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Title: Enhanced Vapor-Phase Processing in Fluorinated Fe4 Single-Molecule Magnets
Authors: Rigamonti, L.
Piccioli, M.
Malavolti, L.
Poggini, L.
Mannini, M.
Totti, F.
Cortigiani, B.
Magnani, Agnese 
Sessoli, R.
Cornia, A.
Keywords: magnetism; XPS; ToF-SIMS; X-ray Crystallography; single molecule magnets
Issue Date: 2013
Project: None 
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
ISSN: 0020-1669
DOI: 10.1021/ic400037c
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