2-(4-Hydroxyphenyl)-1H-benzimidazol-3-ium chloride monohydrate

The title molecular salt, C13H11N2O+·Cl−·H2O, crystallizes as a monohydrate. In the cation, the phenol and benzimidazole rings are almost coplanar, making a dihedral angle of 3.18 (4)°. The chloride anion and benzimidazole cation are linked by two N+—H⋯Cl− hydrogen bonds, forming chains propagating along [010]. These chains are linked through O—H⋯Cl hydrogen bonds involving the water molecule and the chloride anion, which form a diamond core, giving rise to the formation of two-dimensional networks lying parallel to (10-2). Two π–π interactions involving the imidazolium ring with the benzene and phenol rings [centroid–centroid distances = 3.859 (3) and 3.602 (3) Å, respectively], contribute to this second dimension. A strong O—H⋯O hydrogen bond involving the water molecule and the phenol substituent on the benzimidazole unit links the networks, forming a three-dimensional structure.

The title molecular salt, C 13 H 11 N 2 O + ÁCl À ÁH 2 O, crystallizes as a monohydrate. In the cation, the phenol and benzimidazole rings are almost coplanar, making a dihedral angle of 3.18 (4) . The chloride anion and benzimidazole cation are linked by two N + -HÁ Á ÁCl À hydrogen bonds, forming chains propagating along [010]. These chains are linked through O-HÁ Á ÁCl hydrogen bonds involving the water molecule and the chloride anion, which form a diamond core, giving rise to the formation of two-dimensional networks lying parallel to (102). Twointeractions involving the imidazolium ring with the benzene and phenol rings [centroid-centroid distances = 3.859 (3) and 3.602 (3) Å , respectively], contribute to this second dimension. A strong O-HÁ Á ÁO hydrogen bond involving the water molecule and the phenol substituent on the benzimidazole unit links the networks, forming a threedimensional structure.
The title compound crystallizes as the monohydrate of a hydrochloride salt, Fig. 1. Bond lengths (Allen et al., 1987) and angles are within normal ranges. The phenol and benzimidazole rings are almost coplanar with a dihedral angle of 3.18 (4) °.
One water molecule was included in the asymmetric unit which, besides the chloride anion, directs the organization in the lattice forming hydrogen bonding interactions (Table 1 and Fig. 2), as has been observed in other halohydrates Baktır et al., 2010).
In the crystal, the chloride anion and the benzimidazole molecule give rise to the first dimension through two N + -H···Clinteractions (Table 1); forming chains propagating along [010].
The water molecule and chloride anion form a diamond core through O-H···Cl hydrogen bonds, giving rise to the second dimension (Table 1); forming two-dimensional networks lying parallel to plane (10-2).
The third dimension is built by a strong O-H···O hydrogen bond between the water molecule, as the acceptor, with the phenol group of benzimidazole, as donor (Table 1 and Fig. 2); forming a three-dimensional structure.
The molecular structure of the title compound is similar to that of the neutral compound 4-(1H-benzimidazol-2yl)phenol (Zhan et al., 2007), where the dihedral angle between the benzimidazole ring system and the phenol ring is 8.11 (5) °. In the crystal lattice, only N-H···O and O-H···N (benzimidazole-phenol) hydrogen bonds are present.

Refinement
The OH, water and NH H atoms could be located in Fourier difference maps. The water H atoms were refined as riding atoms with U iso (H)= 1.5U eq (O). In the final cycles of refinement the OH, NH and C-bound H atoms were positioned geometrically and treated as riding atoms: O-H = 0.82 Å, N-H = 0.86 Å, C-H = 0.93 Å for CH H atoms, with U iso (H) = 1.5U eq (O) and = 1.2U eq (N,C) for other H atoms.

Figure 1
The molecular structure of the title compound, with atom labelling. The displacement ellipsoids are drawn at the 30% probability level.  The crystal packing of the title compound viewed along direction [101]. The hydrogen bonds and centroid-centroid interactions are shown as dashed lines (see Table 1 for details). H atoms not involved in hydrogen bonding have been omitted for clarity.  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.002 Δρ max = 0.24 e Å −3 Δρ min = −0.19 e Å −3 Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles 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 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.