Theoretical study on the emeraldine salt – impact of the computational protocol

Aniline oligomers versus polyaniline

“…When discussing short aniline oligomers and their molecular structure, the papers on this topic can be divided in two groups. The first group assumes that aniline molecules are linked entirely in para ‐positions,67–73 as they appear in PANI. The second group admits also the possibility of the ortho ‐coupling of aniline units at the oligomeric stage,74 leading to phenazine‐like constitutional units 1–8, 27, 30–32, 34, 35, 54.…”

Functional block-like structures from electroactive tetra(aniline) oligomers

“…As discussed above, oligo(aniline)s can adopt different oxidation states; the key repeating unit can usually be captured by di-, tri-or tetramers. Fortuitously, given the main focus of this review, TANIs are often chosen as computational models for longer chains at the DFT level, as reasonable agreement with most types of experimental data can be achieved, 117,118 although, as discussed below, their doping may not give rise to the full polaron lattice, 119 and the validity of extrapolating polymer properties from oligomers has been questioned. 120 Computationally, if the system size needs to be limited to permit calculations of sufficient accuracy within a sensible timeframe, these oligomers can either be capped by suitable end units such as NH 2 or phenyl groups, treating the anilines as isolated units (e.g.…”

“…For DFT calculations, structural change in response to changing the basis set is often limited once basis sets of reasonable (double-z) quality have been used, 118,126 but energetic results may be more sensitive. Several computational studies also indicate that chain-chain interactions 127 or a reasonable approximation of the solvent medium 118,122 may be necessary to achieve good agreement with available experimental data, and the inclusion of some Hartree-Fock exchange in the chosen density functional can affect spinstate energy preferences. 118 Early computational studies were predominantly aimed at exploring whether ab initio approaches to aniline oligomers would achieve reasonable agreement with available experimental data, as well as the results of higher level calculations.…”

“…Several computational studies also indicate that chain-chain interactions 127 or a reasonable approximation of the solvent medium 118,122 may be necessary to achieve good agreement with available experimental data, and the inclusion of some Hartree-Fock exchange in the chosen density functional can affect spinstate energy preferences. 118 Early computational studies were predominantly aimed at exploring whether ab initio approaches to aniline oligomers would achieve reasonable agreement with available experimental data, as well as the results of higher level calculations. These focused on the geometric structures of different oxidation states, especially considering the co-planarity of phenyl rings, as well as the reproduction of experimental absorption spectra and band gaps.…”

Excited-state hydrogen-bonding dynamics of camphorsulfonic acid doped polyaniline: a theoretical study

“…[23][24][25][26] Furthermore, most recent papers have applied DFT methods to the study of PANi and concluded that these methods are suitable for modeling. For instance, the doping process of PANi has been investigated using DFT methods, [27][28][29] and the theoretical calculation of hydrogen bonding in PANi has been carried out as well; 23,30 these investigations were mainly focused on structural and electronic influences on the hydrogen bonding complexes. However, as far as we know, there are few investigations on the hydrogen-bonding dynamics of hydrogen-bonded PANi acid complexes in electronically excited states.…”