Chair-like [Ln(4)(III)Co(2)(III)] (Ln = Dy, Eu, Gd, Tb) clusters including a [(Dy4Co2III)-Co-III] single molecule magnet

摘要

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 [Ln(4)Co(2)(mu(3)-OH)(2)(NO3)(4)(CH3COO)(4)L-4(DMF)(2)]center dot 2C(2)H(5)OH [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 Ln(4) 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 Dy-4 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 Dy-4 SMMs with defect-dicubane cores. This value is also much higher than those reported for [(Dy4Co2III)-Co-III] SMMs. This work further illustrates that hydroxide-containing Schiff bases are very effective ligands for designing 3d-4f-based SMMs.