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Cooperative water oxidation catalysis in a series of trinuclear metallosupramolecular ruthenium macrocycles
Energy & Environmental Science ( IF 32.5 ) Pub Date : 2017-09-04 00:00:00 , DOI: 10.1039/c7ee01557g
Valentin Kunz 1, 2, 3, 4 , Joachim O. Lindner 2, 3, 4, 5 , Marcus Schulze 1, 2, 3, 4 , Merle I. S. Röhr 2, 3, 4, 5, 6 , David Schmidt 1, 2, 3, 4, 6 , Roland Mitrić 2, 3, 4, 5 , Frank Würthner 1, 2, 3, 4, 6
Affiliation  

A series of trinuclear metallosupramolecular Ru(bda) macrocycles has been synthesized and the impact of the ring size on the catalytic activity in homogeneous water oxidation has been elucidated (bda = 2,2′-bipyridine-6,6′-dicarboxylate). Kinetic experiments revealed that for all macrocyclic catalysts a proton-coupled oxidation event is rate-determining. Distinct H/D kinetic isotope effects (KIE) have been observed for the individual macrocycles, which follow the same tendency like the catalytic activity where an intermediate ring size exhibits the best performance. To get insight into the different molecular properties, molecular dynamics simulations using a QM/MM approach have been performed for all reaction steps, revealing that the size of the cavity strongly influences the hydrogen-bonded water network inside the macrocyclic structure and thus, important proton-coupled reaction steps of the catalytic cycle. For the most active catalysts, all reactive sites point into the interior of the cavity, which is supported by a single crystal X-ray analysis of the largest macrocycle, and a cooperative effect between the individual Ru(bda) centers facilitating proton abstraction has been substantiated. On the other hand, different structural conformations predominate the smaller macrocycles, which prevent efficient interactions between the Ru(bda) centers.

中文翻译:

一系列三核金属超分子钌大环化合物中的协同水氧化催化

合成了一系列三核金属超分子Ru(bda)大环,并阐明了环大小对均相水氧化中催化活性的影响(bda = 2,2'-联吡啶-6,6'-二羧酸酯)。动力学实验表明,对于所有大环催化剂,质子偶联的氧化反应是决定速率的。对于单个大环,已经观察到明显的H / D动力学同位素效应(KIE),其遵循相同的趋势,例如催化活性,其中中间环的尺寸表现出最佳性能。为了深入了解不同的分子特性,已针对所有反应步骤使用QM / MM方法进行了分子动力学模拟,揭示了空腔的大小强烈影响了大环结构内部的氢键水网络,因此,也影响了催化循环中重要的质子耦合反应步骤。对于最具活性的催化剂,所有反应位点都指向腔体内部,这由最大的大环的单晶X射线分析来支持,并且各个Ru(bda)中心之间的协同效应促进了质子的提取证实。另一方面,较小的大环占据了不同的结构构象,这阻止了Ru(bda)中心之间的有效相互作用。它由最大的大环的单晶X射线分析所支持,并且各个Ru(bda)中心之间的促进质子抽象的协同效应也得到了证实。另一方面,较小的大环占据了不同的结构构象,这阻止了Ru(bda)中心之间的有效相互作用。它由最大的大环的单晶X射线分析所支持,并且各个Ru(bda)中心之间的促进质子抽象的协同效应也得到了证实。另一方面,较小的大环占据了不同的结构构象,这阻止了Ru(bda)中心之间的有效相互作用。
更新日期:2017-10-11
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