Lanthanide Complexes with a Tripodal Nitroxyl Radical Showing Strong Magnetic Coupling

A series of isomorphous mononuclear complexes of Ln­(III) ions comprising one stable tripodal oxazolidine nitroxyl radical were obtained in acetonitrile media starting from nitrates. The compounds, [LnRad­(NO3)3] (Ln = Gd, Tb, Dy, Tm, Y; Rad = 4,4-dimethyl-2,2-bis­(pyridin-2-yl)-1,3-oxazolidine-3-oxyl), have a molecular structure. Their coordination polyhedron, LnO7N2, can be described as a tricapped trigonal prism with symmetry not far from D 3h . The extracted value of 23 cm–1 for the antiferromagnetic coupling of Gd–Rad established from the DC magnetic and EPR data is a record strength for the complexes of 4f elements with nitroxyl radicals. The terbium derivative displays frequency-dependent out-of-phase signals in zero field, indicating single-molecule magnetic behavior. With an applied field of 0.1 T, an effective barrier of 57 cm–1 is found.