Density Functional Theory Study of the Structure and Energetics of Negatively Charged Oligopyrroles

作者：Dai Yafei; Chowdhury Sugata; Blaisten Barojas Estela^*

来源：International Journal of Quantum Chemistry, 2011, 111(10): 2295-2305.

DOI：10.1002/qua.22659

• oligopyrrole
• polypyrrole
• density functional theory
• electron affinity
• n-doping conducting polymers

First-principles calculations are used to investigate the electronic properties of negatively charged n-pyrrole oligomers with n = 2-18. Chains of neutral oligomers are bent, whereas the negatively charged oligomers become almost planar due to accumulation of negative charge at the end monomers. Isomers of short oligomers (n < 6) display negative electron affinity although the corresponding anions are energetically stable. For longer oligomers with n >= 6, the electron affinity is small and positive, slowly increasing with oligopyrrole length. Doping of 12-pyrrole with lithium atoms shows that negative oxidation states are possible due to electron transfer from dopant to oligomer at locations close to dopant. These 12-pyrrole regions support extra negative charge and exhibit a local structural change from benzenoid to quinoid structure in the C-C backbone conjugation. Comparison between neutral and doped polypyrrole (PPy) indicates that doped polymers displays a substantial depletion of the band gap energy and the appearance of dopant-based bands in the gap for a 50% per monomer doping level. It is predicted that Li-doped PPy is not metallic.

• 出版日期2011-8-15