1-[4-({4-[(E)-(2-Hydroxynaphthalen-1-yl)methylideneamino]phenyl}sulfanyl)phenyl]ethanone

The title Schiff base compound, C25H19NO2S, crystallizes in a statistically disordered structure comprising keto and enol tautomeric forms. In the enol form, the benzenoid arrangment is promoted by a strong intramolecular O—H...N hydrogen bond and adopts an E conformation about the imine bond. In the keto form there is an intramolecular N—H...O hydrogen bond. In the crystal, an extended network of C—H...O hydrogen bonds stabilizes columns parallel to the c axis, forming large voids (there are four cavities of 108 3 per unit cell) with highly disordered residual electron density. The SQUEEZE procedure in PLATON [Spek (2009). Acta Cryst. D65, 148–155] was used to eliminate the contribution of this electron density from the intensity data, and the solvent-free model was employed for the final refinement. The contribution of this undetermined solvent was ignored in the calculation of the unit-cell characteristics.