4-Chloroanilinium bromide

In the title compound, C6H7ClN+·Br−, the amino N atom is protonated. All non-H atoms of the cation are essentially coplanar [r.m.s. deviation = 0.004 (3) Å]. In the crystal, N—H⋯Br hydrogen bonds connect the ions, forming a ribbon-like structure propagating along [010].


Min-Min Zhao Comment
Simple organic salts containing strong intrermolecular H-bonds have attracted an attention as materials which display ferroelectric-paraelectric phase transitions (Fu et al., 2011a, b, c). With the purpose of obtaining phase transition crystals of organic salts, various organic molecules have been studied and a series of new crystal materials have been elaborated (Wang et al., 2002;Xue et al., 2002;Ye et al., 2008).
In the title compound ( Fig. 1), the bond lengths and angles have normal values. The asymmetric unit is composed of one 4-chloroanilinium cation and one Branion. The protonated N atom is involved in strong intermolecular N-H···Br hydrogen bonds (Table 1) which connect the ions into a 2D network parallel to the ab-plane (Fig. 2). The crystal packing is further stabilized by aromatic π-π interactions between the benzene rings of the neighbouring cations with the Cg···Cg distances of 4.399 (1)Å (Cg is the centroid of the benzene ring).

Experimental
The HBr (1 mL, 2 mol/L), 4-chloroaniline (10 mmol) and ethanol (50 mL) were added into a 100 mL flask. The mixture was stirred at 333 K for 2 h, and then the precipitate was filtered out. Colourless crystals suitable for X-ray diffraction were obtained by slow evaporation of the solution.

Refinement
All the H atoms attached to C atoms were placed into the idealized positions and treated as riding with C-H = 0.93Å (aromatic) and U iso (H) = 1.2U eq (C). The H atoms based on N were placed into the calculated positions with the N-H = 0.89Å and refined with U iso (H) = 1.5U eq (N).

4-Chloroanilinium bromide
Crystal data C 6 H 7 ClN + ·Br − M r = 208.49 Triclinic, P1 Hall symbol: -P 1 a = 4.3989 (2) Å b = 6.2553 (2) Å c = 13.8907 (8)  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.84 e Å −3 Δρ min = −1.47 e Å −3 Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq