Solvatochromism of fluorescein in aqueous aprotic solvents

Fluorescein solvatochromism was studied in pure aprotic solvents dimethylsulfoxide, N,N-dimethylformamide, acetonitrile and acetone, and their aqueous mixtures. The type and extent of solvent effects were identified and interpreted based on the electronic structure of fluorescein and the nature of the solvent. The main effect of hydrogen bonding interaction was observed on solvatochromism. A modified preferential solvation model was used to gain a reliable insight into the contribution of solvent–solvent interactions to solvatochromism as well as the local and bulk mole fraction distribution of solvation species. Results indicate that the solvation shell of the solute is mainly affected by the solvent–solvent interaction.