Electronic Photodissociation Spectroscopy of Metal-Polypyridine Complex Ions

<p>The properties of many important molecules are only known from condensed phase studies, where the interaction with solvent or other chemical environments masks the intrinsic properties of the solute molecule. Consequently, these intrinsic properties cannot be easily obtained from condensed phase experiments. Spectroscopy of gas-phase molecular ions in vacuo is an attractive alternative to spectroscopic studies in the condensed phase. Ions in vacuo are isolated systems and free from perturbation inflicted by a chemical microenvironment such as a solvent or crystal lattice. Consequently, it becomes possible to examine the intrinsic properties of the ions in vacuo. Furthermore, gas-phase ions can be trapped, cooled and mass-analyzed, which provides researchers with the opportunity for controlling and selecting ion species and conditions. This thesis comprises my work on photodissociation spectroscopy of several series of metal-polypyridine ions in vacuo. These species have been extensively studied in inorganic chemistry because they serve as potential candidates for broad industrial applications and as prototypical systems to study fundamental scientific questions such as the mechanisms of metal-ligand interaction and chemical reaction. This thesis describes the first investigation of such systems in the gas phase using laser spectroscopy in the visible and UV spectral ranges.\&nbsp;</p> <p>In this work, the gas-phase ions are produced by electrospray ionization. The ions are trapped and buffer-gas cooled in a cryogenic quadrupole ion trap and then undergo mass-selection in a time-of-flight mass spectrometer. The selected ion species are irradiated by a laser pulse with widely tunable photon energy. If photoabsorption leads to dissociation, fragments will be separated and analyzed by a reflectron. The yield of fragment ions is monitored as a function of photon energy and recorded as a photodissociation spectrum. While absorption spectra in solutions of the species studied here are usually broad and featureless, the photodissociation spectra acquired in the gas phase show new resolved features, often even at room temperature.\&nbsp;</p>
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University of Colorado Boulder
Advisors - JILA Fellows