2,9-Dimethyl-1,10-phenanthrolin-1-ium (6-carb­oxy-4-hy­droxy­pyridine-2-carboxyl­ato-κ³O²,N,O⁶)(4-hy­droxy­pyridine-2,6-dicarboxyl­ato-κ³O²,N,O⁶)zincate(II) 2.35-hydrate: a proton-transfer compound

In the title compound, (C₁₄H₁₃N₂)[Zn(C₇H₃NO₅)(C₇H₄NO₅)]·2.35H₂O, 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. R₂²(16) and R₆⁶(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.