Rhodamine 3B+ClO4− in water:toluene mixtures: Evidence of water cluster formation

Rhodamine 3B perchlorate coexists solubilized in mixtures of water:toluene as a distribution of ion pair (74%) and cation (26%). The quantum yield variation shows that the fluorescence quenching process of the ion pair is diffusion controlled with a rate constant oscillating within the limits of slip and stick boundary conditions. The driving force for the excited-state conversion is the unbalance of electrostatic forces and changes in inter-ionic distances in the water cluster solvation sphere created around the ion pair by dielectric enrichment.