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 Å3 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.

The title Schiff base compound, C 25 H 19 NO 2 S, 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-HÁ Á ÁN hydrogen bond and adopts an E conformation about the imine bond. In the keto form there is an intramolecular N-HÁ Á ÁO hydrogen bond. In the crystal, an extended network of C-HÁ Á ÁO hydrogen bonds stabilizes columns parallel to the c axis, forming large voids (there are four cavities of 108 Å 3 per unit cell) with highly disordered residual electron density. The SQUEEZE procedure in PLATON [Spek (2009). Acta Cryst. D65,[148][149][150][151][152][153][154][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.  Schiff bases are important compounds owing to their wide range of biological activities and industrial applications (Li et al., 2003;Villar et al., 2004). They have also been used as ligands in coordination chemistry (Kagkelari et al., 2009;Ourari et al. 2008;Zidane et al., 2011). The Schiff base adopts a E conformation about the C12═N13 bond with a C11-C12-N13A-C14A torsion angle = -178.5 (3) Å. The central part of the molecule is planar with a dihedral angle between the benzene and naphthalene rings being less than 1 °. The molecule is twisted around the sulfide atom, so the average dihedral angle between the acetyl phenyl ring and the oxo naphthalen ring system is about 71°. The electron delocalisation between the two sulfur-bound lone pairs and π electrons of the adjacent phenyl rings leads to a slightly tighter Ssp 3 angle (C17A-S1-C20 = 104.88 (15)°). The two similar sulfide carbone single bonds [C17A-S1 1.780 (3) Å and C20-S1 1.764 (3) Å] are as expected. The short bond C3-C4 distance [1.354 (5) Å] adjacent to the O1 oxygen atom of the naphthalen core indicates the presence of quinoid effect.

Related literature
In the crystal, molecules are aligned head to foot along b axis, in columns parallel to [0 0 1] axis and the structure is stabilized by four kinds of C-H···O interactions (Fig. 2, Table 1). This arrangement separates the equivalent groups in columns by 4.444 (1) Å.
The large void channels in the structure (Fig. 3) contains residual electrons density with high disorder. The residual electron density were difficult to model and therefore, the SQUEEZE function of PLATON (Spek, 2009) was used to eliminate the contribution of the electron density in the solvent region from the intensity data, and the solvent-free model was employed for the final refinement. There are four cavities of 108 Å 3 per unit cell. PLATON estimated that each cavity contains 12 electrons which may correspond to a solvent molecule.

Experimental
The title Schiff base was prepared by the condensation of 4-amino-4-acetyl diphenylsulfide and 2-hydroxy naphthaldehyde in a 1:1 molar ratio in ethanol solution. The mixture was stirred under reflux three hours. The crystals of title compound crystallized from a mixture of chloroforme/hexane (1/1). The orange needles were collected by filtration and dried in air. Yield: 61%. Melting Point: 451 K.

Refinement
H atoms were positioned geometrically, using a riding model with C-H = 0.98 Å [U iso (H) = 1.5 × U eq (methyl-C)] and Since one hydrogen is not very well localized between N13 and O1, the structure is described as the presence of two tautomers. Hydrogen is bonded to O1 in the first one (part A) and to N13 in the second (part B). This disorder was modeled by refining part A (except H on N13), with O-H = 0.84 Å (U iso (H) = 1.5), and part B (except H on O1) with equivalence of N13 and central phenyl ring (C14 to C19) atoms, with N-H = 0.88 Å (U iso (H) = 1.5).
Large voids in the structure contains residual electrons density with hight disorder and or thermal motions. The SQUEEZE procedure of PLATON was used to eliminate the contribution of this residual electron density from the intensity data, and the solvent-free model was employed for the final refinement.  The molecular structure of (I) with atom labels and 50% probability displacement ellipsoids for non-H atoms. Disorder is present between the (illustrated) enol and keto forms.  The four intermolecular C-H···O interactions bonds (symmetry codes: C9-H9···O28 i , C19A-H19A···O28 i , C27-

Figure 3
A view of the unit-cell contents in projection down the c axis in (I), highlighting large void channels within the unit cell. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger. Since hydrogen is not very well localized between N13 and O1, the structure is described as the presence of two tautomers. Hydrogen is bonded to O1 in the first one (part A) and to N13 in the second (part B). This disorder was modeled by refining part A (except H on N13) and part B (except H on O1) with equivalence of N13 and central phenyl ring (C14 to C19) atoms.