title: Triclinic polymorph of sulfasalazine.
abstract: In this modification of the title compound, 5-(4-[(2-pyridylamino)sulfonyl]phenyldiazenyl)salicylic acid, C(18)H(14)N(4)O(5)S, the molecule is present in the amide tautomeric form. Two azo-bridged phenyl rings render the bulk of the molecule planar, with the carboxylic acid group at one terminal and the pyridylamino residue at the other. The repeating unit in the crystal is a centrosymmetric dimer containing two identical R-2/2-(8) hydrogen-bonded ring systems, each involving the carboxylic acid and pyridylamino moieties. Additional stabilization is due to an intramolecular hydrogen bond between the 2-hydroxyl group and the carbonyl O atom of the carboxylic acid group, as well as intermolecular pi-pi stacking.
authors: University of Medicine and Pharmacy, Iuliu Hatieganu, Department of Drugs Control, Cluj-Napoca RO-3400, Romania.
authors: L A
authors: LA
authors: Filip
authors: M R
authors: MR
authors: Caira
authors: S I
authors: SI
authors: Fărcaş
authors: M T
authors: MT
authors: Bojiţa
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008968:Molecular Conformation; D012460:Sulfasalazine / Q000737:chemistry*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D012460:Sulfasalazine