Synthesis, structures and magnetic properties of cyano- and amide-bridged FeIII-LnIII tetranuclear heterometallic clusters

Three Fe(2)(III)Ln(2)(III) tetranuclear heterometallic clusters, [H4LGd(H2O)Tp*Fe(CN)(3)](2)8H(2)O2MeOH (1) and [H(4)LLn(MeOH)Tp*Fe(CN)(3)](2)6MeOH2MeCN (Ln=Tb and Dy for 2 and 3, respectively, H6L = N,N-(2,6-pyridine-dicarboxyl)-disalicylhydrazide, Tp* = hydridotris(3,5dimethylpyrazol-1-yl)-borate), were synthesized by use of the [(Tp*)Fe(CN)(3)](-) unit as a metalloligand toward LnCl(3) and H6L species. Structural analyses reveal that Fe-III and Ln(III) ions in all complexes are connected to each other by one cyanide to form a heterobinuclear unit of [Ln(H4L)][(Tp*)Fe(CN)(3)], which is dimerized through Ln-N-C=O-Ln interaction. Magnetic susceptibility measurements show weak antiferromagnetic interactions between cyano-bridged Fe-III and Gd-III ions and amide-bridged Gd-III ions are operative. Complex 1 displays the magnetocaloric effect with -S-m(max) = 12.70 Jkg(-1)K(-1) at 4.0 K for H=7 T. No single-molecule magnetic properties are observed for 2 or 3 down to 1.8 K. [GRAPHICS] .