Aqua­[6-carboxyl­ato-N′-(pyridin-2-yl­methyl­idene)pyridine-2-carbohydrazidato]copper(II) trihydrate

In the title compound, [Cu(C₁₃H₈N₄O₃)(H₂O)]·3H₂O, the complex molecule, except for the aqua ligand, is essentially planar [r.m.s. deviation = 0.034 (2) Å]. The coordination polyhedron of the Cu²⁺ cation is a square-pyramid, with the aqua ligand at the apex. The compound exhibits a three-dimensional structure, which is is stabilized by O—H...O and O—-H...N hydrogen bonds and π–π inter­actions [centroid–centroid distance = 2.987 (3) Å].

Diethyl pyrazine-2,5-dicarboxyl­ate

The mol­ecule of the title compound, C₁₀H₁₂N₂O₄, is located around an inversion center. The carboxyl­ate groups are twisted slightly with respect to the pyrazine ring, making a dihedral angle of 2.76 (19)°. In the crystal, mol­ecules are stacked along the c axis via weak C—H...O hydrogen bonds.