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Tetranuclear Manganese Models of the OEC Displaying Hydrogen Bonding Interactions: Application to Electrocatalytic Water Oxidation to Hydrogen Peroxide
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2017-06-27 , DOI: 10.1021/jacs.7b03044
Zhiji Han 1 , Kyle T. Horak 1 , Heui Beom Lee 1 , Theodor Agapie 1
Affiliation  

Toward the development of structural and functional models of the oxygen evolving complex (OEC) of photosystem II, we report the synthesis of site-differentiated tetranuclear manganese complexes featuring three six-coordinate and one five-coordinate Mn centers. To incorporate biologically relevant second coordination sphere interactions, substituents capable of hydrogen bonding are included as pyrazolates with arylamine substituents. Complexes with terminal anionic ligands, OH- or Cl-, bound to the lower coordinate metal center are supported through the hydrogen-bonding network in a fashion reminiscent of the enzymatic active site. The hydroxide complex was found to be a competent electrocatalyst for O-O bond formation, a key transformation pertinent to the OEC. In an acetonitrile-water mixture, at neutral pH, electrochemical water oxidation to hydrogen peroxide was observed, albeit with low (15%) Faradaic yield, likely due to competing reactions with organics. In agreement, 9,10-dihydroanthracene is electrochemically oxidized in the presence of this cluster both via H-atom abstraction and oxygenation with ∼50% combined Faradaic yield.

中文翻译:

OEC 的四核锰模型显示氢键相互作用:在电催化水氧化成过氧化氢中的应用

为了开发光系统 II 的析氧复合物 (OEC) 的结构和功能模型,我们报告了具有三个六配位和一个五配位锰中心的位点分化四核锰复合物的合成。为了结合生物学相关的第二配位球相互作用,包括能够形成氢键的取代基作为具有芳胺取代基的吡唑酯。带有末端阴离子配体 OH- 或 Cl- 的配合物与较低配位的金属中心结合,通过氢键网络以一种让人联想到酶活性位点的方式得到支持。发现氢氧化物复合物是形成 OO 键的有效电催化剂,这是与 OEC 相关的关键转化。在乙腈-水混合物中,在中性 pH 值下,观察到电化学水氧化成过氧化氢,尽管法拉第产率低(15%),这可能是由于与有机物的竞争反应。一致地,9,10-二氢蒽在该簇的存在下通过氢原子提取和氧化被电化学氧化,法拉第总产率约为 50%。
更新日期:2017-06-27
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