6-(Tetrazol-5-yl)-2,2鈥?bipyridine: A Highly Selective Ligand for the Separation of Lanthanides(III) and Actinides(III)
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- 作者：Jochen Kratsch ; Bj枚rn B. Beele ; Carsten Koke ; Melissa A. Denecke ; Andreas Geist ; Petra J. Panak ; Peter W. Roesky
- 刊名：Inorganic Chemistry
- 出版年：2014
- 出版时间：September 2, 2014
- 年：2014
- 卷：53
- 期：17
- 页码：8949-8958
- 全文大小：511K
- ISSN：1520-510X
文摘
The coordination structure in the solid state and solution complexation behavior of 6-(tetrazol-5-yl)-2,2鈥?bipyridine (HN4bipy) with samarium(III) was investigated as a model system for actinide(III)/lanthanide(III) separations. Two different solid 1:2 complexes, [Sm(N4bipy)2(OH)(H2O)2] (1) and [Sm(N4bipy)2(HCOO)(H2O)2] (2), were obtained from the reaction of samarium(III) nitrate with HN4bipy in isopropyl alcohol, resuspension in N,N-dimethylformamide (DMF), and slow crystallization. The formate anion coordinated to samarium in 2 is formed by decomposition of DMF to formic acid and dimethylamine. Time-resolved laser fluorescence spectroscopy (TRLFS) studies were performed with curium(III) and europium(III) by using HN4bipy as the ligand. Curium(III) is observed to form 1:2 and 1:3 complexes with increasing HN4bipy concentration; for europium(III), formation of 1:1 and 1:3 complexes is observed. Although the solid-state samarium complexes were confirmed as 1:2 species the 1:2 europium(III) solution complex in ethanol was not identified with TRLFS. The determined conditional stability constant for the 1:3 fully coordinated curium(III) complex species is more than 2 orders of magnitude higher than that for europium(III) (log 尾3[Cm(N4bipy)3] = 13.8 and log 尾3[Eu(N4bipy)3] = 11.1). The presence of added 2-bromodecanoic acid as a lipophilic anion source reduces the stability constant for formation of the 1:2 and 1:3 curium(III) complexes, but no ternary complexes were observed. The stability constants for the 1:3 metal ion鈥揘4bipy complexes equate to a theoretical separation factor, SFCmIII/EuIII 鈮?500. However, the low solubility of the HN4bipy ligand in nonpolar solvents typically used in actinide鈥搇anthanide liquid鈥搇iquid extractions prevents its use as a partitioning extractant until a more lipophilic HN4bipy-type ligand is developed.