Solvation statics and dynamics in electrolyte solutions. the ion-solvent exchange model

We have studied the solvation energetics and dynamics of coumarin 153 in various electrolyte solutions of polar organic solvents. We used a model of two distinct solvates to explain the experimental data. The first distinct solvate was a coumarin dye molecule surrounded by H solvent molecules in the first solvation shell. In the second distinct solvate, one of the surrounding solvent molecules was replaced by a cation. Upon photoexcitation of the coumarin dye, an ion-solvent exchange reaction occurred, which was followed by time-resolved fluorescence measurements. The model was successfully applied to coumarin 153 dye in all the solvents used, as well as in a wide range of electrolyte concentrations.