Applications of Hückel-Su-Schrieffer-Heeger method

Abstract The equilibrium carbon-carbon (C-C) bond lengths in π -electron hydrocarbons are very sensitive to the electronic ground-state characteristic. In recent two papers by Stolarczyk and Krygowski (J Phys Org Chem, 34:e4154,e4153, 2021) a simple quantum approach, Augmented Hückel Molecular Orbital (AugHMO) model, is proposed for qualitative, as well quantitative, study of this phenomenon. simplest realization AugHMO model Hückel-Su-Schrieffer-Heeger (HSSH) method, which resonance integral β HMO linear function length. present paper, HSSH method applied C-C set 34 selected polycyclic aromatic (PAHs). This exactly molecules analyzed Riegel Müllen 23:315, 2010) context their electronic-excitation spectra. These PAHs have been obtained chemical synthesis, but most cases no diffraction data (by X-rays or neutrons) sufficient quality available provide us with geometry. On other hand, these rather big (up 96 carbon atoms), ab initio methods chemistry too expensive reliable geometry optimization. That makes attractive alternative. Our calculations uncover modular architecture certain classes PAHs. For studied (and fragments – modules), we calculate values aromaticity index HOMA.