Pentanuclear lanthanide pyramids based on thiacalix[4]arene ligand exhibiting slow magnetic relaxation

Abstract

A series of pentanuclear Ln^III clusters, [Ln₅(μ₄-OH)(μ₃-OH)₄(L₁)(acac)₆] (H₄L₁ = p-tert-butylthiacalix[4]arene; acac = acetylacetonate; Ln = Dy, Ho, Er) and [Ln₅(μ₅-OH)(μ₃-OH)₄(L₁)(L₂)₂(acac)₂(CH₃OH)₂] (H₃L₂ = 5,11,17,23-tetrakis(1,1-dimethylethyl)-25,26,27-trihydroxy-28-methoxy thiacalix[4]arene; Ln = Dy, Ho, Er), have been synthesized based on the thiacalix[4]arene ligand. All of these complexes feature a square-based pyramid with four triangular Ln₃ structural motifs. One μ₄-OH group bridges four Ln^III ions in the basal plane of 1–3, while the OH group in complexes 4–6 adopts the μ₅-coordination mode. Our results illuminate the coordination modes of the versatile thiacalix[4]arene ligands and their application to new cluster compounds. The structural and magnetic studies confirm that the molecular symmetries and coordination geometries for lanthanide metal cores have a significant effect on some parameters as single-molecule magnets. Among them, two Dy₅ pyramids exhibit distinct slow magnetic relaxation.