Tseng Huan-Wei, Zong Ruifa, Muckerman James T, Thummel Randolph
Department of Chemistry, University of Houston, 136 Fleming Building, Houston, Texas 77204-5003, USA.
Inorg Chem. 2008 Dec 15;47(24):11763-73. doi: 10.1021/ic8014817.
Two series of mononuclear ruthenium(II) complexes involving polypyridine-type ligands have been prepared, and their ability to act as catalysts for water oxidation has been examined. One series is of the type Ru(tpy)(NN)Cl (tpy = 2,2'; 6,2''-terpyridine), where NN is one of 12 different bidentate ligands, and the other series includes various combinations of 4-picoline, 2,2'-bipyridine (bpy), and tpy as well as the tetradentate 2,9-dipyrid-2'-yl-1,10-phenanthroline (dpp). The electronic absorption and redox data for these compounds have been measured and reported. The long-wavelength metal-to-ligand charge-transfer absorption and the first oxidation and reduction potentials are found to be consistent with the structure of the complex. Of the 23 complexes, 14 catalyze water oxidation and all of these contain a tpy or dpp. Kinetic measurements indicate a first-order reaction and together with a catalyst recovery experiment argue against the involvement of RuO(2). A tentative mechanism is proposed that involves a seven-coordinate Ru(VI)=O species that is attacked by water to form the critical O-O bond. Density functional theory calculations, which support the proposed mechanism, are performed.
已制备了两类涉及多吡啶型配体的单核钌（II）配合物，并研究了它们作为水氧化催化剂的能力。一类是Ru(tpy)(NN)Cl型（tpy = 2,2'; 6,2''-三联吡啶），其中NN是12种不同双齿配体之一，另一类包括4-甲基吡啶、2,2'-联吡啶（bpy）和tpy的各种组合以及四齿的2,9-二吡啶-2'-基-1,10-菲咯啉（dpp）。已测量并报道了这些化合物的电子吸收和氧化还原数据。发现长波长的金属到配体的电荷转移吸收以及首次氧化和还原电位与配合物的结构一致。在这23种配合物中，有14种催化水氧化，并且所有这些都含有tpy或dpp。动力学测量表明是一级反应，并且与催化剂回收实验一起排除了RuO₂的参与。提出了一种暂定机制，该机制涉及一种七配位的Ru(VI)=O物种，该物种被水攻击形成关键的O - O键。进行了支持所提出机制的密度泛函理论计算。
