Adenin-1-ium hydrogen isophthalate dimethylformamide monosolvate

• Main Authors: Vandavasi Koteswara Rao, Tausif Siddiqui, Matthias Zeller, Sherri R. Lovelace-Cameron
• Format: Article
• Language: English
• Published: International Union of Crystallography 2014-02-01
• Series: Acta Crystallographica Section E
• Online Access: http://scripts.iucr.org/cgi-bin/paper?S1600536813034971

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 interaction is assisted by another N—H...O hydrogen bond originating from the adeninium NH2 group towards the isophthalate keto O atom, with an R22(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.