Solvation dynamics in molten salts

We have observed time-dependent shifts in the fluorescence spectra of solvatochromic probe molecules in several molten tetraalkylammonium salts. The phenomenon is a general one and is observed in a variety of fluorophores. The steady-state emission position shows a pronounced dependence on the molten salt cation size. Frequency shifts in steady-state emission spectra are a function of the solute. The solvation of excited large dipoles occurs on two time scales which are both dependent on the cation size. The larger the cation size, the longer the relaxation time. The average experimental solvation time, 〈T〉, for the same molten salt depends on the solute. The observed results suggest that molten salts are an appropriate medium for studying excited large dipole solvation.