Synthesis of New Thienylene Pyrrole Monomers and Their Electropolymerizations

In this study, four new 2,5-dithienylpyrroles (SNS) 1-(3-fluoro-phenyl)-2,5-di(thiophen-2-yl)-1H-pyrrole (m-FPTP), 1-(3-chlorophenyl)-2,5-di(thiophen-2-yl)-1H-pyrrole (m-ClPTP), 1-(3-bromo-phenyl)-2,5-di(thiophen-2-yl)-1H-pyrrole (m-BrPTP) and 1-(4-bromo-phenyl)-2,5-di(thiophen-2-yl)-1H-pyrrole (p-BrPTP) containing meta and para substituted benzene ring at the nitrogen atom were synthesized via Paal-Knorr condensation of 1,4-di(2-thienyl)-1,4-butanedione with corresponding halo-substituted anilines. The monomers were polymerized via potential cycling in LiClO4-acetonitrile (ACN) electrolytic solution. The replacement effect of halogen atoms as a substituent from para-to meta-positions and different halogen units (F, Cl, Br) at only meta-/para-positions in the structure on the electrochemical and optical properties of synthesized monomers/polymers were investigated. Computational investigations (M06/TZVP) were also performed on the monomer structures to support the electrochemical behavior of the monomers and to get more insight about the conformation of the structures. Furthermore, the synthesized polymer films exhibited reversible redox behavior accompanied with a reversible electrochromic behavior. It was also observed that the optical contrast value (Delta T%) for polymers was significantly improved when compared with their analogs in the literature. (C) The Author(s) 2014. Published by ECS. All rights reserved