N-(Quinolin-8-yl)quinoline-2-carboxamide

In the title compound, C19H13N3O, the dihedral angle between the two quinoline systems is 11.54 (3)°. The molecular conformation is stabilized by intramolecular N—H⋯N and C—H⋯O hydrogen bonds, with N—H⋯N being bifurcated towards the two N atoms of the two quinoline rings. In the crystal, there are weak intermolecular π–π interactions present involving the quinoline rings [centroid–centroid distance 3.7351 (14) Å].


Comment
The title compound (Hqcq) can act as a tridentate ligand, and has been incorporated into the cyanometalate building block [Fe(qcq)(CN) 3 ] -{qcq = 8-(2-quinolinecarboxamido)quinoline anion}, in which the Fe III ion is coordinated by three carbon atoms of cyanide groups and three N-donors from the qcq ligand in a mer-arrangement (Kim et al., 2009).
Through replacement of the cyanide ligands the Fe(qcq) fragment can coordinate to transition metal ions to form various polynuclear and one-dimensional structures with fascinating magnetic properties such as single molecular magnets and single-chain magnets (Kim et al., 2009;Wang et al., 2011). Herein, the crystal structure of the tridentate ligand of Hqcq is presented.
In the crystal structure, no significant intermolecular hydrogen bonds are observed. The crystal structure features intermolecular π-π interactions between different types of quinoline rings with a distance of ca. 3.735 Å between the centroids of the respective rings ( Fig. 2), and the adjacent rings tilted against each other.

Experimental
The compound of 8-(2-quinolinecarboxamido)quinoline (Hqcq) was preparecd according to a literature method (Kim et al., 2009). Then, 0.3 mmol of Hqcq was added to MeCN (20 mL) with stirring. The resulting solution was filtered and the filtrate was left for slow evaporation in the dark at room temperature. Yellow block-shaped crystals of the title compound suitable for single-crystal X-ray diffraction were obtained after two weeks. Melting point = 429.6-430. Friedel-pair reflections have been merged (using a MERG 3 command) during the refinement. Assignment of the absolute structure is arbitrary.

Figure 1
ORTEP diagram of the title compound with displacement ellipsoids drawn at the 30% probability level.

Figure 2
The crystal packing diagram of the title compound showing the intermolecular π-π interactions.The distances shown are between the centroids of the respective rings, and the symmetry operator codes for generating adjacent aromatic rings are -1+x, y, z and 1+x, y, z. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.10 e Å −3 Δρ min = −0.13 e Å −3 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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.