Series behavior of lanthanoid(III) complexes with the alpha-1-Wells-Dawson heteropolyoxoanion in acetonitrile: electrochemistry and Ln coordination.
Series behavior of lanthanoid(III) complexes with the alpha-1-Wells-Dawson heteropolyoxoanion in acetonitrile: electrochemistry and Ln coordination.
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DOI：
10.1039/c0dt00394h
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发表时间：
2010-08
影响因子：
4
通讯作者：
M. Antonio;Jing Jing-Jing;Benjamin P. Burton‐Pye;L. Francesconi
中科院分区：
文献类型：
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作者：
M. Antonio;Jing Jing-Jing;Benjamin P. Burton‐Pye;L. Francesconi
一系列镧系元素（III）的四正丁基铵（TBA（+））盐合成了（Ln = Nd，Sm，Eu，Tb，Dy，Yb，Y）与Wells-Dawson杂多阴离子α-1-异构体α-1-[P（2）W（17）O（61）]（10-）的配合物，用伏安法、控制电位电解法、EuL（3）边XANES光谱电化学、和Ln L（3）边X射线吸收光谱。详细描述了具有标称1：1 Ln（III）：alpha-1-[P（2）W（17）O（61）]（10-）化学计量比的络合阴离子在4f周期内的系列行为。单独的α-1配体在无水乙腈（含0.1 M（TBA）PF（6）电解质）中的伏安响应与浓度无关，并且非常明确地定义了五个波，这些波可归因于W基氧化还原过程。电化学还原后形成的杂多蓝溶液会导致化学不稳定和异构化。有意添加水将原本理想的响应转变为宽且分辨差的响应，其中第一还原过程向更正的电极电位偏移150 mV。在其与Ln（III）离子的协调，伏安响应开发显着的复杂性与多达10个浓度依赖性的夫妇归因于W为基础的氧化还原过程的Ln：α-1配合物。来自Eu（III）：α-1络合物的原位Eu L（3）-边缘XANES的结果没有提供Eu（III）在受控电极电位下的单电子还原的证据，所述单电子还原与先前发现的在水性电解质中还原时在相应Eu（III）络合物的钾盐中形成Eu（II）的那些单电子还原相当。为了解释这两种截然不同的体系行为，我们研究了TBA（5）H（2）[（H（2）O）（n）Ln]中的Ln（III）配位环境（α-1-P（2）W（17）O（61））]固体盐，包括溶解在乙腈中时Ln水合的程度（n），通过使用EXAFS测定，这证明了盐及其乙腈溶液之间的结构均匀性，其中平均Ln-O原子间距离和O配位数显示出与镧系收缩效应一致的变化。固体和溶液数据的并排比较提供了与在MeCN中溶解时部分溶剂（H（2）O-CH（3）CN）交换一致的证据。Ln（III）配位化学的细节，其中离子半径从大的、轻的Nd（III）到小的、重的Yb（III）的减小，在乙腈溶剂化物、水离子和相应的水溶性K（7）[（H（2）O）（4）Eu（alpha-1-P（2）W（17）O（61））]络合物的已知结构和物理现象的上下文中呈现。
The tetra-n-butylammonium (TBA(+)) salts for a series of lanthanoid(III) (Ln = Nd, Sm, Eu, Tb, Dy, Yb, and Y) complexes with the alpha-1-isomer of the Wells-Dawson heteropolyoxoanion, alpha-1-[P(2)W(17)O(61)](10-), were prepared and characterized by voltammetry, controlled-potential bulk electrolysis, Eu L(3)-edge XANES spectroelectrochemistry, and Ln L(3)-edge X-ray absorption spectroscopy. Aspects of the series behavior across the 4f period for the complex anions with nominal 1 : 1 Ln(III):alpha-1-[P(2)W(17)O(61)](10-) stoichiometries are detailed. The voltammetric response of the alpha-1 ligand alone in dry acetonitrile (with 0.1 M (TBA)PF(6) electrolyte) is concentration independent and remarkably well-defined with five waves attributable to W-based redox processes. The formation of heteropoly blue solutions upon electrochemical reduction results in chemical instabilities and isomerization. The deliberate addition of water turns an otherwise ideal response into a broad and poorly resolved one, wherein the first reduction process is shifted 150 mV to more positive electrode potentials. Upon its coordination with Ln(III) ions, the voltammetric response develops notable complexities with as many as ten concentration-dependent couples attributable to W-based redox processes of the Ln:alpha-1 complexes. The results from in situ Eu L(3)-edge XANES of the Eu(III):alpha-1 complex provide no evidence for the one-electron reduction of Eu(III) at controlled electrode potentials comparable to those that were previously found to form Eu(II) in the potassium salt of the corresponding Eu(III) complex upon reduction in an aqueous electrolyte. To explain the contrasting system behaviors, the Ln(III) coordination environments in the TBA(5)H(2)[(H(2)O)(n)Ln(alpha-1-P(2)W(17)O(61))] solid salts, including the extent of Ln hydration (n) upon their dissolution in acetonitrile, were determined through use of EXAFS, which demonstrates a structural uniformity among the salts and their acetonitrile solutions, wherein the average Ln-O interatomic distances and O coordination numbers reveal variations that are consistent with the effects of the lanthanoid contraction. The side-by-side comparison of the solid and solution data provides evidence that is consistent with a partial solvent (H(2)O-CH(3)CN) exchange upon dissolution in MeCN. Details of the Ln(III) coordination chemistry, wherein the decrease in the ionic radius from the large, light Nd(III) to the small, heavy Yb(III), are presented in the context of known structural and physical phenomena of acetonitrile solvates, aqua ions, and the corresponding water-soluble K(7)[(H(2)O)(4)Eu(alpha-1-P(2)W(17)O(61))] complex.