Three Novel Rare-earth Complexes with Nitronyl Nitroxide Radical [RE(hfac)3 (NITPhOCH3)2] [RE = GdIII, YIII and ErIII]: Syntheses, Crystal Structures and Magnetic Properties

Three novel isomorphous complexes of formula RE(hfac)₃(NITPhOCH₃)₂], where RE = Gd^III, Y^III and Er^III; hfac = hexafluoroacetylacetonate; NITPhOCH₃ = 4′-methoxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, were synthesized, structurally and magnetically characterized. The crystal structure consists of isolated molecules where the nitronyl nitroxide radicals act as monodentate ligands towards RE(III) through the oxygen atom of the N–O group. The magnetic properties of the complexes were studied by measuring their magnetic susceptibilities at various temperatures in the 5–300 K range. The analyses of these magnetic measurements showed that the spin coupling between the gadolinium ion and the radicals in the Gd^III complex is ferromagnetic, while antiferromagnetic superexchange interaction exists between the two radicals in the Gd^III and Y^III complexes. The Er^III complex reveals an overall intramolecular antiferromagnetic exchange interaction.