C-C coupling of polymer chains in thin films of oxidized polypyrrole doped by BF4- and PF6- anions: Quantum chemical modeling

Oligopyrrole-acceptor (BF4 or PF6) complexes, i.e., positively charged oligopyrrole (OPy) clusters with BF4- or PF6- doping anions, represent a model of a charged region of the polymer chain inside a polypyrrole film deposited on the electrode surface via electropolymerization of the pyrrole monomer in a non-aqueous electrolyte containing BF4- or PF6- anions. The ratio of 4 to 1 used in the calculation for the ratio of the monomer units-to-anion numbers has been chosen in accordance with the typical electronic charge of the polymer chain (about + 0.25 per monomer unit) for polypyrrole films on the electrode surface at a potential close to the polymerization one. Interaction between such oligopyrrole complexes inside polymer chains in thin films near the electrode surface is considered. Calculations have been performed for the variants: PBE/PAW, omega B97XD/6-31G(d,p), and M062X/6-311+G(2d,p), taking into account periodic conditions as well as in the cluster approximation. It has been shown that such interactions can lead to the new C-C bond formation under certain conditions. Based on calculations of IR spectra of such systems, manifestation of such structures in the form of an intense peak in the region of 1700-1740 cm(-1) has been revealed.