The title compound, [HgCl2(C14H12N2)], consists of one 2,9-dimethyl-1,10-phenanthroline (dmphen) ligand chelating the HgII ion and two chloride ligands coordinating to the HgII ion, forming a distorted tetra­hedral environment. The dmphen ligand is nearly planar (r.m.s. deviation = 0.0225 Å). The dihedral angle between the normal to the plane defined by the HgII atom and the two Cl atoms and the normal to the plane of the dmphen ring is 81.8 (1)°.

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 HgII 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.

The title salt, C20H26N3O2 +·Cl−, lies across a twofold crystallographic axis with the central N atom of the cation and the chloride anion sitting on this axis, Z′ = 0.5. There is an intra­molecular hydrogen bond between the hy­droxy H atom and the imino N atom. The chloride anion and the cation are connected into chains along the a axis by an N—H⋯Cl hydrogen bond. In the crystal, the chains are linked via C—H⋯Cl interactions forming two-dimensional networks lying parallel to (101).

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.

In the title salt, C6H10N2 2+·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 Npy—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.

In the title mol­ecular salt, C10H10N2 2+·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 R 2 1(7), R 4 2(10), R 4 2(11) and two different R 4 2(12) loops. This structure was originally reported by Nakatsu et al. [Acta Cryst (1972), A28, S24], but no atomic coordinates are available.

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.

The asymmetric unit of the title compound, [Hg(SCN)2(C14H12N2)], contains two complex mol­ecules in which the HgII atoms are both four-coordinated in a distorted tetra­hedral configuration by two N atoms from a chelating 2,9-dimethyl-1,10-phenanthroline ligand and by two S atoms from two thio­cyanate anions. The 1,10-phenanthroline ligand is slightly folded for one complex, the dihedral angle between the pyridine planes being 5.3 (1)°. In contrast it is nearly planar [0.5 (1)°] as it complexes with the other HgII atom. The thio­cyanate ligands are virtually linear and the S atom is bonded to HgII with N⋯S—Hg angles ranging from 99.3 (1) to 103.5 (1)°. Despite the presence of six aromatic rings in the asymmetric unit, there are no significant inter­molecular π–π contacts between phenanthroline ligands as the centroid–centroid distance of the closest contact between six-membered rings is 4.11 (1) A°.

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.

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.

The asymmetric unit of the title compound, (C5H6Br2N3)2[SnBr6], contains one cation and one half-anion in which the Sn atom is located on a crystallographic centre of inversion and is in a quasi-octa­hedral geometry. The crystal structure is assembled via hydrogen-bonding inter­actions of two kinds, N(pyridine/amine)—H⋯Br—Sn, along with C—Br⋯Br—Sn interactions [3.4925 (19) Å]. The cations are involved in π–π stacking, which adds an extra supra­molecularity as it presents a strong case of offset-face-to-face motifs [centroid–centroid distance = 3.577 (3) Å]. The inter­molecular hydrogen bonds, short Br⋯Br inter­actions and π–π stacking result in the formation of a three-dimensional supra­molecular architecture.

The asymmetric unit of the title compound, (C5H8N2)[HgBr4]·H2O, consists of one cation, one anion and one water mol­ecule. The anion exhibits a distorted tetra­hedral arrangement about the Hg atom. The crystal structure contains alternating sheets of cations (in the ac plane) and stacks of anions. Several strong hydrogen-bonding inter­actions (pyN—H⋯Br and C—H⋯Br; py is pyridine), along with O—H⋯Br inter­actions, connect the sheets of cations to the stacks of anions. Cation–cation π–π stacking is also present (C⋯C distances in the range 3.424–3.865 Å). The shortest Br⋯Br distance is 3.9527 (9) Å.

The asymmetric unit of the title compound, (C5H5BrN)2[SnBr6], contains one cation and one half-anion. The [SnBr6]2− anion is located on an inversion center and forms a quasi-regular octa­hedral arrangement. The crystal structure consists of two-dimensional supra­molecular layers assembled via hydrogen-bonding inter­actions of N—H⋯Br—Sn [D⋯A = 3.375 (13)–3.562 (13) Å and D—H⋯A = 127–142°, along with C—Br⋯Br synthons [3.667 (2) and 3.778 (3) Å]. These layers are parallel to the bc plane and built up from anions inter­acting extensively with the six surrounding cations.

In the crystal structure of the title compound, (C6H9N2)2[CuBr4], the geometry around the Cu atom is inter­mediate between tetra­hedral (Td) and square planar (D4h). Each [CuBr4]2− anion is connected non-symmetrically to four surrounding cations through N—H⋯X (pyridine and amine proton) hydrogen bonds, forming chains of the ladder-type running parallel to the crystallographic b axis. These layers are further connected by means of offset face-to-face inter­actions (parallel to the a axis), giving a three-dimensional network. Cation π–π stacking [centroid separations of 3.69 (9) and 3.71 (1) Å] and Br⋯aryl inter­actions [3.72 (2) and 4.04 (6) Å] are present in the crystal structure. There are no inter­molecular Br⋯Br inter­actions.

The asymmetric unit of the title compound, (C5H5BrN)2[SnCl6], contains one cation and one half-anion. The [SnCl6]2− anion is located on an inversion center and forms a quasi-regular octa­hedral arrangement. Hydrogen-bonding inter­actions of two kinds, viz. N—H⋯Cl—Sn and C—H⋯Cl—Sn, along with Cl⋯Br inter­actions [3.4393 (15) Å], connect the ions in the crystal structure into two-dimensional supra­molecular arrays. These supra­molecular arrays are arranged in layers approximately parallel to (110) built up from anions inter­acting with six symmetry-related surrounding cations.

In the crystal structure of the title compound, (C7H10N)2[CoBr4], the [CoBr4]2− anion is connected to two cations through N—H⋯Br and H2C—H⋯Br hydrogen bonds to form two-dimensional cation–anion–cation layers normal to the crystallographic b axis. Inter­actions of the π–π type are absent between cations in the stacks [centroid–centroid separation = 5.01 (5) Å]. Significant inter­molecular Br–aryl inter­actions are present in the structure, especially an unusually short Br–ring centroid inter­action of 3.78 (1) Å. The coordination geometry of the anion is approximately tetrahedral and a twofold rotation axis passes through the Co atom.

In the title compound, C18H16N4O2, the central six-membered ring has a boat conformation.