Condensation of a Nickel Tetranuclear Cubane into a Heptanuclear Single-Molecule Magnet

详细信息    查看全文

• 作者：Sarah Petit ; Petr Neugebauer ; Guillaume Pilet ; Guillaume Chastanet ; Anne-Laure Barra ; Arlei B. Antunes ; Wolfgang Wernsdorfer ; Dominique Luneau
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：June 18, 2012
• 年：2012
• 卷：51
• 期：12
• 页码：6645-6654
• 全文大小：470K
• 年卷期：v.51,no.12(June 18, 2012)
• ISSN：1520-510X

文摘

A tetranuclear complex, [Ni₄], with a cubane-like structure synthesized from hexafluoroacetylacetone gives, after drying at high temperature and treatment with pyridine, a heptanuclear nickel(II) complex, [Ni₇]. The crystal structures of both compounds have been determined by single-crystal X-ray diffraction. Their magnetic properties have been studied by SQUID and 渭-SQUID magnetometry as well as by high-frequency EPR spectroscopy (HF-EPR). For [Ni₄], the temperature dependence of the magnetic susceptibility can be fitted by taking into account strong Ni路路路Ni ferromagnetic interactions which lead to an S = 4 ground-state spin, in good agreement with the HF-EPR study. For [Ni₇], the temperature dependence of the magnetic susceptibility shows that the Ni路路路Ni ferromagnetic interactions are kept within the metal core. However, it was not possible to fit this with a clear set of parameters, and the ground-state spin was undetermined. The field dependence of the magnetization indicates an S = 7 ground-state spin at high field. In contrast, the temperature dependence of the magnetic susceptibility indicates a ground-state spin of S = 6 or even S = 5. These results agree with complicated high-frequency EPR spectra which have been ascribed to the superposition of signals from the ground spin multiplet and from an excited spin multiplet very close in energy, with the excited state having a larger S value than the ground state. Very low temperature studies show that only the heptanuclear complex behaves as a single-molecule magnet.