CAS: Nickel and Cobalt Hybrid Macrocycles for Oxidative Transformations of Organic Substrates

在化学系化学合成计划的支持下，弗吉尼亚联邦大学的希瑟·R·卢卡斯和凯瑟琳·贝莱基正在合成和研究一系列可以催化目标分子转化为增值产品的金属化合物。在自然的指导下，该项目利用从生物系统和生物无机模型化合物中获得的知识来综合设计有效和强大的过渡金属氧化剂。这些催化剂通过利用策略性设计的有机支架中持有的富含地球的金属(镍或钴)，并通过使用过氧化氢或二氧化碳等天然氧化剂进行氧化反应，促进了绿色化学的原则。这个项目将集中在这些设计催化剂的化学结构的一系列变化如何调整它们的反应活性，重点是促进对这些催化剂如何工作的分子理解。为了实现这些目标，将合成和表征催化剂变体，并对其反应性分布进行评估。精选的金属络合物还将被固定在易于从反应混合物中分离的颗粒上，从而能够回收和循环使用设计的催化剂，从而进一步推进部分启发了这项工作的绿色化学原则。该项目将为各种应用提供基础，包括以环境友好的方式制备基础和精细化学品或催化降解持久性化学污染物。它还有可能产生基础知识，为其他生物启发的氧化剂的合成设计提供信息。参与这项研究的学生不仅将接受尖端技术方面的培训，还将接受如何以战略和科学严谨的心态解决问题的培训。此外，生物启发催化和绿色化学的概念很容易与现实世界的现象联系在一起，因此将被PI和共同PI用来激发更广泛社区的自然科学好奇心，特别是通过与当地青年进行STEM(科学、技术、工程和数学)的扩展努力来激励下一代科学家。在化学系化学合成计划的支持下，弗吉尼亚联邦大学的希瑟·R·卢卡斯和凯瑟琳·贝莱基正在进行合成开发、表征、以及在一类新的过氧化氢激活的过渡金属络合物上的电子变化的应用，这些络合物被战略性地设计为使用瞬时金属(二)氧加合物作为有机分子的绿色氧化剂。该项目将包括合成同时含有二胺和二氨基供体原子的杂化N4大环配体家族，表征和评价它们的金属络合物作为有效的氧化催化剂，以及通过流动化学固定这些催化剂以提高可回收性和扩大操作窗口。将评估N4大环配体支架芳环上的取代对调节所产生的金属络合物的反应活性的贡献。这一系列电子类似物的催化物种的结构、电子和化学表征将通过广泛的光谱和分析技术来实现。将通过反应监测、同位素标记研究、动力学分析和Hammett分析进行高级机理研究。该系列催化剂在氧原子转移、氢原子提取和C-H活化反应中具有活性，广泛应用于工业(精细化工、医药)或学术(化学生物探针、仿生模型体系)目标分子的合成。这个项目旨在加深对金属-(二)氧配位络合物的基本了解，它们促进的氧化转化反应，以及配位络合物的配体和金属中心之间的电子转移考虑。这些研究的成功完成将为生物灵感绿色氧化剂的合成设计提供新的视角。此外，利用金属催化剂通过能效反应轨迹结合地球上丰富的金属，有可能为开发更经济和可持续的催化氧化程序做出贡献。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。

With the support of the Chemical Synthesis program in the Division of Chemistry, Heather R. Lucas and Katherine Belecki of Virginia Commonwealth University are synthesizing and studying a family of metal-containing compounds that can catalyze the conversion of target molecules into value-added products. Guided by Nature, this project uses knowledge gained from biological systems and bioinorganic model complexes to synthetically design potent and robust transition metal oxidants. These catalysts promote the principles of green chemistry by making use of earth-abundant metals (nickel or cobalt) held in a strategically designed organic scaffolds, and by performing oxidation reactions using natural oxidants like hydrogen peroxide or dioxygen. This project will focus on how a series of changes to the chemical structure of these designer catalysts can tune their reactivity, with an emphasis on advancing a molecular understanding of how these catalysts work. To accomplish these goals, catalyst variants will be synthesized and characterized, and their reactivity profiles will be evaluated. Select metallocomplexes will also be immobilized onto particles that are easily separated from reaction mixtures, enabling recovery and recycling of the designer catalysts and thus further advancing the green chemical principles that have, in part, inspired this work. This project will provide the basis for applications including the environmentally-friendly preparation of basic and fine chemicals or the catalytic degradation of persistent chemical contaminants. It also has the potential to generate fundamental knowledge that could inform the synthetic design of other bio-inspired oxidants. Students participating in this research will receive training not only in cutting-edge techniques but also in how to approach problem solving with a strategic and scientifically rigorous mentality. Moreover, concepts of bio-inspired catalysis and green chemistry are easily relatable to real-world phenomena, and thus will be used by the PI and the co-PI to pique the natural scientific curiosity of the broader community with a particular focus on inspiring the next generation of scientists through ongoing STEM (science, technology, engineering and mathematics) outreach efforts with local youth.With the support of the Chemical Synthesis program in the Division of Chemistry, Heather R. Lucas and Katherine Belecki of Virginia Commonwealth University are pursuing the synthetic development, characterization, and application of electronic variations on a new class of hydrogen peroxide-activating transition-metal complexes that are strategically designed to employ transient metal-(di)oxygen adducts as green oxidants of organic molecules. This project will involve the synthesis of hybrid N4 macrocyclic ligand families containing both diamido and diamino donor atoms, the characterization and evaluation of their metallocomplexes as effective oxidation catalysts, and the immobilization of these catalysts for improved recyclability and expanded windows of operability enabled by flow chemistry. Substitutions on the aromatic ring of the N4 macrocyclic ligand scaffold will be assessed for their contributions to tuning the reactivity of the resulting metallocomplexes. Structural, electronic, and chemical characterization of the catalytic species for this series of electronic analogues will be achieved through a wide range of spectroscopic and analytical techniques. Advanced mechanistic studies will be pursued through reaction monitoring, isotopic labelling studies, kinetic profiling, and Hammett analyses. This catalyst family is active in oxygen atom transfer, hydrogen atom abstraction, and C-H activation reactions, all of which are broadly applicable in the synthesis of target molecules related to industrial (fine chemicals, pharmaceuticals) or academic (chemical biology probes, biomimetic model systems) applications. This project aims to deepen fundamental understanding of metal-(di)oxygen coordination complexes, the oxidative transformation reactions that they promote, and electron transfer considerations between ligands and metal centers of coordination complexes. Successful completion of these studies will provide new perspectives for the synthetic design of bioinspired green oxidants. Moreover, harnessing metal catalysts that incorporate earth abundant metals through energy efficient reaction trajectories has the potential to contribute to the development of more economical and sustainable catalytic oxidation procedures.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.