New D–A–D luminophores of the [1,2,5]thiadiazolo[3,4-d]pyridazine series

Three [1,2,5]thiadiazolo[3,4-d]pyridazines containing 4,7-positioned indole-type substituents were synthesized from the corresponding 4,7-dibromo precursor employing the SNAr aromatic nucleophilic substitution. Photophysical properties and DFT calculations showed that the D–A–D dyes based on [1,2,5]thiadiazolo[3,4-d]pyridazine core exhibited fluorescence in the near infrared region of the spectrum, which makes them promising for use as an active emitting layer in NIR-OLEDs as well as for other possible applications as an IR luminophore.