Isonicotinonitrile–4-methylbenzoic acid (1/1)

The title structure, C6H4N2·C8H8O2, is built up from an assembly of isonicotinonitrile and 4-methylbenzoic acid molecules and may be regarded as a co-crystal. The two planar molecules [r.m.s. deviations of 0.002 (6) and 0.0028 (11) Å, respectively] are linked by O—H⋯N and C—H⋯O hydrogen bonds. They are nearly coplanar and only twisted from each other by a dihedral angle of 2.48 (6)°. In the crystal, the components are interconnected by slipped π–π stacking [centroid–centroid distance = 3.6797 (11), slippage = 1.304 Å] and intermolecular C—H⋯N interactions.


Crystal data
This work was supported by a start-up grant from Jiangsu University of Science and Technology, China.

Comment
The amino derivatives have found wide range of applications in material science, such as magnetic, fluorescent and dielectric behaviors. And there has been an increased interest in the preparation of amino co-crystal compounds (Aminabhavi et al., 1986;Dai & Fu 2008a;Dai & Fu 2008b;Fu, et al. 2009). As an extension on the structural characterization, we report here the crystal structure of the title compound isonicotinonitrile 4-methylbenzoic acid.
The asymmetric unit contains an organic isonicotinonitrile molecule and a 4-methylbenzoic acid organic molecule which are linked by a strong O-H···N and a weak C-H···O hydrogen bonds forming a C22(7) ring ( Etter et al., 1990;Bernstein et al., 1995) (Fig. 1). The benzene and pyridine rings are nearly coplanar and only twisted from each other by a dihedral angle of 2.48 (6)°. The geometric parameters of both the organic molecules are within the normal range.
Experimental isonicotinonitrile and 4-methylbenzoic acid were obtained commercially from Alfa Aesar. The two organoc compounds were solved in the solution (ethanol/water). Colourless block-shaped crystals suitable for X-ray analysis were obtained by slow evaporation of an ethanol/water (2:1 v/v) solution.

Refinement
All the H atoms attached to C atoms were located into the idealized positions and treated as riding with C-H = 0.93 Å (aromatic) and 0.96 Å (methyl) with U iso (H)=1.2U eq (aromatic) and U iso (H)=1.5U eq (methyl). The positional parameters of the H atom (O1) was refined freely. In the last cycles of the refinement, it was treated as riding with the H1-O1 = 0.82 (2)Å) and U iso (H)=1.5U eq (O).

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.