A series of tetranuclear lanthanide compounds constructed by in situ polydentate ligands: synthesis, structure, and SMM behaviour of the Dy₄ compound

Four tetranuclear lanthanide compounds with formulas [Ln₄(HL)₂(H₃L)₂(H₂L′)₂(PhCOO)₂]·6CH₃OH (Ln = Nd (1), Sm (2) and Gd (3)) and [Dy₄(DFMP)₂(H₂L)₂(HL)₂]·6CH₃OH·2H₂O (4) (H₄L = 3-((1,3-dihydroxy-2-(hydroxymethyl)propan-2-ylimino)methyl)-2-hydroxy-5-methylbenzaldehyde and H₃L′ = 3-(4,4-bis(hydroxymethyl)oxazolidin-2-yl)-2-hydroxy-5-methylbenzaldehyde) have been successfully synthesized by a one-pot route at room temperature. The in situ polydentate ligands reveal various coordination modes in forming compounds 1–4. Structure analysis reveal that all four compounds have a centrosymmetric “parallelogram” core, where four μ₃-CH₂O– arms are linked on both sides of the Ln₄ plane in compounds 1–3, while two μ₃-CH₂O– arms connected Dy₄ in compound 4. In addition, magnetic susceptibility studies reveal that compound 4 shows single-molecule magnet (SMM) behaviour with a high-temperature energy barrier of 50.2 K and a low-temperature energy barrier of 4.5 K. The relaxation behaviour is probably attributed to the individual Dy ions and the magnetic coupling between neighboring Dy ions.