Crystal structure of (2E)-1-(1-benzofuran-2-yl)-3-(2-bromophenyl)prop-2-en-1-one monohydrate

The title compound, C17H11BrO2·H2O, crystallizes as a monohydrate in the chiral orthorhombic space group P212121, and has non-linear optical (NLO) properties. The molecule has an E conformation about the C=C bond and is relatively planar with the benzofuran and bromophenyl rings being inclined to one another by 10.60 (14)°. In the crystal, the water molecule is linked to the organic molecule by O—H⋯O hydrogen bonds, forming an R 2 2(7) ring motif while C—H⋯O hydrogen bonds lead to the formation of helices along the b-axis direction.


S1. Commentary
Chalcones are among the most abundant and ubiquitous group of natural products (Tomazela, et al., 2000). Some of the chalcone derivatives shows high second-harmonic generation conversion efficiency (Gu et al., 2008;Choudary et al., 1999;Jayarama et al., 2013). The title compound crystallizes in a non-centrosymmteric space group and exhibits interesting nonlinear optical properties.
In the title compound, Fig. 1, the benzofuran and bromophenyl groups are linked by a prop-2-en-1-one group. The benzofuran and bromophenyl rings are slightly non-planar with a dihedral angle of 10.60 (14) °. The torsion angle C7-C8-C9-O2 is 175.9 (4)° indicating that the O3 methoxy group is coplanar with the attached benzofuran ring. The C═C double bond shows an E conformation.
In the crystal, the water molecule is linked to the organic molecule by O-H···O hydrogen bonds forming an R 2 2 (7) ring motif (Table 1 and Fig. 2). The organic molecule is linked to the water molecule by C-H.·O hydrogen bonds so forming helices along the b-axis direction (Table and Fig. 2).
Sodium hydroxide (2 ml, 20%) was then added drop wise to the solution which was then stirred for 1.5 h. The contents of the flask were cooled using ice-cold water, and the resulting powder content was collected by filtration. The compound was dried and re-crystallized twice using acetone as solvent, yielding golden-yellow block-like crystals.

S3. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The water H atoms were located in a difference Fourier map. They were refined with distance restraints: O-H = 0.88 (2) Å, H···H = 1.43 (2) Å with U iso (H) = 1.5U eq (O). The C-bound H atoms were placed in calculated positions and included in the refinement in the riding model approximation: C-H = 0.93 Å with U iso (H) = 1.2U eq (C).

Figure 1
A view of the molecular structure of title compound, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
A view along the a-axis of the crystal packing of the title compound. The intermolecular interactions are represented by dashed lines (see Table 1). Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness 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 threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq  (5)