Two hydration products of 3,4,5,6-tetrachloro-N-(methyl-2-pyridyl)phthalmic acids.

In 2-amino-6-methylpyridin-1-ium 2-carboxy-3,4,5,6-tetrachlorobenzoate, C(6)H(9)N(2)(+)·C(8)HCl(4)O(4)(-), there are two perpendicular chains of hydrogen-bonded ions, one arising from the interaction between 2-carboxy-3,4,5,6-tetrachlorobenzoate ions and the other from the interaction between the 2-amino-6-methylpyridin-1-ium and 2-carboxy-3,4,5,6-tetrachlorobenzoate ions. These chains combine to form a two-dimensional network of hydrogen-bonded ions. Cocrystals of bis(2-amino-3-methylpyridin-1-ium) 3,4,5,6-tetrachlorophthalate-3,4,5,6-tetrachlorophthalic acid (1/1), 2C(6)H(9)N(2)(+)·C(8)Cl(4)O(4)(2-)·C(8)H(2)Cl(4)O(4), form finite aggregates of hydrogen-bonded ions. π-π interactions are observed between 2-amino-3-methylpyridin-1-ium cations. Both structures exhibit the characteristic R(2)(2)(8) motif as a result of the hydrogen bonding between the 2-aminopyridinium and carboxylate units.