4-(3-Fluoroanilino)thieno[2,3-b]pyridine-6-carboxylic acid

In the title compound, C14H9FN2O2S, the thieno[2,3-b]pyridine residue is almost planar (r.m.s. deviation = 0.0194 Å), with the carboxylic acid group [dihedral angle = 11.9 (3)°] and the benzene ring [71.1 (4)°] being twisted out of this plane to different extents. An intramolecular N—H⋯O(carbonyl) hydrogen bond closes an S(6) ring. Supramolecular chains along [01-1] mediated by O—H⋯N(pyridine) hydrogen bonds feature in the crystal. A three-dimensional architecture is completed by π–π interactions occurring between the benzene ring and the two rings of the thieno[2,3-b]pyridine residue [centroid–centroid distances = 3.6963 (13) and 3.3812 (13) Å]. The F atom is disordered over the two meta sites in a near statistical ratio [0.545 (5):0.455 (5)].

The use of the EPSRC X-ray crystallographic service at the University of Southampton, England, and the valuable assistance of the staff there is gratefully acknowledged. JLW acknowledges support from CAPES (Brazil). We also thank the Ministry of Higher Education (Malaysia) for funding structural studies through the High-Impact Research scheme (UM.C/HIR/MOHE/SC/12).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: HB6844). Among the reported thienopyridine derivatives is a family of 4-(arylamino)thieno[2,3-b]pyridine-5-carboxylic acids, whose anti-virial and anti-bacterial activities have been investigated (Leal et al., 2008;Bernardino et al., 2007;Pinheiro et al., 2008). The structure of one of these derivatives, the title compound (I), is now reported.
In (I), Fig. 1, the nine atoms comprising the thieno[2,3-b]pyridine fused ring system are planar with a r.m.s. deviation of 0.0194 Å and maximum deviations of 0.0343 (19) and -0.0227 (16) for the C7 and C6 atoms, respectively. The carboxylic acid residue is twisted out of this plane, forming a dihedral angle of 11.9 (3)°, and the terminal benzene ring, which is orientated towards the thienyl ring, is almost orthogonal, the dihedral angle being 71.1 (4)°. There is an intramolecular N -H···O(carbonyl) hydrogen bond, Table 1, which closes an S(6) loop.

Experimental
The title compound was prepared as reported (Leal et al., 2008). The dark orange blade used in the structure determination was grown from its toluene/acetonitrile solution.

Refinement
The C-bound H atoms were geometrically placed (C-H = 0.95 Å) and refined as riding with U iso (H) = 1.2U eq (C). The Oand N-bound H atoms were located from a difference map and refined with distance restraints of O-H = 0.84±0.01 and N-H = 0.88±0.01 Å, and with U iso (H) = zU eq (carrier atom); z = 1.5 for O and z = 1.2 for N. The F1 atom is disordered over two position. Each site was refined with individual anisotropic displacement parameters. The major component refined to a site occupancy factor = 0.545 (5). The (022) reflection was omitted from the final refinement owing to poor agreement.

Computing details
Data collection: COLLECT (Hooft, 1998); cell refinement: DENZO (Otwinowski & Minor, 1997) and COLLECT (Hooft, 1998); data reduction: DENZO (Otwinowski & Minor, 1997) and COLLECT (Hooft, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).  The molecular structure of (I) showing displacement ellipsoids at the 50% probability level.     (9) 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.