DETERMINATION OF ELECTRONIC AND GEOMETRIC STRUCTURES OF NOVEL FE-S SYSTEMS

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个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 研究中心，而研究中心不一定是研究者所在的机构。 多边缘X射线吸收光谱研究的改性Fe-S矿物表面和纳米粒子的建议，以映射的Fe-S相图作为一个功能的长度尺度（微米与纳米），合成（表面/光束，蛋白笼控制合成），和制备条件（曝光时间，温度，pH值，存在的其他离子）。我们假设使用能量（表面/束）和结构（蛋白笼或病毒衣壳）控制的Fe-S系统的合成，可以访问Fe-S相图的区域，这通过常规合成方法是不可能的。最近获得的初步数据已经表明存在以前未观察到的还原态的黄铁矿，这是通过暴露原始[100]黄铁矿表面的氢原子/氢气等离子体。我们将利用XAS数据在Fe K边、Fe L边和S K边的互补性。BL 4 -3最近的光束线开发现在允许收集硫EXAFS，其与铁EXAFS结合可以为难以表征的中间体或过渡态提供更可靠的几何结构拟合。XANES分析Fe L边和S K边光谱的前沿和上升边特征提供了关于金属/配体中心的有效核电荷、轨道组成、金属中心的配体场分裂和配体的非无辜行为的电子结构信息。从拟议的实验中获得的结构见解对Fe-S系统作为前生物代谢催化剂的作用产生了影响（NASA天体生物学研究所支持的MSU研究计划），以及从丰富的含Fe-S材料中提出新型工业催化剂的潜力，用于活化小分子，如二氮或二氢。

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. Multi-edge x-ray absorption spectroscopic investigations of modified Fe-S mineral surfaces and nanoparticles are proposed in order to map the Fe-S phase diagrams as a function of length scale (micrometer vs. nanometer), synthesis (surface/beam, protein-cage controlled synthesis), and preparation conditions (exposure time, temperature, pH, presence of other ions). We hypothesize that using energy- (surface/beam) and structure- (protein cage or viral capsid) controlled synthesis of Fe-S systems, areas of Fe-S phase diagrams can be accessed that would not be possible by conventional synthetic methods. Recently obtained preliminary data already indicate the existence of a previously unobserved reduced state of pyrite, which was prepared by exposing pristine [100] pyrite surface to hydrogen atom/hydrogen gas plasma. We will take advantage of the complementarity of XAS data at the Fe K-edge, Fe L-edge, and S K-edge. Recent beamline development at BL4-3 now allows for collection of sulfur EXAFS, which in combination with iron EXAFS can provide more reliable fits of geometric structure for hard to characterize intermediates or transition states. XANES analysis of preedge and rising-edge features of Fe L-edge and S K-edge spectra provides electronic structural information about effective nuclear charges of metal/ligand centers, orbital compositions, ligand-field splitting of metal centers, and non-innocent behavior of ligands. Structural insights from the proposed experiments have an impact on the role of Fe-S systems as pre-biotic metabolic catalysts (NASA Astrobiology Institute supported research program at MSU), as well as, potential in proposing novel industrial catalysts from abundant Fe-S containing materials for activation of small molecules such as dinitrogen or dihydrogen.