A new Ru complex with the formula [Ru(bpn)(pic)₂]Cl₂ (where bpn is 2,2′-bi(1,10-phenanthroline) and pic stands for 4-picoline) (1Cl₂) is synthesized to investigate the true nature of active species involved in the electrochemical and chemical water oxidation mediated by a class of N4 tetradentate equatorial ligands. Comprehensive electrochemical (by using cyclic voltammetry, differential pulse voltammetry, and controlled potential electrolysis), structural (X-ray diffraction analysis), spectroscopic (UV-vis, NMR, and resonance Raman), and kinetic studies are performed. 1²⁺ undergoes a substitution reaction when it is chemically (by using NaIO₄) or electrochemically oxidized to Ru^III, in which picoline is replaced by an hydroxido ligand to produce [Ru(bpn)(pic)(OH)]²⁺ (2²⁺). The former complex is in equilibrium with an oxo-bridged species {[Ru(bpn)(pic)]₂(μ-O)}⁴⁺ (3⁴⁺) which is the major form of the complex in the Ru^III oxidation state. The dimer formation is the rate determining step of the overall oxidation process (k_dimer = 1.35 M⁻¹ s⁻¹), which is in line with the electrochemical data at pH = 7 (k_dimer = 1.4 M⁻¹ s⁻¹). 3⁴⁺ can be reduced to [Ru(bpn)(pic)(OH₂)]²⁺ (4²⁺), showing a sort of square mechanism. All species generated in situ at pH 7 have been thoroughly characterized by NMR, mass spectrometry, UV-Vis and electrochemical techniques. 1²⁺ and 4²⁺ are also characterized by single crystal X-ray diffraction analysis. Chemical oxidation of 1²⁺ triggered by Ce^IV shows its capability to oxidize water to dioxygen.

中文翻译：

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基于Ru–bpn配合物的水氧化催化的复杂性的广泛观点

具有式[Ru（bpn）（pic）₂ ] Cl ₂（其中bpn是2,2​​'-bi（1,10-菲咯啉），pic代表4- picoline）的新Ru配合物（1 Cl ₂）为合成以研究涉及一类N4四齿赤道配体介导的电化学和化学水氧化的活性物质的真实性质。进行了全面的电化学（通过使用循环伏安法，微分脉冲伏安法和受控电势电解），结构化（X射线衍射分析），光谱学（UV-vis，NMR和共振拉曼光谱）以及动力学研究。1 ²⁺发生化学反应时发生取代反应（通过使用NaIO ₄）或用电化学方法将其氧化为Ru ^III，其中甲基吡啶被羟基配体取代，生成[Ru（bpn）（pic）（OH）] ²⁺（2 ²⁺）。前一个配合物与氧桥化合物{[Ru（bpn）（pic）] ₂（μ-O）} ⁴⁺（3 ⁴⁺）处于平衡状态，这是Ru ^III氧化态下配合物的主要形式。二聚体的形成是整个氧化过程的速率决定步骤（k_二聚体= 1.35 M ^-1 s ^-1），这与pH = 7时的电化学数据一致（k_二聚体= 1.4 M ^-1 s）^-1）。3 ⁴⁺可以还原为[Ru（bpn）（pic）（OH ₂）] ²⁺（ 4 ²⁺），显示出一种平方机制。已通过NMR，质谱，UV-Vis和电化学技术对在pH 7下原位产生的所有物种进行了全面表征。1 ²⁺和4 ²⁺的特征还在于单晶X射线衍射分析。Ce ^IV触发的1 ^2+的化学氧化显示了其将水氧化为双氧的能力。