Date of Award
Program or Major
Master of Science
Ion/molecule reactions happens in the very diluted low-pressure environment provided by mass spectrometer. Studying ion/molecule reactions in gas phase may reveal novel chemistries of the pertinent reactants and products. The convenience of isolating target reactant ions with multistage MS in the gas phase eliminates the involvement of solvent or counterions which could add unnecessary complexity for interpreting novel chemistry. A lot of research has been applied to the metal-bipyridine system in the solution phase, but not too much research reported in the gas phase.In this work, the study of metal-bipyridine system has been extended to the gas phase with aid of Mass Spectrometer. Monocationic metal-bipyridyl [M-bpy]+ complexes (Metal = Cu, Ag, Au) were produced in the gas phase with electrospray coupled with MS/MS, reactions with water gas and nitrogen gas were performed inside the Linear Quadrupole Ion Trap, and the full reaction process was detected by Mass Spectrometer synchronously. Product peaks for water adduct ([H2OM-bpy]+) and nitrogen adduct ([N2M-bpy]+) are observed on the mass spectrum. Kinetic study shows the gas phase reaction follows pseudo-first order with respect to [M-bpy]+ for Cu and Au. The attributes of products were further investigated with Density Functional Theory (DFT) at PBE0/cc-pVTZ/cc-pVTZ-PP level, including the geometry optimization and IR prediction. Thermo stability was calculated for the dissociation process. For a given gas, gold complex has the highest binding ability followed by copper and silver complexes. For the dissociation process from the respective bound complexes, they are all indicated as endothermic processes under vacuum and at room temperature. The metal complexes are also found to act as mild bond activation reagents for small gas molecules, with gold complex being the best candidate for O-H activation of water and copper complex being the best for nitrogen bond activation of N2. Compared with the bond length in free gases, the bond lengths of O-H and N≡N get elongated in the complexes with the optimized structures. In addition, the IR spectra predict a major red-shift in correspond to the stretch frequency of O-H and N≡N in the complexes. Ligands effects are also predicted with calculations, and the results show that phenanthroline perform similar ability binding with water and nitrogen gas molecules as bipyridine.
Chen, Shan, "GAS PHASE ION/MOLECULE REACTIONS BETWEEN MONOCATIONIC METAL-BIPYRIDYL (METAL = CU, AG, AU) COMPLEXES AND SMALL GAS MOLECULES USING ION TRAP MASS SPECTROMETER" (2021). Master's Theses and Capstones. 1503.