Pentanuclear lanthanide pyramids based on thiacalixarene ligand exhibiting slow magnetic relaxation†
A series of pentanuclear LnIII clusters, [Ln5(μ4-OH)(μ3-OH)4(L1)(acac)6] (H4L1 = p-tert-butylthiacalixarene; 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 thiacalixarene; Ln = Dy, Ho, Er), have been synthesized based on the thiacalixarene ligand. All of these complexes feature a square-based pyramid with four triangular Ln3 structural motifs. One μ4-OH group bridges four LnIII 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 thiacalixarene 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.