Crystal structure, magnetic properties and luminescent behavior of four mononuclear lanthanide-radical complexes

Abstract

Four mononuclear lanthanide complexes based on a long nitronly nitroxide radical NIT-PhOPyrim, [Ln(hfac)3(NIT-PhOPyrim)(H2O)] (Ln(Ⅲ) = Gd 1, Tb 2, Dy 3, Er4; hfac = hexafluoroacetylacetonate; NIT-PhOPyrim = 2-[4-(pyrimidin-2-yloxy)phenyl]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) have been synthesized and characterized. Single crystal X-ray diffraction analyses revealed that these four complexes are isomorphic in which each Ln(Ⅲ) ion is eight-coordinated by six oxygen atoms from three hfac ligands, one oxygen atom from one water molecule and one oxygen atom from the NO group of NIT-PhOPyrim ligand. Particularly, the coordinated water molecules were connected other mononuclear units through their hydrogen bonds into tetra-nuclear complexes and/or dimers. Variable temperature magnetization of complex 1 was shown the ferromagnetic interaction between Gd(III) ion and nitroxide radical, while weak intermolecular antiferromagnetic interactions through hydrogen bonds. Alternating-current (ac) magnetic susceptibility of complexes 2–4 revealed no magnetic relaxation behavior. Furthermore, Tb complex can detect Fe3+anion with a high sensitivity and selectivity through the fluorescence quenching effect.