CAREER: Mapping the Mechanisms of Photoredox Catalysis with Multidimensional Optical Spectroscopy

在化学系化学结构、动力学和机制A(CSDM-A)计划的支持下，亚利桑那大学的Vanessa Huxter正在使用先进的光谱方法研究光驱动催化反应的初始步骤，这种反应在温和的条件下产生简单和复杂的分子。为了了解这些反应是如何起作用的，赫克斯特博士和她的学生们将使用短至十亿分之一秒(一飞秒)的光脉冲来跟踪光引发的化学反应在广泛的时间范围内产生的化学物质。该项目将解决与推动这种反应有关的中间自由基物种的短寿命与发生这些反应所需的较长时间的扩散之间的知识差距。他们的发现可能会让人们更好地理解在合成工业和医药上重要的化学品时使用的催化剂，否则这些化学品很难生产。此外，参与该项目的研究生将接受多学科的高级培训，包括光学、化学和物理，该项目将通过开发和部署3D打印光谱仪吸引服务不足社区的学生，这将为历史上代表不足的群体的学生带来实践学习。Huxter团队使用时间分辨荧光、超快宽带瞬时吸收和跨越广泛时间和能量范围的二维电子光谱来研究光氧化还原催化体系中的光致单电子转移。将跟踪有机光氧化还原催化过程的初始步骤，以揭示与此类反应机制相关的自由能图景。这项研究将确定光氧化还原催化反应的驱动力和中间态，这可能为设计新的、高效的催化剂开辟道路。这项工作可能有助于解决关于自由基中间体的短寿命与扩散限制的双分子相互作用要求之间的不匹配的争议。我们将使用可分离的中性自由基来进一步研究自由基在光氧化还原催化中作为中间体的作用。此外，Huxter小组将调查振动模式对光催化电荷转移事件的影响。该奖项反映了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 support from the Chemical Structure, Dynamics, and Mechanisms A (CSDM-A) program in the Division of Chemistry, Vanessa Huxter of the University of Arizona is using advanced spectroscopic methods to study the initial steps of light-driven catalytic reactions that generate both simple and complex molecules under mild conditions. To understand how these reactions work, Dr. Huxter and her students will use pulses of light as short as a millionth of a billionth of a second (one femtosecond), to track the chemical species produced by light-triggered chemical reactions over a wide range of times. The project will address the knowledge gap between the short lifetimes of intermediate radical species that are implicated in driving such reactions, and the longer timescales of diffusion required for those reaction to happen. Their discoveries could lead to a better understanding of catalysts used in the synthesis of industrially and pharmaceutically important chemicals that are otherwise difficult to produce. In addition, graduate students working on this project will receive advanced training in multiple disciplines, including optics, chemistry, and physics, and the project will engage students of underserved communities through the development and deployment of 3D-printed spectrometers that will bring hands-on learning to students from historically underrepresented groups. The Huxter group uses time-resolved fluorescence, ultrafast broadband transient absorption, and two-dimensional electronic spectroscopy across a wide range of time and energy scales to study photoinduced single-electron transfer in photoredox catalytic systems. The initial steps of organic photoredox catalytic processes will be tracked to reveal the free energy landscapes associated with such reaction mechanisms. This research will identify the driving forces and intermediate states for photoredox catalytic reactions, which could open pathways to design new, efficient catalysts. This work could contribute to the resolution of a controversy regarding the mismatch between the short lifetimes of radical intermediates and the requirement for diffusion-limited bimolecular interactions. The role of radicals as intermediates in photoredox catalysis will be further studied using isolatable neutral radicals. In addition, the Huxter group will investigate the influence vibrational modes on photocatalytic charge transfer events.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.