Capture and characterization of key intermediates in the catalytic activation of small molecules: Clarifying the roles of oxidation states and frustrated Lewis pairs
Abstract
We propose a five year program to design, develop and exploit new and general experimental methods for the purpose of identifying the reaction pathways that govern the catalytic transformations of small molecules like H2, N2 and CO2. Our specific long term goal is to trap key species deep in the catalytic cycle that have been calculated or inferred to play an important role but have never been isolated. The scope of these studies involves both traditional mono- and bi-metallic homogeneous catalytic platforms as well as more recently introduced strategies based on the unique properties of frustrated Lewis pairs. Our approach involves the development of a new type of instrument that combines high resolution mass spectrometry, cryogenic ion processing, and laser photofragmentation spectroscopy. It is an on-going enterprise as capabilities are specifically tailored to the requirements demanded by the rational preparation of fragile molecular assemblies that are too fleeting to be characterized by traditional methods of chemical analysis. We first extract catalysts from solution in their resting state using redox-enhanced electrospray. The active site is then exposed using gas phase ion chemistry so that substrate molecules can be added to it using temperature controlled condensation in an ion trap. These trapped intermediates are then cryogenically cooled and structurally characterized using electronic and vibrational spectroscopy. Finally, we follow the chemical pathways for H-atom rearrangements required to form stable neutral product molecules such as methanol and formic acid from CO2. The methods proposed here are generally applicable, and we outline several specific projects to be carried out in conjunction with the Holland group at Yale regarding the hydride chemistry at the heart of reduction strategies inspired by the nitrogenase enzyme.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 30, 2018
- Source ID
- FA95501810213
Entities
People
- Mark A. Johnson
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- Yale University