title: Enhanced vapor-phase processing in fluorinated Fe4 single-molecule magnets.
abstract: A new tetrairon(III) single-molecule magnet with enhanced volatility and processability was obtained by partial fluorination of the ancillary β-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 (1)H 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(-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 thermally activated process for magnetic relaxation, with τ0 = 2.3(1) 10(-7) s and U(eff)/kB = 9.9(1) K at zero static field and τ0 = 2.0(2) 10(-7) s and U(eff)/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 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.
authors: Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Modena e Reggio Emilia & INSTM RU of Modena and Reggio Emilia, via G. Campi 183, 41125 Modena, Italy.
authors: Luca
authors: L
authors: Rigamonti
authors: Marco
authors: M
authors: Piccioli
authors: Luigi
authors: L
authors: Malavolti
authors: Lorenzo
authors: L
authors: Poggini
authors: Matteo
authors: M
authors: Mannini
authors: Federico
authors: F
authors: Totti
authors: Brunetto
authors: B
authors: Cortigiani
authors: Agnese
authors: A
authors: Magnani
authors: Roberta
authors: R
authors: Sessoli
authors: Andrea
authors: A
authors: Cornia