Polarizable QM/Classical Approaches for the Modeling of Solvation Effects on UV–Vis and Fluorescence Spectra: An Integrated Strategy

Hybrid methods combining quantum chemistry and classical models are largely used to describe solvent effects in absorption and emission processes of solvated chromophores. Here we compare three different formulations of these hybrid approaches, using a continuum, an atomistic, or a mixed description of the solvent. In all cases mutual polarization effects between the quantum and the classical subsystems are taken into account. As a molecular probe, 3-hydroxyflavone has been selected due to its rich photophysics, which involves different tautomeric and anionic forms. We show that a clear assignment of the measured spectroscopic signals to each specific form can be achieved by combining the different solvation models into an integrated and cost-effective strategy. Previously proposed mechanisms for the excited-state proton transfer (ESIPT), specific solvent perturbation effects on ESIPT, and solvent-assisted anion formation are also validated in terms of short- and long-range solvation effects.