Unsymmetrical boron diketonates containing strong electron-donating groups as mechanochromic fluorescent solids

New π-conjugated unsymmetrical β-diketones were synthesized thanks to a modular synthetic approach involving in situ generated acylketenes through thermal degradation of 1,4-dioxin-2-ones. This method gave access family new chromophores featuring either an indoline or benzothiazole as electron-donating groups one side and various aromatic moieties the other side. After complexation with boron difluoride, BDK (Boron DiKetonates) compounds obtained fluorescence non-polar solvents. These also found be fluorescent solid state quantum yield up 0.22, their emission wavelength was very sensitive crystallinity. Two these successfully recrystallized provide small single crystals spectra recorded crystal phase ground which showed mechanochromism spectral shift 37 nm.