(E,E)-1,5-Di-2-thienylpenta-1,4-dien-3-one

In the title compound, C13H10OS2, the dihedral angle between the thiophene rings is 14.3 (1)°. The molecular structure is stabilized by C—H⋯π interactions between a thiophene H atom and an adjacent thiophene ring, and by intermolecular C—H⋯O hydrogen bonds.

In the title compound, C 13 H 10 OS 2 , the dihedral angle between the thiophene rings is 14.3 (1) . The molecular structure is stabilized by C-HÁ Á Á interactions between a thiophene H atom and an adjacent thiophene ring, and by intermolecular C-HÁ Á ÁO hydrogen bonds.

Comment
Chalcones with the general formula Ar-CH═CH-CO-Ar are an important class of compounds, with the common structural entity being the central -CH═CH-C(═O)-group, in the H atoms can be substituted. The -C═C-double bond can be photoreactive and can produce various products through solid-state photo cycloaddition. Therefore, chalcones are widely used in organic solid-state photochemistry (Gould et al., 1995). Reviews on the bioactivities of various chalcones have been reported (Go et al., 2005). Bis-chalcones are also found to exhibit good NLO properties (Uchida et al., 1998). In view of this biological importance, the crystal structure of the title compound (I), (1E, 4E)-1,5-Bis(2-thienyl)penta-1,4-dien-3-one  (Arshad et al., 2008). The dihedral angle between the two thiophene rings is 14.3 (1)°. The crystal packing (Fig. 2) is stabilized by C-H···π interactions between a thiophene H atom and a neighbouring thiophene ring, with a C11-H11···Cg iii separetion of 2.34 Å ( Fig. 2 and Table 1; Cg is the centroid of the C10/C11/C12/C13/S1 thiophene ring, symmetry code as in Fig.   2). The molecular packing is further stabilized by intermolecular C-H···O hydrogen bonds ( Fig. 2 and Table 1; symmetry code as in Fig. 2).

Experimental
A solution of sodium hydroxide (10 g, 0.25 mol) in water (50 ml) was added to a solution of acetone (5 ml) and 2-thiophenecarboxaldehyde (22.4 g, 0.2 mol) in methanol (50 ml) at 273 K. This mixture was stirred overnight and the product was filtered. Single crystals suitable for X-ray diffraction was obtained by slow evaporation of a solution of the title compound in ethyl acetate.

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 > 2sigma(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.