STUDY OF PREFERENTIAL SOLVATION IN BINARY SOLVENT MIXTURES BY THE SPECTRO-STREAK PICOSECOND TECHNIQUE

Using the picosecond spectre-streak method we monitored the dynamics o f preferential solvation of a charge-transfer dipole in binary mixture s 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 d ielectric enrichment of the solvation shell around the dipolar solute molecules by diffusion of polar molecules from the bulk of the solvent mixture.