(E)-4-[(4-Diethylamino-2-hydroxybenzylidene)amino]benzoic acid

In the title compound, C18H20N2O3, a potential bidentate N,O-donor Schiff base ligand, the benzene rings are inclined at an angle of 12.25 (19)°. The molecule has an E conformation about the C=N bond. One of the ethyl groups is disordered over two positions, with a refined site-occupancy ratio of 0.55 (1):0.45 (1). An intramolecular O—H...N hydrogen bond makes an S(6) ring motif. In the crystal, pairs of O—H...O hydrogen bonds link molecules, forming inversion dimers with R22(8) ring motifs.