CuII-Azide Polynuclear Complexes of Three Different Building Clusters with the Same Schiff-Base Ligand: Synthesis, Structures, Magnetic Behavior, and Density Functional Theory Studies

Abstract

Three copper-azido complexes [Cu4(N3)8(L1)2(MeOH)2]n (1), [Cu4(N3)8(L1)2] (2), and [Cu5(N3)10(L1)2]n (3) [L1 is the imine resulting from the condensation of pyridine-2-carboxaldehyde with 2-(2-pyridyl)ethylamine] have been synthesized using lower molar equivalents of the Schiff base ligand with Cu(NO3)2·3H2O and an excess of NaN3. Single crystal X-ray structures show that the basic unit of the complexes 1 and 2 contains CuII4 building blocks; however, they have distinct basic and overall structures due to a small change in the bridging mode of the peripheral pair of copper atoms in the linear tetranuclear structures. Interestingly, these changes are the result of changing the solvent system (MeOH/H2O to EtOH/H2O) used for the synthesis, without changing the proportions of the components (metal to ligand ratio 2:1). Using even lower proportions of the ligand, another unique complex was isolated with CuII5 building units, forming a two-dimensional complex (3). Magnetic susceptibility measurements over a wid...