Crystal structure of (E)-2-[(4-hy­droxy­benzyl­idene)aza­nium­yl]benzoate

The title Schiff base, C₁₄H₁₁NO₃, crystallizes as a zwitterion (i.e. proton transfer from the carb­oxy­lic acid group to the imine N atom). The dihedral angle between the aromatic rings is 19.59 (6)° and an intra­molecular N—H...O hydrogen bond closes an S(6) ring. In the crystal, inversion dimers linked by pairs of O—H...O hydrogen bonds generate R₂⁴(24) loops. The dimers are linked by C—H...O inter­actions, generating (211) sheets.