Rhombus-Shaped Tetranuclear [Ln4] Complexes [Ln = Dy(III) and Ho(III)]: Synthesis, Structure, and SMM Behavior

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• 作者：Vadapalli Chandrasekhar ; Sakiat Hossain ; Sourav Das ; Sourav Biswas ; Jean-Pascal Sutter
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：June 3, 2013
• 年：2013
• 卷：52
• 期：11
• 页码：6346-6353
• 全文大小：385K
• 年卷期：v.52,no.11(June 3, 2013)
• ISSN：1520-510X

文摘

The reaction of a new hexadentate Schiff base hydrazide ligand (LH₃) with rare earth(III) chloride salts in the presence of triethylamine as the base afforded two planar tetranuclear neutral complexes: [{(LH)₂Dy₄}(渭₂-O)₄](H₂O)₈路2CH₃OH路8H₂O (1) and [{(LH)₂Ho₄}(渭₂-O)₄](H₂O)₈路6CH₃OH路4H₂O (2). These neutral complexes possess a structure in which all of the lanthanide ions and the donor atoms of the ligand remain in a perfect plane. Each doubly deprotonated ligand holds two Ln(III) ions in its two distinct chelating coordination pockets to form [LH(Ln)₂]⁴⁺ units. Two such units are connected by four [渭₂-O]^{2鈥?/sup> ligands to form a planar tetranuclear assembly with an Ln(III)₄ core that possesses a rhombus-shaped structure. Detailed static and dynamic magnetic analysis of 1 and 2 revealed single-molecule magnet (SMM) behavior for complex 1. A peculiar feature of the 蠂_M鈥?versus temperature curve is that two peaks that are frequency-dependent are revealed, indicating the occurrence of two relaxation processes that lead to two energy barriers (16.8 and 54.2 K) and time constants (蟿₀ = 1.4 脳 10鈥? s, 蟿₀ = 7.2 脳 10鈥? s). This was related to the presence of two distinct geometrical sites for Dy(III) in complex 1.}