Chair-like [LnIII4CoIII2] (Ln = Dy, Eu, Gd, Tb) clusters including a [DyIII4CoIII2] single molecule magnet
The employment of a Schiff base ligand 2-((2-(hydroxymethyl)phenylimino)methyl)phenol (H2L) in the synthesis of LnIII–CoIII 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 CoIII 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 Ueff 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 [DyIII4CoIII2] SMMs. This work further illustrates that hydroxide-containing Schiff bases are very effective ligands for designing 3d–4f-based SMMs.