Crystal structure of a 1:1 salt of 4-aminobenzoic acid (vitamin B 10 ) with pyrazinoic acid

The title 1:1 salt, C 7 H 8 NO 2 + ·C 5 H 3 N 2 O 2 − (systematic name: 4-carboxyanilinium pyrazine-2-carboxylate), was synthesized successfully by slow evaporation of a saturated solution from water–ethanol (1:1 v / v ) mixture and characterized by X-ray diffraction (SCXRD, PXRD) and calorimetry (DSC). The crystal structure of the salt was solved and refined at 150 and 293 K. The salt crystallizes with one molecule of 4-aminobenzoic acid (PABA) and one molecule of pyrazinoic acid (POA) in the asymmetric unit. In the crystal, the PABA and POA molecules are associated via COOH...N arom heterosynthons, which are connected by N—H...O hydrogen bonds, creating zigzag chains. The chains are further linked by N—H...O hydrogen bonds and π–π stacking interactions along the b axis [centroid-to-centroid distances = 3.7377 (13) and 3.8034 (13) Å at 150 and 293 K, respectively] to form a layered three-dimensional structure.