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

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

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.