2-Bromo-1-chlorophenyl-3-(4-methoxy-phenyl)prop-2-en-1-one

The geometrical parameters for the title compound, C16H12BrClO2, are normal. The observed bond lengths and angles imply that there is little electronic conjugation between the two benzene ring systems. An intramolecular C-H center dot center dot center dot Br interaction may help to establish the molecular conformation. The crystal packing results in a centrosymmetric structure.

The geometrical parameters for the title compound, C 16 H 12 BrClO 2 , are normal. The observed bond lengths and angles imply that there is little electronic conjugation between the two benzene ring systems. An intramolecular C-HÁ Á ÁBr interaction may help to establish the molecular conformation. The crystal packing results in a centrosymmetric structure.

Comment
Many chalcone (C 15 H 12 O) derivatives crystallize as noncentrosymmetric structures and display significant non-linear optical (NLO) properties (Uchida et al., 1998). The title compound, (I), (Fig. 1), was prepared as part of our ongoing studies in this area (Harrison et al., 2005). However, (I) crystallizes in a centrosymmetric space group, thus it has a zero NLO response (Watson et al., 1993).
A PLATON (Spek, 2003) analysis of (I) indicated a possible intramolecular C-HÁ Á ÁBr interaction ( Table 2) that might help to maintain near coplanarity between the C8/C9/ Br1 fragment and the C10-benzene ring. The predicted (Bondi, 1964) van der Waals contact distance for H and Br is 3.05 Å . There are no Á Á Á stacking interactions in the crystal structure of (I).
The solvent was removed under reduced pressure and the resulting solid mass obtained on cooling was collected by filtration. The crude product was recrystallized from ethanol to yield blocks of (I) in 60% yield. M.p.: 403 K. Analysis for C 16 Extinction correction: SHELXL Extinction coefficient: 0.0135 (6) Table 1 Selected geometric parameters (Å , ).
H atoms were positioned geometrically (C-H = 0.95-0.98 Å ) and refined as riding with U iso (H) = 1.2U eq (carrier) or 1.5U eq (methyl carrier). The methyl group was rotated to fit the electron density.
Data collection: COLLECT (Nonius, 1998); cell refinement: HKL SCALEPACK (Otwinowski & Minor 1997); data reduction: HKL SCALEPACK and DENZO (Otwinowski & Minor 1997), SCALE-PACK and SORTAV (Blessing 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97.  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.