Crystal structure and Hirshfeld surface analysis of 1-(4-chlorophenyl)-2-{[5-(4-chlorophenyl)-1,3,4-oxadiazol-2-yl]sulfanyl}ethanone

The title heterocyclic compound is contains an oxadizole and two chloro-substituted phenyl rings. In the crystal, C—H⋯N hydrogen bonding links the molecules into undulating ribbons parallel to the b axis. Hirshfeld surface analysis indicates that the most important contributions for the crystal packing are the H⋯C (18%), H⋯H (17%), H⋯Cl (16.6%), H⋯O (10.4%), H⋯N (8.9%) and H⋯S (5.9%) interactions.


Chemical context
Heterocyclic compounds are well known for their applications in agriculture (Jakobi et al., 1999) and for the synthesis of pharmaceuticals (Vitaku et al., 2014). The broad range of biological activities of heterocyclic compounds has always fascinated chemists and the literature reveals many approaches to synthesize and derivatize libraries of heterocyclic compounds (Khan et al., 2011;Chohan et al., 2006;Khan et al., 2005). The wide range of applications and biological activities of this class of compounds is due to the presence of heteroatoms (N, O, S) in the molecule (Kashtoh et al., 2014). Oxadiazoles are among the most widely studied moieties of organic chemistry due to their many important chemical and biological properties including antimycobacterial (Jha et al., 2009), antioxidant (Fadda et al., 2011), anticancer (Zhang et al., 2011), antitumor (Loetchutinat et al., 2003, antimicrobial (Ş ahin et al., 2002), antifungal (Zou et al., 2002), anti-inflammatory (Palaska et al., 2002 and hypotensive (Tyagi & Kumar, 2002) activities. ISSN 2056-9890

Structural commentary
The title compound ( Fig. 1) is an oxadiazole derivative containing two chlorophenyl substituents attached to a central oxadiazole thioethanone unit. The C1-C6 and C11-C16 phenyl rings form dihedral angles of 6.54 (9) and 6.94 (8) , respectively, with the oxadiazole ring. The dihedral angle between the oxadiazole ring and the mean plane through the S1/O1/C7-C8 fragment is 10.75 (8) . Bond lengths and angles are not unusual.

Figure 2
Partial crystal packing of the title compound showing the formation of a undulating ribbon parallel to the b axis through C-HÁ Á ÁN hydrogen bonds (dashed lines).  The molecular structure of the title compound with displacement ellipsoids drawn at 30% probability level.

Synthesis and crystallization
The title compound was synthesized by the procdure reported by Kashtoh et al. (2014). 4-Chloro-1,3,4-oxadiazole-2-thiol (212 mg,1 mmol) and triethyl amine (0.1 mL) were taken in ethanol (10 mL) and stirred for 10 min. 2-Bromo-4 0 -chloroacetophenone (232 mg, 1 mmol) was then added slowly into the mixture and refluxed, while progress of the reaction was monitored by TLC. After completion of the reaction, the precipitate was filtered and washed with ethanol. The precipitate was crystallized from methanol to give the title compound in 344 mg, 94% yield.

Refinement
Crystal data, data collection and structure refinement details are summarized in (Table 2). H atoms were located in a difference-Fourier map, but were positioned with idealized geometry and refined with C-H = 0.93-0.97 Å , and with U iso (H) = 1.2U eq (C).

1-(4-Chlorophenyl)-2-{[5-(4-chlorophenyl)-1,3,4-oxadiazol-2-yl]sulfanyl}ethanone
Crystal data 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. 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 > 2sigma(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.