Characterization of the O2-evolving reaction catalyzed by [(terpy)(H2O)MnIII(O)2MnIV(OH2)(terpy)](NO3) (terpy=2,2′:6,2"-terpyridine)
Characterization of the O2-evolving reaction catalyzed by [(terpy)(H2O)MnIII(O)2MnIV(OH2)(terpy)](NO3) (terpy=2,2′:6,2"-terpyridine)
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DOI：
10.1021/ja001090a
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发表时间：
2001-01-24
影响因子：
15
通讯作者：
Brudvig, GW
中科院分区：
文献类型：
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作者：
Limburg, J;Vrettos, JS;Brudvig, GW
配合物[(terpy)(H2O)Mn-III(O)(2)Mn-IV(OH2)(terpy)](NO3)(3)(terpy=2，2‘：6，2“-联吡啶)(1)催化KHSO5(氧化钾)或NaOCl制得O-2。反应遵循Michaelis-Menten动力学，氧酮([1]=7.5um)的V-max=2420+/-490molO-2(Mol1)(-1)hr(-1)，K-M=53+/-5 mm；次氯酸盐([1]=70um)的V-max=6.5+/-0.3molO-2(Mol1)(-1)hr(-1)和K-M=39+/-4 mm。在[(Terpy)(SO4)Mn-IV(O)(2)Mn-IV(O4S)(Terpy)](2)的分离和结构表征的支持下，提出了1与HSO5-或OCL-之间存在预平衡的机理。用(H2O)-O-18和(KHSO5)-O-16进行的同位素标记研究表明，氧的析出是通过一个可以与水交换的中间体进行的，其中拉曼光谱已经证实HSO5-的活性氧是非交换的(t(1/2)>；>；1h)。O-32(2)：O-34(2)：O-96(2)，当[HSO5-]=50 mm(0.5 mm 1)时，O-32(2)：O-34(2)：O-96(2)为91.9+/-0.3：7.6+/-0.3：0.51+/-0.48；当[HSO5-]=15 mm(0.75 mm 1)时，为49+/-21：39+/-15：12+/-6。Oz演化的限速步骤被认为是形成形式上的Mn-V=O部分，然后该部分可以与氧酮或水/氢氧化物竞争反应生成O-2。这些结果表明，1可作为光合作用水氧化的功能模型。
The complex [(terpy)(H2O)Mn-III(O)(2)Mn-IV(OH2)(terpy)](NO3)(3) (terpy = 2,2':6,2"-terpyridine) (1) catalyzes O-2 evolution from either KHSO5 (potassium oxone) or NaOCl. The reactions follow Michaelis-Menten kinetics where V-max = 2420 +/- 490 mol O-2 (mol 1)(-1) hr(-1) and K-M = 53 +/- 5 mM for oxone ([1] = 7.5 muM), and V-max = 6.5 +/- 0.3 mol O-2 (mol 1)(-1) hr(-1) and K-M = 39 +/- 4 mM for hypochlorite ([1] = 70 muM), with first-order kinetics observed in 1 for both oxidants. A mechanism is proposed having a preequilibrium between 1 and HSO5- or OCl-, supported by the isolation and structural characterization of [(terpy)(SO4)Mn-IV(O)(2)Mn-IV(O4S)(terpy)] (2). Isotope-labeling studies using (H2O)-O-18 and (KHSO5)-O-16 show that O-2 evolution proceeds via an intermediate that can exchange with water, where Raman spectroscopy has been used to confirm that the active oxygen of HSO5- is nonexchanging (t(1/2) >> 1 h). The amount of label incorporated into O-2 is dependent on the relative concentrations of oxone and 1. O-32(2):O-34(2):O-96(2) is 91.9 +/- 0.3:7.6 +/- 0.3:0.51 +/- 0.48, when [HSO5-] = 50 mM (0.5 mM 1), and 49 +/- 21:39 +/- 15:12 +/- 6 when [HSO5-] = 15 mM (0.75 mM 1). The rate-limiting step of Oz evolution is proposed to be formation of a formally Mn-V=O moiety which could then competitively react with either oxone or water/hydroxide to produce O-2. These results show that 1 serves as a functional model for photosynthetic water oxidation.