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

The crystal structure of the title compound, C16H13N3O3S, 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) A.