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

The molecular structure of the title compound consists of a 2,5-dichlorothiophene ring and a 2-chlorophenyl ring linked via a prop-2-en-1-one spacer. The molecule has an E configuration about the C=C bond and the carbonyl group is syn with respect to the C=C bond. In the crystal, the molecules are linked along the a-axis direction through van der Waals forces and by face-to-face π-stacking between the thiophene rings and between the benzene rings of neighbouring molecules along the b axis into zigzag sheets lying parallel to the bc plane.


Chemical context
Chalcone is an aromatic ketone that forms a central core for a variety of biological compounds, which are collectively known as chalcones. Chalcones, considered to be the precursors of flavonoids and isoflavonoids, are abundant in edible plants.
As part of our studies in this area, we report the crystal and molecular structures of the title compound.

Figure 1
The molecular structure of the title compound, showing the atom labelling and displacement ellipsoids drawn at the 50% probability level. Intramolecular hydrogen bonds (Table 1) are shown as dashed lines.

Table 2
Summary of short interatomic contacts (Å ) in the title compound.

Figure 2
View along the b-axis direction of the zigzag sheets lying parallel to (011).
-stacking is observed between the thiophene rings (centroid Cg1) of adjacent molecules in alternating sheets along the [100] direction and between the benzene rings (centroid Cg2) of the same molecules.

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: ( chains by means of C-HÁ Á ÁO hydrogen bonds. In (V), there are again no hydrogen bonds nor anystacking interactions 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 nonplanar, 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 three-dimensional 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. Neighbouring dimers are further linked into chains along the c-axis direction by N-HÁ Á ÁN hydrogen bonds. In (XII), the dihedral angle between the thiophene and benzene rings increases to12.24 (15) . The molecular conformation is stabilized by intramolecular C-HÁ Á ÁCl contacts, forming S(6) and S(5) ring motifs. In the crystal, the molecules are linked through face-toface -stacking between the thiophene rings and the benzene rings of the molecules into zigzag sheets lying parallel to the bc plane.

Synthesis and crystallization
The title compound was synthesized by a reported procedure (Kumar et al., 2013a,b). 1-(2,5-Dichlorothiophen-3-yl)ethanone (0.01 mol) (Harrison et al., 2010b) and 2-chlorobenzaldehyde (0.01 mol) were dissolved in 20 ml of methanol. A catalytic amount of NaOH was added to the solution dropwise with vigorous stirring. The reaction mixture was stirred for about 4 h at room temperature. The formed crude products were filtered, washed successively with distilled water and recrystallized from methanol. The melting point (352-363 K) was determined using a Stuart Scientific (UK) apparatus.

(E)-3-(2-chlorophenyl)-1-(2,5-dichlorothiophen-3-yl)prop-2-en-1-one
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.