Pedersen Anders H, Geoghegan Blaise L, Nichol Gary S, Lupton David W, Murray Keith S, Martínez-Lillo José, Gass Ian A, Brechin Euan K
EaStCHEM School of Chemistry, The University of Edinburgh, David Brewster Road, EH9 3FJ Edinburgh, Scotland, UK.
School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton BN2 4GJ, UK.
Dalton Trans. 2017 Apr 19;46(16):5250-5259. doi: 10.1039/c7dt00752c.
Eight coordination compounds of formulae [Fe(L˙)][ReCl] (1a), [Fe(L˙)][ReBr] (1b), [Co(L˙)][ReCl]·CHCN (2a), [Co(L˙)][ReBr] (2b), [Ni(L˙)(CHCN)][ReCl]·CHCN (3a), [Ni(L˙)(CHCN)][ReBr]·3CHCN (3b), [Cu(L˙)][ReCl] (4a) and [Cu(L˙)][ReBr] (4b), where L˙ is the aminoxyl radical chelating ligand, 4,4'-dimethyl-2,2'-di(2-pyridyl)oxazolidine-N-oxide, have been synthesised. Structural and magnetic studies reveal metal-radical intramolecular antiferromagnetic interactions in the [M(L˙)] cations in the iron, cobalt and copper based compounds (1a, 1b, 2a, 2b, 4a and 4b) with the central metal ion low-spin in the case of iron (1a and 1b) and a gradual, cobalt based, spin-crossover transition present in 2a and 2b. The nickel based compounds, 3a and 3b, were analysed in the dried form (3a(dried) and 3b(dried)) and directly in acetonitrile (3a(solvated) and 3b(solvated)). Microanalysis and IR spectroscopy on 3a(dried) and 3b(dried) suggest that the dried samples are best formulated as [Ni(L˙)(HO)][ReX], where X = Cl (3a(dried)) and Br (3b(dried)). All forms of 3a and 3b exhibit cationic metal-radical ferromagnetic interactions resulting in S = 3/2 ground states. In addition, 3a(dried) exhibits spin-canting behaviour with an ordering temperature of 2.7 K, an open hysteresis loop with a coercive field H = 580 Oe, and a remanent magnetisation M = 0.21μ, resulting in a canting angle of ∼1.8°. In contrast, 3b(dried) shows no spin-canting behaviour; a maximum in χvs. T at T = 3 K suggesting long-range antiferromagnetic ordering. 3a(solvated) and 3b(solvated) show no indication of long-range magnetic ordering, unlike 4a and 4b where anomalies are evident in the low-temperature magnetic susceptibility measurements.
已合成了八种通式为[Fe(L˙)][ReCl] (1a)、[Fe(L˙)][ReBr] (1b)、[Co(L˙)][ReCl]·CHCN (2a)、[Co(L˙)][ReBr] (2b)、[Ni(L˙)(CHCN)][ReCl]·CHCN (3a)、[Ni(L˙)(CHCN)][ReBr]·3CHCN (3b)、[Cu(L˙)][ReCl] (4a)和[Cu(L˙)][ReBr] (4b)的配位化合物，其中L˙为氨氧基自由基螯合配体4,4'-二甲基-2,2'-二(2-吡啶基)恶唑烷-N-氧化物。结构和磁性研究表明，在铁、钴和铜基化合物(1a、1b、2a、2b、4a和4b)的[M(L˙)]阳离子中存在金属-自由基分子内反铁磁相互作用，铁(1a和1b)情况下中心金属离子为低自旋，2a和2b中存在基于钴的逐渐自旋交叉转变。对镍基化合物3a和3b以干燥形式(3a(干燥)和3b(干燥))以及直接在乙腈中(3a(溶剂化)和3b(溶剂化))进行了分析。对3a(干燥)和3b(干燥)的微量分析和红外光谱表明，干燥样品最好配制成[Ni(L˙)(HO)][ReX]，其中X = Cl (3a(干燥))和Br (3b(干燥))。3a和3b的所有形式都表现出阳离子金属-自由基铁磁相互作用，导致基态S = 3/2。此外，3a(干燥)表现出自旋倾斜行为，有序温度为2.7 K，具有矫顽场H = 580 Oe的开放磁滞回线和剩余磁化强度M = 0.21μ，导致倾斜角约为1.8°。相比之下，3b(干燥)没有表现出自旋倾斜行为；χ对T在T = 3 K处出现最大值，表明存在长程反铁磁有序。3a(溶剂化)和3b(溶剂化)没有显示出长程磁有序的迹象，这与4a和4b不同，在4a和4b的低温磁化率测量中异常明显。
