[Fe(bpym)(CN)4]-: A New Building Block for Designing Single-Chain Magnets

详细信息    查看全文

• 作者：Luminita Marilena Toma ; Rodrigue Lescouë ; zec ; Jorge Pas&aacute ; n ; Catalina Ruiz-Pé ; rez ; Jacqueline Vaissermann ; Joan Cano ; Rosa Carrasco ; Wolfgang Wernsdorfer ; Francesc Lloret ; and Miguel Ju
• 刊名：Journal of the American Chemical Society
• 出版年：2006
• 出版时间：April 12, 2006
• 年：2006
• 卷：128
• 期：14
• 页码：4842 - 4853
• 全文大小：450K
• 年卷期：v.128,no.14(April 12, 2006)
• ISSN：1520-5126

文摘

We herein present the preparation, crystal structure, magnetic properties, and theoretical studyof new heterobimetallic chains of formula {[Fe^III(bpym)(CN₄)]₂M^II(H₂O)₂}·6H₂O [bpym = 2,2'-bipyrimidine;M = Zn (2), Co (3), Cu (4), and Mn (5)] which are obtained by using the building block PPh₄[Fe(bpym)(CN)₄]·H₂O (1) (PPh₄⁺ = tetraphenylphosphonium) as a ligand toward the fully solvated M^II ions. Thestructure of complex 1 contains mononuclear [Fe(bpym)(CN)₄]^- anions. Compounds 2-5 are isostructural4,2-ribbonlike bimetallic chains where the [Fe(bpym)(CN)₄]^- unit acts as a bis-monodenate ligand throughtwo of its four cyanide ligands toward the M atom. Water hexamer clusters (4) and regular alternatingfused six- and four-membered water rings with two dangling water molecules (2, 3, and 5) are trappedbetween the cyanide-bridged 4,2-ribbonlike chains. 1 and 2 behave as magnetically isolated low-spin iron(III)centers. 3 behaves as a single-chain magnet (SCM) with intrachain ferromagnetic coupling, slow magneticrelaxation, hysteresis effects, and frequency-dependent ac signals at T < 7 K). As expected for a thermallyactivated process, the nucleation field (H_n) in 3 increases with decreasing T and increasing v. Below 1.0K, H_n becomes temperature independent but remains strongly sweep rate dependent. In this temperaturerange, the reversal of the magnetization may be induced by a quantum nucleation of a domain wall thatthen propagates due to the applied field. 4 and 5 are ferro- and ferrimagnetic chains respectively, withmetamagnetic-like behavior (4). DFT-type calculations and QMC methodology provided a good understanding of the magnetic properties of 3-5.