Quantum chemistry and raman spectroscopy studies of anion hydration

Craig, J. D. C. (2000) Quantum chemistry and raman spectroscopy studies of anion hydration. Masters thesis, Memorial University of Newfoundland.

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Abstract

The low frequency vibrational spectra of aqueous halides and selected pseudohalides are interpreted in terms of interactions between the anions and the water. A weak band in the isotropic Raman spectrum at ca . 200 cm⁻¹ originates with the symmetric stretching mode of the A⁻···HOH species. This assignment is based on experimental studies of aqueous anions in H₂O₁ D₂O and H₂¹⁸O and calculations using a model two body harmonic oscillator comprising one water molecule and the anion. The model is shown to be consistent with quantum mechanics and ab initio molecular orbital calculations. The integrity of the model is reaffirmed at high levels of theory and the inclusion of electron correlation in the calculations. An octahedral structure is proposed to reconcile evidence of larger complexes with the observation of only one hydrogen bond on the picosecond time scale of the Raman measurement. It is conjectured that the dynamics of the A⁻ ···HOH vibration is influenced by neighbouring molecules.

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