Theoretical studies on the structure and dynamics of room-temperature ionic liquids

In this thesis, we present our studies on the structure and dynamics of novel Room-Temperature Ionic Liquids. Through our computer simulations we demonstrate that the kinetics of photo induced electron transfer reaction between S1 and S2 states of Crystal Violet Lactone in N-propyl-N-methylpyrrolidiniumbis(trifluoromethylsulfonyl)imide([Pr31][NTf2]) room temperature ionic liquid is local solvent environment dependent, because emission time scales are smaller than solvent relaxation time scales. This behavior is characteristic of ionic liquids but uncommon in conventional solvents. Therefore ionic liquids open a window of opportunity for manipulating the outcome of chemical reactions simply by tuning the initial excitation wavelength. We performed Molecular dynamics simulations of mixtures of 1-hexyl-3-methyl imidazoliumhexafluorophosphate ([C6MIM][PF6 ] ) and water in order to investigate how small amounts of water affect the translational and rotational dynamics of ionic liquids. We find that water is closely associated with the anions and that its presence enhances both the translational and rotational dynamics of the ionic liquid. In agreement with experiments, we find that the fluorescence spectra of Coumarin-153 is red-shifted because of the presence of water. Small amounts of water enhance the speed of relaxation of the solvent surrounding the solute probe after photo-excitation, but only at a local environment level. Interconversion between environments still occurs on a long time scale compared with the fluorescence lifetime of the probe. To interpret the features of x-ray scattering structure factor of room temper-