4,4′-Dimethyl-1,1′-[ethylenedioxybis(nitrilomethylidyne)]dibenzene

The Schiff base, C18H20N2O2, which lies about an inversion centre, adopts a linear conformation. The molecules are packed by C—H⋯π interactions, forming a two-dimensional supramolecular network.

The Schiff base, C 18 H 20 N 2 O 2 , which lies about an inversion centre, adopts a linear conformation. The molecules are packed by C-HÁ Á Á interactions, forming a two-dimensional supramolecular network.

Experimental
Cg1 is the centroid of the C3-C8 ring.
The molecule of the title compound is disposed about a crystallographic inversion centre (Symmetry codes: -x, -y,-z) and twofold screw axis (symmetry code: -x, 1/2 + y, 1/2 -z). The oxime, methyl groups and benzene rings have anti-conformation.
The two benzene rings of the molecule are parallel, and the methyl and oxime (-CH 2 -O-N=C-) functional groups are coplanar with the benzene ring in each half of the molecule.
The molecule adopts a linear-shaped configuration with respect to the oxime C=N bonds, which is different from our previous reported bisoxime of 3,3'-dibromo-1,1'-[ethylenedioxybis(nitrilomethylidyne)]dibenzene in which the molecule assumes an E configuration (Dong et al., 2008). The packing of the molecule is controlled by C-H···π(Ph) interactions linking molecules into infinite supramolecular structure along b axis (Fig. 2).
The product was dried under vacuum to yield 90.0 mg of the title compound. Yield, 58.6%. mp. 359-360 K. Anal. Calcd.
Colorless needle-like single crystals suitable for X-ray diffraction studies were obtained after about four days by slow evaporation from an diethyl ether solution of the title compound.

Refinement
Non-H atoms were refined anisotropically. H atoms were treated as riding atoms with distances C-H = 0.97 (CH 2 ), 0.93 Å (CH), C-H = 0.96 (CH 3 ) Å and U iso (H) = 1.2 U eq (C) and 1.5 U eq (O). 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 Rfactors(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.