Di-aqua-bis-[5-(2-pyrazin-2-yl)tetra-zolato]copper(II)-pyrazine-2-carbo-nitrile (1/2)

The title compound, [Cu(C5H3N6)2(H2O)2]·2C5H3N3, is a 1:2 co-crystal between the mononuclear complex di-aqua-bis-[5-(pyrazin-2-yl)tetra-zolato]copper(II) and the reagent pyrazine-2-carbo-nitrile which was used in the synthesis. The Cu(II) atom is located on an inversion centre and has a distorted octa-hedral [4 + 2]-coordination environment formed by four N atoms of two chelating bidentate 5-(pyrazin-2-yl)tetra-zolate 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 inter-actions [centroid-centroid distance 3.6139 (8) Å], forming layers parallel to (100). These layers alternate with layers of pyrazine-2-car-bo-nitrile mol-ecules and both are held together via C-H⋯N hydrogen bonds and further π-π stacking inter-actions.