Gas Phase Ion Reaction Dynamics of Catalytic Systems

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My research focuses on the dynamics of the reactions of gas-phase ions. We pursue this work with mass spectrometry, imaging photoelectron photoion coincidence spectroscopy (iPEPICO) and infrared multiphoton photodissociation (IRMPD) spectroscopy coupled with statistical rate theory and computational chemistry. A principle focus of my group is the development of models to extract reliable energetics and entropics for the dissociation of gas-phase ions in a wide variety of mass spectrometry experiments. Previously we have focused on small polycyclic aromatic hydrocarbons and explored the unique ion chemistry of atomic metal anions. This proposal involves a new focus on the fundamental properties of ions of interest in catalysis, notably organometallic systems of interest in solution and interstellar catalysis.***The intrinsic properties of catalytic systems are often difficult to ascertain, and often the actual key, active species is not known. Ligand binding energies, structural rearrangements and intermediate species are all key to understanding how catalysts work. Charged organometallic ions can be characterized by their accurate mass, collision cross-section and dissociation characteristics, all of which are accessible on the mass spectrometry instrumentation in my lab. The dissociation of organometallic ions will be carried out as a function of collision energy, and the resulting mass spectral breakdown diagrams modeled using experimental parameters, RRKM theory and an internal energy distribution that is a function of the collision energy. This yields bond strengths for the dissociating ligands and entropic information on the reaction pathway. This work is aided by the availability of kinetic data from iPEPICO experiments. Ion structure will be probed using IRMPD spectroscopy to obtain the IR spectra of gaseous ions, done at the French CLIO free electron laser. Extending the information obtained from these experiments to describe complex ion reaction mechanisms, which can shed light on catalytically-active intermediates, has only seen limited application. This research program will target a wide variety of organometallic species, leading ultimately to the synthesis and examination of active, air and moisture sensitive catalysts. One goal of the current proposal is to develop nano-droplet reaction chemical ionization as a routine tool for the synthesis and characterization of these catalysts. We have demonstrated in our lab that reactions can take place when the micro- to nano-sized droplets from two electrospray emitters mix, permitting solution-phase chemistry to take place prior to the final desolvation of the droplets. Preliminary experiments have shown that a wide variety of organometallic complexes, including novel species not previously observed, can be formed by mixing a ligand from one spray emitter with a metal salt from the other. **