(E)-3-[(3-Bromophenyl)iminomethyl]benzene-1,2-diol: a combined X-ray and computational structural study

The title compound, C13H10BrNO2, exists as an enol–imine form in the crystal and adopts an E configuration with respect to the C=N double bond. The molecule is close to planar, with a dihedral angle of 6.88 (14)° between the aromatic rings. Intramolecular O—H⋯N and O—H⋯O hydrogen bonds generate S(6) and S(5) ring motifs, respectively. The crystal structure is stabilized by intermolecular O—H⋯O hydrogen-bond interactions, forming R 2 2(10) and R 2 2(20) chains along [100]. ab initio Hartree–Fock (HF), density-functional theory (DFT) and semi-empirical (AM1 and PM3) calculations and full-geometry optimizations were also performed. Although there are some discrepancies between the experimental and calculated parameters, caused presumably by the O—H⋯O hydrogen-bond interactions, there is an acceptable general agreement between them.

The title compound, C 13 H 10 BrNO 2 , exists as an enol-imine form in the crystal and adopts an E configuration with respect to the C N double bond. The molecule is close to planar, with a dihedral angle of 6.88 (14) between the aromatic rings. Intramolecular O-HÁ Á ÁN and O-HÁ Á ÁO hydrogen bonds generate S(6) and S(5) ring motifs, respectively. The crystal structure is stabilized by intermolecular O-HÁ Á ÁO hydrogenbond interactions, forming R 2 2 (10) and R 2 2 (20) chains along [100]. ab initio Hartree-Fock (HF), density-functional theory (DFT) and semi-empirical (AM1 and PM3) calculations and full-geometry optimizations were also performed. Although there are some discrepancies between the experimental and calculated parameters, caused presumably by the O-HÁ Á ÁO hydrogen-bond interactions, there is an acceptable general agreement between them.
Ab-initio Hartree-Fock (HF), density-functional theory (DFT) (Schmidt & Polik, 2007) and semi-empirical (AM1 and PM3) calculations and full-geometry optimizations were performed by means of GAUSSIAN 03 W package (Frisch et al., 2004). The selected bond lengths and angles together with the torsion angles are compared with the obtained ones from semi-empirical, ab-initio HF and DFT/B3-LYP (Becke 3 parameter Lee-Yang-Parr) (Becke, 1988(Becke, , 1993Lee et al., 1988) ( Table 2). We observe an acceptable general agreement between them. Although the DFT molecular orbital theory was considered as the most accurate method for geometry optimization for free and complex ligands (Friesner, 2005;Liu et al., 2004), the HF method led to better results in regard to the bond lengths and angles.
supplementary materials sup-2 Refinement Due to their taking part in H-bonding interactions, the hydroxyl H atoms were preferred to locate in difference Fourier map and refined freely with U iso (H) = 1.5 U eq (O). All other H-atoms were refined using a riding model with d(C-H)= 0.93 Å and U iso (H)= 1.2 U eq (C). Fig. 1. An ORTEP view of (I), with the atom-numbering scheme and 30% probability displacement ellipsoids. Dashed lines indicate H-bonds.

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.