Toward a Quantum-Mechanical Description of 2D-IR Spectra of Solvated Systems: The Vibrational Mode Coupling within A Polarizable Continuum Model

The extension of the polarizable continuum model (PCM) to evaluate solvent effects on vibrational coupling is reported for both the transition dipole coupling and the Hessian matrix reconstruction (HMR) methods. A comparative analysis of the two approaches is reported for a model system, i.e., formaldehyde dimers in different spatial arrangements, with the aim of dissecting solvent effects in their two main contributions, the modification of the transition dipole moments and the screening of their interaction. The HMR-PCM formalism is finally applied to the evaluation of the vibrational coupling for (s)-N-methyl acetylproline amide in aqueous and dichloromethane solutions. In the latter case, a comparison with experimental findings is presented and used to gain a better understanding of the conformational state.