CAREER: Direct Interrogation of Proton-Coupled Electron Transfer Reaction Dynamics and Mechanisms with Cryogenic Ion and Ultrafast Vibrational Spectroscopies

在化学系化学结构、动力学和机理-A（CSDM-A）项目的支持下，圣路易斯华盛顿大学的Joseph Fournier博士和他的小组正在使用复杂的激光技术研究非常快速的化学反应。 具体来说，Fournier博士的团队正在研究一类特殊的反应，其中质子和电子同时从一个分子移动到另一个分子。这些反应是许多基本生物和化学过程的核心，包括光合作用和细胞呼吸，但很难用现有的实验方法进行研究。为了克服这些困难，福尼尔博士和他的学生正在开发一种新的方法，使他们能够直接跟踪反应在真实的时间与分子水平的细节。他们的测量结果有助于揭示和量化驱动这些反应的最重要因素，这是理解关键生物过程和开发用于绿色能源和化学合成的新分子的重要信息。该项目还包括在本科和研究生阶段实现物理化学教育现代化的努力，以及向圣路易斯地区高中学生介绍原子和分子的量子力学行为影响我们周围世界的方式的外联活动。 由质子耦合电子转移（PCET）反应驱动的催化过程在化学和生物学中普遍存在，然而目前对这些反应的理解以及定量预测涉及PCET的机制和反应动力学的能力仍然有限。Fournier博士和他的团队正在使用一套红外光谱技术来研究一系列仿生模型复合物的PCET反应。这些光谱技术包括气相低温离子振动光谱（CIVS），溶液相二维红外光谱（2DIR），以及一种称为时间分辨低温离子振动光谱（TR-CIVS）的新方法的开发和实施。TR-CIVS测量将以高频率分辨率和超快时间分辨率系统地探测气相中定义良好的系统，其目标是比以前更详细地表征难以捉摸的质子转移坐标。实验的目标是识别瞬态中间体及其形成的动力学，并将探讨隧道和低频氢键模式在质子转移过程中的作用。这项工作旨在为理解PCET机制提供重要的见解，并帮助开发新的计算模型，预测催化系统的化学结构如何决定其反应特性。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

With support from the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) Program in the Division of Chemistry, Dr. Joseph Fournier and his group at Washington University in St. Louis are using sophisticated laser techniques to study very fast chemical reactions. Specifically, Dr. Fournier’s group is investigating a special class of reactions in which protons and electrons simultaneously move from one molecule to another. These reactions are at the heart of many fundamental biological and chemical processes, including photosynthesis and cellular respiration, but are difficult to study with existing experimental methods. In order to overcome such difficulties, Dr. Fournier and his students are developing a new approach that allows them to directly track the reactions in real time with molecular-level detail. The results of their measurements help to unravel and quantify the most important factors that drive these reactions, which is vital information for understanding key biological processes and for developing new molecules for applications in green energy and chemical synthesis. The project also includes an effort to modernize physical chemistry education at the undergraduate and graduate levels, as well as outreach events that introduce St. Louis-area high school students to the ways in which the quantum mechanical behavior of atoms and molecules affects the world around us. Catalytic processes driven by proton-coupled electron transfer (PCET) reactions are ubiquitous in chemistry and biology, yet the current understanding of these reactions and the ability to quantitatively predict mechanisms and reaction dynamics involving PCET remains limited. Dr. Fournier and his team are using a suite of infrared spectroscopy techniques to study PCET reactions for a series of biomimetic model complexes. These spectroscopic techniques include gas-phase cryogenic ion vibrational spectroscopy (CIVS), solution-phase two-dimensional infrared spectroscopy (2DIR), as well as the development and implementation of a novel approach called time-resolved cryogenic ion vibrational spectroscopy (TR-CIVS). The TR-CIVS measurements will systematically probe well-defined systems in the gas phase with both high frequency resolution and ultrafast temporal resolution, with the goal of characterizing the elusive proton transfer coordinate in more detail than previously possible. The experiments target the identification of transient intermediates and the dynamics of their formation, and will probe the role of tunneling and low-frequency hydrogen-bonding modes in the proton transfer process. This work aims to provide important insight for understanding PCET mechanisms and to aid in the development of new computational models that predict how the chemical architecture of catalytic systems determines their reactive properties.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.