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

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。 铜酶表现出与氧气的一系列反应，而小分子模型的使用提供了一种详细和系统地探索酶机理的手段。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目前研究的热点。一个这样的例子，半乳糖氧化酶(GOase)，是一种单核铜酶，催化伯醇的有氧氧化。为了了解铜与有机自由基相互作用的复杂性，合成了一系列席夫碱(Salen)、半还原Salen和全还原Salen铜(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，我们的目标是更深入地了解控制其单电子氧化形式的氧化轨迹的因素。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配合物可以以两种极限电子形式存在：金属配体自由基(Mn(L？))或高价金属络合物(M(N 1)(L-))。对于氧化的铜-Salen络合物，可能存在铜(III)-苯酚或铜(II)-苯氧基自由基物种，它们可能通过改变配位场和/或温度而存在于价互变异构平衡中。XAS研究将提供有关这些络合物的氧化位置以及稳定这些活性形式之一的电子因素的信息。XAS对于这项工作是一项特别有用的技术，因为它对金属的氧化态特别敏感，而且它提供了一种了解几何结构和电子结构如何相互作用的方法(通过分析K-EDGE、EXAFF和L-EDGE)。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.