Synthesis and Electropolymerization of Donor-Acceptor-Donor Type Monomers based on Azobenzene-substituted thieno[3,4-c]pyrrole-4,6-dione Acceptors
By Çakal, Deniz; Cihaner, Atilla; Önal, Ahmet M.
Published in Electrochimica Acta
2021
Abstract
By using donor-acceptor-donor approach, a new series of photo responsive and electroactive trimeric monomers, namely (E)-5-(4-(phenyldiazenyl)phenyl)-1,3-di(thiophen-2-yl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione (T2-AB), (E)-1,3-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-5-(4-(phenyldiazenyl)phenyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione (E2-AB) and (E)-1,3-bis(3,3-didecyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-6-yl)-5-(4-(phenyldiazenyl)phenyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione (P2-AB), was synthesized and characterized. The oxidation potential of the monomers was controlled by the strength of donor units and the following trend was observed for them: Eox (T2-AB) > Eox (P2-AB) > Eox (E2-AB). Also, a similar behavior was observed for their band gap values: 2.53 eV for T2-AB, 2.18 eV for E2-AB and 2.28 eV for P2-AB. The monomers were polymerized successfully via electrochemical methods in order to give electrochromic ambipolar conjugated polymers bearing narrow optical band gaps: 1.71 eV, 1.54 eV and 1.68 eV for PT2-AB, PE2-AB, and PP2-AB, respectively. Also, the polymer films are stable and robust. Moreover, the three monomers and soluble PP2-AB polymer exhibited trans to cis photo-isomerization upon irradiation with UV light. In addition, the photoluminescence intensity of the monomers in toluene was found to decrease with increasing acid concentration, which makes them potential candidates to be amenable as pH sensors.