The molecules of the title compounds, C 16 H 15 NOS 2 , (I), and C 16 H 13 Br 2 NOS 2 , (II), are E,E-isomers and consist of an extensive conjugated system, which determines their molecular geometries. Compound (I) crystallizes in the monoclinic space group P2 1 /c. It has one thiophene ring disordered over two positions, with a minor component contribution of 0.100 (3). Compound (II) crystallizes in the noncentrosymmetric orthorhombic space group Pca2 1 with two independent molecules in the unit cell. These molecules are related by a noncrystallographic pseudo-inversion center and possess very similar geometries. The crystal packings of (I) and (II) have a topologically common structural motif, viz. stacks along the b axis, in which the molecules are bound by weak C-HÁ Á ÁO hydrogen bonds. The noncentrosymmetric packing of (II) is governed by attractive intermolecular BrÁ Á ÁBr and BrÁ Á ÁN interactions, which are also responsible for the very high density of (II) (1.861 Mg m
À3).
CommentCross-conjugated dienones of the bis-arylidenecycloalkanone series and related piperidones have recently attracted considerable attention. These compounds are used in the construction of different polymers (Yakimansky et al., 2002;Aly et al., 2003), and in the design of crystals with nonlinear optical (Kishore & Kishore, 1993;Kawamata et al., 1995Kawamata et al., , 1996Sarkisov et al., 2005) and fluorescent (Nesterov et al., 2003(Nesterov et al., , 2008 properties. Furthermore, it is well known that they possess a variety of biological activities, such as antiviral (ElSubbagh et al., 2000), antibacterial (Lyrand et al., 1999;Amal Raj et al., 2003) and antiphlogistic activity (Rovnyak et al., 1982).Recently, instead of aryl substituents, the use of heterocyclic ligands was suggested, as these are able to bind important metal cations to form diverse coordination associates One purpose of our investigation was to analyze the influence of small structural modifications of the molecules on their structurally dependent properties. It should be noted that these compounds are potential antitumor (anticancer) agents (Dimmock et al., 1992(Dimmock et al., , 1994(Dimmock et al., , 2001, and even small differences in the structures may cause significant changes in their biological activity.Compound (I) crystallizes in the monoclinic space group P2 1 /c. One thiophene ring is disordered over two positions related by a 180 rotation about the C6-C7 bond. The minor component contribution refined to 0.100 (3) (Fig. 1). The molecular structure of (I), showing the atom-numbering scheme. The alternative position of the disordered thiophene ring is drawn with open lines. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.