CAS: Spectroscopy and Reactivity of Isolated Metal-oxo Complexes

有了这笔赠款，化学结构、动力学和机制-B项目将支持威斯康星大学麦迪逊分校的艾蒂安·加兰德教授的研究。该项目的重点是提高将太阳能转化为化学燃料所涉及的基本过程的效率。人工光合作用是一种很有前途的太阳能储存方式。水氧化过程是人工光合作用的关键，它包括分解水(H2O)为氧(O2)和质子(H+)。水分解的研究挑战在于降低执行该反应所需的大量额外能量。为了降低这一能量，人们报道了大量的催化剂。对催化剂的研究强调了理解催化水氧化本身的必要性，以便能够应用合理的催化剂设计。这项研究项目使用了多种工具--质谱学和激光光谱学--来探测水氧化反应中的中间产物--关键的催化络合物。这些研究的结果阐明了这些活性络合物的结构和反应活性，并为计算化学方法提供了严格的基准，这些方法可以用于未来的催化剂设计。此外，该研究项目通过为学生提供指导、高级培训和职业发展，使多样化和具有竞争力的STEM劳动力受益。该项目将支持该团队参与三个旨在增加STEM多样性的项目；即旨在增加申请研究生课程的竞争较少的博士生的ACS桥梁；为学生提供访问化学系并了解研究生项目的机会的CHAPS；以及为目标一年级研究生提供个人指导和支持的CATALYER。本研究项目阐述了利用太阳能进行水氧化的机制。在这个机制中的一个关键步骤包括水分子对金属-氧物种的亲核攻击和O-O键的形成。在早期NSF支持下开发的方法的基础上，该实验方法基于顺序低温离子陷阱，用于受控操纵和表征离子和团簇。这提供了产生高活性中间体并直接探测它们的结构和反应性的能力。通过低温离子预解离光谱对其化学结构进行了精确的表征。本项目：1)表征金属-氧配合物的电子结构和自旋态，以及它们与金属中心的性质和配体的影响的关系；2)探索金属-氧配合物与水分子之间的内在反应性和相互作用，特别是O-O键的形成倾向及其与M=O基团的电子结构的关系；以及3)定义碱和扩展的水溶剂网络在诱导结构变化和相互作用中的作用，这些变化和相互作用促进和促进关键的O-O形成步骤。这项研究通过提供研究生水平的培训和职业发展来促进多样化和有竞争力的劳动力的发展。这一奖项反映了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 this grant, the Chemical Structure, Dynamics, and Mechanisms-B program is supporting the research of Professor Etienne Garand at the University of Wisconsin-Madison. The project focuses on improving the efficiency of fundamental processes involved in the conversion of solar energy into chemical fuels. Artificial photosynthesis is a promising option for the storage of solar energy. The water oxidation process is key to artificial photosynthesis, it includes the splitting water (H2O) into oxygen (O2) and protons (H+). The research challenge in water splitting resides in lowering its substantial extra energy needed to perform this reaction. To reduce this energy, a large number of catalysts have been reported. The search for catalysts underscores the need for understanding the catalytic water oxidation itself, such that rational catalyst design can be applied. This research project utilizes a combination of tools - mass spectrometry and laser spectroscopy - to probe critical catalytic complexes which are intermediates in the water oxidation reaction. The results from these studies clarify the structures and reactivity of these reactive complexes and provide stringent benchmarks for computational chemistry methods, which can then be used to design future catalysts. In addition, this research project benefits a diverse and competitive STEM workforce by providing mentorship, high-level training and career development for students. The project will support the team's participation in three programs aimed at increasing diversity in STEM; namely, the ACS Bridge to the doctorate which aims at increasing the pool of competitive underrepresented students applying to graduate program; CHOPS which provides an opportunity for students to visit the chemistry department and learn about the graduate program, and CATALYST which provides individual mentoring and support to targeted first-year graduate students.This research project addresses the mechanism for water oxidation using solar energy. A critical step in this mechanism involves nucleophilic attack of a water molecule on a metal-oxo species and the formation of an O-O bond. Building on methodology developed with earlier NSF support, the experimental approach is based on sequential cryogenic ion traps for the controlled manipulation and characterization of ions and clusters. This provides the capabilities to generate highly reactive intermediates and directly probe their structure and reactivity. Precise chemical structure characterizations of the complexes are obtained via cryogenic ion predissociation spectroscopy. This project: 1) Characterizes the electronic structure and spin state of metal-oxo complexes and their relationship with the nature of the metal center and the influence of the ligands; 2) Explores the intrinsic reactivity and interactions between metal-oxo complexes and water molecules, with particular focus on the propensity to form O-O bond and its relationship to the electronic structure of the M=O group; and 3) Defines the role of bases and an extended water solvent network in inducing structural changes and interactions that promote and facilitate the critical O-O formation step. This research promotes the development of a diverse and competitive workforce by providing training and career development at the graduate level.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.