On the effect of solute-solvent Pauli repulsion on n → π* transition for acrolein in water solution

In this work, we present a method to compute the Pauli repulsion contribution to the solute-solvent interaction that exploits solute electronic configurations sampled by Quantum Monte Carlo simulations. Starting from the inspiring model of Amovilli and Mennucci, the discreteness of the solvent is recovered by the definition of molecular domains and the concept of probe molecule. The method can be calibrated on the solute ground state but it offers the advantage of being able to be applied also to electronic-excited states. We show the results for the formaldehyde-water intermolecular pair, here used for the calibration, and two clusters containing acrolein surrounded by 11 and 19 water molecules simulating the solvation shell. In these systems, hydrogen bonds are formed between the solute and the water molecules and we found that, in such case, the Pauli repulsion contribution gives a red shift in the n → π* vertical transition energy.