title: UV-vis spectroscopy of the coupling products of the palladium-catalyzed C-H arylation of the BODIPY core.
abstract: The steady-state, UV-vis electronic absorption and fluorescence emission properties of a large set of 3-aryl and 3,5-diaryl substituted difluoroboron dipyrromethene dyes obtained via direct, palladium-catalyzed C-H (het)arylation of the BODIPY core are reported. The spectra display the narrow absorption and fluorescence emission bands and the generally quite small Stokes shifts characteristic of classic difluoroboron dipyrrins. As a function of the solvent, the spectral maxima are located within a very narrow wavelength range and are slightly red-shifted with increasing solvent polarizability, which is shown to be the crucial parameter influencing the wavelength position of the maxima. The extended π-conjugation in the 3,5-diaryl products always leads to bathochromically shifted absorption and emission spectra compared to those of the 3-aryl analogues. The derivative with a 3-mesityl substituent has blue-shifted spectra in comparison to its 3-phenyl substituted analogue, reflecting the diminished π-conjugation in the former due to steric strain. The nature of the meso-aryl has only a small effect on the spectral positions but affects the fluorescence quantum yield Φ. The majority of the dyes have high Φ (>0.85), except the compounds with meso-phenyl and meso-(p-nitrophenyl) substituents. Quantum-chemical calculations were performed to evaluate the differences in spectroscopic properties upon substitution of the BODIPY core and to compare them with the corresponding experimental results.
authors: Department of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200f - bus 02404, 3001 Leuven, Belgium.
authors: Lina
authors: L
authors: Wang
authors: Bram
authors: B
authors: Verbelen
authors: Claire
authors: C
authors: Tonnelé
authors: David
authors: D
authors: Beljonne
authors: Roberto
authors: R
authors: Lazzaroni
authors: Volker
authors: V
authors: Leen
authors: Wim
authors: W
authors: Dehaen
authors: Noël
authors: N
authors: Boens