(E)-3-(2-Chlorophenyl)-1-(2,4-dichlorophenyl)prop-2-en-1-one

In the title chalcone derivative, C15H9Cl3O, the dihedral angle between the 2-chlorophenyl and 2,4-dichlorophenyl rings is 41.79 (14)°. Weak C—H⋯O and C—H⋯Cl intramolecular interactions involving the enone unit generate S(5) ring motifs. In the crystal structure, the molecules are arranged in a head-to-tail manner along the a axis. These chains are stacked along the b axis.

In the title chalcone derivative, C 15 H 9 Cl 3 O, the dihedral angle between the 2-chlorophenyl and 2,4-dichlorophenyl rings is 41.79 (14) . Weak C-HÁ Á ÁO and C-HÁ Á ÁCl intramolecular interactions involving the enone unit generate S(5) ring motifs. In the crystal structure, the molecules are arranged in a headto-tail manner along the a axis. These chains are stacked along the b axis.

Comment
Nonlinear optical properties of chalcone derivatives have been widely investigated recently (Agrinskaya et al., 1999;Fun, Chantrapromma et al., 2007;Fun, Patil et al., 2007;Patil, Dharmaprakash et al., 2007;Patil, Chantrapromma et al., 2007;Patil, Fun et al., 2007). These molecules show potential in optical-limiting applications due to their large excited-state absorption cross sections (Gu et al., 2008). In view of the importance of chalcones and the continuation of our non-linear optic materials research the title chalcone derivative, (I), was synthesized and its crystal structure is reported here.

Experimental
The title compound was synthesized by the condensation of 2-chlorobenzaldehyde (0.01 mol) with 2,4-dichloroacetophenones (0.01 mol) in methanol (60 ml) in the presence of a catalytic amount of sodium hydroxide solution (5 ml, 30%). After stirring (4 h), the contents of the flask were poured into ice-cold water (500 ml) and left to stand for 6 h. The resulting crude solid was filtered and dried. Colorless block-shaped single crystals of the title compound suitable for X-ray structure determination were recrystallized from acetone by slow evaporation of the solvent at room temperature.

Refinement
All H atoms were placed in calculated positions (C-H = 0.93 Å) and treated as riding, with U iso (H) = 1.2U eq (C). The highest residual electron density peak is located at 1.90 Å from C13 and the deepest hole is located at 0.93 Å from Cl2.
supplementary materials sup-2 Figures   Fig. 1. The asymmetric unit of (I), showing 50% probability displacement ellipsoids and the atomic numbering. Weak intramolecular C-H···O and C-H···Cl interactions are drawn as dashed lines.

Special details
Experimental. The low-temperature data was collected with the Oxford Cyrosystem Cobra low-temperature attachment. 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq  (7)