Solvent-Dependent Fluorescence Properties of CH₂-bis(BODIPY)s

Biocompatible luminophores based on organic dyes, which have fluorescence characteristics that are highly sensitive to the properties of the solvating medium, are of particular interest as highly sensitive, selective, and easy-to-use analytical agents. We found that BODIPY dimers (2,2'-, 2,3'-3,3'-CH₂-bis(BODIPY) (1-3)) demonstrate fluorescence characteristics with a high sensitivity to the presence of polar solvents. The intense fluorescence of 1-3 in nonpolar/low-polarity solvents is dramatically quenched in polar media (acetone, DMF, and DMSO). It has been established that the main reason for CH₂-bis(BODIPY) fluorescence quenching is the specific solvation of dyes by electron-donating molecules (Solv) with the formation of stable supramolecular CH₂-bis(BODIPY)·2Solv structures. Using steady-state absorption and fluorescence spectroscopy, time-resolved fluorescence spectroscopy, and computational modeling, the formation mechanism, composition, and structure of CH₂-bis(BODIPY)·2Solv supramolecular complexes have been substantiated, and their stability has been evaluated. The results show the promise of developing fluorescent probes based on CH₂-bis(BODIPY)s for detecting toxic N/O-containing compounds in solutions.