LAUSR

Abstract This paper is a continuation of our studies on the dependence of the first electrochemical oxidation potential, Ep1, on the electronic structures of flavonoids. For this purpose, a set of 20 flavonoids and their cation and radical forms were optimized by semi-empirical PM6 and DFT in water methods. Using differences in net atomic charges ΔNACCat-Neut calculated using PM6 we determined active OH oxygens. DFT in some cases gave different results, which were also in opposition to the literature. The models for the estimation of Ep1 based on the sum of atomic orbital spin populations on carbon atoms in skeleton of radicals, Σ s C AOSPRad, calculated by PM6 method yielded much better statistics than those calculated using DFT (S.E. = 0.064 vs. 0.118).