Computational Modeling of the Electronic Structure of Oligothiophenes with Various Side Chains

Oligothiophenes are promising candidates as organic molecular wires. Density functional theory is employed to investigate eight oligothiophene series with various side chains, end groups, and spacers ranging in length from 3 to 12 monomers. Redox potentials are evaluated for a number of species on the basis of the thermodynamic cycle formalism (J. Phys. Chem. A 2002, 106, 7407) and agree well with the experimental results. It is confirmed that polarons rather than bipolarons play the role of charge carriers for charged oligomers with sufficiently long backbone. Our calculations also shed light on the detailed oxidization processes in cyclic voltammetry experiments and, hence, provide significant implications on the design of novel oligothiophene-based conductive materials.