Carbazole-modified thiazolo[3,2-<i>c</i>][1,3,5,2]oxadiazaborinines exhibiting aggregation-induced emission and mechanofluorochromism
Mykhaylo A. Potopnyk, Mykola Kravets, Roman Luboradzki, Dmytro Volyniuk, Volodymyr Sashuk, Juozas V. Gražulevičius
Abstract
Two highly emissive carbazole-containing thiazole-fused oxadiazaborinines were designed and synthesized. These N,O-chelated organoboron dyes displayed large Stokes shifts and remarkable solvatofluorochromism in solutions, as well as good thermal stability and comparatively high photoluminescence quantum yields (up to 34%) in the solid state. The presence of a carbazole donor unit, linked with the oxadiazaborinine acceptor via a phenyl linker, restricted intramolecular rotation, leading to enhanced aggregation-induced emission properties of the compounds: in THF/water mixtures with a large water percentage, they demonstrated the formation of emissive nanoaggregates with an average size of 79 and 89 nm for complexes 2 and 3, respectively. The introduction of bulky tert-butyl groups attached to the carbazole moiety induced significant mechanofluorochromic properties of the compounds.