Low Band Gap Donor-Acceptor Conjugated Systems Based on 3-Alkoxy or 3-Pyrrolidino-4-cyanothiophene and Benzothiadiazole Units.

3-Hexyloxy-4-cyanothiophene, 3-pyrrolidil-4-cyanothiophene, and 3,4-ethylenedioxythiophene (EDOT) units are used with benzothiadiazole as building blocks for the development of three new conjugated donor-acceptor-donor (DAD) derivatives. The DAD molecules have the central acceptor part, which is formed by combining electron-withdrawing cyano groups and the benzothiadiazole moiety, in common. Theoretical calculations and UV/Vis and electrochemical data reveal the key role of the end-capped donor to tune the electronic properties of the derivatives.

Unprecedented Demonstration of Regioselective SE Ar Reaction giving Unsymmetrical Regioregular Oligothiophenes.

Aromatization of 4-cyano-3-oxotetrahydrothiophene by sulfuryl chloride gives the new building block 4-cyano-3-pyrrolidylthiophene, which forms unsymmetrical regioregular oligothiophenes with a strict alternation of the donor and acceptor groups along the conjugated system. The self-coupling reactions that form the oligomers are shown to proceed by a regioselective electrophilic aromatic substitution mechanism involving a stabilized Wheland intermediate.

Synthesis and electronic properties of D-A-D triads based on 3-alkoxy-4-cyanothiophene and benzothienothiophene blocks.

3-Alkoxy-4-cyanothiophene units are used as building block for the synthesis of conjugated donor-acceptor-donor (D-A-D) triads. The donor part consists of benzothienothiophene end groups associated with the alkoxy groups of the 3-alkoxy-4-cyanothiophene, while the central acceptor part is formed by combining the electron-withdrawing cyano group with thiophene or benzothiadiazole units.

Facile synthesis of 3-alkoxy-4-cyanothiophenes as new building blocks for donor-acceptor conjugated systems.

3-Alkoxy-4-cyanothiophenes are efficiently synthesized in two steps from the readily available 4-cyano-3-oxotetrahydrothiophene. Regioisomers of bithiophene derivatives are easily synthesized by playing on the strong electronic dissymmetry of the thiophene ring induced by the alkoxy and cyano groups.