Influence of the Crystallization Solvent on the Molecular Structures of Copper(II) Saccharinato Complexes with Pyridazine: Synthesis, X-Ray Crystallography, Spectroscopy, Photoluminescence, and Thermal Properties

Abstract

X-Ray structural analysis has shown that the products of the reaction of [Cu(sac)2(H2O)4]·2H2O (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(μ-OH)(μ-sac)(μ-pydz)]n. The individual molecules of [Cu(sac)2(H2O)(pydz)2] are doubly bridged into dimers by O–H…O hydrogen bonds. All ligands in [Cu(sac)2(H2O)(pydz)2] are monodentate, whereas copper(ii) ions in [Cu(μ-OH)(μ-sac)(μ-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 π–π and CH–π stacking interactions. Complex [Cu(sac)2(H2O)(pydz)2] is paramagnetic, whereas complex [Cu(μ-OH)(μ-sac)(μ-pydz)]n exhibits a significantly low μeffective value due to very strong exchange coupling between the copper atoms with a relatively short Cu–Cu distance of 3.360(3) Å. In addition, the full spectroscopic, luminescence, and thermal properties of the complexes are reported.