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The title compound, C18H14N2O2, crystallized with two independent zwitterion molecules (A and B) in the asymmetric unit. They are both close to planar, the dihedral angle between the benzene ring and naphthalene ring system being 4.30 (9)° in A and 4.69 (9)° in B. Each molecule has an E conformation with respect to the azo double bond. In each of the independent molecules, an intramolecular N—H...O hydrogen bond forms an S(6) ring motif. In the crystal, molecules are linked via C—H...O hydrogen bonds, forming –A—A—A– and –B—B—B– chains parallel to one another and propagating along the a-axis direction. There are also π–π interactions between adjacent molecules involving benzene and naphthalene rings [centroid–centroid distance of 3.626 (3) Å for adjacent A molecules and 3.652 (3) Å for adjacent B molecules].