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|Title:||Enhanced Vapor-Phase Processing in Fluorinated Fe4 Single-Molecule Magnets||Authors:||Rigamonti, L.
|Keywords:||magnetism; XPS; ToF-SIMS; X-ray Crystallography; single molecule magnets||Issue Date:||2013||Project:||None||Journal:||INORGANIC CHEMISTRY||Abstract:||
A new tetrairon(III) single-molecule magnetwith enhanced volatility and processability was obtained bypartial ﬂuorination of the ancillary β-diketonato ligands.Fluorinated proligand Hpta = pivaloyltriﬂuoroacetone wasused to assemble the bis(alkoxido)-bridged dimer[Fe2(OEt)2(pta)4] (1) in crystalline form, from which thenew tetranuclear complex [Fe4(L)2(pta)6] (2) was synthesizedin a one-pot reaction with H3L = 2-hydroxymethyl-2-phenylpropane-1,3-diol, NaOEt, and FeCl3 in a Et2O:EtOHsolvent mixture. The structure of compound 2 was inferredfrom 1H NMR, mass spectrometry, magnetic measurements, and DFT calculations. Direct current magnetic data are consistentwith the expected metal-centered triangular topology for the iron(III) ions, with an antiferromagnetic coupling constant J =16.20(6) cm−1 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 thermallyactivated process for magnetic relaxation, with τ0 = 2.3(1) 10−7 s and Ueff/kB = 9.9(1) K at zero static ﬁeld and τ0 = 2.0(2) 10−7 sand Ueff/kB = 13.0(2) K at 1 kOe. At a pressure of 10−7 mbar, compound 2 sublimates at (440 ± 5) K vs (500 ± 10) K for thenonﬂuorinated variant [Fe4(L)2(dpm)6] (Hdpm = dipivaloylmethane). According to XPS, ToF-SIMS, and ac susceptibilitystudies, the chemical composition, fragmentation pattern, and slow magnetic relaxation of the pristine material are retained insublimated samples, suggesting that the molecular structure remains totally unaﬀected upon vapor-phase processing
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