4-Hydroxy-1,2,6-trimethylpyridinium bromide monohydrate

The title salt, C8H12NO+·Br−·H2O, is isomorphous with the chloride analogue [Seethalakshmi et al. (2013). Acta Cryst. E69, o835–o836]. In the solid state, the cations, anions and water molecules are interlinked by a network of O—H⋯O, O—H⋯Br and C—H⋯Br interactions. The water molecule makes two O—H⋯Br hydrogen bonds, generating [010] zigzag chains of alternating water molecules and bromide anions. The cation is involved in two intermolecular C—H⋯Cl interactions in the chloride salt, whereas three intermolecular C—H⋯Br interactions are observed in the title bromide salt. This additional intermolecular C—H⋯Br interaction links the adjacent water and bromide zigzag chains via cationic molecules. In addition, weak π–π stacking interactions are observed between pyridinium rings [centroid–centroid distance = 3.5664 (13) Å].

The title salt, C 8 H 12 NO + ÁBr À ÁH 2 O, is isomorphous with the chloride analogue [Seethalakshmi et al. (2013). Acta Cryst. E69, o835-o836]. In the solid state, the cations, anions and water molecules are interlinked by a network of O-HÁ Á ÁO, O-HÁ Á ÁBr and C-HÁ Á ÁBr interactions. The water molecule makes two O-HÁ Á ÁBr hydrogen bonds, generating [010] zigzag chains of alternating water molecules and bromide anions. The cation is involved in two intermolecular C-HÁ Á ÁCl interactions in the chloride salt, whereas three intermolecular C-HÁ Á ÁBr interactions are observed in the title bromide salt. This additional intermolecular C-HÁ Á ÁBr interaction links the adjacent water and bromide zigzag chains via cationic molecules. In addition, weakstacking interactions are observed between pyridinium rings [centroid-centroid distance = 3.5664 (13) Å ].
As shown in Fig. 1, the asymmetric unit contains one 4-hydroxy-1,2,6-trimethylpyridinium cation, a bromide anion and a water molecule. The corresponding bond distances and angles of the cation in (I) are comparable with those of related structures (Seethalakshmi et al., 2006a,b,c;2007;2013a,b). There are three weak intermolecular C-H···Br (C3-H3···Br, C5-H5···Br and C9-H9A···Br) interactions observed in (I), whereas only two C-H···Cl (C3-H3···Cl and C9-H9A···Cl) interactions are found in the crystal structure of chloride salt (Seethalakshmi et al., 2013a). Atom C3 of the cation is involved in a weak C-H···Br intermolecular interaction with bromide anion. As shown in Fig. 4, this weak interaction combines with O-H···O and O-H···Br hydrogen bonds forming a graph-set motif of R 2 3 (8) (Bernstein et al., 1995). One of the methyl atoms C9 (via H9A) participates in a weak intermolecular C-H···Br interaction with the bromide anion. Again, this interaction combines with C3-H3···Br and two O-H···Br interactions forming a ring which has a graph-set motif of R 2 4 (10). The R 2 3 (8) and R 2 4 (10) ring motifs are arranged alternately as a helical ribbon which run parallel to the b axis (Fig. 4). Atom C5 of the cation (via H5) is involved in a weak intermolecular C-H···Br interaction. This additional C-H···Br interaction links the adjacent water and bromide zigzag chains via cationic molecules (Fig. 2). In constrast to chloride salt, bromide anion is pentacoordinated by five hydrogen atoms in the crystal structure of (I). The pentacoordination angles in the range of 55-89°. In (I), a weak aromatic π-π stacking interaction is observed between two pyridinium rings related by center of inversion (2 -x, -y, 1 -z) with a centroid-to-centroid distance of 3.5664 (13) Å.

Experimental
The title salt was prepared by dissolving 1-methyl-2,6-dimethyl-4-hydroxypyridine (1.37 g) with hydrobromic acid (2.43 ml) in distilled water (5 ml). The mixture was stirred at room temperature for 7 h and the clear solution was kept for supplementary materials sup-2 Acta Cryst. (2013). E69, o941-o942 evaporation at 60 °C after filtration. Finally crystalline powder was obtained and dissolved in double distilled water.
Single crystals suitable for X-ray diffraction were obtained by slow evaporation.

Refinement
Since the title salt is isomorphous with its chloride counterpart, it was refined with the coordinates of the cation moiety of chloride salt (Seethalakshmi et al., 2013a). The positions of the Br atom and water molecule were determined from a difference Fourier map and refined anisotropically. The positions of hydroxy H atom and H atoms of water molecule were determined from a difference Fourier map and refined freely along with their isotropic displacement parameters. In the final round of refinement, the O-H bond lengths of the water molecule and hydroxy group are restrained to 0.84 (2) Å. The methyl H atoms were constrained to an ideal geometry (C-H = 0.98 Å), with U iso (H) = 1.5U eq (C), but were allowed to rotate freely about the C-C and N-C bonds. The remaining H atoms were placed in geometrically idealized positions (C-H = 0.95 Å), with U iso (H) = 1.2U eq (C) and were constrained to ride on their parent atoms.