Theoretical investigation of the interaction of cytosine and its tautomers with alkali metals

Quantum chemistry calculations have been applied in order to explore the interaction of alkali metals with cytosine and its tautomers. The optimized geometries, harmonic vibrational frequencies, and the energies of cytosine, metallated cytosine, and its tautomers have been calculated. The calculations show that metallated cytosine is more stable than nonmetallated cytosine. The metallated cytosine through C(3) (C(1)) is most structured. NBO calculations have shown that, after metallation, the basicity of N(2) in C(2) and C(3) increases rather than nonmetallated cytosine. Calculation of the stretching vibrations shows that, after metallation, the frequency shift, Delta nu(OH), of the nu stretching vibrations of O-H in C(2) and C(3) is related to the atomic number of the metal.