4-Ethoxyanilinium hexafluorophosphate monohydrate

In the crystal of the title compound, C8H12NO+·PF6 −·H2O, intermolecular N—H⋯F, N—H⋯O and O—H⋯F hydrogen bonds link the molecules into chains along the c axis and C—H⋯π contacts further stabilize the structure. The F atoms of one of the hexafluorophosphate anions are disordered over two sets of sites with site-occupancy factors of 0.27 (3) and 0.73 (3).

In the crystal of the title compound, C 8 H 12 NO + ÁPF 6 À ÁH 2 O, intermolecular N-HÁ Á ÁF, N-HÁ Á ÁO and O-HÁ Á ÁF hydrogen bonds link the molecules into chains along the c axis and C-HÁ Á Á contacts further stabilize the structure. The F atoms of one of the hexafluorophosphate anions are disordered over two sets of sites with site-occupancy factors of 0.27 (3) and 0.73 (3).

Related literature
For related structures, see: Fu (2009a,b). The title compound was studied as part of our search for ferroelectric compounds, which usually have a phase transition.For background to phase transition materials, see: Li et al. (2008); Zhang et al. (2009 Table 1 Hydrogen-bond geometry (Å , ).

Comment
As a continuation of our study of dielectric-ferroelectric materials, including organic ligands (Li et al., 2008), metal-organic coordination compounds (Zhang et al., 2009), and organic-inorganic hybrids, we studied the dielectric properties of the title compound. Unfortunately, there was no distinct anomaly observed from 93 to 350 K. In this article, the crystal structure of this compound is presented. The crystal structures of 4-ethoxyanilinium together with other anions are known (Fu, 2009a,b).
The asymmetric unit of the crystal structure consists of one almost coplanar protonated 4-ethoxyanilinium cation with the C2-C1-O1-C7 and C1-O1-C7-C8 torsion angles of 172.9 (3) and 177.4 (3)°, respectively, one hexafluorophosphate anion for which the F atoms are disordered over two sets of positions with site-occupancy factors of 0.27 (3) and 0.73 (3), and one water molecule ( Fig.1). In the crystal structure, several intermolecular N-H···F and O-H···F hydrogen bonds link all species to chains along the c axis ( Fig.2). In addition, C-H···π interactions further stabilize the crystal structure.
Experimental 1.37 g (10 mmol) of 4-Ethoxybenzenamine was firstly dissolved in 50 ml ethanol, to which hexafluorophosphoric acid (70%, w/w) was then added until the solution becomes acidic under stirring. Single crystals of the title compond were prepared by slow evaporation at room temperature of the acidic solution after 3 days.

Refinement
The water H atoms were found in Fourier difference maps and were refined freely. Positional parameters of all other H atoms were calculated geometrically and allowed to ride on the C and N atoms to which they are bonded, with U iso (H) = 1.2U eq (C,N). The F atoms of the hexafluorophosphate anion are disordered in two orientations with site-occupancy factors of 0.73 (3) and 0.27 (3). 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.
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 > σ(F 2 ) is used only for calculating Rfactors(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.