Slow magnetic relaxation of Ln(III)-nitronyl nitroxide radical complexes with shortest non-covalent O⋯O contacts

Abstract

Abstract Two new complexes, Ln(hfac)3(NITPhOA)2 (Ln\u202f=\u202fTb(1), Dy(2); NITPhOA\u202f=\u202f2-(4′-amyloxyphenyl)−4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; hfac\u202f=\u202fhexafluoroacetylacetonate) have been synthesized and characterized. Single crystal X-ray diffraction analysis reveals that both complexes show mononuclear tri-spin structures. The central Ln(III) ion is eight-coordinated by three hfac anions and two NITPhOA molecules, in which the NITPhOA radical acts as monodentate ligand through the NO groups, and the Ln(III) center exhibits a dodecahedron environment. It s interesting that the mononuclear units form a pseudo-one-dimensional chain structure through intermolecular non-covalent N–O⋯O–N contacts of nitroxide groups for 1. Alternating current (ac) magnetic susceptibilities show a frequency-dependent characteristic for both 1 and 2, typical of slow relaxation of magnetization. It s the first time for a lanthanide–radical complex to form a pseudo one-dimensional structure through non-covalent O⋯O contacts.