4,4'-Imino-dipyridinium bis-(hydrogen phthalate).

Abstract

In the title salt, C10H11N3 2+·2C8H5O4 −, doubly protonated 4,4′-dipyridylamine (dpa) cations participate in N—H⋯O hydrogen bonding with two hydrogen phthalate anions to form a neutral unit. Both anions contain an intramolecular O—H⋯O hydrogen bond. In the crystal structure, these units form two-dimensional layers through π–π stacking inter­actions with a centroid-to-centroid distance of 3.763 (3) Å. In turn, these layers aggregate in three dimensions by additional N—H⋯O hydrogen bonding. The assignment to the noncentrosymmetric space group P1 is corroborated by chemically unreasonable aromatic ring bond distances and poor K scale factor distributions for a disordered model in the centrosymmetric P space group.