A novel triphenylamine-BODIPY dendron: click synthesis, near-infrared emission and a multi-channel chemodosimeter for Hg2+ and Fe3+

A novel triphenylamine-BODIPY based Schiff base fluorescent probe (TPA-BODIPY-OH) with an emission in the near-infrared (NIR) region was designed and prepared by click reaction. TPA-BODIPY-OH showed three emission bands at 510 nm, 598 nm and 670 nm, and can detect Fe3+ and Hg2+ ions with remarkable fluorescence enhancement in THF/H2O (v/v, 1:1, buffered with 10 mM HEPES pH = 7.4) based on the hydrolysis reaction of the –CN bond, and naked eye detection was realized with an obvious color change. The stoichiometry between the probe and ions was deduced from a Job's plot, which is 1:3 for TPA-BODIPY-OH/Fe3+ and 1:2 for TPA-BODIPY-OH/Hg2+, respectively. The dissociation constant value was found to be 1.35 × 10−16 M for TPA-BODIPY-OH/Fe3+ and 2.06 × 10−11 M for TPA-BODIPY-OH/Hg2+. The low detection limit was calculated from the titration results with the values of 5.15 × 10−7 M for TPA-BODIPY-OH/Fe3+ and 6.81 × 10−7 M for TPA-BODIPY-OH/Hg2+, respectively. In order to investigate the biological applications of TPA-BODIPY-OH, a living cell imaging experiment was carried out. The results demonstrate that TPA-BODIPY-OH can be successfully applied as a bioimaging agent in living cells. In addition, amino-group-functionalized silica fluorescent nanoparticles (FNPs) encapsulating the TPA-BODIPY-OH dyes were prepared and characterized by transmission electron microscopy. TPA-BODIPY-OH/SiO2 nanoparticles exhibit good dispersibility, and the quantum yield of FNPs at 657 nm was 42.3%.