Crystal structure of a 1: 1 salt of 4-aminobenzoic acid (Vitamin B₁₀) with pyrazinoic acid

The title 1:1 salt, C₇H₈NO₂ ⁺·C₅H₃N₂O₂ ^- (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⋯Narom 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.