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(NO)] (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, LnON, can be described as a tricapped trigonal prism with symmetry not far from . The extracted value of 23 cm 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 is found.
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