Pyrromethene‐BF2 complexes (4,4′‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacenes). Synthesis and luminescence properties

BF2 complexes of alkylated pyrromethenes were prepared by reacting the corresponding pyrromethenes with BF3·OEt2 under basic conditions. A striking aspect of these complexes is a pronounced fluorescence in organic solvents, even at room temperature, with fluorescence quantum yields between 0.3-0.8. The efficiency and wavelength maximum of the fluorescence seems to be correlated with the substitution pattern at the 2 and 6 position. In none of these systems could phosphorescence be detected.