Isolation and Characterization of a Highly Reducing Aqueous Chromium(II) Complex
Isolation and Characterization of a Highly Reducing Aqueous Chromium(II) Complex
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高还原性水性铬 (II) 配合物的分离和表征
DOI：
10.1021/acs.inorgchem.2c00699
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发表时间：
2022
影响因子：
4.6
通讯作者：
Marshak, Michael P.
中科院分区：
文献类型：
--
作者：
Waters, Scott E.;Robb, Brian H.;Scappaticci, Steven J.;Saraidaridis, James D.;Marshak, Michael P.
从水溶液中分离出高还原的CrPdTa-(1，3-丙二胺四乙酸酯)络合物(−1.1V vs Se)，并描述了它的固态结构。用单晶X射线衍射、元素分析、红外光谱、紫外可见光谱、磁矩和密度泛函理论计算对还原的CrIIPDTA络合物进行了表征。在液流电池系统中，用吸收光谱和pH探针法对CrPDTA电解液的浓度分布、荷电状态和pH进行了现场监测。CrIIPDTA在水环境中的稳定性是通过分离CaCrPDTA的能力来证明的，尽管人们普遍错误地认为水在这样的电位下会自发放氢。还原的CrIIPDTA通过保持与氧化的CrIIIPDTA相同的配位饱和的伪八面体结构来防止水与金属中心配位，尽管经历了由于高自旋CrIIion的Jahn-Teller扭曲而增加的几何应变。通过比较CrPDTA的还原物种在不同有机溶剂中的电化学行为和其在水溶液中的行为，考察了溶剂反应性和溶剂热力学窗口之间的重要区别。当在四氢呋喃中考察时，观察到CrPDTA的还原电位为−1.19V(−2.52V vs二茂铁)。在水溶液中还原的CrPDTA也暴露在大气中的O2中，没有表现出任何铬(III)或铬(II)物种的分解。详细的技术为液流电池电解液种类的表征提供了更高的标准方法。
The highly reducing CrII-(1,3-propylenediaminetetraacetate) (CrPDTA) complex (−1.1 V vs SHE) has been isolated from aqueous solution and the solid-state structure is described. The reduced CrIIPDTA complex is characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy, UV–vis spectroscopy, magnetic moment, and density functional theory calculations. The concentration profile, state of charge, and pH of CrPDTA electrolyte were monitored in a flow battery system in situ by absorption spectroscopy and a pH probe. The stability of CrIIPDTA in aqueous environments is demonstrated by the ability to isolate CaCrPDTA, despite the common misconception that water spontaneously evolves hydrogen at such potentials. The reduced CrIIPDTA prevents water from coordinating to the metal center by maintaining the same coordinatively saturated pseudo-octahedral structure as the oxidized CrIIIPDTA, despite experiencing an increased geometric strain from a Jahn–Teller distortion of the high-spin CrIIion. The important difference between solvent reactivity and solvent thermodynamic window is examined by comparing the electrochemical behavior of the reduced species of CrPDTA in various organic solvents to its behavior in aqueous solution. When examined in tetrahydrofuran (THF), the reduction potential of CrPDTA is observed to be −1.19 V vs cobaltocene (−2.52 V vs ferrocene). Reduced CrPDTA in aqueous solution is also exposed to atmospheric O2without exhibiting any decomposition of the Cr(III) or Cr(II) species. The techniques detailed provide a higher standard method of characterization for flow battery electrolyte species.