4-Bromoanilinium hexafluorophosphate monohydrate

In the title compound, C6H7BrN+·PF6 −·H2O, N—H⋯F, N—H⋯O and O—H⋯F hydrogen-bonding interactions stabilize the crystal structure and give rise to to chains running parallel to the c axis. In the anion, four of the F atoms are disordered over two sets of sites of equal occupancy.


Comment
As a continuation of our study of phase transition materials, including organic ligands (Li et al., 2008), metal-organic coordination compounds (Zhang et al., 2009 ), organic-inorganic hybrids, we studied the dielectric properties of the title compound, unfortunately, there was no distinct anomaly observed from 93 K to 350 K,suggesting that this compound should be not a real ferroelectrics or there may be no distinct phase transition occurred within the measured temperature range. In this article, the crystal structure of (I) has been presented.
The asymmetric unit of the title compound is made up of a almost coplanar 4-bromoanilimium cation with the mean deviation from the plan of 0.013 Å, a hexafluorophosphate anion disordered intwo orientations with site-occupancy factors of 0.7365 and 0.2635, and a water molecule. The chains of the molecular arrangement in the crystal structure is mainly determined by relatively strong and directional N-H···F, N-H···O and O-H···F hydrogen bonds (Table 1), and to a lesser degree by a π-π packing interaction between the adjacent aromatic rings, where the interplanar spacing is 5.855 (4) Å.

Experimental
Single crystals of 4-bromoanilimium hexafluorophosphate monohydrate were prepared by slow evaporation at room temperature of an ethanol solution of equal molar 4-bromobenzenamine and hexafluorophosphoric acid.

Refinement
Positional parameters of all the H atoms were calculated geometrically and were allowed to ride on the C and N atoms to which they are bonded, with U iso (H) = 1.2U eq (C), U iso (H) = 1.2U eq (N). Fig. 1. The molecular structure of the title compound, with the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level, and all H atoms have been omitted for clarity.

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.