Two isostructural 3-(5-aryloxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-1-(thiophen-2-yl)prop-2-en-1-ones: disorder and supramolecular assembly

In each of two isostructural 3-(5-aryloxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-1-(thiophen-2-yl)prop-2-en-1-ones, the thiophene unit is disordered over two sets of atomic sites and a combination of C—H⋯N and C—H⋯O hydrogen bonds link the molecules into sheets.


Structural commentary
Compounds (I) and (II) are isomorphous with unit-cell volumes which differ by only ca 1% and, with appropriate adjustment of the substituent at atom C352 (H versus CH 3 ), each structure can be smoothly refined using the atomic coordinates of the other as the starting point.
In each structure, the thienyl group is disordered over two sets of atomic sites having occupancies 0.844 (3) and 0.156 (3) in (I), and 0.883 (2) and 0.117 (2) in (II): in each case, the two disorder components are approximately related by a rotation of ca 180 about the C1-C12 bond (Figs. 1 and 2). It is by no means clear why the occupancies of the two disorder components in each compound are so different, particularly as the two disorder components form similar intermolecular hydrogen bonds (Section 3).
For both compounds, the central space unit between atoms C12 and C34, the pyrazole ring and the major disorder component of the thienyl ring are almost coplanar, and the r.m.s. deviations of the atoms from the mean planes through these units are only 0.055 Å in (I) and 0.102 Å in (II). By contrast, the two pendent aryl rings are markedly displaced from this plane: the dihedral angles between the pyrazole ring and the rings (C311-C316) and (C351-C356) are 29.99 (11) and 78.60 (6) , respectively, in (I), and 27.90 (11) and 81.13 (6) in (II). On the other hand, atom C35 is, in each structure, displaced from the plane (O35/C351-C356) by only 0.097 (3) Å in (I) and 0.017 (3) Å in (II). Associated with this near co-planarity, the two exocyclic C-C-O angles at atom C351 differ in each structure by ca 9 , as typically found in planar alkoxyarenes (Seip & Seip, 1973;Ferguson et al., 1996).

Supramolecular features
The supramolecular assembly of compound (I) depends upon just two hydrogen bonds, one each of C-HÁ Á ÁN and C-HÁ Á ÁO types (Table 1). The C-HÁ Á ÁO hydrogen bonds links molecules which are related by translation to form a C(12) (Etter, 1990;Etter et al., 1990;Bernstein et al., 1995) chain running parallel to the [101] direction (Fig. 3). The C-HÁ Á ÁN hydrogen bond links molecules which are related by the 2 1 screw axis along (0.5, y, 0.25) to form a C(10) chain running The molecular structure of compound (II), showing the atom-labelling scheme, and the disorder in the thiophen-2-yl substituent, where the major disorder component has been drawn using full lines and the minor disorder component has been drawn using dashed lines. Table 1 Hydrogen-bond geometry (Å , ) for (I). Symmetry codes: (i) Àx þ 1; y À 1 2 ; Àz þ 1 2 ; (ii) x À 1; y; z À 1.

Figure 1
The molecular structure of compound (I), showing the atom-labelling scheme, and the disorder in the thiophen-2-yl substituent, where the major disorder component has been drawn using full lines and the minor disorder component has been drawn using dashed lines.

Figure 3
Part of the crystal structure of compound (I) showing the formation of a hydrogen-bonded sheet lying parallel to (101). Hydrogen bonds are drawn as dashed lines and, for the sake of clarity, the minor disorder component and the H atoms which are not involved in the motifs shown have been omitted.
parallel to the [010] direction (Fig. 3). The chain formation along [010] is independent of the disorder, since both atom C14 in the major disorder component and atom C25 in the minor component (cf. Fig. 1) form similar C-HÁ Á ÁN hydrogen bonds. The combination of these two chain motifs generates a sheet in the form of a (4,4) net (Batten & Robson, 1998) built from R 4 4 (35) rings and lying parallel to (101). The supramolecular assembly of compound (II) is entirely similar to that in (I), although the C-HÁ Á ÁN hydrogen bond formed by the minor disorder component is rather long (Table 2).
In view of the similarities in the hydrogen bonds formed by (I) and (II), and their similar molecular conformations (see Section 2), these isomorphous compounds can be described as isostructural, although it is not always the case that isomorphous pairs are strictly isostructural (Bowes et al., 2003;Acosta et al., 2009;Blanco et al., 2012).

Refinement
Crystal data, data collection and structure refinement details are summarized In Table 3. In both compounds, the thienyl unit was disordered over two sets of atomic sites having unequal occupancies. In each case, the bonded distances and the 1,3 non-bonded distances in the minor disorder compo-nent were restrained to be the similar to the equivalent distances in the major disorder component, subject to s.u. values of 0.01 Å and 0.02 for bonds and angles, respectively, and the anisotropic displacement parameters for pairs of partial-occupancy atoms occupying essentially the same physical space were constrained to be equal. All H atoms, apart from those in the minor disorder components were located in difference maps, and then treated as riding atoms in geometrically idealized positions, with C-H distances of 0.93 Å (alkenyl, aromatic and thienyl) or 0.96 Å (methyl), 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 components were included on the same basis. Subject to these conditions, the occupancies of the disorder components refined to 0.844 (3) and 0.156 (3) in (I), and 0.883 (2) and to 0.117 (2) in (II).  For both structures, data collection: APEX2 (Bruker, 2012); cell refinement: SAINT (Bruker, 2017); data reduction: SAINT (Bruker, 2017); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015b) and PLATON (Spek, 2009). Δρ max = 0.20 e Å −3 Δρ min = −0.14 e Å −3 Extinction correction: SHELXL, Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0059 (9) 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. (