Di­aqua­bis­[5-(2-pyrazin-2-yl)tetra­zolato]copper(II)–pyrazine-2-carbo­nitrile (1/2)

The title compound, [Cu(C(5)H(3)N(6))(2)(H(2)O)(2)]·2C(5)H(3)N(3), is a 1:2 co-crystal between the mononuclear complex di­aqua­bis­[5-(pyrazin-2-yl)tetra­zolato]copper(II) and the reagent pyrazine-2-carbo­nitrile which was used in the synthesis. The Cu(II) atom is located on an inversion centre and has a distorted octa­hedral [4 + 2]-coordination environment formed by four N atoms of two chelating bidentate 5-(pyrazin-2-yl)tetra­zolate ligands at shorter distances and two water O atoms at longer distances. The Cu(II) complex molecules are held together by O—H⋯N hydrogen bonds and π–π stacking inter­actions [centroid–centroid distance 3.6139 (8) Å], forming layers parallel to (100). These layers alternate with layers of pyrazine-2-car­bo­nitrile mol­ecules and both are held together via C—H⋯N hydrogen bonds and further π–π stacking inter­actions.