Experimental

R factor = 0.054; wR factor = 0.157; data-to-parameter ratio = 21.3. The title compound, C13H10O4S, crystallizes with two mol-ecules in the asymmetric unit in which the rings make dihedral angles of 3.9 (1) and 6.0 (1); this planarity is due in part to the presence of an intramolecular O—H O hydrogen bond, which generates an S(6) ring in each molecule. Both molecules represent E isomers with respect to the central C C bond. In the crystal, molecules are linked by C—H O interactions into a three-dimensional network. Related literature For pharmacological properties of chalcones, see: Wattenberg et al. (1994); Dinkova-Kostova et al. (1998); Ram et al. (2000); Kidwai et al. (2001); Ballesteros et al. (1995). For their non-linear optical properties, see: Fichou et al. (1988) and for their importance, see: Tomazela et al. (2000). For precursors in the synthesis of flavonoids, see: Drexler & Amiridis (2003). For graph-set notation, see: Bernstein et al. (1995). For standard bond lengths, see: Allen et al. (1987)