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

In the crystal, the molecules are linked by weak C–H⋯F hydrogen bonds into the supramolecular inversion dimers.


Chemical context
Natural products are important sources in the search for new agents for cancer therapies with minimal side effects. Chalcones, considered to be the precursor of flavonoids and isoflavonoids, are abundant in edible plants. Compounds with the 1,3-diphenylprop-2-en-1-one framework are described by its generic term 'chalcone'. They consist of open-chain flavonoids in which the two aromatic rings are joined by a threecarbon ,-unsaturated carbonyl system. These are coloured compounds because of the presence of the -CO-CH CHchromophore, which depends in the presence of other auxochromes. Accumulating evidence has shown that chalcones and their derivatives could inhibit tumor initiation and progression. In view of the above, and as a part of our ongoing research on chalcone derivatives (Naveen et al., 2017;Lokeshwari et al., 2017;Tejkiran et al., 2016), we report herein the synthesis, crystal structure and Hirshfeld surface analysis of the title compound. ISSN 2056-9890

Structural commentary
The molecular structure of the title compound, shown in Fig. 1, is comprised of two aromatic rings (chlorofluorophenyl and dichlorothiophene) linked by C C-C( O)-C enone bridge. The bond lengths and bond angles are normal and the molecular conformation is characterized by a dihedral angle of 12.9 (2) between the mean planes of the two aromatic rings. The olefinic double bond C6 C7 of 1.303 (6) Å is in an E configuration and is Csp 2 hybridized. The unsaturated keto group is in a syn-periplanar conformation with respect to the olefenic double bond, which is evident from the torsion angle value of À0.5 (8) for the atoms O1-C5-C6-C7. The thiophene ring is affected by conjugation. This can be explained by the longer C S values of 1.703 (6) and 1.714 (4) Å for S1 C2 and S1 C1, respectively. The bondangle values O1-C5-C6 [121.9 (4) ], O1-C5-C4 [118.2 (4) ] and C5-C6-C7 = 125.14 (4) about C5 indicate that the carbon atom is in a distorted trigonal-planar configuration, which is due to steric hindrance of the oxygen atom. The molecular structure is stabilized by an intramolecular C6--H6AÁ Á ÁCl1 hydrogen bond ( Table 1) that closes an S(6) motif, as shown in Fig. 1.

Figure 3
View of the three-dimensional Hirshfeld surface of the title compound mapped over d norm .

Figure 1
The molecular structure of the title compound, indicating the atomnumbering scheme. The intramolecular C-HÁ Á ÁCl hydrogen bond (dashed line) closes an S(6) motif. Displacement ellipsoids are drawn at the 50% probability level.
In Fig. 4, the dark spots near atoms Cl1 and F1 result from the C6-H6AÁ Á ÁCl1 and C10-H10AÁ Á ÁF1 interactions, which play a significant role in the molecular packing of the title compound. The Hirshfeld surfaces illustrated in Fig. 4 also reflect the involvement of different atoms in the intermolecular interactions through the appearance of blue and red regions around the participating atoms, which correspond to positive and negative electrostatic potential, respectively. The shape-index surface clearly shows that the two sides of the molecules are involved in the same contacts with neighbouring molecules while the curvedness plots show flat surface patches characteristic of planar stacking.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. C-bound H atoms were positioned geometrically (C-H = 0.95-0.99 Å ) and refined using a riding model with U iso (H) = 1.2U eq (C).

Figure 6
Synthesis of the title compound.

(E)-3-(2-Chloro-4-fluorophenyl)-1-(2,5-dichlorothiophen-3-yl)prop-2-en-1-one
Crystal data Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses 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 observed criterion of F 2 > 2sigma(F 2 ) is used only for calculating -R-factor-obs 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.  (2) 0.008 (2) 0.0071 (19) Geometric parameters (Å, º)