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

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 connected into a tape structure by C—H⋯O and C—H⋯π interactions.


Chemical context
Chalcones, compounds with a 1,3-diphenylprop-2-en-1-one framework, are considered to be the precursors of flavonoids and isoflavonoids, which are abundant in edible plants. These compounds are coloured via the -CO-CH CH-chromophore and other auxochromes. Chalcones attract significant attention because of their availability of high optical nonlinearities arising from the delocalization of -conjugated electron clouds throughout the chalcone system, which provides a large charge-transfer axis with appropriate substituents on the terminal aromatic rings. -conjugated systems have been studied extensively for their optoelectronic properties (Shetty et al., 2016(Shetty et al., , 2017 because of the possibility of developing low-cost, large-area and flexible electronic devices. In view of all the above and in a continuation of our previous work on 3,4-dimethoxy chalcones (Sheshadri et al., 2018a,b), we report herein the crystal and molecular structure of the title compound.
The Hirshfeld surface and two-dimensional fingerprint plots of the title compound were calculated using Crystal-Explorer17.5 (Turner et al., 2017). In the Hirshfeld surface   Table 1 Hydrogen-bond geometry (Å , ).

Figure 3
A packing diagram of the title compound viewed along the a axis, showing intermolecular C-HÁ Á ÁO and C-HÁ Á Á interactions (dashed lines). The minor disorder component and H atoms not involved in the hydrogen bonds are omitted for clarity.

Figure 1
The molecular structure of the title compound, showing the atom labelling and displacement ellipsoids drawn at the 50% probability level.
plotted over d norm (Fig. 4), 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 overall two-dimensional fingerprint plot and those delineated into HÁ Á ÁH (  For these similar compounds, the dihedral angles between the two terminal benzene rings, which are linked by a -CO-CH CH-enone bridge are 18.46 (7) for VIDVEM, 17.91 (17) for BIBWOB, 9.3 (2) and 19.4 (2) (two crystallographically independent molecules) for LAPREB, 5.46 (2) for KUZFOB, 26.59 (9) for LAQWUX and 47.81 (6) and 50.18 (5) (two crystallographically independent molecules) for MEGQOF. In the crystals of VIDVEM and BIBWOB, molecules are linked by C-HÁ Á ÁO hydrogen bonds, forming dimers with R 2 2 (14) ring motifs, and the dimers are further linked by other C-HÁ Á ÁO hydrogen contacts, forming twodimensional supramolecular structures. In the crystal of LAPREB, molecules are also linked through weak intermolecular C-HÁ Á ÁO hydrogen bonds. The crystal structure of KUZFOB is stabilized by intermolecular C-HÁ Á ÁF hydrogen bonds.

Synthesis and crystallization
The title compound was synthesized as per the procedure reported earlier (Kumar et al., 2013a,b). 1-(3,4-Dimethoxyphenyl)ethanone (0.01 mol) and 4-chloro-3-fluorobenzaldehyde (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 3 h at room temperature. The formed crude products were filtered, washed successively with distilled water and recrystallized from methanol to get the title compound (m.p. 384-388 K).   Plot of d norm mapped on the Hirshfeld surfaces of the title compound showing the short HÁ Á ÁO contacts.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The C-bound H atoms were positioned geometrically (C-H = 0.93 or 0.96 Å ) and refined using a riding model, with U iso (H) = 1.2 or 1.5U eq (C). The 4chloro-3-fluorophenyl fragment was found to be disordered in a difference-Fourier map, and the F and H atoms at the meta positions of the benzene ring were treated as disordered over two sites with an occupancy ratio of 0.785 (3):0.215 (3). Computer programs: APEX2 and SAINT (Bruker, 2007), SHELXS97 (Sheldrick, 2008), SHELXL2014 (Sheldrick, 2015), ORTEP-3 for Windows (Farrugia, 2012) and PLATON (Spek, 2009

(2E)-3-(4-Chloro-3-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.