X-Ray structural analysis has shown that the products of the reaction of [Cu(sac)(2)(H2O)(4)]center dot 2H(2)O (sac= saccharinate) with pyridazine (pydz) are markedly dependent on the solvent used in the crystallization. The mononuclear complex [Cu(sac)(2)(H2O)(pydz)(2)] is obtained by slow evaporation of a 1: 2 H2O/methanol solution at room temperature, whereas liquid-phase diffusion of diethyl ether into the same reaction solution produces the polymeric complex [Cu(mu-OH)(mu-sac)(mu-pydz)](n). The individual molecules of [Cu(sac)(2)(H2O)(pydz)(2)] are doubly bridged into dimers by O-H center dot center dot center dot O hydrogen bonds. All ligands in [Cu(sac)(2)(H2O)(pydz)(2)] are monodentate, whereas copper(II) ions in [ Cu(mu-OH)(mu-sac)(mu-pydz)] n are triply bridged by all ligands, leading to a one-dimensional chain structure, which is further assembled to form a three-dimensional framework by non-covalent p-p and CH-p stacking interactions. Complex [ Cu(sac)(2)(H2O)(pydz)(2)] is paramagnetic, whereas complex [Cu(mu-OH)(mu-sac)(mu-pydz)](n) exhibits a significantly low mu effective value due to very strong exchange coupling between the copper atoms with a relatively short Cu-Cu distance of 3.360(3) angstrom. In addition, the full spectroscopic, luminescence, and thermal properties of the complexes are reported.