(2E)-1-(1,3-Benzodioxol-5-yl)-3-(2-bromophenyl)prop-2-en-1-one

The molecule of the title compound, C16H11BrO3, is essentially planar with a maximum deviation of 0.178 (4) Å and the configuration of the keto group with respect to the olefinic double bond is typically s-cis. In the crystal structure, intermolecular Br⋯O interactions [3.187 (3)Å] give rise to chains parallel to the b axis. Adjacent chains are further linked along the a axis by C—H⋯π interactions. The crystal studied was a racemic twin with a 0.595 (13):0.405 (13) ratio.


Related literature
Cg3 is the centroid of the C10-C15 ring.
Mangalore University and the Bioinformatics Infrastructure Facility, University of Hyderabad, are gratefully acknowledged. BN thanks UGC-SAP for financial support. RSR thanks the CSIR, New Delhi, for support under the scientist's pool scheme.

Comment
Chalcones possess many interesting biological and pharmacological properties. They are highly reactive substances of varied nature. Recently, it is shown that few of the derivatives are able to block voltage-dependent potassium channels (Yarishkin et al., 2008). Chalcones have been also implicated in organic nonlinear optical materials for their SHG conversion efficiency (Sarojini et al., 2006). The radical quenching property of the phenolic groups present in many chalcones or chalcone-rich plant extracts has led to their use as drugs or food preservatives (Di Carlo et al., 1999). We earlier reported structures of chalcone derivatives (Harrison et al., 2006;Rathore et al., 2006;Jasinski et al., 2010;Li et al., 2008). In continuation of the study, we have synthesized a new chalcone analog, C 16 H 11 BrO 3 , (I), and discuss its crytal structure herein.
The crystal of (I) studied was racemically twinned in a 0.595 (13):0.405 (13) ratio. Similar racemic twinning in Brcontaining compounds was observed by Gömez et al. (2010). The skeleton of (I) is essentially planar possessing two intramolecular short contacts. The bifurcated C1-H7···(Br1, O1) promote planarity of the molecular skeleton (Table 1). The configuration of the keto group with respect to the olefinic double bond is typically s-cis, with the C7-C8-C9-O1 torsion angle of -1.6 (7)° (Rathore et al., 2006).  (Thallapally et al., 2002). Halogen bonding between halogen atoms (Lewis acid) and neutral or anionic Lewis base, has been subject of great interest in recent years, primarily due to their unique noncovalent bonding characteristics (Metrangolo et al., 2005;Riley et al., 2009). The crystal structure additionally contains a C-H···π short contact, giving rise to an alternate linear pattern along the a axis (Table 1).

Refinement
All H atoms were stereochemically fixed and refined using a riding option with C(Sp 2 )-H = 0.93 Å, C(methylene)-H = 0.97 Å, and U iso (H) = 1.2 U eq (C). The residual electron density observed in the vicinity of Br is due to the result of rotation of the bromophenyl moiety about the C6-C7 bond. The disorder could not be reliably refined presumably due supplementary materials sup-2 to very low occupancy of other conformers. The crystal studied was treated as an inversion twin leading to twin fractions of 0.595 (13):0.405 (13). Fig. 1. The molecular structure of the title compound. Displacement ellipsoids are drawn at 30% probability level. Dotted lines indicate intramolecular hydrogen bonds.

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.
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 Rfactors(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.