Hetero-Metallic 3d-4f-5d Complexes: Preparation and Magnetic Behavior of Trinuclear (LMe2Ni−Ln) W (CN) 8 Compounds (Ln = Gd, Tb, Dy, Ho, Er, Y; LMe2 = Schiff base) and Variable SMM Characteristics for the Tb Derivative

Assembling bimetallic Ni-Ln (3+) units and W (CN) (8) (3-) is shown to be an efficient route toward heteronuclear 3d-4f-5d compounds. The reaction of either the binuclear L (Me2) Ni (H (2) O) (2) Ln (NO (3) ) (3) complexes or their mononuclear components L (Me2) Ni and Ln (NO (3) ) (3) with (HNBu (3) ) (3) W (CN) (8) in dmf followed by diffusion of tetrahydrofuran yielded the trinuclear L (Me2) NiLnW (CN) (8) compounds 1 (Ln = Y), 2a, b (Gd), 3a, b (Tb), 4 (Dy), 5 (Ho), and 6 (Er) as crystalline materials. All of the derivatives possess the trinuclear core resulting from the linkage of the W (CN) (8) to the Ni center of the Ni-Ln unit. Differences are found in the solvent molecules acting as ligands and/or in the lattice depending on the crystallization conditions. For all the compounds ferromagnetic Ni-W and Ni-Ln (Ln = Gd, Tb, Dy, and Er} interactions are operative resulting in high spin ground states. Parameterization of the magnetic behaviors for the Y and Gd derivatives confirmed the strong cyano-mediated Ni-W interaction (J (NiW) = 27. 1 and 28. 5 cm (-1) ) compared to the Ni-Gd interaction (J (NiGd) = 2. 17 cm (-1) ). The characteristic features for slow relaxation of the magnetization are observed for two Tb derivatives, but these are modulated by the crystal phase. Analysis of the frequency dependence of the alternating current susceptibility data yielded U (eff) /k (B) = 15. 3 K and tau (0) = 4. 5 x 10 (-7) s for one derivative whereas no maxima of chi (M) '' appear above 2 K for the second one.