2,7-Dimethyl-1,8-naphthyridine

The asymmetric unit of the title compound, C10H10N2, contains one half-molecule with the two shared C atoms lying on a twofold rotation axis. The 1,8-naphthyridine is almost planar with a dihedral angle of 0.42 (3)° between the fused pyridine rings. In the crystal, molecules are linked into infinite chains along the c axis by intermolecular C—H⋯N hydrogen bonds, generating R 2 2(8) ring motifs. In addition, the crystal structure is further stabilized by C—H⋯π interactions.

The asymmetric unit of the title compound, C 10 H 10 N 2 , contains one half-molecule with the two shared C atoms lying on a twofold rotation axis. The 1,8-naphthyridine is almost planar with a dihedral angle of 0.42 (3) between the fused pyridine rings. In the crystal, molecules are linked into infinite chains along the c axis by intermolecular C-HÁ Á ÁN hydrogen bonds, generating R 2 2 (8) ring motifs. In addition, the crystal structure is further stabilized by C-HÁ Á Á interactions.

Comment
Due to their wide applications in medicine, naphthyridines are one of the most useful group of compounds. They are used as antihypertensives, antitumor agents, immunostimulants and herbicide safeners (Badawneh et al., 2001;Hawes et al., 1977;Gorecki et al., 1977). Naphthyridines are also used as a key molecule in molecular recognition chemistry (Goswami & Mukherjee, 1997;Goswami et al., 2005;Sheldrick, 2008). We report here the single crystal X-ray structure.
In the title compound (I), (Fig. 1), the C1 and C2 atoms are lying on twofold rotation axis [symmetry code: -x, -y, z]. The dihedral angle between the two pyridine rings is equal to 0.42 (3)° indicating that the 1,8-naphthyridine is almost planar.
Experimental 2,7-dimethyl-[1,8]naphthyridine was prepared according to the literature procedure (Chandler et al., 1982). In a sample bottle, 10 mg of compound was taken and dissolved in CHCl 3 and by slow evaporation the crystals are formed as colorless blocks.

Refinement
All hydrogen atoms were positioned geometrically with a riding model approximation with C-H = 0.93-0.96 Å and U iso (H) = 1.2 U eq (C). The rotating-group model was applied for the methyl groups. As there are not enough anomalous dispersion to determine the absolute structure, 923 Friedel pairs were merged before the final refinement. Fig. 1. The molecular structure of the title compound with atom labels and 50% probability ellipsoids for non-H atoms. Symmetry code: (i) -x, -y, z.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1)K.
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.