Modulation of optical properties of BODIPY fluorophore via intramolecular charge transfer

Charge transfer characteristics of BODIPY-benzimidazole conjugate dyes (KT01-03) were investigated using UV-vis, steady state and time-resolved fluorescence spectroscopy measurements. All the synthesized dye molecules exhibited intense intramolecular charge transfer character and displayed a bathochromic shift in their optical spectra. The fluorescence yield and lifetime of dyes were found to be dependent on the polarity and the acidity of the solvents which were supported by the multilinear regression analysis. Interestingly, the photo-physical properties of the dye KT02 were controlled by the two competitive charge transfer processes from styryl and benzimidazole subunits. Quantum mechanical calculations were performed to illustrate the mechanism of charge transfer in these fluorophores.