Maiwald Martin M, Wagner Anna T, Kratsch Jochen, Skerencak-Frech Andrej, Trumm Michael, Geist Andreas, Roesky Peter W, Panak Petra J
Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg, Germany.
Dalton Trans. 2017 Aug 14;46(30):9981-9994. doi: 10.1039/c7dt01864a. Epub 2017 Jul 20.
In the present work, the complexation and extraction behaviour of 4,4'di-tert-butyl-6-(1H-tetrazol-5-yl)-2,2'-bipyridine (HNbubipy) towards trivalent actinides (An(iii)) and lanthanides (Ln(iii)) is studied by spectroscopic methods, liquid-liquid extraction, and quantum chemical calculations. The ligand synthesis of HNbubipy as well as its application in coordination chemistry of the 4f elements is described. Reaction of HNbubipy with [Ln(NO)·6HO] (Ln = Sm, Eu) results in [HNbubipy][Ln(Nbubipy)(NO)(HO)]. Both compounds have been characterized by single crystal X-ray diffraction. The solubility of the ligand in different organic solvents is determined, showing a high solubility in MeOH which decreases with the lipophilicity of the solvent. The pK = 2.4 ± 0.2 of HNbubipy in EtOH (4.4 vol% HO) is determined by absorption spectrophotometry. The complexation of Cm(iii) and Eu(iii) with HNbubipy is studied by time resolved laser fluorescence spectroscopy (TRLFS). For both metal ions the formation of the complexes [M(Nbubipy)] with n = 2, 3 (M = Cm(iii), Eu(iii)) is observed. Slightly higher conditional stability constants for Eu(iii) (log β'(Eu(Nbubipy)) = 8.9 ± 0.3, log β'(Eu(Nbubipy)) = 12.7 ± 0.5), compared to Cm(iii) (log β'(Cm(Nbubipy)) = 8.5 ± 0.4 and log β'(Cm(Nbubipy)) = 12.4 ± 0.6) are determined. Thus, the ligand has no preference for the complexation of An(iii) over Ln(iii). Additionally, no significant extraction of Am(iii) and Eu(iii) is observed in liquid-liquid extraction experiments due to protonation of the ligand at the experimental conditions. The experimental studies are supported by quantum chemical calculations of the free ligand and the [M(Nbubipy)] complexes (M = Cm(iii), Gd(iii)). The results are in excellent agreement with the experimental data and provide a deeper understanding of the complexation properties of HNbubipy.
在本工作中，通过光谱法、液 - 液萃取和量子化学计算研究了4,4'-二叔丁基 - 6-(1H - 四唑 - 5 - 基)-2,2'-联吡啶（HNbubipy）对三价锕系元素（An(iii)）和镧系元素（Ln(iii)）的络合及萃取行为。描述了HNbubipy的配体合成及其在4f元素配位化学中的应用。HNbubipy与[Ln(NO₃)₃·6H₂O]（Ln = Sm、Eu）反应生成[HNbubipy][Ln(Nbubipy)(NO₃)(H₂O)]。两种化合物均通过单晶X射线衍射进行了表征。测定了配体在不同有机溶剂中的溶解度，结果表明其在甲醇中的溶解度较高，且随溶剂亲脂性的增加而降低。通过吸收分光光度法测定了HNbubipy在乙醇（4.4 vol% H₂O）中的pKₐ = 2.4 ± 0.2。通过时间分辨激光荧光光谱法（TRLFS）研究了Cm(iii)和Eu(iii)与HNbubipy的络合情况。对于这两种金属离子，均观察到形成了n = 2、3的[M(Nbubipy)ₙ]络合物（M = Cm(iii)、Eu(iii)）。与Cm(iii)（log β'(Cm(Nbubipy)₂) = 8.5 ± 0.4，log β'(Cm(Nbubipy)₃) = 12.4 ± 0.6）相比，Eu(iii)的条件稳定常数略高（log β'(Eu(Nbubipy)₂) = 8.9 ± 0.3，log β'(Eu(Nbubipy)₃) = 12.7 ± 0.5）。因此，该配体对An(iii)的络合并不优先于Ln(iii)。此外，在液 - 液萃取实验中，由于在实验条件下配体发生质子化，未观察到Am(iii)和Eu(iii)的显著萃取。对游离配体和[M(Nbubipy)ₙ]络合物（M = Cm(iii)、Gd(iii)）的量子化学计算支持了实验研究。结果与实验数据高度吻合，且对HNbubipy的络合性质有了更深入的理解。
