4-(1H-Pyrrolo[2,3-b]pyridin-2-yl)pyridine

The asymmetric unit of the title compound, C12H9N3, contains two independent molecules in which the dihedral angle between the pyridine and azaindole rings are 8.23 (6) and 9.89 (2)°. In the crystal, both types of molecule are connected by pairs of N—H—N hydrogen bonds into inversion dimers.


Comment
The title compound has been shown to be an precursor for the production of luminescent organic compound (Liu et al., 2000). In the crystal structure of the title compound two crystallographically independent molecules are found which shows no large structural differences. Both molecules are nearly coplanar, the dihedral angles between the pyridine and the azaindole rings is 8.23 (6)° and 9.89 (2)° (Huang et al., 2012). Each of these molecules is connected into centrosymmetrically dimers by intermolecular N-H-N hydrogen bonding.

Experimental
The compound was synthesized by the following procedure (Parcerisa et al., 2008). A solution of [3-(2-hydroxy-2pyridin-4-yl-ethyl)-pyridin-2-yl]-carbamic acid tert-butyl ester (1 mmol and acetonitrile (12 ml) was cooled to ice temperature. Afterwards triethylamine (1.2 mmol) and trifluoromethanesulfonic anhydride (1.1 mmol) was added over a period of 5 min. The mixture was stirred at room temperature for 2 h, trifluoroacetic acid was added (1.5 mmol) and afterwards the mixture was heated under reflux for 1 h. The mixture was cooled to room temperature and neutralized using 2 N NaOH. The aqueous layer was extracted with ethyl ether and the organic extract was washed with brine and aqueous Na 2 SO 4 , dried and concentrated. The residue was purified by column chromatography using hexane/ethyl acetate (2:8) as eluent, followed by recrystallization in CH 2 Cl 2 and hexane to give a white solid in 64% yield. Crystals suitable for X-ray diffraction were grown from a CH 2 Cl 2 solution layered with hexane at room temperature. 1 H NMR (CDCl 3 , 300

Refinement
H atoms were located in difference map but were positioned with idealized geometry and refined isotropic with U iso (H) = 1.2U eq (C,N).  Molecular structure of the title compound with labeling and displacement ellipsoids drawn at the 30% probability level.

Computing details
H atoms are shown as small spheres of arbitrary radii.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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 > 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.