Three closely related (2E,2′E)-3,3′-(1,4-phenylene)bis[1-(methoxyphenyl)prop-2-en-1-ones]: supramolecular assemblies in one dimension mediated by hydrogen bonding and C—H⋯π interactions

The three title compounds are centrosymmetric. Their packing features chains linked by either pairwise C—H⋯O or C—H⋯π interactions.


Structural commentary
The molecular structures of (I)-(III) are shown in Figs. 1-3, respectively. The asymmetric unit of each compound consists of a half-molecule, with the complete molecule generated by a crystallographic inversion centre at the centroid of the central benzene ring.

Supramolecular features
The packing of (I) is consolidated by a weak C-HÁ Á Á contact (Table 2) involving a hydrogen atom from the phenyl ring and the centroid of the central benzene ring (C10-C12/C10A-C12A). This C-HÁ Á Á interaction connects the molecules of (I) into chains parallel to the [101] direction with a C-HÁ Á Á distance of 2.74 Å (Fig. 4). In the supramolecular assemblies of compounds (II) and (III), the molecules are connected by pairs of C-HÁ Á ÁO hydrogen bonds (Table 2) into inversion dimers, which form R 2 2 (16) and R 2 2 (14) ring motifs, respectively. The dimers are parts of

Synthesis and crystallization
A mixture of the corresponding methoxyacetophenone (0.02 mol) and terephthaldialdehyde (0.01 mol) was dissolved in methanol (20 ml). A catalytic amount of NaOH was added to the solution dropwise with vigorous stirring. The reaction mixtures were stirred for about 5-6 h at room temperature. The resultant crude products were filtered, washed successively with distilled water and recrystallized from ethanol to obtain the title compounds. Yellow blocks [(I) and (III)] and yellow needles (II) were recrystallized using the solvents noted below.

(I) (2E,2′E)-3,3′-(1,4-Phenylene)bis[1-(2-methoxyphenyl)prop-2-en-1-one]
Crystal data  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 O1 1.3466 (2) 0.50160 (7) 0.83740 (9) 0.0753 (4)   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.