Advanced Time-Resolved Studies of the O-O Bond Formation Mechanisms: Interplay of the Metal and Ligand Redox Reactivity

普渡大学物理与天文学系的Yulia Pushkar教授在化学学部化学结构、动力与机制B项目的支持下，研究了人工光合作用中二氧（O2）形成的时间分辨机制。在人工光合作用中，太阳能通过产生清洁燃料氢和氧转化为化学能，这一过程需要化学键的重新排列。对这一过程的基本理解是开发能够模拟自然光合作用的新催化剂和设备所必需的。人工光合作用的发展及其大规模实施可以解决现代社会的能源需求。这项研究是物理、化学和材料科学的结合，其成果有望影响多个领域，为基础科学、教育和国家能源安全做出贡献。计划中的研究和教育活动旨在增加来自经济弱势背景的代表性不足的学生的参与，改善女学生在STEM（科学、技术、工程和数学）方面的经验，通过将研究成果纳入课程来加强对学生的培训，并向学校提供教学模块。本项目主要研究人工光合作用复杂的多电子化学过程。一个主要的项目目标是确定参与水氧化的关键中间体的结构、电子构型和动力学。在这种多尺度方法中，时间分辨技术监测新设计的钌催化剂的结构和电子态的演变，重点关注氧-氧键形成的关键机制及其对配体结构的依赖。采用实验和量子力学计算模型相结合的方法对分子结构与催化活性之间的关系进行了检验。本研究的原位催化水氧化实验技术是基于同步加速器的x射线光谱学，包括x射线吸收近边结构（XANES）、扩展x射线吸收精细结构（EXAFS）、电子顺磁共振（EPR）和多波长动力学共振拉曼光谱。这些实验技术提供了关于中间体的结构和它们在催化过程中演变的电子构型的信息。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。

In this project supported by the Chemical Structure, Dynamic & Mechanism,B Program of the Chemistry Division, Professor Yulia Pushkar of the Department of Physics and Astronomy at Purdue University studies the time-resolved mechanism of dioxygen (O2) formation in artificial photosynthesis. In artificial photosynthesis, solar energy is converted into chemical energy through generation of the clean fuels hydrogen and oxygen, a process which requires rearrangement of chemical bonds. Fundamental understanding of this process is required for the development of new catalysts and devices which are able to mimic natural photosynthesis. The development of artificial photosynthesis and its large-scale implementation can address energy needs of modern society. This research lies at the interface of physics, chemistry and materials science, with results expected to impact diverse fields and contribute to fundamental science, education and national energy security. Planned research and educational activities are designed to increase participation of under-represented students from economically disadvantaged backgrounds, improve experiences of female students in STEM (Science, Technology, Engineering and Mathematics), enhance training of students via integration of research results into curricula and to deliver teaching modules to schools. Research in this project focuses on the complex multi-electron chemical process of artificial photosynthesis. A major project goal is to determine the structure, electronic configurations and dynamics of the critical intermediates involved in water oxidation. In this multi-scale approach, time-resolved techniques monitor the evolution of structure and electronic states in newly designed ruthenium catalysts, with a focus on the key mechanism of oxygen-oxygen bond formation and its dependence on ligand structure. The relationship between molecular structure and catalytic activity is tested by a combination of experiments and quantum-mechanical computational models. Experimental techniques in this study of in situ catalytic water oxidation are synchrotron-based X-ray spectroscopy, including X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS), electron paramagnetic resonance (EPR) and multi-wavelength kinetic resonance Raman spectroscopy. These experimental techniques deliver information on the structure of the intermediates and their electronic configuration as they evolve during the catalytic process.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.