Polynuclear 3d complexes based on potentially tetra-anionic heptadentate ligands including amido, amino and phenoxo donors: Synthesis, crystal structure and magnetic properties

Abstract

The synthesis and characterization of new dinuclear Mn III and tetranuclear Cu II complexes, [HL 1Mn(DMSO)] 2 ( 1) and [H 2L 2Cu 2(MeO) 2] 2 ( 2), are reported (H 4L 1 = 2-hydroxy- N-[2-({2-[(2-hydroxybenzoyl)amino]ethyl}amino)ethyl]benzamide and H 4L 2 = 2-hydroxy- N-[3-({3-[(2-hydroxybenzoyl)amino]propyl}(methyl)amino)propyl]benzamide). Single crystal X-ray structures have been determined for 1 and 2. In 1 only one of the two amide functions of H 4L 1 is deprotonated in addition to the phenol ones, while in 2 all the amide functions of H 4L 2 are protonated and none of the potential nitrogen donors (amide and amine) is involved in the coordination to copper. HL 1 and H 2L 2 do not play the role of compartmental ligands and do not wrap around one Mn and one Cu ion, respectively, but embrace two metal centers yielding, with the respective assistance of auxiliary DMSO and methoxo ligands, dinuclear manganese and tetranuclear copper complexes, respectively. 1 includes two well isolated Mn III ions (Mn⋯Mn′ = 7.33 Å) that do not interact magnetically. The intermolecular Mn⋯Mn″ distance along the 1D chains (10.17 Å) is also too large to allow extended magnetic interactions. The pairwise magnetic interactions between the copper(II) ions in the tetranuclear complex 2 are so large that the χ M T product is already equal to zero at room temperature, implying that the antiferromagnetic interaction is around −1000 cm −1, as observed previously for di-μ-hydroxo–dicopper complexes.