Hydroxonium hydrate tris­(2,4,6-tri­amino-1,3,5-triazin-1-ium) bis­[bis­(pyri­dine-2,6-dicarboxyl­ato)cuprate(II)] pyridine-2,6-dicarboxylic acid hexa­hydrate

The reaction of copper(II) nitrate hexa­hydrate with pyridine-2,6-dicarboxylic acid (pydcH(2)) and 2,4,6-triamino-1,3,5-triazine (melamine) in aqueous solution in a 1:2:2 molar ratio gave the title compound, (H(5)O(2))(C(3)H(7)N(6))(3)[Cu(C(7)H(3)NO(4))(2)](2)·C(7)H(5)NO(4)·6H(2)O. The hydroxonium hydrate (H(5)O(2))(+), also known as the Zundel cation, resides on a twofold rotation axis. The O—H distance is 1.274 (14) Å, the O⋯O distance is 2.518 (5) Å, and the O—H—O angle is 162 (8)°. One of the melamine H(+) cations, the uncoordinated pydcH(2), and two water mol­ecules also reside on crystallographic twofold axes. The Cu(II) atom has a tetra­gonally distorted octa­hedral coordination environment. The structure features extensive hydrogen bonding, with 21 distinct inter­actions. There is also a centrosymmetric C=O⋯π inter­action with an O⋯centroid distance of 3.288 (3) Å. The structure is similar to a mixed-valence manganese(II/III) structure but shows inter­esting differences in the metal-atom coordination. One of the water molecules is equally disordered with respect to a twofold axis.