Enhanced Vapor-Phase Processing in Fluorinated Fe4 Single-Molecule Magnets

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• 作者：Luca Rigamonti ; Marco Piccioli ; Luigi Malavolti ; Lorenzo Poggini ; Matteo Mannini ; Federico Totti ; Brunetto Cortigiani ; Agnese Magnani ; Roberta Sessoli ; Andrea Cornia
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：May 20, 2013
• 年：2013
• 卷：52
• 期：10
• 页码：5897-5905
• 全文大小：515K
• 年卷期：v.52,no.10(May 20, 2013)
• ISSN：1520-510X

文摘

A new tetrairon(III) single-molecule magnet with enhanced volatility and processability was obtained by partial fluorination of the ancillary 尾-diketonato ligands. Fluorinated proligand Hpta = pivaloyltrifluoroacetone was used to assemble the bis(alkoxido)-bridged dimer [Fe₂(OEt)₂(pta)₄] (1) in crystalline form, from which the new tetranuclear complex [Fe₄(L)₂(pta)₆] (2) was synthesized in a one-pot reaction with H₃L = 2-hydroxymethyl-2-phenylpropane-1,3-diol, NaOEt, and FeCl₃ in a Et₂O:EtOH solvent mixture. The structure of compound 2 was inferred from ¹H NMR, mass spectrometry, magnetic measurements, and DFT calculations. Direct current magnetic data are consistent with the expected metal-centered triangular topology for the iron(III) ions, with an antiferromagnetic coupling constant J = 16.20(6) cm^鈥? between the central iron and the peripheral ones and consequent stabilization of an S = 5 spin ground state. Alternating current (ac) susceptibility measurements in 0 and 1 kOe static applied fields show the presence of a thermally activated process for magnetic relaxation, with 蟿₀ = 2.3(1) 10^鈥? s and U_eff/k_B = 9.9(1) K at zero static field and 蟿₀ = 2.0(2) 10^鈥? s and U_eff/k_B = 13.0(2) K at 1 kOe. At a pressure of 10^鈥? mbar, compound 2 sublimates at (440 卤 5) K vs (500 卤 10) K for the nonfluorinated variant [Fe₄(L)₂(dpm)₆] (Hdpm = dipivaloylmethane). According to XPS, ToF-SIMS, and ac susceptibility studies, the chemical composition, fragmentation pattern, and slow magnetic relaxation of the pristine material are retained in sublimated samples, suggesting that the molecular structure remains totally unaffected upon vapor-phase processing.