2009/12/07 by Yafei Dai, Dai, Yafei, Sugata Chowdhury +4
Engineering · Materials Science · Physics and Astronomy · #Chemical Physics (physics.chem-ph) #Conducting polymers and applications #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #Organic Electronics and Photovoltaics #Polymer Nanocomposite Synthesis and Irradiation #cond-mat.mes-hall #cond-mat.mtrl-sci #physics.chem-ph
paper · pdf · doi:10.48550/arxiv.0912.1153
22 pages, 3 figures, submitted paper
arxiv created 2009/12/07 · openalex publication_date 2009/12/07 · arxiv updated 2009/12/08 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
First-principles calculations are used to investigate the electronic properties of neutral and negatively charged n-pyrrole oligomers with n= 2-18. Chains of neutral oligomers are bent while the negatively charged oligomers become almost flat due to accumulation of negative charge at the end monomers. Several isomers of the short oligomers (n < 5) display negative electron affinity, although they are energetically stable. For longer oligomers with n > 5, the electron affinity turns positive, increasing with oligomer length. The doping of 12-pyrrole with lithium atoms is studied, showing that negative oxidation states are possible due to charge transfer from dopant to oligomer at locations close to dopant. These molecular regions support extra negative charge and exhibit a local structural change from benzenoid to quinoid in the C-C backbone conjugation. Additional calculations of neutral and doped polypyrrole are conducted showing that the doped infinite polymer chain displays a substantial reduction of the energy band gap and the appearance of dopant-based bands in the gap.