6-(tetrazol-5-yl)-2,2′-bipyridine: a highly selective ligand for the separation of lanthanides(III) and actinides(III)
The coordination structure in the solid state and solution complexation behavior of 6-(tetrazol-5-yl)-2,2′-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(...
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| Main Authors: | , , , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
[2014]
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| In: |
Inorganic chemistry
Year: 2014, Volume: 53, Issue: 17, Pages: 8949-8958 |
| ISSN: | 1520-510X |
| DOI: | 10.1021/ic5007549 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1021/ic5007549
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| Author Notes: | Jochen Kratsch, Björn B. Beele, Carsten Koke, Melissa A. Denecke, Andreas Geist, Petra J. Panak, and Peter W. Roesky |
| Summary: | The coordination structure in the solid state and solution complexation behavior of 6-(tetrazol-5-yl)-2,2′-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 β3[Cm(N4bipy)3] = 13.8 and log β3[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-N4bipy complexes equate to a theoretical separation factor, SFCmIII/EuIII ≈ 500. However, the low solubility of the HN4bipy ligand in nonpolar solvents typically used in actinide-lanthanide liquid-liquid extractions prevents its use as a partitioning extractant until a more lipophilic HN4bipy-type ligand is developed. |
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| Item Description: | Gesehen am 10.09.2020 |
| Physical Description: | Online Resource |
| ISSN: | 1520-510X |
| DOI: | 10.1021/ic5007549 |