Some chalcones derived from thio­phene-3-carbaldehyde: synthesis and crystal structures

The synthesis, spectroscopic data and crystal and mol­ecular structures of four 3-(3-phenyl­prop-1-ene-3-one-1-yl)thio­phene derivatives, namely 1-(4-hydroxy­phen­yl)-3-(thio­phen-3-yl)prop-1-en-3-one, C(13)H(10)O(2)S, (1), 1-(4-meth­oxy­phen­yl)-3-(thio­phen-3-yl)prop-1-en-3-one, C(14)H(12)O(2)S, (2), 1-(4-eth­oxy­phen­yl)-3-(thio­phen-3-yl)prop-1-en-3-one, C(15)H(14)O(2)S, (3), and 1-(4-­bromophen­yl)-3-(thio­phen-3-yl)prop-1-en-3-one, C(13)H(9)BrOS, (4), are described. The four chalcones have been synthesized by reaction of thio­phene-3-carbaldehyde with an aceto­phenone derivative in an absolute ethanol solution containing potassium hydroxide, and differ in the substituent at the para position of the phenyl ring: –OH for 1, –OCH(3) for 2, –OCH(2)CH(3) for 3 and –Br for 4. The thio­phene ring in 4 was found to be disordered over two orientations with occupancies 0.702 (4) and 0.298 (4). The configuration about the C=C bond is E. The thio­phene and phenyl rings are inclined by 4.73 (12) for 1, 12.36 (11) for 2, 17.44 (11) for 3 and 46.1 (6) and 48.6 (6)° for 4, indicating that the –OH derivative is almost planar and the –Br derivative deviates the most from planarity. However, the substituent has no real influence on the bond distances in the α,β-unsaturated carbonyl moiety. The mol­ecular packing of 1 features chain formation in the a-axis direction by O—H⋯O contacts. In the case of 2 and 3, the packing is characterized by dimer formation through C—H⋯O inter­actions. In addition, C—H⋯π(thio­phene) inter­actions in 2 and C—H⋯S(thio­phene) inter­actions in 3 contribute to the three-dimensional architecture. The presence of C—H⋯π(thio­phene) contacts in the crystal of 4 results in chain formation in the c-axis direction. The Hirshfeld surface analysis shows that for all four derivatives, the highest contribution to surface contacts arises from contacts in which H atoms are involved.