OXIDIZED CU(II)-PHENOLATE COMPLEXES: THE FACTORS GOVERNING LIGAND VS METAL-BASE

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。 铜酶表现出一系列与分子氧的反应性，并且小分子模型的使用提供了以详细和系统的方式探测酶机制的手段。过渡金属离子与前自由基配体在金属酶活性中心的协同作用是当前的研究热点。一个这样的实例，半乳糖氧化酶（GOase），是催化伯醇的有氧氧化的单核铜酶。为了了解铜与有机自由基相互作用的复杂性，制备了一系列席夫碱（salen），半还原salen和完全还原salen Cu（II）配合物及其单电子氧化形式。通过调整这些平面配体的电子性质，我们的目标是发展一个更深入的了解的因素，管理在其单电子氧化形式的氧化位点。根据氧化还原活性轨道的相对能量，具有前自由基配体的金属络合物可以以两种限制性电子形式存在：金属配体自由基（Mn+（L？））或高价金属络合物（M（n+1）+（L-））。在氧化的Cu-salen络合物的情况下，Cu（III）-酚盐或Cu（II）-苯氧基自由基物质是可能的，其可以通过配体场和/或温度的变化潜在地存在于价态互变异构平衡中。XAS调查将提供有关这些复合物的氧化位点的信息，以及稳定这些反应形式中的一种或另一种的电子因素。XAS是这项工作中特别有用的技术，因为它对金属氧化态特别敏感，并且它提供了一种理解几何和电子结构如何相互作用的方法（通过分析K边，EXAFS和L边）。这项研究中提出的工作涉及生物无机问题以及几个更基本的化学和光谱问题。

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. Copper enzymes exhibit a range of reactivities with dioxygen and the use of small-molecule models offers a means of probing enzyme mechanism in a detailed and systematic manner. The cooperativity of transition metal ions and pro-radical ligands in metalloenzyme active sites is of current research interest. One such example, Galactose oxidase (GOase), is a mononuclear copper enzyme that catalyzes the aerobic oxidation of primary alcohols. In an effort to understand the intricacies of the interaction of Cu with organic radicals, a series of Schiff-base (salen), half-reduced-salen, and fully reduced-salen Cu(II) complexes and their one-electron oxidized form have been prepared. By tuning the electronic properties of these planar ligands we aim to develop a deeper understanding of the factors that govern the oxidation locus in their one-electron oxidized forms. Depending on the relative energies of the redox-active orbitals, metal complexes with pro-radical ligands can exist in two limiting electronic forms: a metal-ligand radical (Mn+(L?)) or a high valent metal complex (M(n+1)+(L-)). In the case of the oxidized Cu-salen complexes, Cu(III)-phenolate or Cu(II)-phenoxyl radical species are possible, which can potentially exist in a valence tautomeric equilibrium through variation of the ligand field and/or temperature. XAS investigations will provide information on the locus of oxidation of these complexes, and the electronic factors that stabilize one or the other of these reactive forms. XAS is an especially useful technique for this work, as it is specifically sensitive to the metal oxidation state, and as it provides a means for understanding how geometric and electronic structure interact (via analysis of K-edge, EXAFS, and L-edge). The work proposed in this study addresses bioinorganic questions as well as several more fundamental chemical and spectroscopic issues.