Syntheses, characterization and optical properties of fluorine containing benzimidazole derivatives

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Bilimleri Enstitüsü, Fen Bilimleri Enstitüsü, Türkiye

Tezin Onay Tarihi: 2015

Öğrenci: Merve İleri

Eş Danışman: LEVENT KAMİL TOPPARE, ALİ ÇIRPAN

Özet:

In the last decades use of conducting polymers as electrochromic materials attracted tremendous attention all over the world due to properties like processability, high optical contrasts, fast switching times and tuning band gap via structural modifications. Low band gap polymers are pursued in order to increase the conductivity. For that matter donor – acceptor – donor theory is the most effective and commonly used method. The donor – acceptor – donor approach is not only used for obtaining low band gap polymers, but also for producing polymers with improved optical, mechanical and electronic properties. Based on donor – acceptor – donor approach, the electron donating groups raise the highest occupied molecular orbital level and electron withdrawing groups lower the lowest unoccupied molecular orbital level. In this study, novel donor – acceptor – donor type monomers were designed, vi synthesized and polymerized electrochemically. In the first part of the thesis study, para- and meta- substituted fluorine containing benzimidazole derivatives as an acceptor moiety and thiophene as the donor moiety were used. Monomers, 2-(4-fluorophenyl)-4,7-di(thiophen-2-yl)-1H-benzo[d]imidazole (M1) and 2-(3-fluorophenyl)-4,7-di(thiophen-2-yl)-1H-benzo[d]imidazole (M2) were synthesized via Stille coupling and electrochemically polymerized. The position of fluorine was varied from para- to meta- in order to investigate position effects on the electrochemical and optical properties of electrochemically synthesized polymers. Both polymers were p-dopable and switched between orange and blue color during doping/dedoping. In the second part of this study, synthesis of two novel monomers including perfluorophenyl containing benzimidazole as the acceptor unit and thiophene and 3,4-ethylenedioxythiophene as the donor units were performed. 2-(Perfluorophenyl)-4,7-di(thiophen-2-yl)-1H-benzo[d]imidazole (M3) and 4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-(perfluorophenyl)-1H-benzo[d]imidazole (M4) were synthesized and polymerized electrochemically. The effect of electron donating moieties on the optical properties of electrochemically polymerized polymers was investigated.