Adenin-1-ium hydrogen isophthalate di­methyl­formamide monosolvate

In the title proton-transfer organic salt, C(5)H(6.3)N(5) (+)·C(8)H(4.7)O(4) (−)·C(3)H(7)NO, 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 inter­action is assisted by another N—H⋯O hydrogen bond originating from the adeninium NH(2) 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 carboxyl­ate 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 [inter­planar distance = 3.305 (3) Å]. Mol­ecules are inclined with respect to this direction and within the stacks they are offset by ca. half a mol­ecule each. Combination of the N—H⋯O and O—H⋯N hydrogen bonds with the π–π inter­actions forms infinitely stacked isophthalate⋯adeninium chains, thus leading to a two-dimensional supra­molecular structure with parallel inter­digitating layers formed by the π stacked isophthalate⋯adeninium chains. The DMF mol­ecules 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 inter­actions, form a three-dimensional network. The crystal under investigation was found to be split and was handled as if non-merohedrally twinned.