Crystal structures of 2-methyl-pyridinium hydrogen 2,3-bis-(4-methyl-benzo-yloxy)succinate and bis-[4-methyl-pyridinium hydrogen 2,3-bis-(4-methyl-benzo-yloxy)succinate] penta-hydrate.

The title salt (I), C(6)H(8)N(+)·C(20)H(17)O(8)(-), comprises a 2-methyl-pyridinium cation and a 2,3-bis-(4-methyl-benzo-yloxy)succinate mono-anion while the salt (II), 2C(6)H(8)N(+)·2C(20)H(17)O(8)(-)·5H(2)O, consists of a pair of 4-methyl-pyridinium cations and 2,3-bis-(4-methyl-benzo-yloxy)succinate mono-anions and five water mol-ecules of solvation in the asymmetric unit. In (I), the dihedral angle between the aromatic rings of the anion is 40.41†(15)°, comparing with 43.0†(3) and 85.7†(2)° in the conformationally dissimilar anion mol-ecules in (II). The pyridine ring of the cation in (I) is inclined at 23.64†(16) and 42.69†(17)° to the two benzene moieties of the anion. In (II), these comparative values are 4.7†(3), 43.5†(3)° and 43.5†(3), 73.1†(3)° for the two associated cation and anion pairs. The crystal packing of (I) is stabilized by inter-ionic N-H⋯O, O-H⋯O and C-H⋯O hydrogen bonds as well as weak C-H⋯π inter-actions, linking the ions into infinite chains along [100]. In the crystal packing of (II), the anions and cations are also linked by N-H⋯O and O-H⋯O hydrogen bonds involving also the water mol-ecules, giving a two-dimensional network across (001). The crystal structure is also stabilized by weak C-H⋯O and C-H⋯π inter-actions.