Fluorescent Properties of 8-Substituted BODIPY Dyes: Influence of Solvent Effects

Three boron-dipyrrine (BODIPY) based dyes with bulky substituents in 8-position of dipyrrin ligand have been synthesized and characterized. Photophysical properties of the obtained compounds have been investigated in different individual solvents and solvent mixtures. Investigated compounds was found to be intensive fluorescent molecular rotors. The influence of different solvent parameters and the substituent nature on rotor characteristics have been observed and discussed. Minor changes in the nature of 8-substituent does not influence the spectral properties, but the presence of nitrogen donor atom in the phenyl substituent could be used for the sensing of the donor-acceptor interactions with solvent or dissolved compounds. The new approach of spectral properties correlation with solvent parameters was proposed, the viscosity parameter should be taken into account in case of BODIPYs with bulky substituents. The intensity of fluorescence molecular rotor properties decrease gradually with the viscosity increase above 1 cP.