The crystal structures of two chalcones: (2E)-1-(5-chlorothiophen-2-yl)-3-(2-methylphenyl)prop-2-en-1-one and (2E)-1-(anthracen-9-yl)-3-[4-(propan-2-yl)phenyl]prop-2-en-1-one

Molecules of (2E)-1-(5-chlorothiophen-2-yl)-3-(2-methylphenyl)-prop-2-en-1-one (I) are linked into simple hydrogen-bonded C(5) chains, while three distinct conformers of (2E)-1-(anthracen-9-yl)-3-[4-(propan-2-yl)phenyl]prop-2-en-1-one (II) co-exist in the crystal but each conformer forms hydrogen-bonded C(8) chains, albeit of two different types.

In the crystal of compound (I), C 14 H 11 ClOS, molecules are linked by C-HÁ Á ÁO hydrogen bonds to form simple C(5) chains. Compound (II), C 26 H 22 O, crystallizes with Z 0 = 2 in space group P1; one of the molecules is fully ordered but the other is disordered over two sets of atomic sites having occupancies 0.644 (3) and 0.356 (3). The two disordered components differ from one another in the orientation of the isopropyl substituents, and both differ from the ordered molecules in the arrangement of the central propenone spacer unit, so that the crystal of (II) contains three distinct conformers. The ordered and disordered conformers each form a C(8) chain built from a single type of C-HÁ Á ÁO hydrogen bond but those formed by the disordered conformers differ from that formed by the ordered form.

Structural commentary
In the molecule of compound (I), Fig. 1, the central spacer unit comprising the atoms (C12,C1,C2,C3,C31) is effectively planar: the maximum deviation from the mean plane of these atoms is 0.21 (2) Å , with an r.m.s. deviation of 0.025 Å . The ISSN 2056-9890 heterocyclic ring is nearly co-planar with the spacer unit, making with it a dihedral angle of 1.41 (1) . The dihedral angles between the phenyl group and the spacer unit, and between the two rings are 10. 95 (11) and 9.81 (10) , respectively. The bond distances within the molecule of (I) show clearly the localized double bond between atoms C2 and C3, and the distances within the thiophene ring clearly rule out the possibility of any orientational disorder of the type sometimes found in thiophene rings Trilleras et al., 2005Trilleras et al., , 2009Insuasty et al., 2014).
Compound (II) crystallizes with Z 0 = 2 in space group P1. The molecule containing atom O11 (Fig. 2) is fully ordered, but the other molecule is disordered over two sets of atomic sites: the major-disorder component containing atom O21 (Fig. 3) has occupancy 0.644 (3) while the minor-disorder component containing atom O31 (Fig. 4) has occupancy 0.356 (3). All three forms exhibit different conformations, as discussed below, and it will be convenient to refer to the molecules containing atoms O11, O21 or O31 as conformers of types 1, 2 or 3, respectively.
In the fully ordered molecule containing atom O11 the torsional angle C119-C11-C12-C13 is 177.72 (16) whereas in the two disordered components containing atoms O21 and O31 the values of the corresponding torsional angles Cn19-Cn1-Cn2-Cn3 are 11 (3) and 12 (5) for n = 2 and 3 respectively, corresponding to a rotation of approximately 180 about the bond Cn1-Cn2 in conformers 2 and 3 as compared with conformer 1. In addition, in conformers 2 and 3 the torsional angles Cn33-Cn34-Cn37-Hn37 are À14 and À170 for n = 2 and 3, respectively, so that the orientation of the CHMe 2 group in these two forms differs by a rotation of approximately 180 about the bond Cn34-Cn37; the corresponding value in conformer 1 is ca 162 . Hence three different conformations of compound (II) co-exist in the same The molecular structure of compound (I), with atom labelling and displacement ellipsoids drawn at the 30% probability level.

Figure 2
The molecular structure of conformer 1 in compound (II), with atom labelling and displacement ellipsoids drawn at the 30% probability level.

Supramolecular features
In the crystal of compound (I), molecule related by a c-glide plane are linked by a single C-HÁ Á ÁO hydrogen bond (Table 1) to form a C(5) chain running parallel to the [001] direction (Fig. 5). In the crystal of compound (II), molecules are also linked into chains by C-HÁ Á ÁO hydrogen bonds (Table 2), but the chains formed by the ordered and disordered forms are different, in that in the chain of ordered molecules the donor is a phenyl C-H unit, while in the disordered forms the donors are part of the anthracene units. In both types of chain molecules related by translation form C(8) chains running parallel to the [100] direction (Fig. 6) Table 2 Hydrogen-bond geometry (Å , ) for (II).

Figure 3
The molecular structure of the major-disorder component, conformer 2 having occupancy 0.644 (3), in compound (II), with atom labelling and displacement ellipsoids drawn at the 30% probability level.

Figure 4
The molecular structure of the minor-disorder component, conformer 3 having occupancy 0.356 (3), in compound (II), with atom labelling and displacement ellipsoids drawn at the 30% probability level. addition, inversion-related pairs of the chains built from the disordered components are weakly linked by C-HÁ Á Á interactions (Table 2).

Synthesis and crystallization
For the synthesis of compound (I), a solution of 2-methylbenzaldehyde (0.075 g, 0.625 mol) in methanol (20 ml) was added to solution of with 2-acetyl-5-chlorothiophene (0.100 g, 0.625 mol) in methanol (10 ml) and to this mixture was added aqueous sodium hydroxide solution (40% w/v, 5 ml). The reaction mixture was then stirred at 301 K for 4 h, when the resulting solid product was collected by filtration, washed with cold water and dried. Crystals suitable for single-crystal X-ray diffraction were grown by slow evaporation, at ambient temperature, of a solution in acetone-dimethylformamide (1:1, v/v): m. p. 387-389 K. For the synthesis of compound (II), aqueous sodium hydroxide solution (10%, w/v, 15 ml) was added to a mixture of 4-isopropylbenzaldehyde (1.5 ml, Part of the crystal structure of compound (I), showing the formation of a hydrogen-bonded C(5) chain parallel to [001]. Hydrogen bonds are shown as dashed lines and, for the sake of clarity, the H atoms not involved in the motif shown are omitted. The atoms marked with an asterisk (*) or a hash (#) are at the symmetry positions (x, 1 2 À y, À 1 2 + z) and (x, 1 2 À y, 1 2 + z), respectively.

Figure 6
Part of the crystal structure of compound (II), showing the formation of two different types of hydrogen-bonded C(8) chain. Hydrogen bonds are shown as dashed lines and, for the sake of clarity, the minor-disorder component and the H atoms not involved in the motifs shown have been omitted. The atoms marked with an asterisk (*) or a hash (#) are at the symmetry positions (À1 + x, y, z) and (1 + x, y, z), respectively. 0.01 mol) and 9-acetylanthracene (2.2 g, 0.01 mol) in ethanol (50 ml), and the resulting mixture was stirred at 278 K for 3 h. The resulting solid product was collected by filtration and recrystallized from ethanol solution: m.p. 369-371 K. Crystals suitable for single-crystal X-ray diffraction were grown by slow evaporation, at ambient temperature, of a solution in dimethylformamide.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. It was obvious from an early stage in the refinement of compound (II) that one of the two independent molecules was disordered over two sets of atomic sites having unequal occupancies. For the minor-disorder component the bonded distances and the one-angle nonbonded distances were restrained to be the same as the corresponding distances in the major component, subject to s.u.s of 0.005 and 0.01 Å respectively. In addition, the anisotropic displacement parameters for corresponding atomic pairs of atomic sites in the two disorder components were constrained to be identical and, subject to these conditions the occupancies for the two components refined to values of 0.645 (4) and 0.355 (4). The H atoms in all but the minordisorder component of compound (II) were located in difference maps and then treated as riding atoms in geometrically idealized positions with C-H distances 0.93 Å (alkenyl, aromatic and heteroaromatic), 0.96 Å (methyl) or 0.98 Å (aliphatic C-H) and with U iso (H) = kU eq (C) where k = 1.5 for the methyl groups, which were permitted to rotate but not to tilt, and 1.2 for all other H atoms. The H atoms in the minor-disorder component were included in the refinement in calculated positions under exactly the same conditions. For compound (II), 16 bad outliers of low intensity were omitted from the final refinements. In the final analysis of variance for compound (I) there was a fairly large value, 2.583, of K = mean (F o 2 )/mean (F c 2 ) for the group of 287 very weak reflections having F c /F c (max) in the range 0.000 < F c /F c (max) < 0.006. For compound (II), there was a large value of K, 10.808, for the group of 733 very weak reflections having F c /F c (max) in the range 0.000 < F c /F c (max) < 0.005.  used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015) and PLATON (Spek, 2009).
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 ) (17) 0.0443 (5)   Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (