CAS: Biologically Inspired Aminopyridine Complexes for CO2 Reduction

在化学系化学催化项目的支持下，南加州大学的Smaranda C. Marinescu将研究生物催化系统的发展，将有害的二氧化碳转化为化学燃料。面对地球迅速变暖，开发清洁能源技术作为化石燃料的替代品是一项迫切需要。作为一种清洁能源，太阳能受到了广泛的关注，但重点主要集中在发电上。这种狭隘的关注不能充分满足运输、供暖和工业用途对可再生燃料的需求，这些燃料占能源需求的70%左右。可持续能源的未来将需要一种非化石燃料的方法来形成化学原料，而利用太阳能产生的电力来电化学还原大量的小分子，如二氧化碳（CO2）和水（H2O），是一种可行的途径。这种方法将允许以化学键的形式储存太阳能，就像大自然通过光合作用完成的那样，光子的能量被用来驱动二氧化碳的减少，形成各种高能产品。受生物系统的启发，Marinescu小组将开发涉及氢键网络的分子催化剂，这种催化剂能够通过多个质子和电子转移激活小分子。该项目将专注于开发一系列具有悬垂胺的生物启发金属配合物，这将有助于理解质子继电器对多电子、多质子反应的影响。配体框架可以很好地控制电子和定位效应，这将有助于结构-活性研究。与该研究计划相结合的是一个教育项目，重点是为少数民族学生比例很高的当地社区大学的学生和教师提供研究机会，以及为博士后级别的女性提供指导项目，以增加这一代表性不足的群体在科学领域的参与。这些拓展和指导活动将长期影响大量个人：教师和他们的几代学生，以及南加州大学的研究人员。重要的是，参与这些努力的学生将培养一种为他们的科学和非科学社区做出贡献的文化，这种文化预计将持续到他们的成长阶段之后。在化学系化学催化项目的支持下，南加州大学的Smaranda C. Marinescu将研究悬浮质子继电器对氨基吡啶钴大环还原CO2的影响。Marinescu小组最近的研究表明，一系列具有0到4个挂载仲胺（NH）的钴配合物在CO2还原速率和挂载NH基团的数量之间表现出线性相关。实验和理论表明，悬垂的NH基团不会直接将质子转移到CO2中，而是与溶液中的酸分子结合，从而形成催化剂-酸加合物，通过氢键网络结合在一起，从而使质子从酸直接转移到活性CO2底物上。研究目标是通过表征和改变这些金属氨基吡啶大环的电子环境（初级和次级配位球），了解控制这些配合物的催化性能的因素，在活性和CO2还原选择性方面。本项目主要研究了各种氨基吡啶配合物的合成和表征，以了解这些部分对催化剂活性和选择性的影响。科学教育的目标将集中在：(1)为喜瑞都学院（一所公立社区学院，学生来自弱势群体的比例很高）的学生组织一次暑期研讨会，并在夏季期间邀请一名喜瑞都学院的学生在Marinescu实验室进行为期8周的本科生研究；(2)建立博士后级别的女性指导项目，提高女性在科学领域的参与度。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。

With the support of the Chemical Catalysis program in the Division of Chemistry, Smaranda C. Marinescu of the University of Southern California will study the development of biologically inspired catalytic systems for the conversion of harmful carbon dioxide into chemical fuels. The development of clean energy technologies as an alternative to fossil fuels is a critical need in the face of rapid planetary warming. Solar energy has received much attention as a clean energy source, but the focus has largely been on electricity generation. This narrow focus does not adequately meet the need for renewable fuels for transportation, heating, and industrial uses, which make up ~70% of energy needs. A sustainable energy future will require a non-fossil fuel method for the formation of chemical feedstocks, and the electrochemical reduction of abundant small molecules such as carbon dioxide (CO2) and water (H2O), using the solar-derived electricity is a viable pathway to do so. This approach will allow for storing of solar energy in chemical bonds in a similar way as nature accomplishes through photosynthesis, where the energy of photons is used to drive the reduction of CO2 to a variety of high-energy products. Inspired by biological systems, the Marinescu group will develop molecular catalysts that involve hydrogen-bonding networks which are capable of small molecule activation through multiple proton and electron transfers. This project will focus on the development of a series of biologically inspired metal complexes with pendant amines, which will allow for understanding the effect of proton relays on multi-electron, multi-proton reactions. The ligand framework allows for excellent control of electronic and positioning effects, which will facilitate structure-activity studies. Integrated into this research plan is an educational program focused on providing research opportunities to both students and teachers from local community colleges with a high percentage of minority students, and a mentoring program for women at the postdoctoral level to increase the participation of this underrepresented group in science. These outreach and mentoring activities will impact a significant number of individuals over the long term: teachers and generations of their students, along with researchers from USC. Importantly, students involved in these efforts will develop a culture of contributing to their scientific and non-scientific communities that is expected to last beyond their formative years.With the support of the Chemical Catalysis program in the Division of Chemistry, Smaranda C. Marinescu of the University of Southern California will study the effect of pendant proton relays on the CO2 reduction with cobalt aminopyridine macrocycles. Recent work in the Marinescu group has demonstrated that a series of cobalt complexes with zero to four pendant secondary amines (NH) displays a linear correlation between the rate of CO2 reduction and the number of pendant NH moieties. Experiment and theory suggest that the pendant NH groups do not directly transfer protons to CO2, but instead bind acid molecules from solution, leading to the formation of a catalyst-acid adduct, held together through a hydrogen-bonding network, that enables direct proton transfer from acid to the activated CO2 substrate. The research goal is to understand the factors that govern the catalytic properties of these complexes, in terms of activity and selectivity for CO2 reduction, by characterizing and altering the electronic environment (the primary and secondary coordination spheres) of these metal aminopyridine macrocycles. This project focuses on the synthesis and characterization of a variety of aminopyridine complexes with pendant hydrogen bond donors or cationic groups to understand the effects of these moieties on the catalyst activity and selectivity. The science education goals will focus on: (1) organizing a summer workshop for students from Cerritos College, a public community college with a high percentage of students from underrepresented groups and hosting a Cerritos College student in the Marinescu laboratory to perform undergraduate research for an 8-week period during the summer; and (2) developing a mentoring program for women at the postdoctoral level to increase the participation of women in science.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.