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- BODIPY (2) (entfernen)
Organisationseinheit der BAM
Triphenylamines (TPAs), boron dipyrromethenes (BODIPYs) and fullerenes C60 are excellent building blocks for the design of artificial photosynthetic systems. In the present work, we report the synthesis, characterization and detailed photophysical studies of a novel (TPA)2–BODIPY–C60 tetrad in polar and nonpolar solvents. The absorption spectrum of this compound covered virtually the entire visible Region (350–700 nm) and could be interpreted as a superposition of the spectra of individual components.
Upon TPA-part excitation, a fast and very efficient excitation energy transfer (EET) delivers the excitation to the BODIPY moiety resulting in complete quenching of the TPA first excited singlet state as well as the appearance of the BODIPY fluorescence. The efficiency of EET process was estimated to be 1. Direct or indirect (via EET) excitation of the BODIPY-part of the tetrad is followed by photoinduced charge transfer to the charge-separated state BODIPY+–C60- irrespective of the solvent used. In polar N,N-dimethylformamide (DMF)charge recombination occurs directly to the ground state with the Charge recombination rate, kCR, slower than 108 s-1, whereas in nonpolar toluene (TOL) a small energy gap between the charge-separated state and first excited singlet state of the BODIPY moiety facilitates the back charge transfer process. The latter results in the appearance of thermally activated delayed fluorescence. The rate of charge separation was found to be ca. 2 times faster in TOL than in DMF.
Real-time monitoring of newly acidified organelles during autophagy in living cells is highly desirable for a better understanding of intracellular degradative processes. Herein, we describe a reaction-based boron dipyrromethene (BODIPY) dye containing strongly electron-withdrawing diethyl 2-cyanoacrylate groups at the α-positions. The probe exhibits intense red fluorescence in acidic organelles or the acidified cytosol while negligible fluorescence in other regions of the cell. The underlying mechanism is a nucleophilic reaction at the central meso-carbon of the indacene core, resulting in the loss of π-conjugation entailed by dramatic spectroscopic changes of more than 200 nm between its colorless, non-fluorescent leuco-BODIPY form and its red and brightly emitting form. The reversible transformation between red fluorescent BODIPY and leuco-BODIPY along with negligible cytotoxicity qualifies such dyes for rapid and direct intracellular lysosome imaging and cytosolic acidosis detection simultaneously without any washing step, enabling the real-time monitoring of newly acidified organelles during autophagy.