Theoretical study of 2-phenylpyrrole molecule using various quantum-chemical approaches

Abstract

Theoretical study of 2-phenylpyrrole molecule using various quantum-chemical approaches A systematic theoretical study of 2-phenylpyrrole (PhPy) is presented for its neutral and monocharged states. The calculations were performed using the semiempirical Austin Model 1 (AM1) method, ab initio Møller-Plesset perturbation theory up to the second-order (MP2), density functional theory (DFT) and its tight-binding approximation (DFTB+). The comparison of the obtained equilibrium geometries showed that the C—C bond lengths in the phenylene ring are practically identical for the neutral state. Electric charging leads to significant changes in the geometry with respect to the neutral state. The C—N bonds in PhPy are elongated and the negative charging produces the out-of-plane distortion of N—H bond from the aromatic ring plane. The anionic state of the investigated molecule is connected with a higher perturbation of bond length alternation in both rings in comparison to the cationic state. The vibrationaly broadened absorption spectra, based on the on-the-fly molecular dynamics (MD) simulations, are also presented and compared with experimental spectra. Although the DFTB+ method has the tendency to planarize the investigated molecular structure, the agreement of simulated absorption spectra based on the MD DFTB+ geometries with TD-DFT calculations is acceptable.

Theoretical Investigation of New Organic Electroluminescent Materials Based on 4-Azaindole Groups and Oligopyrrole

“…The first four vertical excitation energies are summarized. Only two electronic transitions from ground state (S 0 ) to third excited electronic state (S 3 ) have computed oscillator strength been higher than 0.5 while the other electronic transitions, with smaller oscillator strength have a negligible relevance in experimental works [16][17][18][19].…”

The effect of polyaromatic hydrocarbons on the spectral and photophysical properties of diaryl-pyrrole derivatives: an experimental and theoretical study

“…The latter dihedral angle was found to be higher than the values previously reported for 2-phenylpyrrole where depending of the computational method used, dihedral angles in the range of 241-311 were obtained. 46 However, the most relevant piece of information comes from the substitution in position 3 of the PAH unit. Indeed, depending of the aromatic chromophore attached to the pyrrole unit, dihedral angles-with respect to the plane formed by the pyrrole ring-of B461 (benzene), 601 (naphthalene and anthracene) and 571 (pyrene) were obtained.…”

“…A similar effect was previously reported for 2-phenylpyrrole (with the HOMO orbital delocalized over the pyrrole ring while the LUMO was found delocalized over the phenylene unit) and was attributed to the occurrence of electron transfer between the heterocyclic ring and the phenylene moiety (ICT). 46 NBO analysis has been performed on the investigated diarylpyrroles in order to further elucidate the intra-molecular interactions and delocalization of electron density within the molecule. Natural bond orbital analysis provides an efficient method for studying intra-and inter-molecular bonding and interaction among bonds, and also provides a convenient basis for investigating charge transfer or conjugative interaction in molecular systems.…”