2,4-Dibromo-6-[(E)-({3-[(E)-(3,5-dibromo-2-oxidobenzylidene)azaniumyl]-2,2-dimethylpropyl}iminiumyl)methyl]phenolate

In the title molecule, C19H18Br4N2O2, the dihedral angle between the benzene rings is 73.9 (2)°. Two intramolecular N—H⋯O hydrogen bonds make S(6) ring motifs. In the crystal, molecules are linked via C—H⋯O interactions, forming chains propagating along the a-axis directon. A short C⋯Br [3.401 (5) Å] contact is present in the crystal structure, which is further stabilized by a π–π interaction [centroid–centroid distance = 3.739 (3) Å].


Comment
In continuation of our work on the crystal structure analysis of Schiff base ligands (Kargar et al., 2011;Kia et al., 2010), we synthesized the title compound and report herein on its crystal structure.
The title compound (Fig. 1) is a potential tetradentate Zwitterionic Schiff base ligand. The bond lengths (Allen et al., 1987) and angles are within normal ranges and are comparable to thoses observed for related structures (Kargar et al., 2011;Kia et al., 2010).

Experimental
The title compound was synthesized by adding 3,5-dibromo-salicylaldehyde (2 mmol) to a solution of 2,2-dimethyl-1,3propanediamine (1 mmol) in ethanol (30 ml). The mixture was refluxed with stirring for 30 min. The resultant solution was filtered. Yellow single crystals of the title compound, suitable for X-ray structure determination, were recrystallized from ethanol by slow evaporation of the solvent at room temperature over several days.

Refinement
The NH H-atoms were located in a difference Fourier map and were refined as riding atoms with U iso (H) = 1.2 U eq (N).
The C-bound H-atoms were included in calculated positions and treated as riding atoms: C-H = 0.93, 0.97 and 0.96 Å for CH, CH 2 , and CH 3 H-atoms, respectively, with U iso (H) = k × U eq (parent C-atom), where k = 1.5 for CH 3 H-atoms and

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq