Reductive Side of Water Splitting in Artificial Photosynthesis: New Homogeneous Photosystems of Great Activity and Mechanistic Insight
Reductive Side of Water Splitting in Artificial Photosynthesis: New Homogeneous Photosystems of Great Activity and Mechanistic Insight
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DOI：
10.1021/ja1057357
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发表时间：
2010-11-10
影响因子：
15
通讯作者：
Eisenberg, Richard
中科院分区：
文献类型：
--
作者：
McCormick, Theresa M.;Calitree, Brandon D.;Eisenberg, Richard
若丹明光敏剂（PS）用S或Se取代氧杂蒽环中的O，以[Co-III（dmgH）（2）（py）Cl]（其中dmgH =乙醛肟酸二甲酯，py =吡啶）为催化剂，三乙醇胺为牺牲电子给体，通过还原水产生氢，其转换数（TON）高达9000。的营业额频率分别为0，1700，和5500摩尔H-2/摩尔PS/h的O，S，和Se衍生物，分别（Phi（H2）= 0%，12.2%，和32.8%，分别），这与相对三重态产量估计的量子产率为单线态氧的产生。激发态PS的磷光被牺牲电子供体猝灭。荧光寿命是类似的O-和S-含有罗丹明（类似于2.6纳秒）和较短的硒类似物（类似于0.1纳秒）。这些数据表明，涉及还原猝灭的三重激发态的PS的反应途径，得到还原的PS-，然后转移一个电子的Co催化剂。较长寿命的三重态是有效的双分子电子转移所必需的。虽然钴/罗丹明/三乙醇胺系统为水的光还原提供了前所未有的氢气产量，但关于整个反应途径以及系统降解的机理见解为开发更稳定和有效的光催化系统提供了重要指导。
Rhodamine photosensitizers (PSs) substituting S or Se for 0 in the xanthene ring give turnover numbers (TONs) as high as 9000 for the generation of hydrogen via the reduction of water using [Co-III(dmgH)(2)(py)Cl] (where dmgH = dimethylglyoximate and py = pyridine) as the catalyst and triethanolamine as the sacrificial electron donor. The turnover frequencies were 0, 1700, and 5500 mol H-2/mol PS/h for O, S, and Se derivatives, respectively (Phi(H2) = 0%, 12.2%, and 32.8%, respectively), which correlates well with relative triplet yields estimated from quantum yields for singlet oxygen generation. Phosphorescence from the excited PS was quenched by the sacrificial electron donor. Fluorescence lifetimes were similar for the O- and S-containing rhodamines (similar to 2.6 ns) and shorter for the Se analog (similar to 0.1 ns). These data suggest a reaction pathway involving reductive quenching of the triplet excited state of the PS giving the reduced PS- that then transfers an electron to the Co catalyst. The longer-lived triplet state is necessary for effective bimolecular electron transfer. While the cobalt/rhodamine/triethanolamine system gives unprecedented yields of hydrogen for the photoreduction of water, mechanistic insights regarding the overall reaction pathway as well as system degradation offer significant guidance to developing even more stable and efficient photocatalytic systems.