New Series of Dinuclear Ruthenium(II) Complexes Synthesized Using Photoisomerization for Efficient Water Oxidation Catalysis
New Series of Dinuclear Ruthenium(II) Complexes Synthesized Using Photoisomerization for Efficient Water Oxidation Catalysis
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DOI：
10.1021/acs.inorgchem.5b01264
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发表时间：
2015-08-03
影响因子：
4.6
通讯作者：
Yagi, Masayuki
中科院分区：
文献类型：
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作者：
Hirahara, Masanari;Nagai, Sho;Yagi, Masayuki
一系列新的近端近端-[Ru-2(tpy)(2)(L)XY](n+)（p,p-Ru2XY，tpy = 2,2':6',2''-三联吡啶，L = 5-苯基-2,8-二（2-吡啶基）-1,9,10-蒽啶，X和Y =其他配位位点）合成使用， 单核配合物的光致异构化。 p,p-Ru2XY 配合物经历不寻常的可逆桥交换反应，分别与 mu-Cl、mu-OH 以及 p,p-Ru2XY 的 X 和 Y 位点上的羟基和水合配体生成 p,p-Ru-2(mu-Cl)、p,p-Ru-2(mu-OH) 和 p,p-Ru-2(OH)(OH2)。这些配合物的几何和电子结构根据紫外可见光谱和 H-1 NMR 光谱、X 射线晶体学和密度泛函理论 (DFT) 计算进行了表征。 H-1 NMR数据显示p,p-Ru-2(OH)(OH2)与扭曲的L螯合物的C-2对称性和两个tpy配体的不等价性，与p,p-Ru-2(mu-Cl)和p,p-Ru-2(mu-OH)的C-2对称性相反。然而，尽管对称性较低，p,p-Ru-2(OH)(OH2) 主要在中性和弱碱性条件下形成，这是由于水合、羟基和主链 L 配体之间的多重氢键相互作用产生的特别稳定的核心结构。电化学数据表明，p,p-Ru-2(OH)(OH2) (Ru-II-OH:Ru-II-OH2) 在 0.64 V 相对饱和甘汞电极 (SCE) 下被氧化为 Ru-III-OH:Ru-III-OH 态，并在 pH 7.0 下通过连续的 1-质子耦合 2-电子过程在 0.79 V 下进一步氧化为 Ru-IV=O:Ru-IV-OH。循环伏安数据表明，与类似的单核配合物远端-[Ru(tpy)(L)OH2](2+) (d-RuOH2)和p,p-Ru-2(mu-Cl)和p,p-Ru-2(mu-OH)相比，p,p-Ru-2(OH)(OH2)配合物对电催化水氧化的效率更高，表明p,p-Ru-2核心结构具有 水合配体和羟基配体对于有效的电催化水氧化非常重要。 p,p-Ru-2(OH)(OH2) 溶液的本体电解证实了涉及静止态 Ru-III-OH:Ru-III-OH 态物质的电催化循环。通过在 H2O 和 D2O 介质中 p,p-Ru-2(OH)(OH2) 和 d-RuOH2 电催化水氧化的同位素效应，提供了 O-2 生产中 O-O 键形成的机理见解。
A new series of proximal proximal-[Ru-2(tpy)(2)(L)XY](n+) (p,p-Ru2XY, tpy = 2,2':6',2 ''-terpyridine, L = 5-phenyl-2,8-di(2-pyridyl)-1,9,10-anthyridine, X and Y = other coordination sites) were synthesized using, photoisomerization of a mononuclear complex. The p,p-Ru2XY complexes undergo unusual reversible bridge-exchange reactions to generate p,p-Ru-2(mu-Cl), p,p-Ru-2(mu-OH), and p,p-Ru-2(OH)(OH2) with mu-Cl, mu-OH, as well as hydroxo and aquo ligands at X and Y sites of p,p-Ru2XY, respectively. The geometric and electronic structures of these complexes were characterized based on UV vis and H-1 NMR spectra, X-ray crystallography, and density functional theory (DFT) calculations. H-1 NMR data showed C-2 symmetry of p,p-Ru-2(OH)(OH2) with the distorted L chelate and nonequivalence of two tpy ligands, in contrast to the C-2 symmetry of p,p-Ru-2(mu-Cl) and p,p-Ru-2(mu-OH). However, irrespective of the lower symmetry, p,p-Ru-2(OH)(OH2) is predominantly formed in neutral and weakly basic conditions due to the specially stabilized core structure by multiple hydrogen-bond interactions among aquo, hydroxo, and backbone L ligands. The electrochemical data suggested that p,p-Ru-2(OH)(OH2) (Ru-II-OH:Ru-II-OH2) is oxidized to the Ru-III-OH:Ru-III-OH state at 0.64 V vs saturated calomel electrode (SCE) and further to Ru-IV=O:Ru-IV-OH at 0.79 V by successive 1-proton-coupled 2-electron processes at pH 7.0. The cyclic voltammogram data exhibited that the p,p-Ru-2(OH)(OH2) complex works more efficiently for electrocatalytic water oxidation, compared with a similar mononuclear complex distal-[Ru(tpy)(L)OH2](2+) (d-RuOH2) and p,p-Ru-2(mu-Cl) and p,p-Ru-2(mu-OH), showing that the p,p-Ru-2 core structure with aquo and hydroxo ligands is important for efficient electrocatalytic water oxidation. Bulk electrolysis of the p,p-Ru-2(OH)(OH2) solution corroborated the electrocatalytic cycle involving the Ru-III-OH:Ru-III-OH state species as a resting state. The mechanistic insight into O-O bond formation for O-2 production was provided by the isotope effect on electrocatalytic water oxidation by p,p-Ru-2(OH)(OH2) and d-RuOH2 in H2O and D2O media.