MULTI-EDGE X-RAY ABSORPTION SPECTROSCOPIC STUDIES OF TRANSITION METAL DITHIOLENE

该子项目是利用 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，不一定是研究者的机构。 二硫纶过渡金属配合物由于其独特的物理性质和电子结构而在无机化学中引起了广泛的关注。在生物学中，过渡金属二硫杂环戊烯配体在蝶呤的活性位点中发挥重要作用，这些活性位点参与各种基本的生化反应。在材料科学中，某些二硫纶配合物由于其在近红外区域的巨大吸收带而成为非线性光学器件和激光应用的候选材料。然而，对酶促反应机理的理解或新功能材料的设计应基于对此类化合物的电子结构的透彻理解。在这方面，一个激烈争论的问题是，二硫纶配体是否可以作为自由基或双自由基存在。在这种“非无辜”的配合物中，中心金属的氧化和自旋状态是模糊的，难以通过实验确定。因此，在金属K-和L-边缘以及硫K-边缘处的X射线吸收光谱法理想地适合于提供对这些系统中的功能的基本电子结构洞察。特别是，硫K-边光谱探测电子基态的配体空穴特征，因此非常适合于检测络合物中的开壳层特征。边缘和边缘前区域的金属K边谱提供了中心金属离子的氧化态信息，而EXAFS可以用来了解测量细节。金属的L-边缘是一个特别敏感的探针的dn配置，并将用于探测金属配体共价通过多重峰强度的定量分析。实验将结合准相对论密度泛函以及多重态计算，以获得更多的洞察实验数据。我们的研究将集中在一系列的配合物，系统地不同的氧化态和金属离子。

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. Dithiolene transition metal complexes are of longstanding interest in inorganic chemistry due to their fascinating physical properties and electronic structures. In biology, transition metal dithiolene ligands play an important role in molybdopterin active sites, which are involved in a wide variety of fundamental biochemical reactions. In material sciences, certain dithiolene complexes are candidate materials for nonlinear optical devices and laser applications due to their enormous absorption bands in the near-infrared region. However, the understanding of enzymatic reaction mechanisms or the design of new functional materials should be based on a thorough understanding of the electronic structures of such compounds. In this respect, a hotly debated question is, whether dithiolene ligands can exist as radicals or diradicals. In such 'non-innocent' complexes, the oxidation and spin states of the central metal is ambiguous and difficult to determine experimentally. Thus, x-ray absorption spectroscopy at the metal K-, and L-edges as well as the sulfur K-edges is ideally suited to provide fundamentally electronic structure insights into function in these systems. In particular, sulfur K-edge spectroscopy probes the ligand hole character in the electronic ground state and is therefore ideally suited to detect open shell character in the complexes. The metal K-edge spectra in the edge and pre-edge region will provide oxidation state information of the central metal ion while EXAFS can be used to get insight into metrical details. The metal L-edge is a particularly sensitive probe of the dn configuration and will be used to probe metal-ligand covalency through a quantitative analysis of the multiplet intensities. The experiments will be combined with quasi-relativistic density functional as well as multiplet calculations in order to obtain more insight into the experimental data. Our studies will focus on a series of complexes which systematically differ in their oxidation states and metal ion.