Solvent-dependent 4(4) square grid and 6(4).8(2) NbO frameworks formed by Cu(Pyac)2 (bis[3-(4-pyridyl)pentane-2,4-dionato]copper(II)).

The title compound crystallizes from anhydrous solvents in a simple square-grid topology, but when water is present, crystals form with an unusual interpenetrated 3D NbO topology whose pores contain hydrogen-bonded solvent molecules.