In this work, we describe the synthesis, structural characterization, and redox properties of two new Ru complexes containing the dianionic potentially pentadentate [2,2′:6′,2″-terpyridine]-6,6″-dicarboxylate (tda^2–) ligand that coordinates Ru at the equatorial plane and with additional pyridine or dmso acting as monondentate ligand in the axial positions: [Ru^II(tda-κ-N³O)(py)(dmso)], 1^II and [Ru^III(tda-κ-N³O²)(py)(H₂O)^ax]⁺, 2^III(H₂O)⁺. Complex 1^II has been characterized by single-crystal XRD in the solid state and in solution by NMR spectroscopy. The redox properties of 1^II and 2^III(H₂O)⁺ have been thoroughly investigated by means of cyclic voltammetry and differential pulse voltammetry. Complex 2^II(H₂O) displays poor catalytic activity with regard to the oxidation of water to dioxygen, and its properties have been analyzed on the basis of foot of the wave analysis and catalytic Tafel plots. The activity of 2^II(H₂O) has been compared with related water oxidation catalysts (WOCs) previously described in the literature. Despite its moderate activity, 2^II(H₂O) constitutes the cornerstone that has triggered the rationalization of the different factors that govern overpotentials as well as efficiencies in molecular WOCs. The present work uncovers the interplay between different parameters, namely, coordination number, number of anionic groups bonded to the first-coordination sphere of the metal center, water oxidation catalysis overpotential, pK_a and hydrogen bonding, and the performance of a given WOC. It thus establishes the basic principles for the design of efficient WOCs operating at low overpotentials.

中文翻译：

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七配位Ru水氧化催化剂中的氢键作用可缓解过高的电势

在这项工作中，我们描述了两种新的Ru络合物的合成，结构表征和氧化还原特性，这些络合物含有潜在的五齿双阴离子[2,2'：6'，2”-三吡啶] -6,6”-二羧酸（tda ^2–）配体在赤道平面处，并用另外的吡啶或DMSO中的轴向位置作为monondentate配体坐标茹：的[Ru ^II（TDA-κ-N ³ O）（吡啶）（DMSO）〕，1 ^II和的[Ru ^III（TDA-κ-N ³ ö ²）（PY）（H ₂ O）^斧] ⁺，2 ^III（H ₂ O）⁺。复杂的1个^II通过NMR和固相XRD表征固态和溶液中的单晶XRD。通过循环伏安法和差分脉冲伏安法已彻底研究了1 ^II和2 ^III（H ₂ O）⁺的氧化还原特性。络合物2 ^II（H ₂ O）在水氧化成双氧方面显示出较差的催化活性，并且已根据波动分析和催化Tafel图对其性质进行了分析。2 ^II（H ₂ O）的活性已将其与先前在文献中描述的相关水氧化催化剂（WOC）进行了比较。尽管其活性中等，但2 ^II（H ₂ O）构成了基石，触发了控制过电位以及分子WOC效率的不同因素的合理化。本工作揭示了不同参数之间的相互作用，即配位数，与金属中心第一配位球键合的阴离子基团数，水氧化催化超电势，p K _a和氢键以及给定WOC的性能。 。因此，它建立了设计低过电势的有效WOC的基本原理。