Hydrocarbon and ammonia activation by transition metal cations and cluster ions: Spectroscopy and photofragment imaging of reactants and intermediates

在这个由化学系化学结构、动力学和机制项目资助的项目中，马萨诸塞州阿默斯特大学的里卡多·梅斯教授正在研究金属离子和金属簇离子如何与甲烷和氨相互作用，并催化它们转化为更具工业用途的化学品。虽然天然气被广泛用于加热和发电，但它通常不被用作运输燃料。这是因为甲烷（天然气的主要成分）是一种气体，在室温下不能通过压力变成液体。将甲烷转化为在室温下为液体的化合物，例如较大的烃（例如，辛烷）或甲醇，将使其作为运输燃料更有用。 教授梅斯还帮助介绍八年级的女孩通过尤里卡在干领域的研究！程序.这项工作的更广泛的影响包括改进催化剂的潜在好处，以及对研究生和本科生进行质谱和激光光谱学方面的培训，以及更广泛的技能，如解决问题，仪器设计，数据采集和分析以及结果交流。金属簇离子甲烷/氨络合物在激光烧蚀源中产生，通过超声膨胀冷却并在质谱仪中使用振动和电子光谱学表征。甲烷或氨配体与金属的相互作用削弱了配体中的碳（C）-氢（H）或氮（N）-H键，并且这种削弱是这些键随后催化活化的关键。实验测量了金属的键弱化和极化，因为它们导致振动频率的红移和增强的红外吸收。振动光谱还揭示了反应中间体和产品的身份的情况下，可能涉及多种异构体，如在顺序甲烷活化。通过研究不同的金属和具有不同数量的金属原子的簇，这些研究阐明了导致尺寸依赖性反应性的结构和电子因素。互补速度图成像研究研究电子激发后的离子解离动力学，测量精确的键强度并探测激发电子态之间的耦合。这项工作的更广泛影响包括改进催化剂的潜在好处以及研究生和本科生的培训。

In this project funded by the Chemical Structure, Dynamics, and Mechanisms program of the Chemistry Division, Professor Ricardo Metz of the University of Massachusetts Amherst is studying how metal ions and metal cluster ions interact with methane and ammonia, and catalyze their conversion to more industrially useful chemicals. Although natural gas is widely used for heating and to generate electricity, it is not typically employed as a transportation fuel. This is because methane (the major component of natural gas) is a gas that cannot be turned into a liquid at room temperature using pressure. Converting methane into a compound that is liquid at room temperature, such as a larger hydrocarbon (e.g., octanes) or methanol, will make it much more useful as a transportation fuel. Professor Metz is also helping to introduce eighth-grade girls to research in STEM fields through the Eureka! program. The broader impacts of this work include potential benefits from improved catalysts as well as the training of graduate and undergraduate students in mass spectrometry and laser spectroscopy and in broader skills such as problem solving, instrument design, data acquisition and analysis and communication of their results.Metal cluster ion-methane/ammonia complexes are produced in a laser ablation source, cooled via supersonic expansion and characterized using vibrational and electronic spectroscopy in a mass spectrometer. Interaction of the methane or ammonia ligand with the metal weakens the carbon (C)-hydrogen (H) or nitrogen (N)-H bonds in the ligand, and this weakening is key to the subsequent catalytic activation of these bonds. The experiments measure bond weakening and polarization by the metal, as they lead to red shifts in vibrational frequencies and enhanced IR absorption. Vibrational spectroscopy also reveals the identity of reaction intermediates and products in cases where multiple isomers could be involved, as in sequential methane activation. By studying different metals and clusters with differing numbers of metal atoms, these studies elucidate the structural and electronic factors that lead to size-dependent reactivity. Complementary velocity map imaging studies study ion dissociation dynamics following electronic excitation, measuring accurate bond strengths and probing the couplings between excited electronic states. The broader impacts of this work include potential benefits from improved catalysts as well as the training of graduate and undergraduate students.