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马萨诸塞大学里卡多·梅茨教授和他的学生的研究。梅茨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。电子光谱学将表征激发电子态，而红外(IR)光谱学将探测离子基电子态的成键和振动。红外光谱是通过使用激光激发分子中的振动来获得的；然后第二个激光选择性地光解振动激发的分子。或者，标记了弱结合的旁观者分子的分子在吸收红外光子后光解。当反应从反应物进行到产物时，它形成几个中间体(例如，入口通道复合体、插入中间体和出口通道复合体)。通过研究这些中间体的结构和成键，梅茨和他的学生将能够描述该反应的详细机制。将要研究的具体反应包括由金属氧化物将甲烷转化为甲醇，将甲烷转化为更大的碳氢化合物，以及金属原子和团簇对更大的碳氢化合物的活化。在劳伦斯伯克利国家实验室的高级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。为了最大限度地利用有限的能源，需要改进的催化剂，而C-H和C-C键活化的基础研究通过扩大我们对金属催化机理的理解来帮助我们实现这一目标。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.