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

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• 作者：Cun Li ; Juan Sun ; Meng Yang ; Guifang Sun ; Jianni Guo ; Yue Ma ; Licun Li
• 刊名：Crystal Growth & Design
• 出版年：2016
• 出版时间：December 7, 2016
• 年：2016
• 卷：16
• 期：12
• 页码：7155-7162
• 全文大小：518K
• ISSN：1528-7505

文摘

By reacting nitronyl nirtroxide radical NIT-Ph2OEt (NIT-Ph2OEt = 2-(2′-ethoxyphenyl)-4,4,5,5-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)]_n (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.