Chair-like [LnIII4CoIII2] (Ln = Dy, Eu, Gd, Tb) clusters including a [DyIII4CoIII2] single molecule magnet

Abstract

The employment of a Schiff base ligand 2-((2-(hydroxymethyl)phenylimino)methyl)phenol (H₂L) in the synthesis of Ln^III–Co^III clusters is reported. Four isomorphous hexanuclear clusters of compositions [Ln₄Co₂(μ₃-OH)₂(NO₃)₄(CH₃COO)₄L₄(DMF)₂]·2C₂H₅OH [H₂L = 2-((2-(hydroxymethyl)phenylimino)methyl)-6-methoxyphenol; Ln = Dy (1), Eu (2), Gd (3), Tb (4)] have been prepared under solvothermal conditions. The centrosymmetric hexanuclear metallic core is composed of a defect-dicubane Ln₄ moiety and two Co^III ions which are linked to the defect-dicubane unit through two alkoxo groups and two phenoxido groups. This structure gives a chair-like topology. The magnetic properties of 1–4 were studied. The Dy₄ unit of 1 exhibits slow magnetic relaxation behavior. The U_eff for 1 of 41.9 K is a relatively high value among those reported for Dy₄ SMMs with defect-dicubane cores. This value is also much higher than those reported for [Dy^III₄Co^III₂] SMMs. This work further illustrates that hydroxide-containing Schiff bases are very effective ligands for designing 3d–4f-based SMMs.