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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Hexahalorhenate(IV) salts of metal oxazolidine nitroxides
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Hexahalorhenate(IV) salts of metal oxazolidine nitroxides

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摘要

Eight coordination compounds of formulae Fe-II(L-center dot)(2)(ReCl6)-Cl-IV (1a), Fe-II(L-center dot)(2)(ReBr6)-Br-IV (1b), Co-II(L-center dot)(2)(ReCl6)-Cl-IV .CH3CN (2a), Co-II(L-center dot)(2)(ReBr6)-Br-IV (2b), Ni-II(L-center dot)(CH3CN)(3)(ReCl6)-Cl-IV .CH3CN (3a), Ni-II(L-center dot) (CH3CN)(3)(ReBr6)-Br-IV.3CH(3)CN (3b), Cu-II(L-center dot)(2)(ReCl6)-Cl-IV (4a) and Cu-II(L-center dot) 2(ReBr6)-Br-IV (4b), where L-center dot 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-II(L-center dot)(2)(2+) 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 NiII(L-center dot) (H2O)(3)(ReX6)-X-IV, 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 spincanting behaviour with an ordering temperature of 2.7 K, an open hysteresis loop with a coercive field H-c = 580 Oe, and a remanent magnetisation M-r = 0.21 mu B, resulting in a canting angle of similar to 1.8 degrees. In contrast, 3b(dried) shows no spin-canting behaviour; a maximum in chi(M) vs. 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.

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