From Monomeric Species to One-Dimensional Chain: Enhancing Slow Magnetic Relaxation through Coupling Mononuclear Fragments in Ln-rad System

By reacting nitronyl nirtroxide radical NIT-Ph2OEt (NIT-Ph2OEt = 2-(2'-ethoxyphenyl)-4,4,5,S-tetramethylimidazoline-1-oxyl-3-oxide) with Ln(hfac)(3)(hfac = hexafluoroacetylacetonate), four new Ln-nitronyl nitroxide complexes, namely, mononuclear species [Ln(hfac)(3)(NIT-Ph2OEt)(2)](Ln(III) = Gd 1a, Tb 1b) and one-dimensional chains [Ln(hfac)(3)(NIT-Ph2OEt)] (Ln(III) = Gd 2a, Tb 2b), have been successfully obtained through controlling the reaction temperature and the ratio of radical ligand and Ln(hfac)(3). DC magnetic susceptibilities indicate that the ferromagnetic couplings occur between the coordination radicals and the Ln(III) ions for four complexes. No nonzero out-of-phase signals are observed for mononuclear segment 1b, whereas the corresponding 1D chain 2b exhibits frequency-dependent out-of-phase signals indicating single-chain magnet behavior, which implies that the intrachain next-nearest-neighbor (NNN) Ln-Ln magnetic interactions play a crucial role for enhancing slow magnetic relaxation in the chain. Moreover, Tb chain exhibits rare three-step field-induced metamagnetic behavior.