2-Cyano-anilinium iodide.

The solid-state structure of the title salt, C7H7N2 (+.)I(-), consists of cation-anion sheets lying parallel to (110), with the components linked by N-H⋯I hydrogen bonds.

4-Cyano-anilinium bromide.

In the crystal structure of the title compound, C(7)H(7)N(2) (+)·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 inter-actions and two weak C-H⋯Br inter-actions per cation tie the sheets together.

4-Cyano-anilinium iodide.

In the title compound, C(7)H(7)N(2) (+)·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 {-NH(3) (+)} group. In the crystal, there are two layers perpendicular to the c axis, each containing iodide ions and the {-NH(3) (+)} portions of the cations, with the remainder of the cations extending outwards from these layers.

2-Cyano-1-methyl-pyridinium nitrate.

In the title compound, C(7)H(7)N(2) (+)·NO(3) (-), all atoms except the methyl H atoms lie on a crystallographic mirror plane. The inter-layer 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 inter-actions link cations within each layer. Anion-π inter-actions with the cations assist in binding the layers together.