A second orthorhombic polymorph of (Z)-3-(9-anthryl)-1-(2-thienyl)prop-2-en-1-one

The title heteroaryl chalcone, C(21)H(14)OS, is a second orthorhombic polymorph which crystallizes in the space group P2(1)2(1)2(1). The structure was previously reported [Fun et al. (2009). Acta Cryst. E65, o2168-o2169] in the space group Pna2(1). The bond distances and angles are similar in both structures. In contrast, the overall crystal packing is different from that in the first orthorhombic Pna2(1) polymorph in which molecules were stacked into columns along the b axis and the thiophene units of two adjacent columns were stacked in a head to tail fashion. In the present polymorph, molecules are found to dimerize through a weak S center dot center dot center dot S interaction [3.6513 (7) angstrom] and these dimers are arranged into sheets parallel to the bc plane. There are no classical hydrogen bonds in the packing which features short C center dot center dot center dot O [3.2832 (2)-3.6251 (9) angstrom], C center dot center dot center dot S [3.4879 (17)-3.6251 ( 19) angstrom] and S center dot center dot center dot O [2.9948 (16) angstrom] contacts, together with C-H center dot center dot center dot pi interactions. Similar contacts were found in the other polymorph.