Dynamics and kinetics of ion-molecule gas phase reactions

The present thesis deals with investigations on ion-molecule reactions in the gas phase. Dynamics and kinetics of model systems for catalysis should be studied. Two different experimental setups were used: A modified electrospray ionization mass spectrometer and a 3D velocity map imaging spectrometer. The mass spectrometer was used to investigate transition metal complexes of the type [M(dgpy)2](X)n (M = V - Ni) as model systems for (catalytic) gas phase reactions. Structural characterization of the ionic species were performed, including electron transfer dissociation, collision induced dissociation, ultraviolet photodissociation and infrared multiphoton dissociation experiments. In that way, several different ionic species could be assigned, and evidence for reduction of ligand moieties was found. Finally ion-molecule reactions were measured using a self-built gas mixing and inlet system. These were proof-of-principalexperiments for the modification built in this work, and more important first steps for further kinetic investigations. It was shown that MnIII, MnIV and FeIII react readily towards NEt3 in the gas phase. By combining the gas phase ion molecule reactions and the UV/Vis laser setup, reactions of the electronically excited CoIII complex could be observed as well. In imaging experiments, the dynamics of the oxygen atom transfer reaction of transition metal cations and CO2 was investigated. In this work, the focus is on the reaction of the niobium cation Nb+. Results are compared to earlier studies with the tantalum cation. Angle and energy differential cross sections were measured at two collision energies. An isotropic scattering around the center of mass with a slight trend towards the forwards hemisphere, which is interpreted as a sign for an indirect mechanism, was observed even at higher collision energies. More energy in the system does not result in much more translational energy of the products. Therefore, it must be partitioned into internal degrees of freedom of the products. Prior to this work it was already known, that a two state reactivity is the main pathway for this reaction. The intersystem crossing along the energy surfaces was found to be the bottle neck. The reaction is trapped in the pre-reaction well, which acts as the rate limiting step. Both methods show how reactions of model systems can be investigated from different perspectives, providing information about kinetics and dynamics, respectively.