Sülzner, Niklas and Geissler, Bastian and Grandjean, Alexander and Jung, Gregor and Nuernberger, Patrick (2022) Excited-State Proton Transfer Dynamics of a Super-Photoacid in Acetone-Water Mixtures. CHEMPHOTOCHEM, 6 (7): e202200041. ISSN 2367-0932
Full text not available from this repository. (Request a copy)Abstract
Super-photoacids, that is, photoacids with a negative pK(a) value in the electronically excited state, can trigger an excited-state proton transfer (ESPT) to the solvent. For the neutral pyranine-derived super-photoacid studied here, even indications for ESPT in acetoneous solution are reported. The characteristics of ESPT in this environment, that is, which intermediates exist and what the impact of cosolvents is, remain unsettled though. In this work, we study ESPT in acetone-water mixtures by steady-state and time-resolved fluorescence spectroscopy. Various effects are observed: First, the addition of water supports the formation of a hydrogen-bonded ground-state complex comprising one water molecule and the photoacid, whose excitation triggers the formation of a hydrogen-bonded ion pair on a sub-ns time scale. Second, water has an overall accelerating effect on the fluorescence dynamics of the involved emitting species, whose contributions are disentangled in a global analysis scheme, enabling the identification of emission from the free photoacid, a photoacid-water complex, a hydrogen-bonded ion pair, and the deprotonated photoacid. At least two water molecules are necessary for ESPT in the environment. Third, additional acidification thwarts an efficient ground-state complex formation of the photoacid and water. However, upon excitation, complexation may occur on a timescale faster than the photoacid's excited-state lifetime, so that emission from a nascent complex emerges.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | GEMINATE RECOMBINATION; STEADY-STATE; PHENOL OH; ION-PAIR; SOLVENT; SOLVATOCHROMISM; SPECTROSCOPY; FLUORESCENCE; ALCOHOLS; CARBON; Eigen-Weller model; excited-state proton transfer; photoacid; solvent effects; time-resolved spectroscopy |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie > Chair of Physical Chemistry I > Prof. Dr. Patrick Nürnberger |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 07 Feb 2024 10:40 |
| Last Modified: | 07 Feb 2024 10:40 |
| URI: | https://pred.uni-regensburg.de/id/eprint/57260 |
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