Photoinduced intramolecular charge transfer and solvent-controlled dual emission in click modified [1]benzothieno[3,2-b][1]-benzothiophene

[1]Benzothieno[3,2-b]benzothiophene (BTBT) is one of the most promising small organic semiconductors extensively used in organic transistors. However, most BTBT derivatives show a poor emission that precludes the application of this aromatic compounds in other fields. Here we used a copper catalyzed azide-alkyne cycloaddition to efficiently functionalize the BTBT core with a strong electron donating aniline moiety. The resulted push-pull dyads showed fluorescence solvatochromism as a result of a photoinduced intramolecular charge transfer, and dual emission in polar organic solvents. The photoluminescence quantum yields were dependent on the solvent with values up to 53%. Optical properties depended on the regiochemistry of the triazole ring, and solvatochromism was enhanced when the BTBT core was attached to the N1 position of the triazole.