Collaborative Research: Coupled Proton/Electron Transfer Reactions of Excited States

在这个由化学结构、动力学和机制-B计划资助的项目中，杜兰大学化学系的Russell Schmehl教授和维拉诺瓦大学化学系的Jared Paul教授正在开发新的过渡金属络合物，作为光吸收材料，能够将质子和电子转移到其他分子。研究中的金属络合物是重要的模型系统，可能有助于提高太阳能转换器(太阳能电池)的效率。该项目对水氧化制氧、水还原为氢、二氧化碳还原为氢化产物等太阳能燃料的设计具有直接意义。调查人员致力于教育公众有关能源和环境的问题。作为这项工作的一部分，保罗博士正在建立一个维拉诺瓦中心，以了解和交流与能源和环境有关的问题，并开发了一门关于可持续发展的本科课程。杜兰大学定期开设与能源相关的科学咖啡馆。这两位研究人员都致力于将与能源相关的科学主题带给儿童，特别是中学生。这项研究将涉及杜兰大学博士级别的长期项目，以及两所大学的本科生和硕士级别的研究。在维拉诺瓦大学和杜兰大学的一项合作项目中，化学家计划研究一系列过渡金属络合物的激发态之间的光触发质子转移、电子转移和质子耦合电子转移(PCET)，这些过渡金属络合物具有一个羟化的联吡啶(或邻菲咯啉)配体和各种电子和/或质子受体。能够独立地检查每个反应的动力学对自由能的依赖性，这为研究提供了动力。由于这些反应是由脉冲激光激发的，因此可以跟踪这些过程的时间演变，并将真正的PCET与可能电子转移先于质子转移的反应区分开来。初步工作表明，一系列Ru(II)羟基联吡啶的络合物、单一的去质子化的络合物以及氧化和去质子化的物种的光谱不同。纳秒脉冲激光瞬变吸收光谱学可以用来清楚地区分只表现出质子或电子转移的系统，与其他表现出电子转移之后又发生质子转移的系统以及那些通过质子和电子转移耦合反应的系统。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。

In this project, funded by the Chemical Structure, Dynamics and Mechanisms-B Program, Professors Russell Schmehl of the Department of Chemistry at Tulane University and Jared Paul of the Villanova University Chemistry Department are developing new transition metal complexes that serve as light absorbers capable of transferring both protons and electrons to other molecules. The metal complexes under study are important as model systems which may help improve the efficiency of solar energy converters (solar cells). The project is of direct significance to the design of solar fuels such as water oxidation to oxygen, water reduction to hydrogen and carbon dioxide reduction to hydrogenated products. The investigators are committed to educating the public on issues relating energy and the environment. As a part of this work, Dr. Paul is establishing a Villanova center for understanding and communicating issues relating to energy and the environment and has developed an undergraduate course on sustainability. Tulane has regular science cafes on topics related to energy. Both investigators are committed to bringing energy-related science topics to children, particularly middle school aged students. The research will involve long-term projects at the Ph.D. level at Tulane as well as undergraduate and master's level research at both universities. In a collaborative venture between Villanova University and Tulane University, chemists plan to examine optically-triggered proton transfer, electron transfer, and proton-coupled electron transfer (PCET) between the excited states of a series of transition metal complexes of copper(I), ruthenium(II) and osmium(II) having one hydroxylated bipyridine (or phenanthroline) ligand and a variety of electron and/or proton acceptors. The ability to independently examine the free energy dependence of the kinetics of each of these reactions provides motivation for the research. Since the reactions are initiated by pulsed laser excitation, it is possible to track the temporal evolution of the processes and distinguish true PCET from reactions in which, perhaps, electron transfer precedes proton transfer. Preliminary work has illustrated that the optical spectra differ for the complex, the singly deprotonated complex and the oxidized and deprotonated species in a series of ruthenium(II) hydroxybipyridine complexes. Nanosecond pulsed laser transient absorption spectroscopy can be used to clearly distinguish systems that exhibit solely proton or solely electron transfer from others exhibiting electron transfer followed by proton transfer and those that react by coupled proton and electron transfer.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.