9-Cyano-10-methylacridinium hydrogen dinitrate.

The title compound, C(15)H(11)N(2)(+).HN(2)O(6)(-), crystallizes in the monoclinic space group C2/c with four molecules in the unit cell. The planar 9-cyano-10-methylacridinium cations lie on crystallographic twofold axes and are arranged in layers, almost perpendicular to the ac plane, in such a way that neighbouring molecules are positioned in a 'head-to-tail' manner. These cations and the hydrogen dinitrate anions are linked through C-H.O interactions involving four of the six O atoms of the anion and the H atoms attached to the C atoms of the acridine moiety in ring positions 2 and 4. The H atom of the hydrogen dinitrate anion appears to be located on the centre of inversion relating two of the four O atoms engaged in the above-mentioned C-H.O interactions. In this way, columns of either anions or cations running along the c axis are held in place by the network of C-H.O interactions, forming a relatively compact crystal lattice.