Dinuclear lanthanide complexes bridged by nitronyl nitroxide radical ligands with 2-phenolate groups: structure and magnetic properties

Three novel binuclear lanthanide-radical complexes [Ln(2)(acac)(4)(NITPhO)(2)] (Ln(III) = Gd 1, Eu 2, Dy 3; acac = acetylacetonato and NITPhOH = 2-(2'-hydroxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide) have been achieved. These compounds possess dinuclear structure in which two radical ligands link two lanthanide ions through their phenoxo-O atoms. Magnetic studies show that the Gd(III) ion interacts ferro-magnetically with the directly bonding NO group while magnetic interaction between two lanthanide ions through two phenoxo groups is antiferromagnetic. No frequency-dependent out-of-phase signals were found for the Dy complex, which shows that the ligand field around the metal center plays a crucial role in modulating the magnetic relaxation of lanthanide compounds.