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

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 二硫杂环戊二烯过渡金属络合物因其独特的物理性质和电子结构而在无机化学领域引起了人们的广泛关注。在生物学上，过渡金属二硫杂环戊烯配体在钼杂多酚的活性中心扮演着重要的角色，这些活性中心参与了许多基本的生化反应。在材料科学中，某些二硫杂环化合物由于其在近红外区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，理解酶反应机理或设计新的功能材料应该建立在对这类化合物的电子结构的透彻理解的基础上。在这方面，一个备受争议的问题是，二硫杂环戊烯配体是以自由基还是双自由基存在的。在这种“非无害”的络合物中，中心金属的氧化和自旋状态是模棱两可的，很难通过实验确定。因此，金属K边和L边以及硫K边的X射线吸收光谱非常适合于从根本上提供对这些系统中功能的电子结构的洞察。特别是，硫K边光谱探测了电子基态下的配体空穴特征，因此非常适合于检测络合物中的开壳特征。边缘和前缘区域的金属K边光谱将提供中心金属离子的氧化态信息，而EXAFS可以用来深入了解测量细节。金属L边是dN构型的一种特别灵敏的探针，将通过对多重态强度的定量分析来探测金属-配体的共价性。这些实验将结合准相对论密度泛函以及多重态计算，以便更深入地了解实验数据。我们的研究将集中在一系列氧化状态和金属离子系统不同的配合物上。

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.