Crystal structure and Hirshfeld surface analysis of (2E)-3-(3-bromo-4-fluorophenyl)-1-(3,4-dimethoxyphenyl)prop-2-en-1-one

The title compound is constructed from two aromatic rings (3-bromo-4-fluorophenyl and 3,4-dimethoxyphenyl), which are linked by a C=C—C(=O)—C enone bridge and form a dihedral angle of 17.91 (17)°. In the crystal, molecules are linked by C—H⋯O hydrogen bonds enclosing rings of (14) graph-set motif to form layers parallel to (10).

In the molecule of the title compound, C 17 H 14 BrFO 3 , the aromatic rings are tilted with respect to the enone bridge by 13.63 (14) and 4.27 (15) , and form a dihedral angle 17.91 (17) . In the crystal, centrosymmetrically related molecules are linked by pairs of C-HÁ Á ÁO hydrogen bonds into dimeric units, forming rings of R 2 2 (14) graph-set motif. The dimers are further connected by weak C-HÁ Á ÁO hydrogen interactions, forming layers parallel to (101). Hirshfeld surface analysis shows that van der Waals interactions constitute the major contribution to the intermolecular interactions, with HÁ Á ÁH contacts accounting for 29.7% of the surface.

Chemical context
Natural products are important sources to search for new agents for cancer therapies with minimal side effects. Chalcones, which are considered to be the precursors of flavonoids and isoflavonoids, are abundant in edible plants. They consist of open-chain flavonoids in which the two aromatic rings are joined by a three-carbon ,-unsaturated carbonyl system. These are coloured compounds because of the presence of the -CO-CH CH-chromophore, the colour depending on 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 in a continuation of our previous work on 3,4-dimethoxy chalcones (Sheshadri et al., 2018), herewith we report the crystal and molecular structures of the title compound.

Supramolecular features
In the crystal, centrosymmetrically related molecules are linked by pairs of C-HÁ Á ÁO hydrogen bonds into dimers forming rings with an R 2 2 (14) graph-set motif (Table 1, Fig. 2). The dimeric units are further connected by weak C-HÁ Á ÁO hydrogen bonds, forming layers parallel to (101).

Figure 2
A view along the a axis of the crystal packing of the title compound. H atoms not involved in hydrogen bonding (dashed lines) are omitted for clarity.

Figure 1
The molecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level.
envelope, which other molecules or atoms come into contact with when interactions are present. The Hirshfeld surface and two-diensional fingerprint plots of the title compound were calculated using CrystalExplorer17.5 (Turner et al., 2017). In the Hirshfeld surface plotted over d norm (Fig. 3), the white surfaces indicate contacts with distances equal to the sum of van der Waals radii, and the red and blue colours indicate distances shorter or longer than the van der Waals radii, respectively (Venkatesan et al., 2016). The bright-red spots appearing near to O2, F1, Br1 and hydrogen atoms H15A, H16A, H17C indicate their role as donors and acceptors in the dominant C-HÁ Á ÁO, C-HÁ Á ÁF and C-HÁ Á ÁBr contacts. The shape-index of the Hirshfeld surface is a tool to visualize the stacking interactions by the presence of adjacent red and blue triangles; if there are no adjacent red and/or blue triangles, then there are nointeractions. The Hirshfeld surface of the title compound plotted over shape-index ( Fig. 4)    Hirshfeld surface of the title compound plotted over shape-index.

Figure 5
The

Synthesis and crystallization
The reagents and solvents for the synthesis were obtained from the Aldrich Chemical Co., and were used without additional purification. The title compound was synthesized as per the procedure reported earlier (Kumar et al., 2013a,b;Chidan Kumar et al., 2014). 1-(3,4-Dimethoxyphenyl) ethanone (0.01mol) and 3-bromo-4-fluorobenzaldehyde (0.01mol) were 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 6 h at room temperature. The progress of the reaction was monitored by TLC. The formed crude product was filtered, washed repeatedly with distilled water and recrystallized from ethanol to obtain the title chalcone. Crystals suitable for X-ray diffraction studies were obtained from an acetone solution by the slow evaporation technique at room temperature. The melting point (381-383 K) was determined by a Stuart Scientific (UK) apparatus. The purity of the compound was confirmed by thin layer chromatography using Merck silica gel 60 F254 coated aluminum plates.

(2E)-3-(3-Bromo-4-fluorophenyl)-1-(3,4-dimethoxyphenyl)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.