Solvatochromic shifts vs nanosolvation patterns: Uracil in water as a test case

We address the role played by a different subset of nanosolvation patterns on the lowest π–π∗ and n–π∗ solvatochromic shifts of uracil in water at 298 K. To this end, a computational investigation which compares perturbed electronic properties based on correlated electronic wavefunctions – computed either at the DFT or CCSD level of theory – in conjunction with two nanoseconds time-scale classical trajectories is presented. The simulations are based on the use of either an implicit or an explicit description of polarization. The predicted π–π∗ solvatochromic shifts based on these two simulations are very similar but slightly underestimate the experimental values. This finding reinforce the idea that for a proper estimation of the π–π∗ transition local interactions beyond those of purely electrostatic origin are mandatory. On the other hand, the n–π∗ excitation is seen to increase its shift upon inclusion of explicit polarization, thereby bringing the predicted shift in closer agreement with experimental data.