Thieno[3,4-c]pyrrole-incorporated quinoidal terthiophene with dicyanomethylene termini: synthesis, characterization, and redox properties

Synthesis, characterization, molecular structure, and redox properties of a new quinoidal terthiophene incorporated with a thieno[3,4-c]pyrrole moiety (5) are described. Although an electrochemical reduction of 5 formally produces the non-classical thieno[3,4-c]pyrrole moiety, 5 showed a reversible reduction wave on cyclic voltammogram, indicating that the thieno[3,4-c]pyrrole moiety can be stabilized by delocalized 10π-conjugated system in the dianion state of 5. However, the reduction potential was largely affected by incorporation of the thieno[3,4-c]pyrrole and shifted cathodically by 0.4 V compared to that of the parent quinodial terthiophene (1).