4-Hydroxyanilinium perchlorate dihydrate

In the crystal structure of the title compound, C6H8NO+·ClO4 −·2H2O, intermolecular N—H⋯O and O—H⋯O hydrogen bonds occur. The protonated amine cations and the perchlorate anions are linked through the water molecules, and the hydroxy groups of the cations and the anions are linked through the water molecules. The cations are connected to the perchlorate anions via intermolecular N—H⋯O hydrogen bonds. In addition, the crystal structure exhibits weak intermolecular C—H⋯π interactions.

In the crystal structure of the title compound, C 6 H 8 NO + Á-ClO 4 À Á2H 2 O, intermolecular N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds occur. The protonated amine cations and the perchlorate anions are linked through the water molecules, and the hydroxy groups of the cations and the anions are linked through the water molecules. The cations are connected to the perchlorate anions via intermolecular N-HÁ Á ÁO hydrogen bonds. In addition, the crystal structure exhibits weak intermolecular C-HÁ Á Á interactions.   Table 1 Hydrogen-bond geometry (Å , ).

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.
Here, we report the crystal structure of the title compound (Fig. 1).
The asymmetric unit of the title compound is made up of a 4-hydroxyanilinium cation cation wherein the non-hydrogen atoms are practically co-planar with a mean deviation of 0.015 (2) Å, a perchlorate anion and two solvent molecules of water ( Fig. 1). The crystal packing (Fig. 2) is stabilized by intermolecular N-H···O , O-H···O hydrogen bonds and weak intermolecular C-H···π interactions. (Table 1). Both the protonated amine cations and the perchlorate anions are linked through the water molecules, and the hydroxy groups of the cations and the anions are linked through the water molecules.
Additionally, the cations are connected to the perchlorate anions via intermolecular N-H···O hydrogen bonds. Experimental 1.09g (10 mmol) 4-aminophenol was firstly dissolved in 10ml ethanol, to which perchloric acid aqueous solution (70% w/w) was then added under stirring until the PH of the solution was ca. 6. Ethanol was added until the precipitated substrates disappeared. Colorless prism single crystal for X-ray was obtained by the acid solution slow evaporated at room temperature after two days.

Refinement
Aryl H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93 Å. U iso (H) = 1.2U eq (C).

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.