Density functional theory study of the structure and energetics of negatively charged oligopyrroles

Abstract

First-principles calculations are used to investigate the electronic properties of negatively charged n-pyrrole oligomers with n ¼ 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 CAC 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.

Computational investigation of interaction of polypyrrole on the surface of single-walled carbon nanotube

“…Only the trans-forms (with respect to NCCN bond; see Fig. 1) of bi-and tripyrrole have been considered since they have been found to have the lower energy [12]. The vertical ionization potential of pyrrole, bipyrrole, and tripyrrole has been computed to be 8.21, 7.07, and 6.51 eV, respectively; and the corresponding adiabatic ionization potential values are computed to be 8.0, 6.74, and 6.19 eV, respectively (Table 1).…”

“…Pyrrole and pyrrole oligomers have been subjected to several investigations determining various properties including electronic structure, vibrational frequencies, ionization potential, and electron affinity and effect of doping on these properties [12][13][14]. It has been found that aromatic compounds are adsorbed on CNT surfaces through stacking interactions [15][16][17][18][19][20].…”

Solar elements based on organic and organo-inorganic materials

“…Теоретические исследования PPy и олигопирролов n-Py, n = 2-24 (n число мономерных звеньев) были в основном ограничены изучением изменения структурных, энергетических и электронных свойств при высоких концентрациях легирующего агента [250][251][252][253].…”

Theoretical studies of structural, optic and electronic properties of polypyrrole (PPy) oligomer

“…In addition, it has also been reported that the effect of the doping of different material on electronic and optical properties [20,21]. Furthermore, the theoretical studies on electronic and optical properties of some substitute or doped PPy were also performed [22][23][24][25]. However, to the best of our knowledge, no theoretical study was present on the structural properties and examination of band gap according to chain length (n = 1-29).…”