Structural characterization of organometallic reaction intermediates and vibrational mechanics of water cages with temperature-controlled cryogenic ion spectroscopy

通过这个奖项，化学结构、动力学和机制项目支持耶鲁大学Mark A. Johnson教授的基础研究。约翰逊正在开发一种新型的科学仪器，可以从溶液中提取复杂分子结构的精确结构信息。在这笔资助下，他将扩大该方法的范围，使其能够捕获和结构表征关键反应中间体，这些中间体是当代均相有机金属催化剂激活小分子（例如，烯烃，H2O, H2）机制的基础。识别这些暂态物种的动机是，目前，催化剂设计的大部分努力都是基于总体产量的大量试验和错误，而对于化学转化的哪些方面受到各种修饰的影响，人们通常知之甚少。参与这项工作的学生和访问学者将生物分析化学与原子、分子和光学（AMO）物理学相结合，创造了一个化学分析的新平台。因此，该计划直接将物理化学学生与合成同事所面临的直接挑战联系起来，从而培养具有多种技能的新一代科学家，并以化学科学为中心。他与俄亥俄州立大学的理论同事Anne McCoy教授进行了持续而广泛的合作，通过为年轻理论家创造一个互动场所来提高他们在新兴科学主题上的技能，进一步扩大了这项工作的影响。直接参与该项目的研究生和博士后也与德国的实验室密切合作。这也有助于他们做好准备，在竞争日益激烈的国际基础科学精英舞台上发挥作用。在离耶鲁更近的地方，这个项目通过暑期研究机会整合了本科院校的教师，而来自附近大学的没有研究生课程的学生则通过在耶鲁进行高级研究项目而被纳入正在进行的工作中。最后，这个项目有一个悠久的传统，它向纽黑文学校的学生敞开大门，向他们展示他们正在学习的基本科学原理是如何在开发中的新方法的基础上发挥作用的。低温离子振动预解离光谱（CVIP）是一种集质谱分析和高分辨率红外光谱分析于一体的新型仪器技术。该方法的一个关键特征是对气相离子进行低温处理，以有效地将反应物质淬灭成定义良好的结构，从而在其振动光谱中产生足够清晰的特征，从而可以确定结构。这是使用振动预解离光谱进行的非常弱结合加合物附着在一个定制的目标离子上，保持在5K的射频离子阱。除了将其应用于催化之外，提出的工作还解决了关键的悬而未决的问题，这些问题涉及纯水的体积行为以及与带电溶质直接接触的水分子层的关键局部相互作用。由于水的微观行为是许多科学领域的核心，这方面的工作正在进行中，并影响了从视觉机制到污染环境中重金属修复的努力。

With this award, the Chemical Structure, Dynamics and Mechanisms program is supporting fundamental research of Professor Mark A. Johnson at Yale University. Johnson is developing a new type of scientific instrument that yields precise structural information on complex molecular architectures extracted from solution. Under this grant, he will expand the scope of the method to enable the capture and structural characterization of key reaction intermediates that underlie the mechanisms of small molecule (e.g., alkenes, H2O, H2) activation by contemporary homogeneous organometallic catalysts. The motivation to identify these transient species is that, at present, much of the effort in catalyst design involves extensive trial and error based on overall yield, while little is often known about exactly what aspects of the chemical transformation are being affected by the various modifications. Students and visiting faculty involved in this endeavor integrate elements of bioanalytical chemistry with atomic, molecular and optical (AMO) physics to create a new platform for chemical analysis. As such, this program directly interfaces physical chemistry students with immediate challenges addressed by synthetic colleagues, and consequently prepares a new generation of scientists with a versatile skill set, well centered in the chemical sciences. An ongoing and extensive collaboration with theoretical colleague Prof. Anne McCoy at Ohio State further broadens the impact of the work by creating an interactive venue for young theorists to sharpen their skills on emergent scientific themes. Graduate students and postdocs directly involved in the project also work in close collaborations with laboratories in Germany. This also contributes to their preparedness to perform at an increasingly competitive international level in the elite arena of basic science. Closer to home, this program integrates faculty from undergraduate institutions through summer research opportunities, and students from nearby universities without graduate programs are incorporated into ongoing work by carrying out senior research projects at Yale. Finally, this program has a longstanding tradition of opening its doors to students in the New Haven schools to illustrate how the basic science principles they are learning are in play at the foundation of the new methods under development. Cryogenic Ion Vibrational Predissociation Spectroscopy (CVIP) is a new instrumental technique which integrates mass spectrometry with high resolution infrared spectroscopy. One key feature of the approach is the implementation of cryogenic processing of the gas phase ions to effectively quench the reactive species into well-defined structures that yield sufficiently sharp features in their vibrational spectra to allow structure determination. This is carried out using vibrational predissociation spectroscopy of very weakly bound adducts attached to target ions in a custom built, radio frequency ion trap held at 5K. In addition to its application to catalysis, the proposed work also addresses key unanswered questions regarding the critical local interactions that underlie bulk behavior of pure water as well as the layer of water molecules in direct contact with charged solutes. Because the microscopic behavior of water is central to so many fields of science, this aspect of the work is ongoing, and has impacted efforts ranging from the mechanism of vision to the remediation of heavy metals in contaminated environments.