Study of preferential solvation in binary solvent mixtures by the spectro-streak picosecond technique

Using the picosecond spectro-streak method we monitored the dynamics of preferential solvation of a charge-transfer dipole in binary mixtures of solvents strongly different in dielectric constant. The observed slow (0.25–1 ns) spectral red-shift of the charge-transfer (exciplex) fluorescence is considered to be mainly due to the formation and the dielectric enrichment of the solvation shell around the dipolar solute molecules by diffusion of polar molecules from the bulk of the solvent mixture.