Synthesis, Structure, and Magnetic Properties of Tetranuclear Copper(II) Complexes of Tridentate Dianionic Ligands with an ONO Donor Set

Abstract

Tetranuclear complexes [CuL2H]4 (1), [CuL2Me]4 (2), and [CuL2Cl]4 (3) with a reduced Schiff base type tridentate ligand H2L2H and its homologous with a substituent on the 2-hydroxymethylphenyl moiety (4-Me, H2L2Me; 4-Cl, H2L2Cl) were prepared and characterized by elemental analyses and magnetic measurements. The crystal structure of 1 was determined by X-ray crystallography. Tetracopper core is represented as a dimer-of-dimers structure by the stacking of two dicopper units bridged by alcoholic oxygens. One of the dicopper units contains square pyramidal (SP) Cu(II) ions, whereas the geometry of each Cu(II) ion in the other unit is described as essentially distorted trigonal bipyramid (TBP). Magnetic behaviors of the complexes are explained by modified equation based on the theoretical Spin Hamiltonian. The exchange integrals (-2J) are evaluated at 292–366 cm−1 for SP dicopper cores and 104–120 cm−1 for TBP, respectively, indicating the existence of different type of antiferromagnetic interaction-pathways corresponded to each copper geometry.