A second ortho-rhom-bic polymorph of (Z)-3-(9-anthr-yl)-1-(2-thien-yl)prop-2-en-1-one.

The title heteroaryl chalcone, C(21)H(14)OS, is a second ortho-rhom-bic 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 ortho-rhom-bic Pna2(1) polymorph in which mol-ecules were stacked into columns along the b axis and the thio-phene units of two adjacent columns were stacked in a head to tail fashion. In the present polymorph, mol-ecules are found to dimerize through a weak S⋯S inter-action [3.6513 (7) Å] 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⋯O [3.2832 (2)-3.6251 (9) Å], C⋯S [3.4879 (17)-3.6251 (19) Å] and S⋯O [2.9948 (16) Å] contacts, together with C-H⋯π inter-actions. Similar contacts were found in the other polymorph.