4-Bromo-3-methylanilinium perchlorate

In the title compound, C7H9BrN+·ClO4 −, the cations and anions are linked by intermolecular N—H⋯O hydrogen bonds, forming a two-dimensional network parallel to the ab plane.

, the cations and anions are linked by intermolecular N-HÁ Á ÁO hydrogen bonds, forming a two-dimensional network parallel to the ab plane.

Comment
The construction of metal-organic coordination compounds has attracted much attention owing to potential functions, such as permittivity, fluorescence, magnetism and optical properties (Chen et al., 2001;Xie et al., 2003;Zhao et al., 2004;Xiong et al., 1999). Amine derivatives are a class of excellent ligands for the construction of novel metal-organic frameworks (Fu et al., 2007Wang et al. 2002;. We report here the crystal structure of the title compound, 4-bromo-3-methylanilinium perchlorate. In the title compound ( Fig.1), the amino N atom is protonated. In the crystal structure, all the amine group H atoms are involved in N-H···O hydrogen bonding (Table 1) with O atoms of ClO 4 anion. These hydrogen bonds link the ionic units into a two-dimensional network parallel to the ab plane ( Fig. 2).
Colourless block-shaped crystals of the title compound suitable for X-ray analysis were obtained by slow evaporation at room temperature.

Refinement
H atoms were positioned geometrically and treated as riding [C-H = 0.93 Å (aromatic), 0.96 Å (methyl) and N-H = 0.89 Å (N)], with U iso (H) = 1.2U eq (aromatic C) and 1.5U eq (methyl C or N). A rotating-group model was used for the methyl and -NH 3 groups.
Figures Fig. 1. The molecular structure 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.