Syntheses, crystal structures, and magnetic properties of cyclic dimer Ln2L2 complexes constructed from (3-pyridinylmethoxy)phenyl-substituted nitronyl nitroxide ligands

Abstract

Herein, five lanthanide-radical cyclic dimer complexes [Ln(hfac)₃(NIT-3PyPh)]₂ derived from (3-pyridinylmethoxy)phenyl-substituted nitronyl nitroxide ligands, 2-(4-(3-pyridinylmethoxy)phenyl)-4,4,5,5-tetramethyl-imidazolyl-1-oxyl-3-oxide (NIT-3PyPh), and Ln(hfac)₃ (Ln^III = Gd (1), Tb (2), Dy (3), Ho (4), and Er (5); hfac = hexafluoroacetylacetonato), were synthesized as well as structurally and magnetically characterized. The single-crystal structures show that these complexes are isostructural, in which the NIT-3PyPh molecule acts as a bridging ligand linking two Ln^III ions through the oxygen atom of the N–O group and nitrogen atom from the pyridine ring to form a four-spin system. Tb and Dy complexes exhibit a frequency-dependence of ac magnetic susceptibilities, slowing the relaxation of the magnetization.