SPECTROCHEMICAL INVESTIGATIONS OF PREFERENTIAL SOLVATION - FLUORESCENCE EMISSION BEHAVIOR OF SELECT POLYCYCLIC AROMATIC HYDROCARBON SOLUTE PROBES DISSOLVED IN MIXED-SOLVENTS

A spectrofluorometric method is developed to examine preferential solvation of a probe molecule dissolved in binary solvent mixtures. The method assumes that the solvational sphere around every fluorophore is solvated by only one type of solvent component and that each solvated fluorophore contributes to the measured emission intensity. Expressions derived from the model are illustrated using observed fluorescence emission behavior of pyrene, benzo[e]pyrene, benzo[ghi]perylene, and coronene dissolved in binary n-heptane + 1,4-dioxane, n-heptane + tetrahydrofuran, methanol + acetonitrile, and dibutyl ether + acetonitrile solvent mixtures, which were measured as part of the present study. Also discussed are deficiencies inherent in several of the spectrofluorometric probe methods published in the chemical literature.