Department of Chemistry, School of Chemical Science and Engineering, Royal Institute of Technology (KTH), 100 44 Stockholm, Sweden.
Inorg Chem. 2010 Jan 4;49(1):209-15. doi: 10.1021/ic9017486.
Discovery of an efficient catalyst bearing low overpotential toward water oxidation is a key step for light-driven water splitting into dioxygen and dihydrogen. A mononuclear ruthenium complex, Ru(II)L(pic)(2) (1) (H(2)L = 2,2'-bipyridine-6,6'-dicarboxylic acid; pic = 4-picoline), was found capable of oxidizing water eletrochemically at a relatively low potential and promoting light-driven water oxidation using a three-component system composed of a photosensitizer, sacrificial electron acceptor, and complex 1. The detailed electrochemical properties of 1 were studied, and the onset potentials of the electrochemically catalytic curves in pH 7.0 and pH 1.0 solutions are 1.0 and 1.5 V, respectively. The low catalytic potential of 1 under neutral conditions allows the use of Ru(bpy)(3) and even Ru(dmbpy)(3) as a photosensitizer for photochemical water oxidation. Two different sacrificial electron acceptors, [Co(NH(3))(5)Cl]Cl(2) and Na(2)S(2)O(8), were used to generate the oxidized state of ruthenium tris(2,2'-bipyridyl) photosensitizers. In addition, a two-hour photolysis of 1 in a pH 7.0 phosphate buffer did not lead to obvious degradation, indicating the good photostability of our catalyst. However, under conditions of light-driven water oxidation, the catalyst deactivates quickly. In both solution and the solid state under aerobic conditions, complex 1 gradually decomposed via oxidative degradation of its ligands, and two of the decomposed products, sp(3) C-H bond oxidized Ru complexes, were identified. The capability of oxidizing the sp(3) C-H bond implies the presence of a highly oxidizing Ru species, which might also cause the final degradation of the catalyst.
发现一种对水氧化具有低过电势的高效催化剂是将光驱动的水分解为氧气和氢气的关键步骤。单核钌配合物 Ru(II)L(pic)(2)（1）（H2L = 2,2'-联吡啶-6,6'-二羧酸；pic = 4-吡啶甲酸）被发现能够在相对较低的电势下电化学氧化水，并使用由光敏剂、牺牲电子受体和配合物 1 组成的三组分体系促进光驱动的水氧化。详细研究了 1 的电化学性质，在 pH 7.0 和 pH 1.0 溶液中电化学催化曲线的起始电位分别为 1.0 和 1.5 V。1 在中性条件下的低催化电势允许使用Ru(bpy)(3)甚至Ru(dmbpy)(3)作为光敏剂进行光化学水氧化。两种不同的牺牲电子受体，[Co(NH3)5Cl]Cl2和 Na2S2O8，被用于产生钌三（2,2'-联吡啶）光敏剂的氧化态。此外，在 pH 7.0 磷酸盐缓冲液中，1 进行两小时的光解并没有导致明显的降解，表明我们的催化剂具有良好的光稳定性。然而，在光驱动水氧化的条件下，催化剂会迅速失活。在有氧条件下的溶液和固态中，配合物 1 会通过其配体的氧化降解逐渐分解，并且鉴定出两种分解产物，即 sp(3) C-H 键氧化的 Ru 配合物。氧化 sp(3) C-H 键的能力表明存在一种高氧化态的 Ru 物种，这也可能导致催化剂的最终降解。
