Antunes Maria A, Coutinho Joana T, Santos Isabel C, Marçalo Joaquim, Almeida Manuel, Baldoví José J, Pereira Laura C J, Gaita-Ariño Alejandro, Coronado Eugenio
C2TN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, 2695-066 Bobadela LRS (Portugal).
Instituto de Ciencia Molecular, Universitat de València, C/Catedrático José Beltrán 2, 46980 Paterna (Spain).
Chemistry. 2015 Dec 1;21(49):17817-26. doi: 10.1002/chem.201503133. Epub 2015 Nov 5.
A tetravalent uranium compound with a radical azobenzene ligand, namely, [{(SiMe2 NPh)3 -tacn}U(IV) (η(2) -N2 Ph2 (.) )] (2), was obtained by one-electron reduction of azobenzene by the trivalent uranium compound [U(III) {(SiMe2 NPh)3 -tacn}] (1). Compound 2 was characterized by single-crystal X-ray diffraction and (1) H NMR, IR, and UV/Vis/NIR spectroscopy. The magnetic properties of 2 and precursor 1 were studied by static magnetization and ac susceptibility measurements, which for the former revealed single-molecule magnet behaviour for the first time in a mononuclear U(IV) compound, whereas trivalent uranium compound 1 does not exhibit slow relaxation of the magnetization at low temperatures. A first approximation to the magnetic behaviour of these compounds was attempted by combining an effective electrostatic model with a phenomenological approach using the full single-ion Hamiltonian.
通过三价铀化合物[U(III){(SiMe2NPh)3 - tacn}] (1)对偶氮苯进行单电子还原，得到了一种带有偶氮苯自由基配体的四价铀化合物，即[{(SiMe2NPh)3 - tacn}U(IV)(η(2)-N2Ph2(.) )] (2)。化合物2通过单晶X射线衍射以及(1)H NMR、IR和UV/Vis/NIR光谱进行了表征。通过静态磁化和交流磁化率测量研究了2及其前体1的磁性，结果表明，对于前者，在单核U(IV)化合物中首次揭示了单分子磁体行为，而三价铀化合物1在低温下未表现出磁化强度的缓慢弛豫。通过将有效的静电模型与使用完整单离子哈密顿量的唯象方法相结合，尝试对这些化合物的磁行为进行初步近似。
