, C9H6O6·3CH4N2O, has been redetermined by X-ray powder diffraction data exploiting simulated annealing in direct space followed by Rietveld refinement. The compound crystallizes in the monoclinic space group P21/c. The structure consists of hydrogen-bonded assemblies formed by one trimesic acid mol-ecule and three urea mol-ecules. Two urea mol-ecules are approximately coplanar with the aromatic acid mol-ecule, whereas the third is oriented nearly perpendicular to such planes and links adjacent layers into a three-dimensional hydrogen-bonded network. The present study provides a deeper insight of the inter-molecular inter-actions by the means of Hirshfeld surface analysis, and supplies the preparation method and the atomic coordinates of the structure, which were not present in the original work [Videnova-Adrabinska (1996 ▸). J. Mol. Struct. 374, 199-222].