Electrochemistry and Electrogenerated Chemiluminescence of Some BODIPY Derivatives

The electrochemistry, spectroscopy, and electrogenerated chemiluminescence (ECL) of three BODIPY derivatives, PB, MCPB, and DCPB, are investigated. Cyclic voltammetry of all three derivatives shows at low scan rates reversible reduction waves and less reversible oxidation waves (consistent with lack of substitution in the 2 and 6 positions). The three compounds are highly fluorescent in MeCN emitting in the green to the red regions. All of the three compounds produce intense ECL, strong enough to be seen with the naked eye in a lighted room, but are not stable under continued pulsing of potential because of instability of the radical cation, ultimately producing an insulating polymer layer on the electrode surface. The ECL spectra are at essentially the same wavelengths as the photoluminescence (PL) spectra for MCPB and DCPB, assigned as emission by the T- or ST-route. The ECL spectra of PB show four peaks at 516, 581, 663, and 752 nm. The peaks at 581, 663, and 752 nm are not present in the PL spectrum. The first ECL peak is attributed to the singlet excited state at essentially the same wavelength as PL, while oligomers or other byproducts are probably responsible for the additional two ECL peaks (581 and 663 nm) based on the results from bulk electrolysis and mass spectroscopy.