EXAFS STUDIES OF AN AQUEOUS FE(IV) INTERMEDIATE

水相 FE(IV) 中间体的 EXAFS 研究

• 批准号: 7370698
• 负责人: LAWRENCE QUE
• 金额: $ 0.02万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-03-01 至 2007-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7370698
• 关键词: EXAFS; STUDIES; AQUEOUS; FE; IV

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. The mechanistic complexity and wide-spread involvement of the Fenton reaction in catalytic chemistry, atmospheric and environmental processes, aging and disease have made it one of the most studied and debated reactions of all time. Strictly speaking, the Fenton reaction is the oxidation of aqueous iron(II) ions with hydrogen peroxide in acidic aqueous solutions. This transformation is also proposed to occur in biological milieu where the pH is closer to 7-8 and the iron(II) center is presumably coordinated to ligands available within the cell. Such chemistry has been used to rationalize the production of some reactive oxygen species and to explain the effects of the combination of iron complexes, H2O2 and a reductant on DNA cleavage. Regarding the nature of the reactive intermediate(s), experimental evidence and arguments have been advanced for hydroxyl radicals, [(H2O)nFeIVO]2+, and metal-coordinated peroxide, [(H2O)5Fe(H2O2)]2+. In principle, the answer to this mechanistic question lies in reactivity studies of each proposed intermediate that can be generated independently. Until recently, only hydroxyl radicals can be obtained independently from other chemical sources. Recently, we have established that an FeIV intermediate is generated at pH 1 in aqueous solution from the reaction of [Fe(H2O)6]2+ and O3. This short-lived species was freeze-trapped and characterized by M¿¿¿auer spectroscopic studies that confirm the existence of a high-spin FeIV species with an S = 2 ground state. We carried out initial XAS studies on two samples for which M¿¿¿auer spectroscopy established the purity of 50% and 58%. We noted a pronounced 1s 3d transition in the XANES spectrum. The current project will continue these studies.

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。芬顿反应的机制复杂性和广泛涉及催化化学、大气和环境过程、衰老和疾病，使其成为有史以来研究最多和争论最多的反应之一。严格来说，芬顿反应是酸性水溶液中水铁（II）离子与过氧化氢的氧化反应。这种转化也被认为发生在pH接近7-8的生物环境中，并且铁（II）中心可能与细胞内可用的配体协调。这种化学已被用来合理化一些活性氧的产生，并解释铁配合物、H2O2和还原剂的结合对DNA切割的影响。关于反应中间体的性质，已经提出了羟基自由基[(H2O)nFeIVO]2+和金属配位过氧化物[(H2O)5Fe(H2O2)]2+的实验证据和争论。原则上，这个机制问题的答案在于对每一种可以独立生成的中间体的反应性研究。直到最近，只有羟基自由基可以独立地从其他化学来源获得。最近，我们已经确定了在水溶液中[Fe(H2O)6]2+和O3的反应在pH为1时产生FeIV中间体。这种短寿命的物质被冷冻捕获，并通过能谱研究进行了表征，证实了具有S = 2基态的高自旋FeIV物质的存在。我们对两个样品进行了初步的XAS研究，其中M¿¿¿auwer光谱确定的纯度为50%和58%。我们注意到XANES光谱中明显的1s - 3d跃迁。目前的项目将继续进行这些研究。