Abstract
The title compound, C13H10N2O4, crystallized as the zwitterionic tautomer. As a result, the phenolate C-O- bond [1.296 (2) angstrom] is shorter than a normal Csp(2) - O(H) bond, and the azomethine C=N bond [1.314 (2) angstrom] is longer than a normal C=N double bond. The molecule is nearly planar, the mean plane of the nitro-substituted benzene ring forming dihedral angles of 9.83 (7) and 8.45 (9)degrees with the other benzene ring and with the nitro group, respectively. The molecular conformation is stabilized by an intramolecular N-H center dot center dot center dot O hydrogen bond. In the crystal, strong O-H center dot center dot center dot O hydrogen bonds link the molecules into double-stranded chains along the b-axis direction. Within the chains there are pi-pi interactions involving the benzene rings of adjacent molecules [centroid-centroid distance = 3.669 (1) angstrom]. The chains are linked via C-H center dot center dot center dot O hydrogen bonds, forming R-2(1) (6), R-2(1) (7) and R-2(2) (10) ring motifs.