Perturbative multireference configuration interaction (CI-MRPT2) calculations in a focused dynamical approach: A computational study of solvatochromism in pyrimidine

We have investigated solvatochromic effects over a solvent series of increasing polarity on the prototype molecule pyrimidine as a solute species. The line shape profiles, obtained by a time-dependent approach based on quantum mechanical calculations performed over frames sampled from classical molecular dynamics trajectories, were directly compared to the available experimental bands. The multireference configuration interaction second-order perturbation (CI-MRPT2) calculations are in quantitative agreement with the experiment. The results also confirm how nonprotic solvents can be confidently modeled by continuous solvation models as the polarizable continuum model, whereas protic solvents, as water, require the inclusion of explicit solvent molecules to account for the effects of hydrogen bonds.