2,9-Dimethyl-1,10-phenanthrolin-1-ium (6-carb­oxy-4-hy­droxy­pyridine-2-carboxyl­ato-κ(3) O (2),N,O (6))(4-hy­droxy­pyridine-2,6-dicarboxyl­ato-κ(3) O (2),N,O (6))zincate(II) 2.35-hydrate: a proton-transfer compound

In the title compound, (C(14)H(13)N(2))[Zn(C(7)H(3)NO(5))(C(7)H(4)NO(5))]·2.35H(2)O, the Zn(II) atom is coordinated by two N atoms and four O atoms from the carboxyl­ate groups of the 4-hy­droxy­pyridine-2,6-dicarboxyl­ate and 6-carb­oxy-4-hy­droxy­pyridine-2-carboxyl­ate ligands, forming a distored octa­hedral geometry. In the anion, the two pyridine rings are inclined to one another by 87.75 (13)°. Two types of robust O—H⋯O hydrogen bond synthons, viz. R (2) (2)(16) and R (6) (6)(42), link the anions to form a two-dimensional network parallel to the bc plane. Furthermore, O—H⋯O, N—H⋯O, N—H⋯N and weak C—H⋯O hydrogen bonds connect the two dimensional networks, forming a three-dimensional structure. In the crystal, there are also C—H⋯π and π–π inter­actions [centroid–centroid distances of 3.5554 (18) and 3.7681 (18) Å], and C=O⋯π inter­actions [O⋯centroid distance = 3.117 (2) Å] present. One of the three crystal water molecules shows an occupancy of 0.35.