3-Cyanoanilinium bromide

In the cation of the title compound, C7H7N2 +·Br−, all non-H atoms are essentially coplanar [r.m.s. deviation = 0.010 (5) Å]. The compound is isomorphous with the chloride analogue. In the crystal, the cations and anions are connected by N—H⋯Br hydrogen bonds.

In the cation of the title compound, C 7 H 7 N 2 + ÁBr À , all non-H atoms are essentially coplanar [r.m.s. deviation = 0.010 (5) Å ]. The compound is isomorphous with the chloride analogue. In the crystal, the cations and anions are connected by N-HÁ Á ÁBr hydrogen bonds.

Comment
The construction of metal-organic coordination compounds has attracted much attention owing to potential functions, such as permittivity, fluorescence, magnetism and optical properties (Fu et al., 2007;Chen et al., 2001;Xie et al., 2003;Zhao et al.,2004;Xiong et al., 1999). Nitrile derivatives are a class of excellent ligands for the construction of novel metal-organic frameworks. (Wang et al. 2002;. We report here the crystal structure of the title compound, which is isomorphous with the chloride analogue (Wen, 2008). In the cation all non-H atoms are essentially coplanar [r.m.s. deviation 0.010 (5) Å]. In the crystal structure, the organic cations and bromide ions are connected by N-H···Br hydrogen bonds along b axis, (Table 1), (Fig. 2).

Experimental
The commercial 3-aminobenzonitrile (3 mmol, 0.55 g) and HBr (0.5 ml) were dissolved in ethanol (20 ml). Colourless block-shaped crystals of the title compound suitable for X-ray analysis were obtained by slow evaporation at room temperature.

Refinement
All H atoms attached to C and N atoms were positioned geometrically and treated as riding, with C-H = 0.93 Å, N-H = 0.89 Å and U iso (H) = 1.2U eq (C) and U iso (H) = 1.5U eq (N). A rotating-group model was used for the -NH 3 group. Fig. 1. A view of the title compound with the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.

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.