Investigating the Dioxygen Activation Mechanisms of Biologically Relevant Nonheme Iron Complexes

细菌利用多种含铁酶来分解环境中天然的和人为产生的化合物。这种反应通常是通过切断分子的碳-碳键来进行的，这一过程需要大气中的二氧。生物铁位点促进这些依赖O2的反应的机制尚不完全清楚，这阻碍了能够使用O2作为廉价和环保氧化剂的人造分子的设计。在这个项目中，Adam Fiedler博士正在生成一系列模型系统，从小型复合物到超分子组装，以获得在生物和人造环境下铁的O2反应性的分子水平的见解。利用光谱和计算工具的强大组合来表征在自然中提出（但很少观察到）的不稳定和瞬态物种。通过这种方式，该项目提供了对修复受污染土壤和地下水至关重要的反应的更全面的了解。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。Adam Fiedler博士与当地教师合作，让高中生参与将化学与艺术表达相结合的活动。这个拓展项目让学生接触到项目中使用的概念和仪器，从而提高科学素养和学生追求科学学位的机会。在化学部门CSDM-B项目的资助下，马凯特大学的Adam Fiedler博士正在开发合成含铁复合物，模仿非血红素铁双加氧酶的关键特征。分解碳-碳键的双加氧酶对于微生物降解和吸收来自自然和人类来源的有机化合物至关重要。然而，这些酶所使用的氧激活机制尚不完全清楚。特别是，控制以超氧、过氧和/或底物自由基配体为特征的关键中间体的反应性的几何和电子因素存在不确定性。本项目结合配位化学、反应动力学、光谱技术和计算方法，阐明生物启发铁配合物的结构和反应性之间的复杂关系，包括催化意义的瞬态中间体。此外，还开发了结合定义良好的第二球和第三球配体结构的新方法。这些努力为各种金属酶的O2活化过程提供了基础知识，并有助于设计新的氧化催化剂。本研究中使用的方法为本科生和研究生水平的科学家提供了跨学科的培训。Adam Fiedler博士还从事针对高中生的外展活动，通过强调无机化学和晶体学的视觉吸引力来激发学生对科学的兴趣。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.