1,2-Bis- and 1,2,3-tris(2,5-dimethylthiophen-3-yl)azulenes: Synthesis, structure and properties

Abstract The efficient protocols for the synthesis of unique 1,2-bis(2,5-dimethylthiophen-3-yl)azulene and 1,2,3-tris(2,5-dimethylthiophen-3-yl)azulene as potential multi-responsive molecules have been developed. Lack of photoactivity of obtained azulenes was explained by means of DFT calculations and X-ray powder diffraction data. Protonation of the dithienylazulene results in the stable azulenium carbocation, and its π-electronic system (optical properties) can be irreversibly controlled by the condensation with various aromatic aldehydes. This property can be used for the modification of electronic properties of azulene-based materials after protonation.