Theoretical Investigation on PEDOT Polymeric Chain Structure through Dimeric Rotational Barrier

Organic semiconductors have unique molecular properties that hardly ever are found in biochemical macromolecules, as charge transport and planarity of polymeric chain. The first step to understand these properties is based on reliable geometric description of these systems, where semi-empirical methodologies can provide good geometric results with low computational cost. In this study, PEDOT dimer rotational barrier was investigated by three semi-empirical methodologies (PM6, PM7 and RM1) and B3LYP/6-31+G(d,p) DFT level of theory, comparing with experimental results for bond length, dihedral angle and band-gap energy. The results show better description by DFT methodology for PEDOT dimer bond length and band-gap energy, while PM6 methodology provides better long range description, especially dihedral angle, indicating that this methodology can be used for predict geometric parameters of organic semiconductor polymeric chain.