Tetranuclear copper(II) complexes incorporating short and long metal–metal separations: synthesis, structure and magnetism

Abstract

Synthesis, structural and magnetic characterization of tetranuclear [(Cu₂L)₂B] complexes [where H₃L is the Schiff’s-base ligand, 1,3-bis(salicylideneamino)propan-2-ol; B is the dipyrazolate entities: methylenebis(3,5-dimethylpyrazolate) (mbdpz) or 4,4′-bi-3,5-dimethylpyrazolate (mdpz)] are reported. The structures reveal short intra- and inter-molecular Cu⋯Cu separations (ca. 3.4 Å), in combination with long intramolecular copper distances (ca. 10 Å). The magnetic behaviour of [(Cu₂L)₂(mbdpz)] (1) is indicative of an intramolecular antiferromagnetic interaction between the copper(II) centres [2J = −460 cm⁻¹], whilst that of [(Cu₂L)₂(mdpz)] (2) is characteristic of an antiferromagnetically coupled system with intramolecular coupling in the order of 2J = −380 cm⁻¹, with the presence of a further intermolecular interaction indicated.