(E)-1-[2-(2-Cyano-phen-yl)diazen-2-ium-1-yl]naphthalen-2-olate.

There are two independent zwitterion mol-ecules (A and B) in the asymmetric unit of the title compound, C17H11N3O, which belongs to the family of azo dyes. The dihedral angle between the benzene ring and the naphthalene ring system is 6.99 (6)° in mol-ecule A and 4.38 (6)° in mol-ecule B. The azo group adopts an E conformation with respect to the -N=N- bond and each of the independent mol-ecules has an intra-molecular N-H⋯O hydrogen bond. In the crystal, mol-ecules are linked by C-H⋯O and C-H⋯N hydrogen bonds, forming ribbons propagating along [-110]. The ribbons are linked via π-π inter-actions involving the benzene and naphthalene rings of inversion-related A and inversion-related B mol-ecules, forming a three-dimensional structure. The most significant centroid-centroid distances vary from 3.6599 (6) to 3.7538 (9) Å.