[(Cu-Radical)₂‑Ln]: Structure and Magnetic Properties of a Hetero-tri-spin Chain of Rings (Ln = Y^III, Gd^III, Tb^III, Dy^III)

Novel hetero-tri-spin coordination polymers formed of ring-shaped Cu-nitronyl nitroxide spin clusters and Ln^III linkers are reported. These mixed 2p-3d-4f compounds of formula {[Ln­(hfac)₃]­[Cu­(hfac)₂(NIT-3Py)]₂·C₆H₁₄}_<i>n</i> [Ln^III = Y (<b>1</b>), Gd (<b>2</b>), Tb (<b>3</b>), and Dy (<b>4</b>); NIT-3Py = 2-(3-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; hfac = hexa-fluoroacetylacetonate], exhibit a 1D chain structure consisting of [Cu­(NIT-3Py)]₂ rings linked by Ln­(hfac)₃ units. Their magnetic behavior is characteristic for ferromagnetic interactions between the metal centers and the coordinated radical units. The Tb derivative was found to exhibit slow relaxation of its magnetization