Crystal structure of 4-bromo-2-(1H-imidazo[4,5-b]pyridin-2-yl)phenol

In the title compound, C12H8BrN3O, the 4-bromophenol ring is coplanar with the planar imidazo[4,5-b]pyridine moiety (r.m.s deviation = 0.015 Å), making a dihedral angle of 1.8 (2)°. There is an intramolecular O—H⋯N hydrogen bond forming an S(6) ring motif. In the crystal, molecules are linked via N—H⋯N and O—H⋯Br hydrogen bonds, forming undulating sheets parallel to (10-2). The sheets are linked by π–π interactions [inter-centroid distance = 3.7680 (17) Å], involving inversion-related molecules, forming a three-dimensional structure.


S1. Comment
Coordination chemistry of transition metal complexes with Schiff base ligands is an important and fascinating branch of chemistry (Ouari et al., 2015b;Benghanem et al., 2012;Basu et al., 2010). A literature survey revealed that this kind of compound possesses diverse biological activities such as antibiotic (Yıldız et al., 2015) and antimicrobial (Salama et al., 2015;Zayed et al., 2015). The photoluminescence of the title compound has been reported (Köse et al., 2015;Pal et al., 2015;Ray et al., 2014).
The molecular structure of the title compound is shown in Fig. 1. The bond distances and angles are normal and similar to those in related compounds (Belguedj et al., 2015).

S2. Synthesis and crystallisation
The title compound was prepared following a literature method (Ouari et al., 2015a). To a MeOH solution (15 ml) of 5bromosalicylaldehyde (0.122 g, 1 mmol) was added drop wise to a MeOH solution (5 ml) of 2,3-diaminopyridine (0.109 g, 1 mmol). The mixture was refluxed with constant stirring under a nitrogen atmosphere for 3 h, yielding an abundant orange precipitate that was collected by filtration. The product was washed with methanol (3 × 5 ml) then with diethyl ether (3 × 5 ml) and dried under vacuum for 4 h. Orange crystals of the title compound, suitable for X-ray diffraction analysis, were obtained after two weeks by slow evaporation of the DMSO solvent (yield: 70%; m.p.: 528-531 K).

S3. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2 The molecular structure of the title compound, with atom labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. The intramolecular O-H···N hydrogen bond is shown as a dashed line (see Table 1).

Figure 2
A view along the c axis of the crystal packing of the title compound. The hydrogen bonds are shown as dashed lines (see Table 1), and H atoms not involved in these interactions have been omitted for clarity. Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s 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 > 2σ(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.