Some chalcones derived from thio-phene-3-carbaldehyde: synthesis and crystal structures.

The synthesis, spectroscopic data and crystal and mol-ecular structures of four 3-(3-phenyl-prop-1-ene-3-one-1-yl)thio-phene derivatives, namely 1-(4-hydroxy-phen-yl)-3-(thio-phen-3-yl)prop-1-en-3-one, C13H10O2S, (1), 1-(4-meth-oxy-phen-yl)-3-(thio-phen-3-yl)prop-1-en-3-one, C14H12O2S, (2), 1-(4-eth-oxy-phen-yl)-3-(thio-phen-3-yl)prop-1-en-3-one, C15H14O2S, (3), and 1-(4--bromophen-yl)-3-(thio-phen-3-yl)prop-1-en-3-one, C13H9BrOS, (4), are described. The four chalcones have been synthesized by reaction of thio-phene-3-carbaldehyde with an aceto-phenone 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, -OCH3 for 2, -OCH2CH3 for 3 and -Br for 4. The thio-phene 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 thio-phene 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 mol-ecular 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 inter-actions. In addition, C-H⋯π(thio-phene) inter-actions in 2 and C-H⋯S(thio-phene) inter-actions in 3 contribute to the three-dimensional architecture. The presence of C-H⋯π(thio-phene) 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.