Noncovalent Interactions Involving Microsolvated Networks Of Trimethylamine N-Oxide
This thesis research focuses on the effects of the formation of hydrogen-bonded networks with the important osmolyte trimethylamine N-oxide (TMAO). Vibrational spectroscopy, in this case Raman spectroscopy, is used to interpret the effects of noncovalent interactions by solvation with select hydrogen bond donors such as water, methanol, ethanol and ethylene glycol in the form of slight changes in vibrational frequencies. Spectral shifts in the experimental Raman spectra of interacting molecules are compared to the results of electronic structure calculations on explicit hydrogen bonded molecular clusters. The similarities in the Raman spectra of microsolvated TMAO using a variety of hydrogen bond donors suggest a comstructural motif in all of the hydrogen bonded complexes. In particular, the arrangement of hydrogen bonds with TMAO's oxygen atom appears to dictate the extended hydrogen bonded network and is likely the origin of TMAO's osmolytic strength via the indirect effect. Hyperconjugation is observed in both TMAO and the hydrogen bonded solvent molecules. This charge transfer leads to blue shifts in TMAO's C-H stretching modes and a dramatic red shift in methanol's symmetric stretch. The effect is larger in the case of water and is likely the origin of TMAO's blue shifted C-H stretching modes in solution.
Electronic Structure Calculations, Noncovalent Interactions, Raman Spectroscopy, Trimethylamine N-Oxide, Physical Chemistry
Networked Digital Library of Theses and Dissertations