(E,E)-1,2-Bis(2,4,5-trimethoxybenzylidene)hydrazine

The asymmetric unit of the title compound, C20H24N2O6, contains one half-molecule, the complete molecule being generated by a crystallographic inversion centre. The molecule is nearly planar with a dihedral angle between the two benzene rings of 0.03 (4)° and the central C/N/N/C plane making a dihedral angle of 8.59 (7)° with each of its two adjacent benzene rings. The two methoxy groups at the ortho and meta positions are slightly twisted [C—O—C—C torsion angles = 7.23 (12) and 5.73 (13)°], whereas the methoxy group at the para position is almost coplanar with the attached benzene ring [C—O—C—C torsion angle = −2.02 (13)°]. The crystal structure is stabilized by a weak C—H⋯π interaction.

The asymmetric unit of the title compound, C 20 H 24 N 2 O 6 , contains one half-molecule, the complete molecule being generated by a crystallographic inversion centre. The molecule is nearly planar with a dihedral angle between the two benzene rings of 0.03 (4) and the central C/N/N/C plane making a dihedral angle of 8.59 (7) with each of its two adjacent benzene rings. The two methoxy groups at the ortho and meta positions are slightly twisted [C-O-C-C torsion angles = 7.23 (12) and 5.73 (13) ], whereas the methoxy group at the para position is almost coplanar with the attached benzene ring [C-O-C-C torsion angle = À2.02 (13) ]. The crystal structure is stabilized by a weak C-HÁ Á Á interaction.
The asymmetric unit of (I) (Fig. 1), C 20 H 24 N 2 O 6 , contains one half-molecule and the complete molecule is generated by a crystallographic inversion centre -x, -y, 1 -z. The molecule of (I) exists in an E,E configuration with respect to the two C═N double bonds [1.2870 (12) Å] and the torsion angle N1A-N1-C7-C1 = -178.99 (9)°. The molecule is nearly planar with the dihedral angle between the two benzene rings being 0.03 (4)°. Atoms C7/N1/N1A/C7A lie on a same plane [r.m.s 0.000 (1) Å]. This C/N/N/C plane makes a dihedral angle of 8.59 (7)° with each of its two adjacent benzene rings.

Experimental
The title compound was synthesized by mixing a solution (1:2 molar ratio) of hydrazine hydrate (0.097 ml, 2 mmol) and 2,4,5-trimethoxybenzaldehyde (0.785 mg, 4 mmol) in ethanol (20 ml). The resulting solution was refluxed for 5 h, yielding the yellow solid. The resultant solid was filtered off and washed with methanol. Yellow block-shaped single crystals of the title compound suitable for x-ray structure determination were recrystallized from acetone by slow evaporation of the solvent at room temperature over several days, m.p. 523 K (decompose).

Refinement
All H atoms are located from a difference map and refined isotropically [refined distances: C-H = 0.924 (13)-0.995 (12) Å]. Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme. Atoms with suffix A were generated by symmetry code -x, -y, 1 -z.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K. 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.