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

Figure 4 A view of the [pi]

stacking interactions involving the aromatic rings of the anions [(hpydc)^2- and (hpydcH)^-] and the cations [(dmpH)⁺], and the C=O

and C-H

interactions (see Comment section and Table 1 for details).