Altering Electronic and Optical Properties of Novel Benzothiadiazole Comprising Homopolymers via pi Bridges

Four novel benzo[c][1,2,5]thiadiazole comprising monomers namely 5-fluoro-6-((2-octyldodecyl)oxy)-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (TBTT), 5-fluoro-4,7-bis(4-hexylthiophen-2-yl)-6-((2-octyldodecyl)oxy)benzo[c][1,2,5]thiadiazole (HTBTHT), 5-fluoro-4,7-di(furan-2-yl)-6-((2-octyldodecyl)oxy)benzo- [c][1,2,5]thiadiazole (FBTF), and 5-fluoro-6-((2-octyldodecyl)oxy)-4,7-bis(thieno[3,2-b]thiophen-2-yl)benzo[c][1,2,5]thiadiazole (TTBTTT) were designed, and synthesized successfully via Stille polycondensation reaction. The structural characterizations of the monomers were performed by H-1 and C-13 NMR spectroscopy and High Resolution Mass Spectroscopy (HRMS). The monomers were then electropolymerized in a three electrode cell system via cyclic voltammetry. The electrochemical, and spectroelectrochemical characterization of the polymers were reported in detail. Besides, theoretical calculations were performed to elucidate observed experimental properties. According to the cyclic voltammogram of the polymers, HOMO and LUMO energy levels were calculated as -5.68 eV/-3.91 eV, -5.71 eV/-3.72 eV, -5.61 eV/-4.04 eV, and -5.51 eV/-3.71 eV and the electronic band gaps were 1.77 eV, 1.99 eV, 1.57 eV, and 1.80 eV for PTBTT, PHTBTHT, PFBTF, and PTTBTTT, respectively.