A study of the gas phase chemistry of partially solvated atomic metal ions; the selected ion flow tube-triple quadrupole instrument
Abstract
This thesis examines the structure, thermochemistry and reactivity of partially solvated atomic first row transition metal ions in the gas phase. The work includes the detection and quenching of electronically excited metal ions, determination of metal-solvent binding energies, and the reactions of selected solvated transition metal ions with organic compounds. Additionally, the selected ion flow tube-triple quadrupole instrument is described. It was found that a substantial fraction of the atomic chromium ions produced by electron impact ionization of Cr(CO)$\sb{\rm 6}$ exist in an excited state. The exothermic appearance of CrO$\sp+$ upon reaction of Cr$\sp+$ with O$\sb2$ both in the flow tube and the second quadrupole region of the instrument place a lower limit of the highest excited state at 1.79 eV. Similar experiments confirmed that electronically excited iron ions are produced by EI on Fe(CO)$\sb5$. The quenching of these ions to the ground state by several reagents is discussed. Collision induced dissociation experiments performed on atomic transition metal ions solvated by water and ammonia have yielded metal-ligand dissociation energies for ions containing up to four solvent molecules. The unprecedented trend in solvation energies observed is that, for most of the metals studied, the solvent molecules bond more strongly to monosolvated metal ions (MS$\sp+$) than bare metal ions. Structural and electronic considerations were tested as possible explanations for the observed behavior. Bare iron ions, as well as those of ions solvated to various degrees with either ammonia or water, were reacted with several organic compounds in order to determine the effect of solvation on the reactivity of metal ions. Comparison of the results for the reactions of Fe$\sp+$($\sb2$O)$\sb{\rm n}$ and Fe$\sp+$(NH$\sb3$)$\sb{\rm n}$ ions with organic compounds also provided insights into the ways that the type of solvent affects the reactivity of Fe$\sp+$. The final section of this work is a detailed description of the selected ion flow tube-triple quadrupole instrument designed and built in our laboratory. Several custom electronic components used as control devices for the instrument were built, and their design and construction are also described. Typical operating conditions for preliminary experiments, including lens and ion source voltages, are also included.
Degree
Ph.D.
Advisors
Squires, Purdue University.
Subject Area
Organic chemistry
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