The microsolvation patterns of the uracil radical anion in water clusters U-(H2O)n with n ranging from 3 to
5 were investigated by the density functional theory approach. The electron detachment energies (VDE) of
the stable anionic complexes with different numbers of hydration water are predicted. The linear dependence
of the VDE value of the most stable anionic complexes with respect to the hydration number suggests the
importance of the clustered waters in the microsolvation of the radical anion of the nucleobases. The formation
of the water clusters is found to be necessary in the most stable conformers of the tri-, tetra-, and pentahydrated
radical anion of uracil. The microsolvation pattern with three or more well-separated hydration water molecules
in the first hydration layer is less stable than the arrangement with the waters in tight clusters. The charge
transfer between the anionic uracil and the hydration water is high. Good agreement between the experimental
and the theoretical vertical detachment energy yield in this study further demonstrates the practicability of
the B3LYP/DZP++ approach in the study of radical anions of the DNA subunits.