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• 作者：Takefumi Hamamatsu ; Kazuya Yabe ; Masaaki Towatari ; Shutaro Osa ; Naohide Matsumoto ; Nazzareno Re ; Andrzej Pochaba ; Jerzy Mrozinski ; Jean-Louis Gallani ; Alessandro Barla ; Paolo Imperia ; Carley Paulsen ; J
• 刊名：Inorganic Chemistry
• 出版年：2007
• 出版时间：May 28, 2007
• 年：2007
• 卷：46
• 期：11
• 页码：4458 - 4468
• 全文大小：417K
• 年卷期：v.46,no.11(May 28, 2007)
• ISSN：1520-510X

文摘

An extensive series of tetranuclear Cu^II₂Ln^III₂ complexes [Cu^IILLn^III(hfac)₂]₂ (with Ln^III being all lanthanide(III) ionsexcept for the radioactive Pm^III) has been prepared in order to investigate the nature of the Cu^II-Ln^III magneticinteractions and to try to answer the following question: What makes the Cu^II₂Tb^III₂ and Cu^II₂Dy^III₂ complexes singlemolecule magnets while the other complexes are not? All the complexes within this series possess a similar cyclictetranuclear structure, in which the Cu^II and Ln^III ions are arrayed alternately via bridges of ligand complex (Cu^IIL).Regular SQUID magnetometry measurements have been performed on the series. The temperature-dependentmagnetic susceptibilities from 2 to 300 K and the field-dependent magnetizations from 0 to 5 T at 2 K have beenmeasured for the Cu^II₂Ln^III₂ and Ni^II₂Ln^III₂ complexes, with the Ni^II₂Ln^III₂ complex containing diamagnetic Ni^II ionsbeing used as a reference for the evaluation of the Cu^II-Ln^III magnetic interactions. These measurements haverevealed that the interactions between Cu^II and Ln^III ions are very weakly antiferromagnetic if Ln = Ce, Nd, Sm,Yb, ferromagnetic if Ln = Gd, Tb, Dy, Ho, Er, Tm, and negligible if Ln = La, Eu, Pr, Lu. With the same goal ofbetter understanding the evolution of the intramolecular magnetic interactions, X-ray magnetic circular dichroism(XMCD) has also been measured on Cu^II₂Tb^III₂, Cu^II₂Dy^III₂, and Ni^II₂Tb^III₂ complexes, either at the L- and M-edgesof the metal ions or at the K-edge of the N and O atoms. Last, the Cu^II₂Tb^III₂ complex exhibiting SMM behavior hasreceived a closer examination of its low temperature magnetic properties down to 0.1 K. These particularmeasurements have revealed the unusual very slow setting-up of a 3D order below 0.6 K.