A lanthanide(iii) dodecanuclear structure with a acylhydrazone Schiff-base ligand: slow magnetic relaxation and magnetocaloric effects

Abstract

In the complex synthesis process, the design of new type structures of lanthanide clusters with high nuclearity provides an opportunity to understand the nature of magnetic dynamics. Here, the homometallic dodecanuclear complexes with the formula [Ln₁₂(H₂L1)₄(μ₃-O)₄(μ₃-OH)₄(CH₃COO)₁₅]·(CH₃COO)·(CH₃OH)₆ (Ln = Dy (1) and Gd (2)) were synthesized using 2,6-bis(2-((E)-2-hydroxybenzylidene)hydrazine-1-carbonyl)pyridine 1-oxide (H₄L1) ligand and Ln(CH₃COO)₃·6H₂O in CH₃OH. The structural analysis showed that those complexes had novel cores in Ln-clusters. In the main core of [Ln₁₂(μ₃-OH)₄(μ₃-O)₄(μ₂-O)₁₄], the center was a cubic [Ln₄(μ₃-O)₄]⁴⁻ structure. In the [Ln₄(μ₃-O)₄]⁴⁻ structure, each Ln(III) ion and the other two Ln(III) ions formed a triangular [Ln₃(μ₃-O)(μ₂-O)₃] structure under the connection of oxygen bridges. Magnetic property measurements revealed that complex 1 showed weak single-molecule magnetic behavior, while complex 2 showed large magnetocaloric effects (MCEs).