(4-Aminosulfonylphenyl)[(2-oxidonaphthalen-1-yl)imino]azanium

The crystal structure of the title compound, C 16 H 13 N 3 O 3 S, shows that the two independent zwitterions in the asymmetric unit are approximately planar. Intramolecular N—H...O hydrogen bonds occur and the aromatic rings have a trans configuration with respect to the azo double bond. In the crystal, the molecules are linked via N—H...O hydrogen bonds and π–π stacking, forming a three-dimensional supramolecular network, the π–π stacking interactions between adjacent benzene and naphthalene rings having centroid-to-centroid distances of 3.764 (3) and 3.775 (3) Å.