Density functional study of the dicationic hypoxanthine tautomeric forms

The study of the chemical and physicochemical properties of purine derivatives and isomers has received heightened attention for several years. Accordingly, the Density Functional Theory study of the dicationic state of purine derivative hypoxanthine was performed. In this study, the relative energetic stabilities, several molecular and electronic structure properties and the IR vibrational spectra of the four energetically most stable dicationic hypoxanthine tautomers were calculated. Additionally, we calculated <Delta(G)over bar> for the heterocyclic protonic transfer processes and the constants of the tautomeric equilibria. The theoretical properties of the comparatively most stable K1379 ketonic form are discussed and compared with those for the energetically most stable hypoxanthine tautomers and isomers in different protonation levels. The results obtained are employed to analyze some features of the experimental physicochemical and chemical behavior of both the predominantly dicationic tautomer and hypoxanthine in diverse heterocyclic protonation states. (C) 1999 Elsevier Science B.V. All rights reserved.