Quantum-chemical study of radical ions and molecules incorporating solvent effect.: II. Calculation of electronic transitions and spin densities of various conjugated radical anions in π-approximation

Abstract

Possibilities of improving the interpretation of electronic and ESR spectra of radical anions derived from aza, cyano, keto and nitro derivatives of aromatic hydrocarbons within the restricted SCF π method are investigated. With regard to the standard parametrization (method A) two modifications are made: (i) incorporation of the polarization of the σ skeleton and the effect of the non-uniform distribution of π-electrons (method B), (ii) incorporation of the solvent effect directly into the Fock operator according to the procedure proposed by Germer (method C). It is shown that method B overestimates the σ-polarization and yields poorer results as compared to the standard method A. On the contrary, inclusion of the solvent effect directly in the Fock operator (method C) is shown to be significant for the mentioned systems of radical anions and convenient for characterization of this effect — improvement of the electronic and ESR spectra being considerable as compared to methods A and B.