6,6′-Dimethoxy-2,2′-[4,5-dimethyl-o-phenylenebis(nitrilomethylidyne)]diphenol monohydrate

In the title compound, C24H24N2O4·H2O, the dihedral angles between the central benzene ring and the two outer benzene rings of the Schiff base are 65.06 (9) and 3.02 (9)°. Strong intramolecular O—H⋯N hydrogen bonds generate S(6) ring motifs. The H atoms of the water molecule act as donors in the formation of bifurcated O—H⋯(O,O) intermolecular hydrogen bonds with the O atoms of the hydroxy and methoxy groups with R 1 2(5) ring motifs; these may influence the molecular conformation.

In the title compound, C 24 H 24 N 2 O 4 ÁH 2 O, the dihedral angles between the central benzene ring and the two outer benzene rings of the Schiff base are 65.06 (9) and 3.02 (9) . Strong intramolecular O-HÁ Á ÁN hydrogen bonds generate S(6) ring motifs. The H atoms of the water molecule act as donors in the formation of bifurcated O-HÁ Á Á(O,O) intermolecular hydrogen bonds with the O atoms of the hydroxy and methoxy groups with R 1 2 (5) ring motifs; these may influence the molecular conformation.

Related literature
For bond-length data, see: Allen et al. (1987). For hydrogenbond motifs, see: Bernstein et al. (1995).   Table 1 Hydrogen-bond geometry (Å , ).  The asymmetric unit of the title compound, Fig. 1, comprises a Schiff base ligand and a water molecule of crystallization.
The bond lengths (Allen et al., 1987) and angles are within the normal ranges and comparable to previously reported structures (Eltayeb & Ahmed, 2005;Eltayeb et al., 2007;Cakir et al. 2002;Kargar et al., 2009 ). The dihedral angles between the central benzene ring and the two outer benzene rings of the Schiff base are 65.06 (9) and 3.02 (9)°. Strong intramolecular O-H···N hydrogen bonds generate S(6) ring motifs (Bernstein et al., 1995). The hydrogen atoms of the water molecule form bifurcated intermolecular hydrogen bonds with the oxygen atoms of the hydroxy and methoxy groups with R 2 1 (5) ring motifs (Bernstein et al., 1995), which may, in part, influence the molecular configuration (Table 1). A view of part of the crystal structure is shown in Fig .2.

Experimental
The title compound was synthesized by adding 3-methoxy-salicylaldehyde (4 mmol) to a solution of 4,5-dimethyl-ophenylenediamine (2 mmol) in ethanol (20 ml). The mixture was refluxed with stirring for half an hour. The resultant yellow solution was filtered. Yellow single crystals of the title compound suitable for X-ray structure determination were recrystallized from ethanol by slow evaporation of the solvents at room temperature over several days.

Refinement
H atoms of the hydroxy groups of the Schiff base and water were located in a difference Fourier map. Initially the O-H distances were restrained to 0.96 (1) and 0.98 (1) Å, respectively and in the final cycles of refinement these H atoms were allowed to ride on the parent O atom with U iso (H) = 1.5 U eq (O), see Table 1. The remaining H atoms were positioned geometrically with C-H = 0.93-0.96 Å and included in a riding model approximation with U iso (H) = 1.2 or 1.5 U eq (C). A rotating group model was used for the methyl groups. Fig. 1. The asymmetric unit of the title compound, showing 30% probability displacement ellipsoids and the atomic numbering. Intra-and intermolecular hydrogen bonds are drawn as dashed lines.

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.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.