Synthesis, luminescence and magnetic properties of tetranuclear lanthanide-based (Eu4, Gd4 and Dy4) clusters

Abstract

Three analogous lanthanide-containing complexes were isolated, with the molecular formula [Ln₄(μ₃-OH)₂(tmhd)₄L₆]·2CH₃CN (where Ln = Eu(1), Gd(2) and Dy(3); HL = 5-phenyl-8-hydroxylquinoline; and Htmhd = 2,2,6,6-tetramethyl-3,5-heptanedione). Single-crystal X-ray diffraction measurements performed on 1–3 revealed that they were all composed of [Ln₄(μ₃-OH)₂] centers with butterfly-shaped arrangements. Investigations into the luminescence properties and lifetime of 1 showed characteristic emission peaks of the Eu³⁺ ion and an average luminescence lifetime of 9.26 μs. Detailed magnetic studies suggested that antiferromagnetic interactions existed in 2 and 3, and that there was a remarkable magnetocaloric effect with a −ΔS_m value of 17.94 J K⁻¹ kg⁻¹ for 2, and a slow magnetic relaxation process with an energy barrier ΔE/k_B of 35.8 K for 3.