5-Fluorouracil tautomers and their interactions with Ca++ ion – A DFT treatment

5-Fluorouracyl is an important cancer chemotropy agent widely used in medicine. In the present study, its 1,3- and 1,5-type proton tautomers and their interactions with calcium cation have been investigated within the restrictions of density functional theory at the level of B3LYP/6-311++G(d,p). All the structures considered are electronically stable, thermodynamically exothermic and have favorable Gibbs’ free energy of formation values at the standard states. Various quantum chemical properties of them, including UV-VIS spectra, the HOMO and LUMO energies etc., have been obtained and discussed. The calculations have indicated that in the case of the composites some electron population transfer occurs from the tautomers to the cation, thus the initial formal charge of the calcium decreases in certain extent depending on the tautomeric structure.