Theoretical study of neutral, anionic, and cationic uracil-Ag and uracil-Au systems: nonconventional hydrogen bonds.

The interaction of Ag and Au with uracil has been studied using the B3LYP density-functional approach. Neutral, cationic, and anionic systems were analyzed in order to study the influence of the atomic charge on bond formation. This interaction becomes stronger as the charge increases. In the case of neutral systems, a weak association is present. In the case of cations, the interaction is mainly electrostatic. The extra electron of the anions is localized on the metal atom. Consequently, nonconventional hydrogen bonds are formed. The ionization energy of uracil-Ag and uracil-Au is lower than the corresponding values for the metal atoms and uracil molecule, while the electron affinity is higher for uracil-Ag and uracil-Au than the analogous values for the isolated Ag, Au, and uracil. This might have significance for further experiments and possibly for applications, where the movement of the electrons is important. In the case of uracil-Ag and uracil-Au (anions), it may be possible to induce the detachment of one electron from the anion and also to remove a single hydrogen atom. It is possible that tight competition exists between the H dissociation and electron aloofness.