Speciation of the catalytic oxygen evolution system:: [MnIII/IV2(μ-O)2(terpy)2(H2O)2](NO3)3+HSO5-
Speciation of the catalytic oxygen evolution system:: [MnIII/IV2(μ-O)2(terpy)2(H2O)2](NO3)3+HSO5-
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DOI：
10.1021/ic060499j
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发表时间：
2007-01-08
影响因子：
4.6
通讯作者：
Brudvig, Gary W.
中科院分区：
文献类型：
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作者：
Chen, Hongyu;Tagore, Ranitendranath;Brudvig, Gary W.
[Mn-2（III/IV）（μ-O）（2）（terpy）（2）（OH 2）（2）]（NO3）（3）（1，其中terpy = 2，2“：6”2 "-三联吡啶）+过硫酸氢钾（oxone）（2KHSO（5）中心点KHSO 4中心点K2 SO 4）提供了基于结构相关的Mn-（μ-O）（2）-Mn部分的光系统II的放氧复合物的功能模型系统（林布尔格，J.;等.美国2001，123，423-430）。在这项研究中，电子顺磁共振，紫外-可见光谱，电喷雾电离质谱，X-射线吸收光谱，气相稳定同位素比质谱被用来确定催化溶液中的标题化合物。我们发现：（a）O-2的析出不是通过MnO_2或其它分解产物的多相催化进行的;（B）来自溶剂水的O原子在很大程度上掺入析出的O-2中，但不掺入过硫酸氢钾中;（c）Mn-2（III/IV）标题化合物1在过硫酸氢钾的O-2析出催化循环中是一种活性预催化剂;而Mn-2（IV/IV）氧化态不是，（d）同位素标记物结合到放出的O-2中，与上述a-c点一起，与涉及过硫酸氢钾和水与O-O键形成步骤中的“（MnO）-O-V”中间体的竞争反应的机理一致。
[Mn-2(III/IV)(mu-O)(2)(terpy)(2)(OH2)(2)](NO3)(3) (1, where terpy = 2,2':6'2' '-terpyridine) + oxone (2KHSO(5)center dot KHSO4 center dot K2SO4) provides a functional model system for the oxygen-evolving complex of photosystem II that is based on a structurally relevant Mn-(mu-O)(2)-Mn moiety (Limburg, J.; et al. J. Am. Chem. Soc. 2001, 123, 423-430). In this study, electron paramagnetic resonance, ultraviolet-visible spectroscopy, electrospray ionization mass spectrometry, X-ray absorption spectroscopy, and gas-phase stable isotope ratio mass spectrometry were utilized to identify the title compounds in the catalytic solution. We find that (a) O-2 evolution does not proceed through heterogeneous catalysis by MnO2 or other decomposition products, that (b) O atoms from solvent water are incorporated into the evolved O-2 to a significant extent but not into oxone, that (c) the Mn-2(III/IV) title compound 1 is an active precatalyst in the catalytic cycle of O-2 evolution with oxone, while the Mn-2(IV/IV) oxidation state is not, and that (d) the isotope label incorporation in the evolved O-2, together with points a-c above, is consistent with a mechanism involving competing reactions of oxone and water with a "(MnO)-O-V" intermediate in the O-O bond-forming step.