Water oxidation by a ruthenium complex with noninnocent quinone ligands: possible formation of an O-O bond at a low oxidation state of the metal.
Water oxidation by a ruthenium complex with noninnocent quinone ligands: possible formation of an O-O bond at a low oxidation state of the metal.
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DOI：
10.1021/ic701892v
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发表时间：
2008-03
影响因子：
4.6
通讯作者：
J. Muckerman;Dmitry E. Polyansky;Tohru Wada;Koji Tanaka;E. Fujita
中科院分区：
文献类型：
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作者：
J. Muckerman;Dmitry E. Polyansky;Tohru Wada;Koji Tanaka;E. Fujita
Tanaka和同事报道了一种新的双核Ru配合物，[Ru2(OH)2(3,6- bu2q)2(btpyan)](SbF6)2 （3,6- bu2q = 3,6-二叔丁基-1,2-苯醌，btpyan = 1,8-双（2,2':6',2' -三吡啶-4'-基）蒽），它含有氧化还原活性醌配体，当固定在铟锡氧化物电极上时具有优异的水氧化电催化活性（Inorg）。化学。科学通报，2001,40,329-337)。本文总结了具有醌配体的双核和相关的单核Ru类化合物的新特征，以及它们与具有bpy配体（bpy = 2,2'-联吡啶）取代醌的Ru类似物的性质的比较，并总结了新的理论和实验结果，这些结果显示了双核和单核Ru类化合物的显著特征。包括先前报道的氧自由基在内的关键单核物种的身份和氧化态已被重新分配。我们的气相理论计算表明，Tanaka Ru-双核催化剂似乎主要保持Ru（II）中心，而醌配体和水部分在整个水氧化催化循环中参与氧化还原反应。我们的理论研究确定[Ru2(O2(-))(Q(-1.5))2(btpyan)](0)是一个关键的中间体，也是在四电子氧化发生之前通过去除所有四个质子形成的最还原的催化剂物种。虽然我们对催化循环中可能中间体复杂的电子和几何结构的研究仍在进行中，但本文讨论了Tanaka催化剂（及其与Cl（-）或NO（2-）取代醌的类似物和以杂蒽桥代替蒽的物种）在水氧化中的关键问题和挑战，动力学和机理研究的现状和新方向。
Tanaka and co-workers reported a novel dinuclear Ru complex, [Ru2(OH)2(3,6-Bu2Q)2(btpyan)](SbF6)2 (3,6-Bu2Q = 3,6-di tert-butyl-1,2-benzoquinone, btpyan = 1,8-bis(2,2':6',2''-terpyrid-4'-yl)anthracene), that contains redox active quinone ligands and has an excellent electrocatalytic activity for water oxidation when immobilized on an indium-tin-oxide electrode (Inorg. Chem., 2001, 40, 329-337). The novel features of the dinuclear and related mononuclear Ru species with quinone ligands, and comparison of their properties to those of the Ru analogues with the bpy ligand (bpy = 2,2'-bipyridine) replacing quinone, are summarized here together with new theoretical and experimental results that show striking features for both the dinuclear and mononuclear species. The identity and oxidation state of key mononuclear species, including the previously reported oxyl radical, have been reassigned. Our gas-phase theoretical calculations indicate that the Tanaka Ru-dinuclear catalyst seems to maintain predominantly Ru(II) centers while the quinone ligands and water moiety are involved in redox reactions throughout the entire catalytic cycle for water oxidation. Our theoretical study identifies [Ru2(O2(-))(Q(-1.5))2(btpyan)](0) as a key intermediate and the most reduced catalyst species that is formed by removal of all four protons before four-electron oxidation takes place. While our study toward understanding the complicated electronic and geometric structures of possible intermediates in the catalytic cycle is still in progress, the current status and new directions for kinetic and mechanistic investigations, and key issues and challenges in water oxidation with the Tanaka catalyst (and its analogues with Cl(-) or NO(2-)substituted quinones and a species with a xanthene bridge instead an antheracene) are discussed.