N-(4-Chlorophenyl)-5-(4,5-dihydro-1H-imidazol-2-yl)thieno[2,3-b]pyridin-4-amine

In the title compound, C16H13ClN4S, the thienopyridine fused-ring system is nearly planar (r.m.s. deviation = 0.0333 Å) and forms a dihedral angle of 4.4 (3)° with the attached dihydroimidazole ring (r.m.s. deviation = 0.0429 Å) allowing for the formation of an intramolecular (exocyclic amine)N—H⋯N(imine) hydrogen bond. The benzene rings of the disordered (50:50) –N(H)—C6H4Cl residue form dihedral angles of 59.1 (3) and 50.59 (15)° with the fused ring system. In the crystal, (imidazole amine)N—H⋯N(pyridine) hydrogen bonds lead to a supramolecular helical chain along the b axis. The chains assemble into layers (ab plane) with inter-digitation of the chlorobenzene rings which results in weak C—H⋯Cl interactions in the c-axis direction.

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).   (Kaigorodova et al., 2000;Bernardino et al., 2006;Pinheiro et al., 2008;El-Kashef et al., 2010;Testa et al., 2010). A primary motivation for the preparation of these compounds is their biological activity, viz. anti-viral (Bernardino et al., 2004), anti-inflammatory (Moloney, 2001), antibacterial Pinheiro et al., 2008;Panchamukhi et al., 2011) and anti-parasitic (Bernardino et al., 2006).
In ( The most prominent feature of the crystal packing is the formation of N-H···N hydrogen bonds between the imidazolyl-amine and the pyridyl-N atom which lead to supramolecular helical chains along the b axis, Fig. 2 and Table   1. These assemble into layers in the ab plane allowing for inter-digitation of the chlorobenzene rings which in turn, allows for the formation of weak C-H···Cl interactions, Table 1. For the illustrated orientation of disordered benzene ring, Fig.   3, the H6···Cl1 separation is 2.95 Å.

Refinement
The C-bound H atoms were geometrically placed (C-H = 0.95-0.99 Å) and refined as riding with U iso (H) = 1.2U eq (C).
The N-bound H atoms were located from a difference map and refined with a distance restraint of N-H = 0.88±0.01 Å, and with U iso (H) = 1.2U eq (carrier atom). The -N(H)-C 6 H 4 Cl residue was disordered over two position. From anisotropic refinement (equivalent pairs of atoms were tied, and C 6 rings were idealized) the orientations were equal and so in the final refinement the site occupancies factors were fixed at 0.5. Several reflections, i.e. (1 0 0), (2 0 0), (0 0 2) and (-1 0 2), were affected by the beam-stop and were omitted from the final refinement.

Figure 1
The molecular structure of (I) showing the atom-labelling scheme and displacement ellipsoids at the 35% probability level. Only one orientation of the disordered -N(H)-C 6 H 4 Cl residue is shown.

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.