Bondarchuk S. Spin-dependent reactivity of the aryl cations

The thesis is devoted to study of the electronic structure and reactivity parameters for the aryl cations in context of its quantification, especially in the reactions with pi-nucleophiles, in the intramolecular cyclization of some ortho-substituted derivatives, and the recombination reaction. It is shown in the thesis, that the electrophilicity of the singlet Ar+ ions is much higher compared to the triplet ones. Based on the comparison of the electrophilicity indexes of the reagents and products as well as the cyclization reaction enthalpies of the singlet ortho-substituted Ar+ cations, the thermochemical sense of both the ‘maximum hardness’ and ‘minimum electrophilicity’ principles, which specify the most favorable reaction path was determined. The particular attention was paid to the mechanism of the reaction of the Ar+ cations with pi-nucleophiles. It has been found that the singlet-triplet splitting of the Ar+ cations correlates with the activation barrier height. The existence of such correlation is clear when combine the Mayr-Patz equation and the transition state theory equation. This fact reveals a multi-configuration nature of the transition state of the AE ractions with pi-nucleophiles. It has been shown in the thesis, that the ethylene interaction with a paramagnetic catalyst, in particular with the copper atom, leads to a decrease in the singlet-triplet splitting energy down to 0.47 eV. It becomes possible due to the exchange mixing mechanism in terms of the Dewar-Chatt-Duncanson model at the distances between the interacting species being not higher than 3 angstrom. Special attention has been paid to the structure, spectra and reactivity parameters of the dications formed upon recombination of the triplet Ar+ cations. The influence of the anions on the UV-spectra of the dications as well as the degradation paths of the dications in neutral and weak alkaline media has been determined. Also, a number of potential «structure-activity» descriptors of carcinogenic activity of benzidine have been found.