High-nuclearity 4f-metal complexes: A {Dy9} cluster bearing N-salicylidene-o-aminophenol and exhibiting slow magnetization relaxation

The reaction of DyBr 3 with the Schiff base ligand N -salicylidene- o -aminophenol (saphH 2 ) in the presence of NEt 3 under a MeOH/MeCN solvent mixture has afforded the new nonanuclear cluster [Dy 9 (OH) 8 (saph) 8 (MeCN)(MeOH) 5 (H 2 O) 3 ]Br 3 ( 1 ) in good yield. Single-crystal X-ray diffraction studies revealed that 1 comprises a structurally unprecedented {Dy 9 (μ 3 -OH) 8 (μ 3 -OR) 2 (μ-OR) 10 } 7+ core assembled through the combined bridging action of eight μ 3 -OH − ions and the phenoxido groups of eight fully deprotonated saph 2− ligands adopting three distinct coordination modes. The metallic skeleton can be described as a central windmill-like {Dy 7 } unit decorated by two additional Dy III ions or, alternatively, as eight edge-sharing {Dy 3 (μ 3 -OH)} 8+ triangular subunits. To the best of our knowledge, such a topology has no structural precedence in homometallic 4f-metal cluster chemistry. Direct-current magnetic susceptibility measurements indicate the presence of weak antiferromagnetic interactions and magnetic anisotropy arising from the Dy III ions. Alternating-current magnetic studies reveal frequency-dependent out-of-phase signals under zero applied dc field, indicating slow relaxation of the magnetization, although efficient quantum tunnelling processes prevent the observation of well-defined maxima. The present results further demonstrate the remarkable ability of the saph 2− Schiff base ligand to facilitate the self-assembly of high-nuclearity dysprosium clusters with unusual topologies and interesting magnetic properties.