Further investigation of intramolecular H-bonding in benzimidazole and EDOT containing monomer

Density functional theory (DFT) calculations of the relative stabilities and harmonic vibrational spectra of four different conformers of 4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-phenyl-1H-benzo[d]imidazole (BImBEd) are presented and compared with experimental IR data. BImBEd, containing phenyl substituted benzimidazole as the acceptor and 3,4-ethylenedioxythiophene (EDOT) as the donor unit, was electrochemically polymerized in different pH media earlier. Electronic states of nitrogen in benzimidazole unit of synthesized polymeric films were analyzed via X-ray photoelectron spectroscopy. Both DFT and XPS results suggest the presence of an intramolecular H-bond between the amine of the imidazole and the oxygen of the EDOT molecules. Additionally, the quantity of the H-bond can be controlled via treatment of an acid (trifloroacetic acid) and a base (sodium hydroxide) as we stated in our previous study.

► This study highlights the importance of manipulating the hydrogen bonding.
► Its effects on the electrochromic properties of conducting polymers are discussed.
► This work stands for a solid proof of whatever proposed in an earlier paper.
► The addition of acid or base affects the amine and imine groups.