Adenin-1-ium hydrogen isophthalate di­methyl­formamide monosolvate

In the title proton-transfer organic salt, C5H6.3N5 (+)·C8H4.7O4 (-)·C3H7NO, the adeninium moiety is protonated at the N atom in the 1-position of the 6-amino-7H-purin-1-ium (adeninium) cation. In the solid state, the second acidic proton of isophthalic acid is partially transferred to the imidazole N atom of the adeninium cation [refined O-H versus N-H ratio = 0.70 (11):0.30 (11)]. Through the partially transferred proton, the adeninium cation is strongly hydrogen bonded (N-H⋯O/O-H⋯N) to the isophthalate anion. This strong inter-action is assisted by another N-H⋯O hydrogen bond originating from the adeninium NH2 group towards the isophthalate keto O atom, with an R (2) 2(8) graph-set motif. This arrangement is linked via N-H⋯O hydrogen bonds to the O atoms of the carboxyl-ate group of an isophthalate anion. Together, these hydrogen bonds lead to the formation criss-cross zigzag isophthalate⋯adeninium chains lying parallel to (501) and (50-1). The adeninium cations and the isophthalate anions are arranged in infinite π stacks that extend along the c-axis direction [inter-planar distance = 3.305 (3) Å]. Mol-ecules are inclined with respect to this direction and within the stacks they are offset by ca. half a mol-ecule each. Combination of the N-H⋯O and O-H⋯N hydrogen bonds with the π-π inter-actions forms infinitely stacked isophthalate⋯adeninium chains, thus leading to a two-dimensional supra-molecular structure with parallel inter-digitating layers formed by the π stacked isophthalate⋯adeninium chains. The DMF mol-ecules of crystallization are bonded to the adeninium cations through strong N-H⋯O hydrogen bonds and project into the lattice space in between the anions and cations. There are also C-H⋯O hydrogen bonds present which, combined with the other inter-actions, form a three-dimensional network. The crystal under investigation was found to be split and was handled as if non-merohedrally twinned.