Successive syntheses and magnetic properties of homodinuclear lanthanide macrocyclic complexes.

A series of homodinuclear β-diketone lanthanide(III) complexes, formulated as [(acac)Ln(L1)] (Ln = Dy (1), Tb (2), and Gd (3), respectively) were first synthesized based on a closed-macrocyclic ligand (HL1) derived from the [2 + 2] cyclocondensation of 4--butyl-2,6-diformylphenol and -phenylenediamine in the presence of lanthanide acetylacetonates. Subsequently, by using the above compounds as building blocks to assemble directly with another Schiff base ligand, ,'-bis(5-chlorosalicylidene)--phenylenediamine (HL2), three new homodinuclear sandwich-type lanthanide complexes with the general formula [Ln(L1)(L2)] (Ln = Dy (4), Tb (5), and Gd (6), respectively) were further designed and prepared. Single-crystal X-ray analyses show that the central Ln ion adopts a distorted square antiprism conformation with local symmetry. Magnetic studies reveal ferromagnetic interaction between Dy and Tb centres and zero-field slow relaxation of magnetization for Dy complexes 1 and 4. The corresponding magneto-structural correlations of SMMs 1 and 4 were further discussed by theoretical calculations and with experimental outcomes.