(E)-3-(2,4-Dichlorophenyl)-1-(2-thienyl)prop-2-en-1-one

In the title chalcone derivative, C13H8Cl2OS, the prop-2-en-1-one unit and the thiophene and 2,4-dichlorophenyl rings are each essentially planar. The interplanar angle between the thiophene and 2,4-dichlorophenyl rings is 19.87 (6)°. Weak intramolecular C—H⋯O and C—H⋯Cl interactions involving the prop-2-en-1-one unit generate an S(5)S(5) ring motif. In the crystal structure, molecules are linked into head-to-tail zigzag chains along the a axis and adjacent chains are cross-linked. These cross-linked chains are arranged into sheets parallel to the ab plane. The crystal structure is stabilized by weak C—H⋯O, C—H⋯Cl and C—H⋯π interactions. A π–π interaction was also observed with a centroid–centroid distance of 3.6845 (6) Å.

In the title chalcone derivative, C 13 H 8 Cl 2 OS, the prop-2-en-1one unit and the thiophene and 2,4-dichlorophenyl rings are each essentially planar. The interplanar angle between the thiophene and 2,4-dichlorophenyl rings is 19.87 (6) . Weak intramolecular C-HÁ Á ÁO and C-HÁ Á ÁCl interactions involving the prop-2-en-1-one unit generate an S(5)S(5) ring motif. In the crystal structure, molecules are linked into head-to-tail zigzag chains along the a axis and adjacent chains are crosslinked. These cross-linked chains are arranged into sheets parallel to the ab plane. The crystal structure is stabilized by weak C-HÁ Á ÁO, C-HÁ Á ÁCl and C-HÁ Á Á interactions. Ainteraction was also observed with a centroid-centroid distance of 3.6845 (6) Å .

Comment
In the last decades, the second-order nonlinear optical properties of chalcone derivatives have been widely investigated due to their possible applications in a variety of optoelectronic and photonic applications (Agrinskaya et al., 1999;Goto et al., 1991;Patil et al., 2007a, b, c;Sarojini et al., 2006;Wang et al., 2004). These derivatives also exhibit the optical limiting property which is a requirement of protecting the human eye or artificial optical sensor from damaging high-energy lasers (Gu et al., 2008a, b, c). In our continuing systematic study on chalcone derivatives, we report here the structure of the title compound.

Experimental
The title compound was synthesized by the condensation of 2,4-dichlorobenzaldehyde (0.01 mol, 1.75 g) with 2-acetylthiophene (0.01 mol, 1.07 ml) in methanol (60 ml) in the presence of a catalytic amount of sodium hydroxide solution (5 ml, 30%). After stirring (6 h), the contents of the flask were poured into ice-cold water (500 ml) and left to stand for 5 h.
The resulting crude solid was filtered and dried. Needle colorless single crystals of the title compound suitable for X-Ray structure determination were grown by slow evaporation of the methanol solution at room temperature.

Refinement
All H atoms were placed in calculated positions with d(C-H) = 0.93Å, U iso =1.2U eq (C) for vinylic and aromatic H atoms.
The highest residual electron density peak is located at 0.70Å from C10 and the deepest hole is located at 0.51Å from S1. 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