Crystal structure and Hirshfeld surface analysis of (2E)-3-(2,4-dichlorophenyl)-1-(2,5-dichlorothiophen-3-yl)prop-2-en-1-one

In the title compound, the 2,5-dichlorothiophene and 2,4-dichlorophenyl rings, linked via a prop-2-en-1-one spacer, make a dihedral angle of 12.24 (15)°. Both the thiophene and benzene rings of adjacent molecules interact attractively in a face-to-face manner, forming zigzag sheets lying parallel to the (011) plane.


Chemical context
Compounds bearing the 1,3-diphenyl-2-propen-1-one framework and belong to the flavonoid family are commonly called by its generic name 'chalcone'. These are abundant in nature, ranging from ferns to higher plants, and are considered to be the precursors of flavonoids and isoflavonoids, in which the two aromatic rings are joined by a three carbon ,-unsaturated carbonyl system. In plants, chalcones are converted to the corresponding (2S)-flavanones in a stereospecific reaction catalysed by the enzyme chalcone isomerase. The chemistry of chalcones remains a fascination among researchers because of the large number of replaceable hydrogen atoms that allows a number of derivatives with a variety of promising biological activities. They are found in fruits and vegetables, which attracted attention because of their pharmacological activities such as anti-inflamatory (Yadav et al., 2011), antifungal (Mahapatra et al., 2015), antiviral (Nowakowska, 2007;Chimenti et al., 2010;Elarfi &Al-Difar, 2012), antioxidant (Ferreira et al., 2006) and anticancer (Stiborova et al., 2011 activities). The synthesis and antimicrobial evaluation of new chalcones containing a 2,5-dichlorothiophene moiety has been reported (Tomar et al., 2007). In recent years, chalcones have been used in the field of materials science as non-linear optical devices (Raghavendra et al., 2017;Chandra Shekhara Shetty et al., 2016). In view of all the above and as part of our ongoing work (Harrison et al., 2010;Jasinski et al., 2010;Dutkiewicz et al., 2010) herewith we report the crystal and molecular structure of the title compound.

Supramolecular features and Hirshfeld surface analysis
In the crystal, conventional hydrogen bonds are not observed.
Hirshfeld surfaces and fingerprint plots were generated for the title compound using CrystalExplorer (McKinnon et al., 2007). Hirshfeld surfaces enable the visualization of intermolecular interactions by different colours and colour intensity, representing short or long contacts and indicating the The molecular structure of the title compound, showing the atom labelling and displacement ellipsoids drawn at the 50% probability level. The two intramolecular C-HÁ Á ÁCl contacts (see Table1) are shown as dashed lines. Table 1 Hydrogen-bond geometry (Å , ).

Figure 2
A view of the offset face-to-face -stacking in the title compound, with the thick dashed lines indicating centroid-to-centroid interactions. The ClÁ Á ÁH and ClÁ Á ÁS interactions are also shown as dashed lines. Table 2 Summary of short interatomic contacts (Å ) in the title compound.

Database survey
The closest related compounds with the same skeleton and containing a similar bis-chalcone moiety to the title compound but with different substituents on the aromatic rings are: (  but in (VI), the molecules are linked into C(5) chains by C-HÁ Á ÁO hydrogen bonds. In each of compounds (I)-(VI), the molecular skeletons are close to planarity, and there are short halogen-halogen contacts in the structures of compounds (II) and (V) and a short BrÁ Á ÁO contact in the structure of compound (VI).
In (VII), the molecule is non-planar, with a dihedral angle of 22.6 (2) between the aromatic rings. The molecules are linked by pairs of C-HÁ Á Á interactions, forming inversion dimers. There are no other significant intermolecular interactions present. In (VIII), the molecule is nearly planar, the dihedral angle between the thiophene and phenyl rings being 9.07 (8) . The molecules are linked via weak C-HÁ Á ÁO and C-HÁ Á ÁS hydrogen bonds, forming chains propagating along the c-axis direction. In (IX), the thienyl ring is not coplanar with the benzene ring, their planes forming a dihedral angle of 13.2 (4) . In the crystal, molecules stack along the a-axis direction, with the interplanar separation between the thienyl rings and between the benzene rings being 3.925 (6) Å . In (X), the thiophene ring forms a dihedral angle of 26.04 (9) with the benzene ring. The molecular conformation is stabilized by an O-HÁ Á ÁN hydrogen bond. The molecules are connected through C-HÁ Á ÁO hydrogen bonds, forming wave-like layers parallel to the ab plane, which are further linked into a threedimensional network by C-HÁ Á Á interactions. In (XI), the molecule is almost planar with a dihedral angle of 3.73 (8) between the phenyl and thiophene rings. An intramolecular N-HÁ Á ÁO hydrogen bond generates an S(6) ring motif. Adjacent molecules are linked into dimers in an anti-parallel face-to-face manner by pairs of C-HÁ Á ÁO interactions. Neighboring dimers are further linked into chains along the caxis direction by N-HÁ Á ÁN hydrogen bonds.

Synthesis and crystallization
The title compound was synthesized as per the procedure reported earlier (Kumar et al., 2013a,b;Chidan Kumar et al., 2014). 1-(2,5-Dichlorothiophen-3-yl)ethanone (0.01 mol) (Harrison et al., 2010) and 2,4-dichlorobenzaldehyde (0.01 mol) was dissolved in 20 ml methanol. A catalytic amount of NaOH was added to the solution dropwise with vigorous stirring. The reaction mixture was stirred for about 2 h at room temperature. The formed crude products were filtered, washed successively with distilled water and recrystallized from methanol to get the title chalcone. The melting point (381-383 K) was determined by Stuart Scientific (UK) apparatus.
Acta Cryst. (2018). E74, 1201-1205 research communications  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 )