[Aqua-bis-(nitrato-κO)copper(II)]-μ-{bis-[5-methyl-3-(pyridin-2-yl)-1H-pyrazol-4-yl]selenide}-[diaqua-(nitrato-κO)copper(II)] nitrate monohydrate.

In the title binuclear complex, [Cu2(NO3)3(C18H16N6Se)(H2O)3]NO3·H2O, the Cu(II) ions are penta-coordinated in a tetra-gonal-pyramidal geometry. In both cases, the equatorial planes are formed by a chelating pyrazole-pyridine group, a water mol-ecule and a nitrate O atom, whereas the apical positions are occupied by a water mol-ecule for one Cu(II) ion and a nitrate O atom for the other. The organic selenide ligand adopts a trans configuration with respect to the C-Se-C plane. Numerous inter-molecular O-H⋯O and N-H⋯O hydrogen bonds between the coordinating and lattice water mol-ecules, nitrate anions and pyrazole groups are observed. π-π stacking inter-actions between the pyridine rings [averaged centroid-centroid distance = 3.652 (5) Å] are also present. The lattice water molecule is equally disordered over two sets of sites.