Slow magnetic relaxation in Dy 2 and Dy 4 complexes of a versatile, trifunctional polydentate N,O-ligand

A tridentate ligand L H 3 (C 11 H 13 N 3 O 4 ) comprising o -vanillin, hydrazone and oxime donor groups has been employed to prepare a new class of di- and tetranuclear Ln III complexes. The reaction of L H 3 with Ln(NO 3 ) 3 · x H 2 O in the presence of a suitable base yields the dinuclear Dy III complex [Dy 2 ( L H 2 ) 4 (CH 3 OH)][NO 3 ] 2 ( 1 ) and the tetranuclear complexes [Dy 4 ( L H) 4 ( L H 2 ) 2 (OH) 2 ]·2H 2 O ( 2 ) and [Gd 4 ( L H) 4 ( L H 2 ) 2 (OMe) 2 ]· n H 2 O, ( 3 ). In these complexes, L H 3 is either monodeprotonated ( 1 ) or a mixture of mono- and doubly-deprotonated ligands ( 2 and 3 ) binding lanthanide ions via N diazine , O hydrazone , and O vanillin donors, while the remaining vacant coordination sites are occupied by O MeOH ( 1 ), O hydroxide ( 2 ) and methoxides ( 3 ). DC magnetic susceptibility studies on the isotropic tetranuclear Gd III complex ( 3 ) reveal weak antiferromagnetic exchange interactions between the Ln III ions. AC studies reveal that the dinuclear complex ( 1 ) exhibits field-induced slow relaxation of magnetization with U eff = 43.4 K, whereas 2 is a single molecule magnet, exhibiting slow relaxation of magnetization under zero field below 18 K, which is modelled using a combination of Orbach ( U eff / k B = 26.7 K) and Raman relaxation processes.