XAS STUDIES OF HIGH-VALENT FE MODEL COMPLEXES RELEVANT TO METHANE MONOOXYGENASE

甲烷单加氧酶相关高价FE模型复合物的XAS研究

• 批准号: 7954370
• 负责人: SERENA D DE BEER GEORGE
• 金额: $ 0.56万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-03-01 至 2010-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7954370
• 关键词: Amines; Biomimetics; Catalysis; Complex; Computer Retrieval of Information on Scientific Projects Database; Data; Drug Formulations; Funding; Grant; Institution; Iron; Laboratories; Ligands; Methane; Methane hydroxylase; Methanol; Modeling; Mononuclear; Reaction; Relative (related person); Research; Research Personnel; Resources; Ribonucleotide Reductase; Ribonucleotides; Solutions; Source; Structure; United States National Institutes of Health; Work; analog; cold temperature; electronic structure; oxidation; phenolate; phenoxy radical; structural biology; synchrotron radiation

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. High-valent iron intermediates are invoked as the active oxidizing species in both methane monooxygenase (MMO) and ribonucleotide reductase (RNR). In MMO, intermediate Q is thought to consist of an FeIV(mu-O)2FeIV core which converts methane to methanol. Whereas in RNR, an oxo-bridged FeIIIFeIV species, intermediate X is the active species in ribonucleotide reduction. The importance of these reactions and the potential utility of synthetic analogues in biomimetic homogeneous catalysis have driven efforts to synthesize analogues. Recent work in our laboratory has focused on the synthesis and characterization of dinuclear Fe-oxo complexes utilizing strongly pi- and sigma- donating phenolates and t-amines as donors. The resultant [LFe(mu2-O)FeL] complex (1) can be oxidized to the monocation [LFe(mu2-O)FeL]+ (1+) and to the dication [LFe(mu2-O)FeL]2+ (12+). EPR data of 1+ suggests an oxo-bridged-FeIIIFeIV formulation. However comparison of UV-vis data for 1+ and 2+ to mononuclear analogues suggests a ligand-centered oxidation occurs in both complexes, forming a diferric phenoxyl radical in 1+ and a diferric diphenoxyl radical in 12+. The greater stability of the dication relative to the monoanionic species is thought to result from a symmetric strengthening of the Fe-oxo bonds in the former (12+), as opposed to the asymmetric situation which is generated in the later (1+). As these species can only be generated at low temperature in solution, XAS provides an ideal means for characterizing the electronic structure and local geometric structure of these complexes.

该子项目是利用该技术的众多研究子项目之一 资源由 NIH/NCRR 资助的中心拨款提供。子项目和 研究者 (PI) 可能已从 NIH 的另一个来源获得主要资金， 因此可以在其他 CRISP 条目中表示。列出的机构是 对于中心来说，它不一定是研究者的机构。 高价铁中间体在甲烷单加氧酶 (MMO) 和核糖核苷酸还原酶 (RNR) 中被用作活性氧化物质。在 MMO 中，中间体 Q 被认为由 FeIV(mu-O)2FeIV 核心组成，可将甲烷转化为甲醇。 而在 RNR（一种氧桥 FeIIIFeIV 物种）中，中间体 X 是核糖核苷酸还原中的活性物种。这些反应的重要性以及合成类似物在仿生均相催化中的潜在用途推动了合成类似物的努力。我们实验室最近的工作重点是利用强π-和σ-供体酚盐和t-胺作为供体来合成和表征双核Fe-氧配合物。所得的 [LFe(mu2-O)FeL] 络合物 (1) 可被氧化为单阳离子 [LFe(mu2-O)FeL]+ (1+) 和双阳离子 [LFe(mu2-O)FeL]2+ (12+)。 1+ 的 EPR 数据表明氧桥联 FeIIIFeIV 配方。然而，1+和2+与单核类似物的UV-vis数据比较表明，两种配合物中都发生了以配体为中心的氧化，在1+中形成二铁苯氧基自由基，在12+中形成二铁二苯氧基自由基。阳离子相对于单阴离子物种具有更高的稳定性，被认为是由于前者 (12+) 中 Fe-氧键的对称强化，而不是后者 (1+) 中产生的不对称情况。由于这些物质只能在低温下在溶液中产生，XAS 为表征这些复合物的电子结构和局部几何结构提供了理想的方法。