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A family of rare earth complexes with chelating furan biradicals: syntheses, structures and magnetic properties

机译:带有螯合呋喃双基的稀土配合物:合成,结构和磁性

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The combination of anisotropic Ln(III) ions and the furan biradical results in six complexes, namely, [Ln(hfac)(3)(NITFumbis)](2) (Ln = La(1), Ce(2), Pr(3), Gd(4), Tb(5), Dy(6); hfac = hexafluoroacetylacetone; NITFumbis = (2,5-bis-(1'-oxyl-3'-oxido-4',4',5',5'-tetramethyl-4,5-hydro-1H-imidazol-2-yl)furan). Compounds 1-3 are isostructural and crystallize in the P (1) over bar space group, while compounds 4-6 crystallize in the P2(1)/c space group. For all the six complexes, the coordination number around the lanthanide ion is eight, and the polyhedron is in a distorted 4,4-bicappped trigonal prism or triangular dodecahedron coordination geometry (D-2d or C-2v symmetry) finished by three bischelate hfac(-) ligands and one bidentate radical ligand. DC magnetic studies show that the Ln(III) ions interact antiferromagnetically with the directly bonding nitronyl nitroxide radicals in all the six complexes. Especially, for complex 4, an intramolecular antiferromagnetic interaction between the two radicals is observed with the largest J (J(Rad-Rad) = -24.89 cm(-1)) ever reported in Ln(III)-radical systems, and at low temperature, intermolecular ferromagnetic interaction also plays an important role. In addition, complex 6 exhibits field-induced single-molecule magnet (SMM) behavior.
机译:各向异性Ln(III)离子与呋喃双自由基的结合产生了六个络合物,即[Ln(hfac)(3)(NITFumbis)](2)(Ln = La(1),Ce(2),Pr( 3),Gd(4),Tb(5),Dy(6); hfac =六氟乙酰丙酮; NITFumbis =(2,5-bis-(1'-oxyl-3'-oxido-4',4',5' ,5'-四甲基-4,5-氢-1H-咪唑-2-基呋喃)。化合物1-3是同构结构,在P(1)上方的空间上结晶,而化合物4-6在P2(1)/ c空间群,对于所有六个配合物,镧系离子周围的配位数为8,多面体为扭曲的4,4-bicapped三角棱镜或三角形十二面体配位几何体(D-2d或C -2v对称)由三个双螯合物hfac(-)配体和一个双齿自由基配体完成。直流磁研究表明,Ln(III)离子与所有六个配合物中的直接键合的硝酰基亚硝基自由基发生反铁磁性相互作用,尤其是对于配合物4分子之间的分子内反铁磁相互作用在Ln(III)自由基系统中观察到最大的J(J(Rad-Rad)= -24.89 cm(-1))两个自由基,并且在低温下,分子间铁磁相互作用也起着重要作用。此外,配合物6表现出场致单分子磁体(SMM)行为。

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