Nature Of Solute-Solvent Interaction : Effect Of Solvent Polarity On Excited State Structure Of 2,2,2-Trifluroacetophenone And Effect Of Hydrogen Bonding In Hydrated Electron Absorption Spectrum

Abstract

In solution, the environment around the solute is determined solely by the solvent molecules, which are present closer to the solute. This interaction between solute and solvent shell is very crucial for equilibrium structure and reactivity of the solute. In the thesis, first we have investigated control of solvent polarity on the excited structure of 2,2,2 trifluroacetophenone and later effect of electronic excitation on the solvent shell organization has been described. It has been reported in literature that the lowest energy triplet configuration of 2,2,2 trifluroacetophenone corresponds to n,π* state. There are some other reports in favor of the probable existence of 2,2,2 trifluroacetophenone in n,π* lowest triplet state. Thus, transient absorption and time resolved resonance Raman spectroscopic methods have been used along with theoretical calculations to investigate the discrepancy in the assignment of the lowest triplet state configuration It has been observed that the lowest triplet state of 2,2,2 trifluroacetophenone is indeed nπ* and there is a solvent polarity induced change in triplet state energy ordering and structure changes. The absorption spectrum of hydrated electron is broad and structureless. So, it was though that the broadening feature could be attributed to homogeneous and inhomogeneous broadening. Transient resonance Raman spectrum of the water bending mode in presence of hydrated electron has been recorded at different excitation wavelengths. Interestingly, it has been observed that, peak position of water bending mode in presence of hydrated electron alters with change of excitation wavelength. A model has been proposed based on the experimental data.