2-Trifluoromethyl-1H-benzimidazol-3-ium perchlorate

In the title salt, C8H6F3N2 +·ClO4 −, the atoms of the benzimidazole ring (including H atoms) are nearly coplanar (r.m.s. deviation of the fitted atoms = 0.0122 Å) and the triflouromethyl group lies out of this plane. The perchlorate anion adopts a distorted tetrahedral conformation with the Cl—O bond distances ranging from 1.412 (3) to 1.439 (2) Å. The benzimidazolium cations are linked to adjacent anions by intermolecular N—H⋯O hydrogen bonds, forming chains.

In the title salt, C 8 H 6 F 3 N 2 + ÁClO 4 À , the atoms of the benzimidazole ring (including H atoms) are nearly coplanar (r.m.s. deviation of the fitted atoms = 0.0122 Å ) and the triflouromethyl group lies out of this plane. The perchlorate anion adopts a distorted tetrahedral conformation with the Cl-O bond distances ranging from 1.412 (3) to 1.439 (2) Å . The benzimidazolium cations are linked to adjacent anions by intermolecular N-HÁ Á ÁO hydrogen bonds, forming chains.
. Experimental 0.144 g(1 mmol) of 2-trifluoromethyl-1H-benzimidazole was firstly dissolved in 30 ml methanol, to which 0.1 g (1 mmol) of perchloric acid was added to give a solution without any precipitate while stirring at the ambient temperature. Single crystals suitable for X-ray structure analysis were obtained by the slow evaporation of the above solution after 2 days in air.
The dielectric constant of the compound as a function of temperature indicates that the permittivity is basically temperature-independent (ε = C/(T-T 0 )), suggesting that this compound is not ferroelectric or there may be no distinct phase transition occurring within the measured temperature within the measured temperature (below the melting point).

Refinement
The asymmetric unit was selected to form a hydrogen-bonded unit. H atoms attached to C atoms were placed in calculated positions with C-H = 0.93Å with U iso = 1.2Ueq and allowed to ride. The H atoms attached to the N atoms were located on a difference map. The N-H distances were restrained to 0.86Å and refined as riding atoms with U iso = 1.2Ueq in the final cycles of refinement. The 2 0 0 reflection was omitted from the refinement because of extinction.  Fig. 1. A view of (I) with the 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 > 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.