Lanthanide–radical complexes derived from a nitronyl nitroxide ligand with chelating and bridging functions: structure and magnetic properties

Abstract

The reaction of the NIT-2Py-3Py nitronyl nitroxide radical (NIT-2Py-3Py: 2-(2′,3′-bipyridine)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) containing two additional pyridine units with Ln(hfac)₃·2H₂O (hfac: hexafluoroacetylacetonate) gave rise to two one-dimensional chains [Ln(hfac)₃(NIT-2Py-3Py)]_n (Ln = Gd^III1, Nd^III2) and a trinuclear complex [Dy₃(hfac)₉(NIT-2Py-3Py)₂] (3). In complexes 1 and 2, the NIT-2Py-3Py radicals are ligated to the Ln^III ions in a “head-to-tail” mode to form zigzag chains. Complex 3 exhibits a linear trinuclear structure composed of one Dy(hfac)₃ with two coordinated pyridine groups and two {Dy^III–NIT radical} chelating units. Magnetic measurements indicate that the trinuclear Dy derivative shows magnetic relaxation characteristics, featuring an energy barrier of reversal of magnetization U_eff/k_B of 22.9 K.