Hexanuclear and Heptanuclear Nickel(II) Complexes of with a Non-Schiff-Base Tetradentate Ligand: an Example of Slow Motion Ferromagnetic Phase Transition at Very Low Temperature

Hexanuclear and heptanuclear nickel(II) complexes with N , N′ -bis(2-hydroxy-3,5-dimethylbenzyl-1,2-ethanediamine (H 2 hdde), [Ni 6 (hdde) 3 (OH) 4 (NO 3 ) 2 (H 2 O) 2 ]·2dmf (dmf = N , N -dimethylformamide) and [Ni 7 (hdde) 3 (OH) 6 (dmac) 3 ](ClO 4 ) 2 (dmac = N , N -dimethylacetamide), were investigated. The latter complex was newly synthesized and the single-crystal X-ray structure analysis revealed a wheel-shaped heptanuclear cluster. These complexes showed a ferromagnetic interaction in the temperature dependence of magnetic susceptibilities. The micro-SQUID data of the former complex did not show SMM property, whereas the AC susceptibility measurements suggested SMM-like behavior and the zero-field-cooled and field-cooled studies showed a ferromagnetic transition near 240 mK for the latter complex.