Broadband fluorescence reveals mechanistic differences in excited-state proton transfer to protic and aprotic solvents
Pragya Verma, Arnulf Rosspeintner, Bogdan Dereka, Eric Vauthey, Tatu Kumpulainen
Abstract
O, MeOH and EtOH) and aprotic (DMSO) solvents utilizing a broadband fluorescence technique with sub-200 fs time resolution. The time-resolved spectra are decomposed into contributions from the protonated and deprotonated species and a clear signature of CIP* is identified in DMSO and MeOH. Interestingly, the CIP* intermediate is not observable in aqueous environment although the dynamics in all solvents are multi-exponential. Global analysis based on the Eigen-Weller model is satisfactory in all solvents, but the marked mechanistic differences between aqueous and organic solvents cast doubt on the physical validity of the rate constants obtained.
Topics & Concepts
Excited statePhotochemistryFluorescenceProtonSolventBroadbandChemistryProtic solventSolvent effectsOrganic chemistryAtomic physicsOpticsPhysicsQuantum mechanicsPhotochemistry and Electron Transfer StudiesSpectroscopy and Quantum Chemical StudiesFree Radicals and Antioxidants