Abstract:

Two novel exocyclic ring-fused dipyrrometheneboron difluoride(BODIPY) dyes substituted with p-hydroxy-phenyl or phenyl subunit at the meso-position have been prepared. Their absorption and steady-state fluorescence properties are investigated in polar and nonpolar solvents. The fluorometric titration measurements were carried out to examine their responsive abilities to pH change in the basic CH3CN-H2O solution. The results indicate that strong fluorescence of dye 1 is significantly quenched by adding OH- to the solution, and the addition of the CF3COOH into the basic solution restores the quenched fluorescence. In CH3CN-H2O(volume ratio 1∶1) solution, dye 1 can be qualified as a very sensitive fluorescent probe for pH sensing in the alkaline region, with a pKa value as 10.23 when the excitation and emission wavelengths of dye 1 are 490 nm and 540 nm, respectively.

Key words: Boradiazaindacene (BODIPY), fused exocyclic rings, the alkaline medium, electron transfer, pH fluorescent probe