Controllable syntheses and magnetic properties of novel homoleptic triple-decker lanthanide complexes

Four novel homoleptic triple-decker lanthanide complexes, [Ln₂(L)(Cl-salphen)₂]·0.5ClCH₂CH₂Cl (Ln³⁺ = Gd³⁺ (1), Ho³⁺ (2), Tb³⁺ (3), and Dy³⁺ (4)), have been designed and synthesized based on a Schiff base ligand N,N′-bis(5-chlorosalicylidene)-o-phenylenediamine (Cl-salphenH₂) and the building blocks [(acac)₄Ln₂(L)]; these complexes were derived from a closed-macrocyclic ligand (H₂L) obtained by the [2 + 2] template condensation of 2,6-diformyl-4-methylphenol and 1,3-diaminopropane in the presence of lanthanide acetylacetonates. Single-crystal X-ray analyses show that central Ln³⁺ ions adopt distorted square antiprism conformations with D_4d symmetry. Theoretical analysis and magnetic measurements reveal that Dy complex 4 behaves as a typical SMM with the characteristics of slow magnetic relaxation behavior and intermetallic ferromagnetic interaction.