Benzoselenadiazole, quinoxaline and thienothiophene based monomers ; electrochemical and spectroelectrochemical properties

Toksabay, Sinem
A new age had been started in macromolecular science with the invention of conducting polymers and they have gained considerable attention due to the their advantages of low cost, high molecular weight, easy fabrication and compability with flexible substrates. It was found that they can be used in many fields, such as organic light emitting diodes, electrochromic materials, organic solar cellsr, organic field effect transistors and sensors . Donor-acceptor phenomenon, which provide the band gap altenation due to the electron rich and electron poor building blocks in the polymer main chain, is one of the most favored technique for designing organic conducting polymers. Through regulating the contribution of intramolecular charge transfer (ICT) , the absorption spectra and energy levels of D-A type polymers can be tuned. Benzoselenadiazole, quinoxaline and thienothiophene are units commonly utilized in conducting polymers due to their suitable electrochemical properties. However there are no reports in the literature on polymers containing both moieties. With this motivation, we designed and synthesized such a monomer. In this study, two novel benzoselenadiazole, quinoxaline and thienothiophene based monomers; 4-(3a,6a-dihydrothieno[3,2-b]thiophen-2-yl)-7-(thieno[3,2-b]thiophen yl)benzo[c][1,2,5]selenadiazole (BSeTT) and 2,3-bis(3,4-bis(decyloxy)phenyl)-5,8-dibromo-2,3-dihydroquinoxaline (QTT) were synthesized via Stille Coupling and polymerized electrochemically. These polymers were then characterized in terms of their spectroelectrochemical and electrochemical properties by cyclic voltammetry and UV-Vis-NIR spectroscopy. Spectroelectrochemistry analysis of P(BSeTT) revealed an electronic transition at 525 nm corresponding to п – п* transition with a band gap of 0.93 eV whereas P(QTT) revealed an electronic transition at 440 and 600 nm corresponding to п‐ п* transition with a band gap of 1.30 eV. Investigation of electrochromic properties showed that P(BSeTT) has gray color and P(QTT) switches between green and gray. Switching times of the polymers were evaluated by a kinetic study upon measuring the percent transmittance (%T) at the maximum contrast point.
Citation Formats
S. Toksabay, “Benzoselenadiazole, quinoxaline and thienothiophene based monomers ; electrochemical and spectroelectrochemical properties,” M.S. - Master of Science, Middle East Technical University, 2014.