4-Bromo-N-(4-hydroxybenzylidene)aniline

In the title compound, C13H10BrNO, the benzene ring planes are inclined at an angle of 48.85 (17)°, resulting in a nonplanar molecule. A characteristic of aromatic Schiff bases with N-aryl substituents is that the terminal phenyl rings are twisted relative to the HC=N plane. In this case, the HC=N unit makes dihedral angles of 11.1 (4) and 38.5 (3)° with the hydroxybenzene and bromobenzene rings, respectively. In the crystal, the molecules are linked by O—H⋯N hydrogen bonds to form infinite (C8) chains along the b axis.

In the title compound, C 13 H 10 BrNO, the benzene ring planes are inclined at an angle of 48.85 (17) , resulting in a nonplanar molecule. A characteristic of aromatic Schiff bases with N-aryl substituents is that the terminal phenyl rings are twisted relative to the HC N plane. In this case, the HC N unit makes dihedral angles of 11.1 (4) and 38.5 (3) with the hydroxybenzene and bromobenzene rings, respectively. In the crystal, the molecules are linked by O-HÁ Á ÁN hydrogen bonds to form infinite (C8) chains along the b axis.
L. Jothi, G. Vasuki, R. Ramesh Babu and K. Ramamurthi Comment Schiff base compounds have been used as fine chemicals and medical substrates. They are important ligands in coordination chemistry due to their ease of preparation and their ability to be modified both electronically and sterically (Li et al., 2008 andZhang, 2010). As a part of our study on the co-ordination behaviour of a ligand having a 4-hydroxy substituent on the benzylidene fragment, X-ray structural analysis of the title compound was carried out, the results are reported herein. The lattice parameters of this compound, determined from precession photographs, were reported previously by Bürgi et al. (1968). The title compound, (I), contains two benzene rings bridged by a C ═N imino moiety, the planes of which are inclined at an angle of 48.85 (17)°, showing significant deviation of the molecule from planarity as observed in a related structure N-p-tolylvanillaldimine (Kaitner & Pavlovic, 1995). The molecule exists in the solid state in an E-Configuration with respect to the C7═N1 bond as indicated by the torsion angle C4-C7-N1-C8 = 171.22 (4)°. In order to minimize the interaction between the hydroxy proton and H6 at C6 the O1-C1-C6 angle [123.4 (4)°] is larger than the O1-C1-C2 angle [117.4 (4)°] (Yeap et al., 1993). The N1-C7-C4 [124.70 (4)°] is greater than the normal value of 120°; this might be a consequence of repulsion between the lone pair of electrons on N1 and H5 attached to C5 (N1···H5 = 2.6583 (1) Å). The C4-C7 [1.454 (6)Å] and N1-C8 [1.412 (6)Å] distances confirm a degree of π-electron delocalization between the benzene rings, and the molecule can be regarded as a partially delocalized πelectron system as observed in the related structures 4-[(3-methoxyphenylimino)methyl]phenol) and N-p-tolylvanillaldimine (Yeap, et al.,, 1993;Kaitner & Pavlovic, 1995). All other bond lengths are within the expected ranges (Allen et al., 1987). The crystal structure is stabilized by intermolecular O-H···N hydrogen bonds linking the neighbouring molecules into infinite chains along the b axis.
Experimental 4-Bromo-4′-hydroxybenzylideneaniline was prepared by mixing equimolar amounts of 4-hydroxy benzaldehyde and 4bromo aniline in ethanol (40 ml). The reaction mixture was refluxed for about 6 h and the resulting solution, kept at room temperature was slowly evaporated. After three days single crystals of the title compound, suitable for X-ray structure analysis were obtained.

Refinement
All the H atoms were positioned geometrically and treated as riding on their parent atoms, with C-H = 0.93Å (aromatic), O-H = 0.82 Å and refined using a riding model with U iso (H)=1.2U eq (C) or 1.5U eq (O) for the hydroxy H atom.

Figure 1
The molecular structure of the title compound, with atom numbering and displacement ellipsoids drawn at the 50% probability level.   Table 1 for details). 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 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.