Crystal structure of (E)-2,6-dimethoxy-4-{[(4-methoxyphenyl)imino]methyl}phenol

The title molecule is comprised of two non-coplanar benzene rings connected by an imino group in a trans-configuration. In the crystal, the molecules are linked via O—H⋯N and C—H⋯O hydrogen bonds, forming chains along [101].


Chemical context
Syringaldehyde is a product of the catalytic decomposition of lignin (Crestini et al., 2010). Syringaldehyde is widely used as a molecular marker to monitor pollution sources and detect the extent of combustion (Robinson et al., 2006). It is also known to be an antioxidant (Ibrahim et al., 2012), anticancer, antiinflammatory (Duke, 2003) and antifungal agent (Gurpilhares et al., 2006). In addition, its Schiff bases are known to exhibit a wide range of biological activities (Shi & Zhou, 2011;da Silva et al., 2011).

Synthesis
4-Hydroxy-3,5-dimethoxybenzaldehyde (syringaldehyde) (0.05 mol) was added to a mixture of 50 ml of methanol and p-methoxyaniline (PMA) (5 ml, 0.05 mol) and 50 ml of distilled water. The reaction mixture was taken in a clean 250 ml round-bottom flask and stirred well with a magnetic stirrer. It was then refluxed for 7 h. The dark-yellow product that formed was separated by filtration, dried under vacuum and recrystallized from methanol solution upon slow evaporation for two days (yield 65%, m.p. 353-357 K).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2 Table 1 Hydrogen-bond geometry (Å , ).

Figure 2
A view along the a axis of the crystal packing. Dashed lines indicate hydrogen bonds (see Table 1).

(E)-2,6-Dimethoxy-4-{[(4-methoxyphenyl)imino]methyl}phenol
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.