Theoretical and Experimental Investigations of Photoheterolysis Reactions

有了这个奖项，化学结构动力学和机制-B计划支持光化学领域的基础研究，由亚瑟温特在爱荷华州州立大学进行。分子对光的吸收会导致化学键的断裂，但通常很难理解为什么或如何特定的键断裂。温特博士和他的学生试图了解一种一般类型的键断裂的结构反应性原理，特别是碳和离去基团之间键的光化学异裂。 异裂反应代表了化学键断裂的可能方式之一，键中的两个电子都被给予其中一个离开的基团。 光异裂解反应在生物学、材料科学和环境化学中具有重要的应用价值。该项目的长期目标是建立一个预测性的理论框架，该框架可以将化学结构与激发态反应性联系起来，从而提供指导光化学反应的新的指导性机械原理。 在更广泛的影响活动中，温特教授还将参与一项新生研究计划，该计划涉及大学一年级学生的早期多学科研究经验。他还将继续从代表性不足的群体中招募本科生和学生进入他的实验室。为了研究这些光异裂解反应，PI将采用理论/实验相结合的方法。高层次的计算方法将被用来映射模型系统中的激发态、过渡态和表面交叉拓扑结构。在实验上，光谱学将确定模型系统中结构对光释放速率和机制的影响。特别是，超快飞秒分辨瞬态吸收光谱将被用来确定选定的基板上的光致异构反应的速率和机制，而高水平的激发态计算将被用来提供一个机械原理。 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 this award, the Chemical Structure Dynamics and Mechanisms-B program is supporting fundamental research in the field of photochemistry, carried out by Arthur Winter at Iowa State University. The absorption of light by molecules can lead to cleavage of chemical bonds but it is often difficult to understand why or how specific bonds break. Dr. Winter and his students seek to understand the structure-reactivity principles for one general type of bond cleavage, specifically photochemical heterolysis of bonds between carbon and a leaving group. Heterolysis represents one of the possible ways in which a chemical bond can break, with both of the two electrons in the bond being given to one of the departing groups. Photoheterolysis reactions are important in biology, materials science and environmental chemistry. The long-term goal in this project is to create a predictive theoretical framework, which can relate chemical structure to excited state reactivity, thereby providing new guiding mechanistic principles that direct photochemical reactions. Among broader impacts activities, Professor Winter will also be involved with a Freshman Research Initiative that involves first year college students in an early multidisciplinary research experience. He will also continue to recruit undergraduates and students from underrepresented groups into his lab. To study these photoheterolysis reactions, the PI will employ a combined theoretical/experimental approach. High-level computational methods will be used to map excited state transition states and surface crossing topologies in model systems. Experimentally, spectroscopy will determine the effect of structure on the rates and mechanisms of photorelease in model systems. In particular, ultrafast femtosecond-resolved transient absorption spectroscopy will be used to determine the rates and mechanisms of photoheterolysis reactions on selected substrates, while high-level excited state calculations will be used to provide a mechanistic rationale. This research will provide a broad range of training for undergraduate and graduate students.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.