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.
Inorg Chem. 2013 May 20;52(10):5897-905. doi: 10.1021/ic400037c. Epub 2013 May 9.
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.
通过部分氟化辅助β-二酮配体，得到了一种具有增强挥发性和加工性能的新型四核（III）单分子磁体。使用氟化前体 Hpta = 三氟乙酰丙酮来组装双（烷氧基）桥联二聚体[Fe2(OEt)2(pta)4]（1），从该二聚体中通过一锅反应，用 H3L = 2-羟甲基-2-苯基-1,3-丙二醇、NaOEt 和 FeCl3 在 Et2O:EtOH 溶剂混合物中合成了新的四核配合物[Fe4(L)2(pta)6]（2）。通过（1）H NMR、质谱、磁性测量和 DFT 计算推断出化合物 2 的结构。直流磁数据与铁（III）离子的预期金属中心三角形拓扑结构一致，中央铁与外围铁之间的反铁磁耦合常数 J = 16.20(6)cm(-1)，导致 S = 5 自旋基态稳定。在 0 和 1 kOe 静态外加磁场中的交流（ac）磁化率测量显示存在磁弛豫的热激活过程，在零静态场下 τ0 = 2.3(1)10(-7)s 和 U(eff)/kB = 9.9(1)K，在 1 kOe 下 τ0 = 2.0(2)10(-7)s 和 U(eff)/kB = 13.0(2)K。在 10(-7)mbar 的压力下，化合物 2 在（440 ± 5）K 升华，而非氟化变体[Fe4(L)2(dpm)6]（Hdpm = 二（异丙基）甲酮）在（500 ± 10）K 升华。根据 XPS、ToF-SIMS 和 ac 磁化率研究，升华样品保留了原始材料的化学组成、碎裂模式和缓慢的磁弛豫，表明在气相处理过程中分子结构完全没有受到影响。
