Crystal structure of (E)-1-[4-({4-[(4-methoxybenzylidene)amino]phenyl}sulfanyl)phenyl]ethan-1-one

The title Schiff base compound, C22H19NO2S, crystallized with two independent molecules (A and B) in the asymmetric unit. Both molecules have an E conformation about the C=N bond. The two molecules differ in the orientation of the aromatic rings with respect to each other. The outer 4-methoxybenzene ring is inclined to the central benzene ring and the outer 4-acetylbenzene ring by 1.80 (19) and 63.73 (19)°, respectively, in molecule A, and by 6.72 (18) and 68.53 (19)°, respectively, in molecule B. The two outer benzene rings are inclined to one another by 63.77 (18) and 63.19 (18)° in molecules A and B, respectively. In the crystal, the individual molecules stack in columns along [010], and are linked by a number of C—H⋯π interactions, forming slabs lying parallel to (001).


S1. Comment
The synthesis and structures of Schiff bases have attracted much attention in biology and chemistry (Kahwa et al., 1986).
One of the aims of investigating their structural chemistry is to develop protein and enzyme mimics (Santos et al., 2001).
There are only a few reported crystal structures of Schiff bases derived from 4-amino-4-acetyldiphenyl sulfide (Hebbachi et al., 2013). As a part of our ongoing research, we have synthesized the title compound and report herein on its crystal structure.
The two molecules differ in the orientation of the aromatic rings with respect to one another. The outer 4-methoxybenzene ring is inclined to the central benzene ring and the outer 3-acetylbenzene ring by 1.80 ( The bond lengths and angles are close to those observed for a very similar structure, viz. (E)-1-(4-((4-(((4-hydroxynaphthalen-1-yl)methylene)amino)phenyl)thio) phenyl)ethan-1-one (Hebbachi et al., 2013). For example, the sulfur atom has sp 3 hybridization as indicated by the C-S-C angle of 106.01 (15) and 105.99 (15) ° in molecules A and B, respectively, compared to 104.88 (15) ° observed in the above mentioned compound.
In the crystal, molecules stack along [010] in columns composed of either A or B molecules, and are linked by a number of C-H···π interactions (Table 1 and Fig. 2) forming slabs lying parallel to (001).

S2. Experimental
The title Schiff base was prepared by condensation of 4-amino-4-acetyl diphenylsulfure and anisaldehyde in a 1:1 molar ratio, in an ethanol solution containing a few drops of dry piperidine. The mixture was stirred under reflux for 3 h. The mixture was then concentrated and cooled. Colourless prismatic crystals of title compound were obtained by recrystallization from a mixture of chloroform/hexane (1/1). They were collected by filtration and dried in air (yield: 64%; m.p.: 421 K).
supporting information

S3. Refinement
H atoms were positioned geometrically and refined using a riding model: C-H = 0.93 -0.98 Å with U iso (H) = 1.5U eq (C) for methyl H atoms and = 1.2U eq (C) for other H atoms.

Figure 1
The molecular structure of the two independent molecules (A and B) of the title compound, with atom labelling.
Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
A view along the b axis of the crystal packing of the title compound. C-H···π interactions are shown as dashed lines (see Table 1 for details; molecule A is red; molecule B is blue; H atoms not involved in these interactions have been omitted for clarity).

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq S1 0.40421 (