Spectroscopic Studies of C-H and C-C Bond Activation by Transition Metal and Metal Oxide Cations

实验物理化学项目支持麻省大学里卡多·梅斯教授和他的学生的研究。Metz将研究过渡金属和金属氧化物阳离子激活C-C和C-H键的中间体、反应物和反应产物的光谱和动力学。电子光谱将表征激发态，而红外（IR）光谱将探测离子的基电子态的键合和振动。红外光谱是通过使用激光激发分子中的振动来获得的；然后，第二束激光选择性地光解振动激发的分子。或者，带有弱结合旁观者分子标记的分子在吸收红外光子后光解离。当反应从反应物到产物进行时，它会形成几种中间体（例如，入口通道络合物，插入中间体和出口通道络合物）。通过研究这些中间体的结构和键合，Metz和他的学生将能够描述反应的详细机制。要研究的具体反应包括金属氧化物将甲烷转化为甲醇，甲烷转化为较大的碳氢化合物，以及金属原子和簇对较大碳氢化合物的活化。由劳伦斯伯克利国家实验室先进光源获得的中性金属氧化物的光电子能谱，将表征光学方法无法获得的中间体。详细的电子结构计算将补充实验。为了优化利用有限的能源，需要改进催化剂，而C-H和C-C键活化的基础研究通过扩大我们对金属基催化机制的理解，有助于这方面的努力。该项目还为研究生和博士后研究人员提供实验和计算物理化学方面的广泛培训。

The Experimental Physical Chemistry Program supports the research of Professor Ricardo Metz and his students at the University of Massachusetts. Metz will study the spectroscopy and dynamics of the intermediates, reactants and products of reactions in which C-C and C-H bonds are activated by transition metal and metal oxide cations. Electronic spectroscopy will characterize excited electronic states, while infrared (IR) spectroscopy will probe bonding and vibrations in the ground electronic states of the ions. IR spectra are obtained by using a laser to excite a vibration in the molecule; a second laser then selectively photodissociates the vibrationally excited molecules. Alternatively, molecules tagged with a weakly bound spectator molecule photodissociate after absorbing an infrared photon. As a reaction proceeds from reactants to products, it forms several intermediates (e.g., entrance channel complexes, insertion intermediates, and exit channel complexes). By studying the structure and bonding of these intermediates, Metz and his students will be able to characterize the detailed mechanism for the reaction. Specific reactions to be studied include the conversion of methane to methanol by metal oxides, the conversion of methane to larger hydrocarbons, and the activation of larger hydrocarbons by metal atoms and clusters. Photoelectron spectra of neutral metal oxides, obtained at the Advanced Light Source, Lawrence Berkeley National Laboratory, will characterize intermediates inaccessible by optical methods. Detailed electronic structure calculations will complement the experiments. Improved catalysts are needed to make optimal use of limited energy resources, and fundamental studies of C-H and C-C bond activation aid in this effort by expanding our understanding of the mechanisms of metal-based catalysis. The project also provides graduate students and postdoctoral researchers with extensive training in experimental and computational physical chemistry.