N,N′-Bis(5-bromo-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine

The crystal structure of the title Schiff base compound, C19H20Br2N2O2, contains two crystallographically independent molecules (A and B) in the asymmetric unit, with similar conformations. Intramolecular O—H⋯N (× 4) and C—H⋯N (× 5) hydrogen bonds form six- and five-membered rings, producing S(6) and S(5) ring motifs, respectively. One of the N atoms in molecule A acts as a trifurcated acceptor, the rest of the N atoms being bifurcated acceptors. The dihedral angles between the benzene rings in molecules A and B are 47.83 (17) and 61.11 (17)°, respectively. The molecular conformation is stabilized by intramolecular O—H⋯N and C—H⋯N hydrogen bonds. The short distances between the centroids of the benzene rings [3.7799 (19)–3.890 (2) Å] indicate the existence of π–π interactions. In addition, the crystal structure is further stabilized by an intermolecular C—H⋯O hydrogen bond, C—H⋯π interactions, and short intermolecular Br⋯Br and Br⋯O contacts [3.4786 (5) and 3.149 (3) Å, respectively].

The crystal structure of the title Schiff base compound, C 19 H 20 Br 2 N 2 O 2 , contains two crystallographically independent molecules (A and B) in the asymmetric unit, with similar conformations. Intramolecular O-HÁ Á ÁN (Â 4) and C-HÁ Á ÁN (Â 5) hydrogen bonds form six-and five-membered rings, producing S(6) and S(5) ring motifs, respectively. One of the N atoms in molecule A acts as a trifurcated acceptor, the rest of the N atoms being bifurcated acceptors. The dihedral angles between the benzene rings in molecules A and B are 47.83 (17) and 61.11 (17) , respectively. The molecular conformation is stabilized by intramolecular O-HÁ Á ÁN and C-HÁ Á ÁN hydrogen bonds. The short distances between the centroids of the benzene rings [3.7799 (19)-3.890 (2) Å ] indicate the existence ofinteractions. In addition, the crystal structure is further stabilized by an intermolecular C-HÁ Á ÁO hydrogen bond, C-HÁ Á Á interactions, and short intermolecular BrÁ Á ÁBr and BrÁ Á ÁO contacts [3.4786 (5) and 3.149 (3) Å , respectively].

Comment
The condensation of primary amines with carbonyl compounds yields Schiff base (Casellato & Vigato, 1977) that are still now regarded as one of the most potential group of chelators for facile preparations of metallo-organic hybrid materials.
In addition, the crystal structure is further stabilized by intermolecular C-H···O hydrogen bond and C-H···π interactions.

Experimental
The synthetic method has been described earlier (Reglinski et al., 2004). Single crystals suitable for X-ray diffraction were obtained by evaporation of an ethanol solution at room temperature.

Refinement
H atoms bound to the O1A, O2A, and O2B were located in a difference Fourier map and refined freely. H atom bound to O1B was located from a difference Fourier map and constrained to refine with the parent atom after distance restraint of 0.84 (1) Å. The rest of the H atoms were positioned geometrically (C-H = 0.95-0.99 Å) and refined using a riding model.  Fig. 1. The molecular structure of (I), with atom labels and 50% probability ellipsoids for non-H atoms. Intramolecular interactions are shown as dashed lines.

Special details
Experimental. The low-temperature data was collected with the Oxford Cyrosystem Cobra low-temperature attachment.
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.