Investigating the Dioxygen Activation Mechanisms of Biologically Relevant Nonheme Iron Complexes

细菌使用各种各样的含铁酶来分解环境中的天然和人类生成的化合物。这类反应通常是通过在需要大气中氧气(O2)的过程中断裂分子的碳-碳键来进行的。生物铁促进这些依赖氧气的反应的机制还不完全清楚，这阻碍了人造分子的设计，这些分子能够将氧气作为一种廉价和环境友好的氧化剂。在这个项目中，Adam Fiedler博士正在建立一系列模型系统，从小的络合物到超分子组装，以获得分子水平上对生物和人造环境中铁的氧气反应性的见解。光谱和计算工具的强大组合被用来描述已经在《自然》杂志上提出(但很少观察到)的不稳定和瞬时物种。通过这种方式，该项目提供了对修复受污染的土壤和地下水至关重要的反应的更完整的图景。该项目的跨学科性质为研究生和本科生提供了宝贵的实验和理论方法培训经验。亚当·菲德勒博士与当地教师合作，让高中生参与将化学与艺术表现相结合的活动。这一外展计划使学生接触到项目中使用的概念和工具，从而提高了科学素养，并增加了学生攻读大学理科学位的机会。在化学系CSDM-B项目的资助下，马奎特大学的Adam Fiedler博士正在开发模仿非血红素铁双加氧酶的关键特征的合成含铁复合体。裂解碳-碳键的双加氧酶对于微生物降解和同化来自自然和人类来源的有机化合物至关重要。然而，这些酶激活O2的机制还不完全清楚。特别是，关于控制具有超氧、过氧基和/或底物自由基配体的关键中间体的反应活性的几何和电子因素存在不确定性。该项目结合了配位化学、反应动力学、光谱技术和计算方法，阐明了生物启发的铁配合物，包括具有催化意义的瞬时中间体，结构和反应性之间的复杂关系。此外，还开发了结合定义良好的第二和第三球配体结构的新方法。这些工作提供了关于各种金属酶中O2活化过程的基础知识，并有助于设计新的氧化催化剂。这项研究中使用的方法为本科生和研究生水平的科学家提供跨学科培训。Adam Fiedler博士还参与了针对高中生的外展活动，通过强调无机化学和结晶学的视觉吸引力来激发学生对科学的兴趣。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Bacteria employ a wide variety of iron-containing enzymes to breakdown natural and human-generated compounds in the environment. Such reactions commonly proceed by cleaving the carbon-carbon bonds of the molecules in a process that requires dioxygen (O2) from the atmosphere. The mechanism by which biological iron sites facilitate these O2-dependent reactions is not fully understood, which hinders the design of man-made molecules capable of using O2 as a cheap and environmentally-friendly oxidant. In this project, Dr. Adam Fiedler is generating a series of model systems, ranging from small complexes to supramolecular assemblies, to obtain molecular-level insights into the O2 reactivity of iron in both biological and man-made contexts. A powerful combination of spectroscopic and computational tools is utilized to characterize unstable and transient species that have been proposed (but rarely observed) in Nature. In this way, the project provides a more complete picture of reactions that are essential for the remediation of polluted soils and groundwaters. The interdisciplinary nature of the project offers a valuable training experience in both experimental and theoretical methods for graduate and undergraduate students. Dr. Adam Fiedler collaborates with local teachers to engage high-school students in activities that combine chemistry with artistic expression. This outreach program exposes students to concepts and instrumentation used in the project, thereby increasing scientific literacy and the chances that students pursue college degrees in science. With funding from the CSDM-B Program of the Chemistry Division, Dr. Adam Fiedler of Marquette University is developing synthetic iron-containing complexes that mimic key features of nonheme iron dioxygenases. Dioxygenases that cleave carbon-carbon bonds are critical for the microbial degradation and assimilation of organic compounds that arise from both natural and human sources. However, the O2 activation mechanisms employed by these enzymes are not fully understood. In particular, there is uncertainty regarding the geometric and electronic factors that govern the reactivity of pivotal intermediates featuring superoxo, peroxo, and/or substrate radical ligands. This project combines coordination chemistry, reaction kinetics, spectroscopic techniques, and computational methods to illuminate the complex relationships between structure and reactivity in bio-inspired iron complexes, including transient intermediates of catalytic significance. In addition, new approaches for incorporating well-defined second- and third-sphere ligand architectures are developed. These efforts provide fundamental knowledge regarding O2 activation processes in a variety of metalloenzymes and aid in the design of new oxidation catalysts. The methods used in this research offer interdisciplinary training for undergraduate and graduate-level scientists. Dr. Adam Fiedler is also engaged in outreach activities directed towards high-school students that stimulate interest in science by emphasizing the visually appealing aspects of inorganic chemistry and crystallography.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.