Duan Lele, Fischer Andreas, Xu Yunhua, Sun Licheng
Department of Chemistry, School of Chemical Science and Engineering, Royal Institute of Technology (KTH), 100 44 Stockholm, Sweden.
J Am Chem Soc. 2009 Aug 5;131(30):10397-9. doi: 10.1021/ja9034686.
With the inspiration from an oxygen evolving complex (OEC) in Photosystem II (PSII), a mononuclear Ru(II) complex with a tetradentate ligand containing two carboxylate groups has been synthesized and structurally characterized. This Ru(II) complex showed efficient catalytic properties toward water oxidation by the chemical oxidant cerium(IV) ammonium nitrate. During the process of catalytic water oxidation, Ru(III) and Ru(IV) species have been successfully isolated as intermediates. To our surprise, X-ray crystallography together with HR-MS revealed that the Ru(IV) species is a seven-coordinate Ru(IV) dimer complex containing a HOHOH bridging ligand. This bridging ligand has a short O...O distance and is hydrogen bonded to two water molecules. The discovery of this very uncommon seven-coordinate Ru(IV) dimer together with a hydrogen bonding network may contribute to a deeper understanding of the mechanism for catalytic water oxidation. It will also provide new possibilities for the design of more efficient catalysts for water oxidation, which is the key step for solar energy conversion into hydrogen by light-driven water splitting, the ultimate challenge in artificial photosynthesis.
受光系统II（PSII）中析氧复合物（OEC）的启发，合成了一种带有含两个羧酸根基团的四齿配体的单核Ru（II）配合物，并对其进行了结构表征。该Ru（II）配合物对化学氧化剂硝酸铈（IV）铵氧化水表现出高效的催化性能。在催化水氧化过程中，成功分离出Ru（III）和Ru（IV）物种作为中间体。令我们惊讶的是，X射线晶体学和高分辨质谱显示，Ru（IV）物种是一种七配位的Ru（IV）二聚体配合物，含有一个HOHOH桥连配体。这个桥连配体具有较短的O...O距离，并与两个水分子形成氢键。这种非常罕见的七配位Ru（IV）二聚体以及氢键网络的发现，可能有助于更深入地理解催化水氧化的机制。它也将为设计更高效的水氧化催化剂提供新的可能性，而水氧化是通过光驱动水分解将太阳能转化为氢气的关键步骤，也是人工光合作用中的最终挑战。
