1-(4-Hy­droxy­phen­yl)-2-(2-oxidonaphthalen-1-yl)diazen-1-ium methanol hemisolvate

In the title compound, C₁₆H₁₂N₂O₂·0.5CH₃OH, the H atom of the –OH group has been transfered to the N atom in the azo group, forming a zwitterion. Hence, there is an intra­molecular N—H...O, rather than an O—H...N, hydrogen bond in the mol­ecule. The mol­ecule is almost planar, the dihedral angle between the benzene ring and the mean plane of the naphthalene ring system being 4.51 (6)°. In the crystal, mol­ecules are linked to and bridged by O—H...O hydrogen bonds involving the methanol mol­ecule, which is located about a twofold rotation axis, and hence half-occupied, forming zigzag chains along [001]. Mol­ecules are also linked via C—H...π and π–π inter­actions, the latter involving adjacent benzene and naphthalene rings and having a centroid–centroid distance of 3.6616 (13) Å, forming a three-dimensional network.