A theoretical study of the molecular structure and torsional potential of styrene

Abstract

State-of-the-art ab initio methodologies have been used to perform calculations on the torsion along the vinyl-phenyl groups in styrene. The methods employed range from the Hartree-Fock and Möller-Plesset perturbation theories and coupled-cluster theory up to density functional (DF) ones. The effect of the basis set has also been considered by using several extrapolation formulae to the complete basis set limit. The torsional profile is analysed in terms of the π-conjugation and steric repulsions. The calculations indicate the existence of a global twisted minimum with a slightly lower energy than the planar structure. However, the exchange-correlation functionals used in the DF calculations are unable to predict this twisted minimum.

Thermochemical Properties of Polycyclic Aromatic Hydrocarbons (PAH) from G3MP2B3 Calculations

“…Figure 2 shows the predicted torsional potential of the styrene molecule (A 1 C 2 H 3 ) at three levels of theory: B3LYP/ cc-pVDZ, MP2/cc-pVDZ, and MP2/cc-pVTZ. Also shown in the figure are the experimental measurements of the torsional potential by Caminati et al 19 As expected, the second-order perturbation theory predicts the energy barrier as well as the 17 entire shape of the potential more accurately. While the secondorder perturbation calculation with the cc-pVDZ basis set is slightly below the experimental measurements, the calculation with the larger cc-pVTZ basis set is slightly above.…”

Assessment of density-functional models for organic molecular semiconductors: The role of Hartree–Fock exchange in charge-transfer processes

“…This theory is not, however, exempted in its current implementation from few shortcomings. As a matter of fact, it is well-known to behave erratically when dealing with breakings of p-conjugation along a torsional path [38][39][40][41][42][43][44][45][46][47][48]. This feature is traced back [49,50] to the self-interaction error [51,52], an inherent consequence of the approximate exchange-correlation functionals being used, which artificially overstabilizes the delocalized planar structures compared to the twisted ones.…”

A quantum mechanical study on polymer flexibility: Extended model from monomer to tetramer of 2- and 4-bromostyrenes

“…We focused our attention onto the comparison of some geometry parameters between 2-bromo, 4-bromostyrene and the parent system styrene [14,15] in order to determine the influence of the position of the halogen in the structural parameters. The most recent theoretical study of the molecular structure and torsional potential of styrene, performed by Sancho-Garcia and Pé rez-Jimé -nez [15], concluded that ab initio (MP2 and Coupled Cluster) methods predict the existence of a global twisted minimum with a slightly lower energy than the planar structure.…”

“…As an approximation to the intermolecular contacts, the benzene dimer interaction has also been studied by different authors as prototype of pi-pi interactions showing that the contribution of the electrostatic quadrupole-quadrupole interaction is significant as compared to the remaining dispersion and exchange-repulsion contributions [9][10][11][12][13]. For styrene, the majority of the published work is concerned with the structure of the monomer [14,15] but there has been little analysis of the fundamental interactions in the styrene dimer and polymer [16][17][18][19]. An earlier electron diffraction study on thin films of polymers of p-chloro-, p-bromo-, and p-iodostyrene concluded that the benzene rings are located alternately on each side of the plane of the zig-zag paraffin chain and the neighboring molecules are closely packed in a ''face-to-face'' configuration in a plane perpendicular to the chain [20].…”