Structure and Electronic Configurations of the Intermediates of Water Oxidation in Blue Ruthenium Dimer Catalysis
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- 作者：Dooshaye Moonshiram ; Jonah W. Jurss ; Javier J. Concepcion ; Taisiya Zakharova ; Igor Alperovich ; Thomas J. Meyer ; Yulia Pushkar
- 刊名：The Journal of the American Chemical Society
- 出版年：2012
- 出版时间：March 14, 2012
- 年：2012
- 卷：134
- 期：10
- 页码：4625-4636
- 全文大小：622K
- 年卷期：v.134,no.10(March 14, 2012)
- ISSN：1520-5126
文摘
Catalytic O2 evolution with cis,cis-[(bpy)2(H2O)RuIIIORuIII(OH2)(bpy)2]4+ (bpy is 2,2-bipyridine), the so-called blue dimer, the first designed water oxidation catalyst, was monitored by UV鈥搗is, EPR, and X-ray absorption spectroscopy (XAS) with ms time resolution. Two processes were identified, one of which occurs on a time scale of 100 ms to a few seconds and results in oxidation of the catalyst with the formation of an intermediate, here termed [3,4]鈥? A slower process occurring on the time scale of minutes results in the decay of this intermediate and O2 evolution. Spectroscopic data suggest that within the fast process there is a short-lived transient intermediate, which is a precursor of [3,4]鈥? When excess oxidant was used, a highly oxidized form of the blue dimer [4,5] was spectroscopically resolved within the time frame of the fast process. Its structure and electronic state were confirmed by EPR and XAS. As reported earlier, the [3,4]鈥?intermediate likely results from reaction of [4,5] with water. While it is generated under strongly oxidizing conditions, it does not display oxidation of the Ru centers past [3,4] according to EPR and XAS. EXAFS analysis demonstrates a considerably modified ligand environment in [3,4]鈥? Raman measurements confirmed the presence of the O鈥揙 fragment by detecting a new vibration band in [3,4]鈥?that undergoes a 46 cm鈥? shift to lower energy upon 16O/18O exchange. Under the conditions of the experiment at pH 1, the [3,4]鈥?intermediate is the catalytic steady state form of the blue dimer catalyst, suggesting that its oxidation is the rate-limiting step.