Tetranuclear Hetero-Metal [CoII2LnIII2] (Ln = Gd, Tb, Dy, Ho, La) Complexes Involving Carboxylato Bridges in a Rare μ4–η2:η2
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- 作者：Sk Md Towsif Abtab ; Mithun Chandra Majee ; Manoranjan Maity ; Ján Titi? ; Roman Bo?a ; Muktimoy Chaudhury
- 刊名：Inorganic Chemistry
- 出版年：2014
- 出版时间：February 3, 2014
- 年：2014
- 卷：53
- 期：3
- 页码：1295-1306
- 全文大小：743K
- ISSN：1520-510X
文摘
A new family of 3d鈥?f heterometal 2 脳 2 complexes [CoII2(L)2(PhCOO)2LnIII2(hfac)4] (1鈥?b>5) (Ln = Gd (compound 1), Tb (compound 2), Dy (compound 3), Ho (compound 4), and La (compound 5)) have been synthesized in moderate yields (48鈥?3%) following a single-pot protocol using stoichiometric amounts (1:1 mol ratio) of [CoII(H2L)(PhCOO)2] (H2L = N,N鈥?dimethyl-N,N鈥?bis(2-hydroxy-3,5-dimethylbenzyl)ethylenediamine) as a metalloligand and [LnIII(hfac)3(H2O)2] (Hhfac = hexafluoroacetylacetone) as a lanthanide precursor compound. Also reported with this series is the Zn鈥揇y analog [ZnII2(L)2(PhCOO)2DyIII2(hfac)4] 6 to help us in understanding the magnetic properties of these compounds. The compounds 1鈥?b>6 are isostructural. Both hexafluoroacetylacetonate and benzoate play crucial roles in these structures as coligands in generating a tetranuclear core of high thermodynamic stability through a self-assembly process. The metal centers are arranged alternately at the four corners of this rhombic core, and the carboxylato oxygen atoms of each benzoate moiety bind all of the four metal centers of this core in a rare 渭4鈥撐?sup>2:畏2 bridging mode as confirmed by X-ray crystallography. The magnetic susceptibility and magnetization data confirm a paramagnetic behavior, and no remnant magnetization exists in any of these compounds at vanishing magnetic field. The metal centers are coupled in an antiferromagnetic manner in these compounds. The [CoII2DyIII2] compound exhibits a slow magnetic relaxation below 6 K, as proven by the AC susceptibility measurements; the activation energy reads U/kB = 8.8 K (蟿0 = 2.0 脳 10鈥? s) at BDC = 0, and U/kB = 7.8 K (蟿0 = 3.9 脳 10鈥? s) at BDC = 0.1 T. The [ZnII2DyIII2] compound also behaves as a single-molecule magnet with U/kB = 47.9 K and 蟿0 = 2.75 脳 10鈥? s.