Bis(2,4,6-trimethyl­pyridinium) tetra­bromidozincate

In the title compound, (C₈H₁₂N)₂[ZnBr₄], the coordination geometry of the anion is approximately tetra­hedral. The Zn—Br bond lengths range from 2.3901 (19) to 2.449 (2) Å and the Br—Zn—Br angles range from 107.09 (8) to 112.48 (8)°. In the crystal, each [ZnBr₄]²⁻ anion is connected to four cations through two N—H...Br and two C—H...Br hydrogen bonds, forming two-dimensional ...(cation)₂...anion...(cation₂)... sheets parallel to the bc plane. Within each sheet, the anions are arranged in stacks with no significant inter-anion Br...Br inter­actions [the shortest being > 4.3 Å], while the cations are in chains, with weak π–π stacking inter­actions [centroid–centroid distance = 3.991 Å] between cations inter­acting with the same anion.

Bis(2,4-dimethyl­pyridinium) tetra­bromido­mercurate(II)

The asymmetric unit of the title compound, (C₇H₁₀N)₂[HgBr₄], consists of one cation and one half-anion, bis­ected by a twofold rotation axis passing through the metal atom. The anion exhibits a distorted tetra­hedral arrangement about the Hg^II atom. In the crystal, the cations and anions are linked by N—H...Br hydrogen-bonding inter­actions along [010]. Cation–cation π–π stacking and Br...Br inter­molecular inter­actions are absent.

Bis(2,6-dimethyl­pyridinium) dibromo­iodate bromide

In the title salt, 2C₇H₁₀N⁺·IBr₂⁻·Br⁻, each of the anions, viz. [IBr₂]⁻ and Br⁻, lie on a twofold axis. The IBr₂⁻ anion is almost linear, with a Br—I—Br angle of 178.25 (3)°. The cation is essentially planar (r.m.s. deviation = 0.0067 Å). In the crystal, each Br⁻ anion links two cations via N—H...Br...H—N hydrogen-bonding inter­actions.

2-Amino-5-methyl­pyridinium dibromo­iodate

In the title salt, C₆H₉N₂⁺·Br₂I⁻, the cation is essentially planar (r.m.s. deviation = 0.0062 Å for the non-H atoms) while the anion is almost linear with a Br—I—Br angle of 177.67 (2)°. The crystal packing shows two anions and two cations connected via N—H...Br and (pyridine)N—H...Br hydrogen-bonding inter­actions, forming centrosymmetric tetra­mers with R₄⁴(16) ring motifs. Very weak offset aromatic π–π stacking interactions [centroid-centroid separation = 4.038 (4), slippage = 1.773 Å] also occur.

2,6-Dimethyl­pyridinium bromide

The asymmetric unit of the title salt, C₇H₁₀N⁺·Br⁻, comprises two 2,6-dimethyl­pyridinium cations and two bromide anions. One cation and one anion are situated in general positions, while the other cation and the other anion lie on a crystallographic mirror plane parallel to (010). Each pair of ions inter­act via N—H...Br and C—H...Br hydrogen bonding, generating motifs depending on the cation and anion involved. Thus, the cation and the anion on the mirror plane generate infinite chains along the c axis, while the other ionic pair leads to sheets parallel to the ac plane. In the overall crystal packing, both motifs alternate along the b axis, with a single layer of the chain motif sandwiched between two double layers of the sheet motif. The sheets and chains are further connected via aryl π–π inter­actions [centroid–centroid distances = 3.690 (2) and 3.714 (2) Å], giving a three-dimensional network.

Redetermination of 2,2′-bipyridine-1,1′-diium dibromide

In the title mol­ecular salt, C₁₀H₁₀N₂²⁺·2Br⁻, the dihedral angle between the aromatic rings is 20.83 (14)° and the N—H groups have a transoid conformaton [N—C—C—N = 158.5 (3)°]. In the crystal, the cations are linked to the anions by two N—H...Br and five C—H...Br hydrogen bonds, generating corrugated sheets incorporating R₂¹(7), R₄²(10), R₄²(11) and two different R₄²(12) loops. This structure was originally reported by Nakatsu et al. [Acta Cryst (1972), A28, S24], but no atomic coordinates are available.

3-(Ammonio­meth­yl)pyridinium dibromide

In the title salt, C₆H₁₀N₂²⁺·2Br⁻, the non-H atoms of the 3-methyl­pyridinium unit of the cation are almost coplanar (r.m.s. deviation = 0.0052 Å). In the crystal, the dications and Br anions are linked by a combination of six hydrogen bonds, viz. one N_py—H...Br, two C—H...Br and three H₂N–H...Br, into supra­molecular layers, parallel to the bc plane, composed of alternating R²₄(10) and R²₄(8) loops. Weak π–π inter­actions between cationic rings with centroid–centroid distances of 3.891 (2) Å are also observed.