Key indicatorsSingle-crystal X-ray study T = 273 K Mean (C-C) = 0.002 Å R factor = 0.025 wR factor = 0.065 Data-to-parameter ratio = 24.3For details of how these key indicators were automatically derived from the article, see

The title compound, C10H9N2+·C8H4NO6−·C8H5NO6·2H2O, consists of singly protonated 2,2′‐bipyridinium cations, 5‐nitroisophthalate anions, 5‐nitroisophthalic acid and water mol­ecules of crystallization, linked by N—H⋯O and O—H⋯O hydrogen bonds. The moieties are linked by multiple hydrogen bonds into an undulating sheet structure.

In the title adduct, C8H13N2+·C2Cl3O2−·C2HCl3O2, the tetra­methyl­pyrazine mol­ecule is protonated at one of the N atoms and linked to the tri­chloro­acetate anion via an N—H⋯O hydrogen bond. The tri­chloro­acetate anion is also linked to the tri­chloro­acetic acid mol­ecule via an O—H⋯O hydrogen bond.

Key indicatorsSingle-crystal X-ray study T = 298 K Mean (C-C) = 0.009 Å R factor = 0.098 wR factor = 0.248 Data-to-parameter ratio = 13.8For details of how these key indicators were automatically derived from the article, see

Key indicatorsSingle-crystal X-ray study T = 298 K Mean (C-C) = 0.008 Å R factor = 0.096 wR factor = 0.326 Data-to-parameter ratio = 12.9For details of how these key indicators were automatically derived from the article, see