2-Cyano-1-methyl­pyridinium nitrate

In the title compound, C₇H₇N₂⁺·NO₃⁻, all atoms except the methyl H atoms lie on a crystallographic mirror plane. The inter­layer distance, including that between aligned N atoms from alternating cations and anions in adjacent layers, is exceptionally short at 3.055 (1) Å. Two-dimensional C—H...O hydrogen-bonded networks link cations to anions, while C—H...N inter­actions link cations within each layer. Anion–π inter­actions with the cations assist in binding the layers together.

4-Cyano-1-methyl­pyridinium bromide

In the crystal of the title mol­ecular salt, C₇H₇N₂⁺·Br⁻, the cations form inversion dimers via weak pairwise C—H...N hydrogen bonds; their mean planes are separated by 0.292 (6) Å. Weak C—H...Br inter­actions involving all of the remaining H atoms tie the cations and anions together into sets of inter­penetrating sheets. The title compound is isostructural with its iodide analogue.

4-Cyano-1-methyl­pyridinium iodide

In the crystal structure of the title compound, C₇H₇N₂⁺·I⁻, the cations form inversion-related dimers via weak pairwise C—H...N hydrogen bonds. In the dimers, the pyridinium rings are parallel to one another with their mean planes separated by a normal distance of ca 0.28 Å. Weak C—H...N inter­actions between adjacent dimers generate a layer lying parallel to (10-1). The remaining H atoms form C—H...I inter­actions, which link the layers into a three-dimensional structure.

4-Cyano­anilinium iodide

In the title compound, C₇H₇N₂⁺·I^-, the cation is located on a site of 4mm symmetry and is thus disordered about the fourfold axis so that there are two perpendicular orientations of the six-membered ring and four rotational orientations of the {-NH₃⁺} group. In the crystal, there are two layers perpendicular to the c axis, each containing iodide ions and the {-NH₃⁺} portions of the cations, with the remainder of the cations extending outwards from these layers.

4-Cyano­anilinium bromide

In the crystal structure of the title compound, C₇H₇N₂⁺·Br⁻, the cations are associated into inversion dimers through weak pairwise C—H...N hydrogen bonds. The dimers further form stepped sheets via weak pairwise C—H...N hydrogen bonds. In the sheets, the spacing between the mean planes of the laterally displaced aromatic rings in adjacent dimers is 1.124 (6) Å. Three N—H...Br inter­actions and two weak C—H...Br inter­actions per cation tie the sheets together.