CC BY 3.0 UnportedBekçioǧlu, G.Allolio, C.Ekimova, M.Nibbering, E.T.J.Sebastiani, D.2020-11-122020-11-122014https://doi.org/10.34657/4510https://oa.tib.eu/renate/handle/123456789/5881We investigate the acid-base proton exchange reaction in a microsolvated bifunctional chromophore by means of quantum chemical calculations. The UV/vis spectroscopy shows that equilibrium of the keto-and enol-forms in the electronic ground state is shifted to the keto conformation in the excited state. A previously unknown mechanism involving a hydroxide ion transport along a short water wire is characterized energetically, which turns out to be competitive with the commonly assumed proton transport. Both mechanisms are shown to have a concerted character, as opposed to a step-wise mechanism. The alternative mechanism of a hydrogen atom transport is critically examined, and evidence for strong solvent dependence is presented. Specifically, we observe electrostatic destabilization of the corresponding πσ* state by the aqueous solvent. As a consequence, no conical intersections are found along the reaction pathway.enghttps://creativecommons.org/licenses/by/3.0/540hydroxyl radicalprotonquinolinol derivativesolventwaterchemical modelchemistrycomputer simulationlightmicrofluidicsproceduresquantum theoryradiation responseComputer SimulationHydroxyl RadicalHydroxyquinolinesLightMicrofluidicsModels, ChemicalProtonsQuantum TheorySolventsWaterArticle