Theoretical Studies of Novel Radon-Containing Molecules

• Author / Creator

  Fitzsimmons, Amelia Caroline

• The chemistry of radon is best understood in the context of the periodic relationship between radon and its lighter cousin xenon. I have studied several classes of radon- containing small molecules, many of which are related to extant xenon-containing molecules. These studies began with an investigation into the structure and prop- erties of HRnF, which I have studied at levels of theory which account for electron correlation and with large pseudopotentials basis sets. My results demonstrated that HRnF is more stable than was previously supposed. Structures and properties of radon halohydrides of the heavier halogens: fluorine, chlorine, bromine, and iodine were also studied with correlated methods and larger pseudopotentials basis sets in order to better understand their chemistry. These compounds have been studied with population analysis methods that analyze the electron density. In the fourth Chapter, I present results of studies of small organic molecules containing radon. Pseudopotentials basis sets and correlated methods were used to predict the stability of several organic compounds of the type ARgB containing heavy rare gas atoms, where Rg is either xenon or radon, and A and B are fluoride or any of the following organic ligands: methyl -CH3, perfluoromethyl -CF3, ethynyl -CCH, fluoroethynyl -CCF, and cyano -CN. The effect of solvents upon the kinetic stability of these molecules was also studied, and I found that the radon-containing organic molecules are equally stable as xenon-containing organic molecules. Related compounds composed of radon with either a methyl or perfluoromethyl ii group on either side (CX3RgCX3, where X=H, F and Rg=Xe, Rn) were studied with a variety of computational methods, including correlated methods for computing structures and population analysis methods for analyzing bonding. I found that bonding in the radon-containing compounds matches the bonding in xenon-containing compounds. Continuing my studies of organic radon-containing compounds, I examined molecules of the type C6H5RgA and C6F5RgA, where Rg is either radon or xenon and A is one of F, CN, CCH, or CCF using correlated methods and pseudopotentials basis sets. I computed structures and properties of these molecules and analyzed their free ener- gies of formation. Analysis of the electron density of these molecules indicates that they are stabilized by π-electron transfer from the aromatic ring to the bond between the rare gas and the aromatic group. Radon-containing molecules of this type were found to be more stable than xenon-containing molecules, which is unsurprising based on the results of the previous chapters. The effects of confinement within a harmonic potential upon the decomposition pathway of molecules of the type HRgX (Rg=Xe Rn; X=F, Cl) were studied next, with both planar and cylindrical confinements used. The reaction was followed both in the gas phase and in confined environments in order to evaluate the effects of con- finement on the energy barrier ∆ETS and kinetic stability of the HRgX compounds. Confinement does not affect the angle at which the HRgX transition state occurs and results in a slight increase in the energy barrier to decomposition of the HRgX species. This same decomposition reaction was also studied in the context of confinement within a pair of planar helium sheets, and the effect of the location of the HRgX molecule within the sheets upon the structure of the transition state and the energy barrier to decomposition was studied. The effect of confinement within helium sheets iii on the electron density of HRgX molecules was studied as well. Anharmonic vibrational frequencies were computed for radon-containing inorganic compounds. Structures of molecules HRnAH and HRnAF(A=O, S), HRnZH2 and HRnZF2 (Z=N, P) were optimized and anharmonic vibrational frequencies computed with the correlation corrected vibrational self-consistent field method. Spectra of HRnSH and HRNPH2 are analyzed and dominant features of each highlighted. The HRnSH spectrum includes the three IR active fundamentals, two overtones, and one combination band. The HRnPH2 spectrum features three high-intensity fundamen- tals and many intense combination bands and overtones. The quartic force field approximation has large errors with respect to the direct method in computation of overtones.

• Subjects / Keywords

  • Computational chemistry
  • MCP
  • Radon

• Graduation date

  Fall 2014

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3RR1PZ0G

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.