Affiliations: Department of Chemistry, Science and Research Branch, Islamic Azad University, Tehran, Iran
Corresponding author: Younes Valadbeigi, Department of Chemistry, Science and Research Branch, Islamic Azad
University, Tehran, Iran. Tel.: +98 21 4486 5001; E-mail: [email protected].
Abstract: Interactions of H+, Li+, Na+, and K+ cations with five isomers of cytosine were studied employing B3LYP and MP2 methods using 6-311++G(d,p) basis set. The cation-cytosine interactions affected the relative stability of the isomers, however, in the all complexes, the keto structure was the most stable isomer. Cation-cytosine interactions influenced the energy barriers of intramolecular proton transfers so that in some cases the cations catalyze the proton transfer and in others they increase the activation energies. The observed difference was attributed to the change in the acidity and basicities of the proton donor and acceptor sites and a linear correlation was obtained between acidity and activation energy.
Keywords: Cytosine, proton transfer, alkali metal cations, activation energy, acidity