Gas Phase Ion Reaction Dynamics of Catalytic Systems

我的研究重点是气相离子的反应动力学。我们用质谱学、成像光电子光离子符合谱(IPEPICO)和红外多光子光解离(IRMPD)谱结合统计速率理论和计算化学进行了这项工作。我的团队的一个主要关注点是开发模型，为各种质谱学实验中的气相离子离解提取可靠的能量学和熵。在此之前，我们已经专注于小的多环芳烃，并探索了原子金属阴离子独特的离子化学。这一建议涉及对催化中感兴趣的离子的基本性质的新的关注，特别是在溶液和星际催化中感兴趣的有机金属体系。 催化体系的内在性质往往很难确定，而且通常实际的关键活性物种是未知的。配体结合能、结构重排和中间物种都是理解催化剂工作原理的关键。带电有机金属离子可以通过其准确的质量、碰撞截面和解离特性来表征，所有这些都可以在我的实验室的质谱仪上获得。有机金属离子的离解将作为碰撞能量的函数进行，并使用实验参数、RRKM理论和作为碰撞能量函数的内部能量分布来模拟所产生的质量谱击穿图。这产生了解离配体的键强度和反应路径上的熵信息。这项工作得到了来自iPEPICO实验的动力学数据的帮助。将使用IRMPD光谱探测离子结构，以获得气体离子的红外光谱，这是在法国CLIO自由电子激光器上完成的。将从这些实验中获得的信息扩展到描述复杂的离子反应机理，这可以揭示催化活性中间体，但应用有限。这项研究计划将针对各种有机金属物种，最终导致活性、空气和湿度敏感催化剂的合成和检测。目前提议的目标之一是发展纳米液滴反应化学电离作为合成和表征这些催化剂的常规工具。我们在实验室中证明，当两个电喷嘴的微米到纳米尺寸的液滴混合时，可以发生反应，从而使溶液相化学在液滴最终解溶之前发生。初步实验表明，通过将一个喷雾发射器的配体与另一个喷雾发射器的金属盐混合，可以形成各种各样的有机金属络合物，包括以前没有观察到的新物种。

My research focuses on the dynamics of the reactions of gas-phase ions. We pursue this work with mass spectrometry, imaging photoelectron photoion coincidence spectroscopy (iPEPICO) and infrared multiphoton photodissociation (IRMPD) spectroscopy coupled with statistical rate theory and computational chemistry. A principle focus of my group is the development of models to extract reliable energetics and entropics for the dissociation of gas-phase ions in a wide variety of mass spectrometry experiments. Previously we have focused on small polycyclic aromatic hydrocarbons and explored the unique ion chemistry of atomic metal anions. This proposal involves a new focus on the fundamental properties of ions of interest in catalysis, notably organometallic systems of interest in solution and interstellar catalysis. The intrinsic properties of catalytic systems are often difficult to ascertain, and often the actual key, active species is not known. Ligand binding energies, structural rearrangements and intermediate species are all key to understanding how catalysts work. Charged organometallic ions can be characterized by their accurate mass, collision cross-section and dissociation characteristics, all of which are accessible on the mass spectrometry instrumentation in my lab. The dissociation of organometallic ions will be carried out as a function of collision energy, and the resulting mass spectral breakdown diagrams modeled using experimental parameters, RRKM theory and an internal energy distribution that is a function of the collision energy. This yields bond strengths for the dissociating ligands and entropic information on the reaction pathway. This work is aided by the availability of kinetic data from iPEPICO experiments. Ion structure will be probed using IRMPD spectroscopy to obtain the IR spectra of gaseous ions, done at the French CLIO free electron laser. Extending the information obtained from these experiments to describe complex ion reaction mechanisms, which can shed light on catalytically-active intermediates, has only seen limited application. This research program will target a wide variety of organometallic species, leading ultimately to the synthesis and examination of active, air and moisture sensitive catalysts. One goal of the current proposal is to develop nano-droplet reaction chemical ionization as a routine tool for the synthesis and characterization of these catalysts. We have demonstrated in our lab that reactions can take place when the micro- to nano-sized droplets from two electrospray emitters mix, permitting solution-phase chemistry to take place prior to the final desolvation of the droplets. Preliminary experiments have shown that a wide variety of organometallic complexes, including novel species not previously observed, can be formed by mixing a ligand from one spray emitter with a metal salt from the other.