Synthesis and Photophysical and Electrochemical Properties of Conjugated Donor–Acceptor–Donor Systems Based on 1,3,4-Thiadiazole and Fused Naphtho[2,1-b]thiophene Derivatives

A series of 2,5-diaryl-1,3,4-thiadiazole derivatives have been synthesized from fused benzothio­phene-2-carboxylates and alkyl-substituted 2,2′-bithiophene-5-carboxylate. Photophysical and electrochemical properties of the synthesized compounds have been studied. Extension of the conjugation chain in the donor moiety of substituted 1,3,4-thiadiazoles has been found to narrow the energy band gap due mainly to increase of the HOMO energy.