N′-[4-(Dimethylamino)benzylidene]-4-methoxybenzohydrazide

The title Schiff base compound, C17H19N3O2, was obtained from the condensation of 4-dimethylaminobenzaldehyde with 4-methoxybenzohydrazide in an ethanol solution. The molecule is twisted with respect to the N—N single bond [C—N—N—C = −159.27 (14)°] and the dihedral angle between the two aromatic rings is 67.1 (2)°. In the crystal structure, the molecules are linked into chains along the c axis by intermolecular N—H⋯O and C—H⋯O hydrogen bonds.

The title Schiff base compound, C 17 H 19 N 3 O 2 , was obtained from the condensation of 4-dimethylaminobenzaldehyde with 4-methoxybenzohydrazide in an ethanol solution. The molecule is twisted with respect to the N-N single bond [C-N-N-C = À159. 27 (14) ] and the dihedral angle between the two aromatic rings is 67.1 (2) . In the crystal structure, the molecules are linked into chains along the c axis by intermolecular N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds.  H atoms treated by a mixture of independent and constrained refinement Á max = 0.14 e Å À3 Á min = À0.18 e Å À3 Table 1 Hydrogen-bond geometry (Å , ).

Comment
As part of our investigation of the crystal structures of Schiff bases derived from the condensation of aldehydes with benzohydrazides (Lu et al., 2008a,b,c), we report here the crystal structure of the title new Schiff base compound.
In the title molecule ( Fig. 1), the bond lengths have normal values (Allen et al., 1987), and are comparable to those observed in similar compounds (Nie, 2008;He, 2008;Shi et al., 2007). The dihedral angle between the two aromatic rings is 67.1 (2)°, indicating that the molecule is twisted. The methoxy group is coplanar with the at- indicates that the molecule is twisted about the N1-N2 bond.
In the crystal structure, the molecules are linked into chains ( Fig. 2) running along the c axis by intermolecular N-H···O and C-H···O hydrogen bonds (Table 1).

Experimental
The title compound was prepared by the Schiff base condensation of 4-dimethylaminobenzaldehyde (0.1 mol) and 4-methoxybenzohydrazide (0.1 mol) in 95% ethanol (50 ml). The excess ethanol was removed by distillation. The colourless solid obtained was filtered and washed with ethanol. Single crystals suitable for X-ray diffraction were obtained by slow evaporation of a 95% ethanol solution at room temperature.

Refinement
The imino H atom was located in a difference map and refined with a N-H distance restraint of 0.90 (1) Å and a fixed U iso of 0.08 Å 2 . The other H atoms were positioned geometrically (C-H = 0.93-0.96 Å) and refined using a riding model, with U iso (H) = 1.2U eq (C) and 1.5U eq (C methyl ). A rotating group model was used for methyl groups. Fig. 1. The molecular structure of the title compound, showing 30% probability displacement ellipsoids and the atom-numbering scheme.

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.