2-[({2-[(2-Hydroxy-5-methoxybenzylidene)amino]ethyl}imino)methyl]-4-methoxyphenol

The asymmetric unit of the title compound, C18H20N2O4, contains one-half molecule with an inversion center located at the centroid of the molecule. In the crystal, molecules are linked by C—H⋯π interactions, forming layers parallel to (101). An intramolecular O—H⋯N hydrogen bond also occurs.

The asymmetric unit of the title compound, C 18 H 20 N 2 O 4 , contains one-half molecule with an inversion center located at the centroid of the molecule. In the crystal, molecules are linked by C-HÁ Á Á interactions, forming layers parallel to (101). An intramolecular O-HÁ Á ÁN hydrogen bond also occurs.
The molecular structure of (I), and the atomic numbering used, is illustrated in Fig. 1. The asymmetric unit of the title compound, consists of one-half of the molecule, with the other half generated by a crystallographic inversion center. The crystal packing in the title structure can be described by a zigzag layers parallel to (101) plane (Fig. 2). There is one intramolecular O-H···N hydrogen bonding in this packing (Table 1, Fig. 2), which it is stabilized C-H···π and Van der Walls interactions (table 1) All these interactions link the molecules within the layers and also link the layers together and reinforcing the cohesion of the structure.
Experimental 60 mg of 1,2-diaminoethane (1 mmol) were dissolved in 10 ml of absolute ethanol. This solution was drop wise added, under stirring, to an ethanolic solution (10 ml) containing 304 mg of 5-methoxysalicylaldehyde (2 mmol). This mixture was refluxed for 1 h after which a yellow precipitate is formed, recovered by filtration, washed several times with diethyl oxide and dried to yield 282 mg (86%) of the title compound. The suitable crystals for X-ray analysis were obtained by slow evaporation from a mixture of solvents ethanol/dichloromethane (8/2, v/v).

Refinement
The H atoms were localized on Fourier maps but introduced in calculated positions and treated as riding on their parent

Figure 2
Diagram of layered packing parallel to (101) plane and showing O-H···N and C-H···π interactions. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.23 e Å −3 Δρ min = −0.16 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.08 (2) Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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.