Tautomerism in 5-Bromouracil: Relationships with Other 5-Haloderivatives and Effect of the Microhydration

A comparative analysis on the effect of the water on the molecular structure and spectroscopy of 5-halogenated uracils was carried out. Solvent effects were considered by using a variable number (1–10) of explicit water molecules surrounding the 5-halouracil derivatives in order to simulate the first hydration shell. More than 300 cluster structures with water were analyzed. B3LYP and MP2 quantum chemical methods were used. For cases where literature data are available, the computed values were in good agreement with previous experimental and theoretical studies. Several general conclusions were underlined.