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Proton‐Transfer Dynamics of Photoacidic Merocyanines in Aqueous Solution
Photoacids attract increasing scientific attention, as they are valuable tools to spatiotemporally control proton‐release reactions and pH values of solutions. We present the first time‐resolved spectroscopic study of the excited state and proton‐release dynamics of prominent merocyanine representat...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
John Wiley and Sons Inc.
2021
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8361770/ https://www.ncbi.nlm.nih.gov/pubmed/33929051 http://dx.doi.org/10.1002/chem.202100168 |
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author | Kaiser, Christoph Halbritter, Thomas Heckel, Alexander Wachtveitl, Josef |
author_facet | Kaiser, Christoph Halbritter, Thomas Heckel, Alexander Wachtveitl, Josef |
author_sort | Kaiser, Christoph |
collection | PubMed |
description | Photoacids attract increasing scientific attention, as they are valuable tools to spatiotemporally control proton‐release reactions and pH values of solutions. We present the first time‐resolved spectroscopic study of the excited state and proton‐release dynamics of prominent merocyanine representatives. Femtosecond transient absorption measurements of a pyridine merocyanine with two distinct protonation sites revealed dissimilar proton‐release mechanisms: one site acts as a photoacid generator as its pK(a) value is modulated in the ground state after photoisomerization, while the other functions as an excited state photoacid which releases its proton within 1.1 ps. With a pK(a) drop of 8.7 units to −5.5 upon excitation, the latter phenolic site is regarded a super‐photoacid. The 6‐nitro derivative exhibits only a phenolic site with similar, yet slightly less photoacidic characteristics and both compounds transfer their proton to methanol and ethanol. In contrast, for the related 6,8‐dinitro compound an intramolecular proton transfer to the ortho‐nitro group is suggested that is involved in a rapid relaxation into the ground state. |
format | Online Article Text |
id | pubmed-8361770 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2021 |
publisher | John Wiley and Sons Inc. |
record_format | MEDLINE/PubMed |
spelling | pubmed-83617702021-08-17 Proton‐Transfer Dynamics of Photoacidic Merocyanines in Aqueous Solution Kaiser, Christoph Halbritter, Thomas Heckel, Alexander Wachtveitl, Josef Chemistry Full Papers Photoacids attract increasing scientific attention, as they are valuable tools to spatiotemporally control proton‐release reactions and pH values of solutions. We present the first time‐resolved spectroscopic study of the excited state and proton‐release dynamics of prominent merocyanine representatives. Femtosecond transient absorption measurements of a pyridine merocyanine with two distinct protonation sites revealed dissimilar proton‐release mechanisms: one site acts as a photoacid generator as its pK(a) value is modulated in the ground state after photoisomerization, while the other functions as an excited state photoacid which releases its proton within 1.1 ps. With a pK(a) drop of 8.7 units to −5.5 upon excitation, the latter phenolic site is regarded a super‐photoacid. The 6‐nitro derivative exhibits only a phenolic site with similar, yet slightly less photoacidic characteristics and both compounds transfer their proton to methanol and ethanol. In contrast, for the related 6,8‐dinitro compound an intramolecular proton transfer to the ortho‐nitro group is suggested that is involved in a rapid relaxation into the ground state. John Wiley and Sons Inc. 2021-06-01 2021-06-21 /pmc/articles/PMC8361770/ /pubmed/33929051 http://dx.doi.org/10.1002/chem.202100168 Text en © 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH https://creativecommons.org/licenses/by-nc/4.0/This is an open access article under the terms of the http://creativecommons.org/licenses/by-nc/4.0/ (https://creativecommons.org/licenses/by-nc/4.0/) License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. |
spellingShingle | Full Papers Kaiser, Christoph Halbritter, Thomas Heckel, Alexander Wachtveitl, Josef Proton‐Transfer Dynamics of Photoacidic Merocyanines in Aqueous Solution |
title | Proton‐Transfer Dynamics of Photoacidic Merocyanines in Aqueous Solution |
title_full | Proton‐Transfer Dynamics of Photoacidic Merocyanines in Aqueous Solution |
title_fullStr | Proton‐Transfer Dynamics of Photoacidic Merocyanines in Aqueous Solution |
title_full_unstemmed | Proton‐Transfer Dynamics of Photoacidic Merocyanines in Aqueous Solution |
title_short | Proton‐Transfer Dynamics of Photoacidic Merocyanines in Aqueous Solution |
title_sort | proton‐transfer dynamics of photoacidic merocyanines in aqueous solution |
topic | Full Papers |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8361770/ https://www.ncbi.nlm.nih.gov/pubmed/33929051 http://dx.doi.org/10.1002/chem.202100168 |
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