Mono-silylated 2,1,3-benzothiadiazole-based precursors. Molecular scaffolds for obtaining fluorescent organic-inorganic hybrid materials with tailored photophysical properties

The present work describes the synthesis of three classes of mono-silylated benzothiadiazole and their application in obtaining organic-inorganic fluorescent hybrid materials. The mono-silylated compounds were obtained through a Pd-catalyzed Sonogashira coupling reaction with silicon-functionalized alkynes (25–61% yield). One of the silylated products was chosen as a model compound and six additional BTD-containing products were obtained using Suzuki-Miyaura (53–91% yield) and Sonogashira (53–89% yield) coupling reactions. All the compounds presented absorption in the UV-A region (360–390 nm) attributed to fully spin- and symmetry-allowed π-π* electronic transitions. The fluorescence emission was located in the green-blue region with moderated Stokes shift and quantum yields. The mono-silylated BTDs were precursors in the synthesis of new organic-inorganic hybrid materials via sol-gel reaction. The materials were obtained over 10 days at 60 °C with low BTD content and presented fluorescence emission in the green-blue region.