Unambiguous Polaron and bipolaron localization in the novel conducting polymer poly(durentetraoxidithiophene) (PDTODT) through electronic structure calculations

Polaron formation in different architectures of durentetraoxidithiophene (DTODT) oligomers was assessed using density functional theory (DFT) calculations at the ωB97XD/6-311G(d,p) level of theory. Oligomers with n = 2-6 structural repetitive units (SRU) at the charged states (q = 0, 1, 2) in three polymerization architectures (linear, crosslinked, and branched) were used as models for PDTODT. At q = 2, linear oligomers tend to form bipolarons, whereas crosslinked and branched form polaron pairs. Changes in Wiberg bond indexes and Natural Atomic Charges, were used as indicators for the change between quinoid and benzoid structures upon oxidation. The α-β-SOMO gap value is defined, and that of linear DTODT is in agreement with experimental band gap measurements, close to that of PEDOT, pointing towards an attractive alternative in the conducting polymer field.