(1E,4E)-1,5-Bis(thiophen-3-yl)penta-1,4-dien-3-one

The title compound, C13H10OS2, exhibits twists between the central C3O and ethene residues [O—C—C—C torsion angles = −8.4 (3) and 11.8 (3)°], and between the ethene and adjacent thiophenyl residues [C—C—C—C torsion angles = −4.2 (3) and 10.5 (3)°]. As a result, the molecule is non-planar, the dihedral angle formed between the terminal thiophenyl groups being 15.45 (10)°. The presence of C—H⋯O interactions involving the bifurcated carbonyl O atom leads to supramolecular arrays in the ac plane. These are linked into a three-dimensional architecture by C—H⋯π interactions involving both thiophenyl residues.

The title compound, C 13 H 10 OS 2 , exhibits twists between the central C 3 O and ethene residues [O-C-C-C torsion angles = À8.4 (3) and 11.8 (3) ], and between the ethene and adjacent thiophenyl residues [C-C-C-C torsion angles = À4.2 (3) and 10.5 (3) ]. As a result, the molecule is non-planar, the dihedral angle formed between the terminal thiophenyl groups being 15.45 (10) . The presence of C-HÁ Á ÁO interactions involving the bifurcated carbonyl O atom leads to supramolecular arrays in the ac plane. These are linked into a three-dimensional architecture by C-HÁ Á Á interactions involving both thiophenyl residues.
Small but significant twists in the molecule are observed so that there are notable deviations from planarity. In particular, the carbonyl and ethene groups deviate from co-planarity as seen in the values of the C5-C6-C7-O1 and C9-C8-C7-O1 torsion angles of -8.4 (3) and 11.8 (3) °, respectively. While the S1-thiophenyl ring is effectively co-planar with the adjacent , the S2-thiophenyl ring is twisted with the C13-C10-C9-C8 torsion angle being 10.5 (3) °. Overall, with reference to the central C 3 O atoms, the thiophenyl groups lie to the same side of the molecule, and form a dihedral angle of 15.45 (10) ° with each other. The conformation of the crystallographic determined molecule structure was subjected to energy minimization calculations using the MOPAC2009 programme with the Parametrization Model 6 (PM6) approximation together with the restricted Hartree Fock closed-shell wavefunction (Stewart, 2009). The minimizations were terminated at a r.m.s. gradient less than 0.01 kJ mol -1 Å -1 . The optimized structure showed that the molecule adopts a non-planar conformation in the gas phase with the dihedral angle between the thiophenyl groups being 9.9 °. A planar arrangement in (I) is precluded owing to the unfavourable H···H interactions that would ensure.
In the crystal packing, the carbonyl-O1 atom plays a prominent role in that it is bifurcated, forming two C-H···O interactions, Table 1. These lead to supramolecular layers in the ac plane, Fig. 2. Connections between layers are of the type C-H···π and involve both thiophenyl rings, Table 1. These interactions result in a three-dimensional architecture, Fig. 3.

Experimental
NaOH (5 g) was dissolved in distilled water (50 ml) and cooled to room temperature. The alkali solution and ethanol (50 ml) were transferred to a 250 ml round bottomed flask. The temperature of the solution was maintained at 298 K and stirred vigorously using a magnetic stirrer. One-half of previously prepared mixture of 0.05 moles of thiophene-3-carboxaldehyde and 0.025 moles of acetone was added to the NaOH-EtOH solution which was then stirred manually. A flocculent precipitate formed within 2-3 minutes of addition. After 15 minutes, the remaining half of the aldehyde-acetone mixture was added to the round bottomed flask, and the mixture was stirred for a further 45 minutes. The solids were filtered under vacuum and washed repeatedly with ice-cold water to eliminate alkali. The solid was pressed between filter paper and dried at room temperature in a desiccator overnight. The compound was recrystallized from EtOH. Yield 82%. M. pt. 407-408 K.
Colourless needles were obtained by its re-crystallization from hot ethanol solution.

Refinement
The C-bound H atoms were geometrically placed (C-H = 0.93 Å) and refined as riding with U iso (H) = 1.2U eq (parent atom). Fig. 1. The molecular structure of (I) showing the atom-labelling scheme and displacement ellipsoids at the 35% probability level.  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 > 2σ(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.