1H-Benzotriazole–4-hydroxybenzoic acid (1/1)

The asymmetric unit of the title compound, C6H5N3·C7H6O3, comprises independent benzotriazole and 4-hydroxybenzoic acid molecules. The dihedral angle between the benzene ring and the benzotriazole ring system is 15.18 (7)°. The mean plane of the carboxyl group is twisted at an angle of 18.55 (1)° with respect to the benzene ring. The crystal structure is stabilized by weak intermolecular N—H⋯N, O—H⋯N, O—H⋯O and C—H⋯O interactions, forming a three-dimensional network.

The asymmetric unit of the title compound, C 6 H 5 N 3 ÁC 7 H 6 O 3 , comprises independent benzotriazole and 4-hydroxybenzoic acid molecules. The dihedral angle between the benzene ring and the benzotriazole ring system is 15.18 (7) . The mean plane of the carboxyl group is twisted at an angle of 18.55 (1) with respect to the benzene ring. The crystal structure is stabilized by weak intermolecular N-HÁ Á ÁN, O-HÁ Á ÁN, O-HÁ Á ÁO and C-HÁ Á ÁO interactions, forming a three-dimensional network.
The benzene ring (C1-C6) is planar, with the maximum deviation of 0.010 (2) Å. The dihedral angle between the benzene ring and benzotriazole ring system is 15.18 (7)

Experimental
Benzotriazole (C 6 H 5 N 3 , 1.1913 g) and p-hydroxy benzoic acid (C 7 H 6 O 3 , 1.3812 g) were mixed in equimolar ratio in methanol and the prepared solution was allowed for slow evaporation at room temperature. Good quality crystals suitable for X-ray intensity data collection were collected in a period of 10 days.

Refinement
H atoms were positioned geometrically and refined using riding model with C-H = 0.93 Å and U iso (H) = 1.2U eq (C) for CH, N-H = 0.86 Å and U iso (H) = 1.2U eq (C) for NH, O-H = 0.82 Å and U iso (H) = 1.5U eq (C) for OH.

Figure 2
The packing of (I), viewed down c axis. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.15 e Å −3 Δρ min = −0.11 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.025 (2) 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.