Direct Observation of Structural Heterogeneity and Tautomerization of Single Hypericin Molecules
| Autor: | Johannes Gierschner, Marc Brecht, Quan Liu, Pierre-Michel Adam, Frank Wackenhut, Alfred J. Meixner, Liangxuan Wang, Otto Hauler, Juan Carlos Roldao |
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| Přispěvatelé: | Lumière, nanomatériaux et nanotechnologies (L2n), Université de Technologie de Troyes (UTT), Institute of Physical and Theoretical Chemistry, University of Tübingen, Germany, Madrid Institute for Advanced Studies in Nanoscience, Madrid, Spain, Université de Technologie de Troyes (UTT)-Centre National de la Recherche Scientifique (CNRS), Eberhard Karls Universität Tübingen = Eberhard Karls University of Tuebingen |
| Rok vydání: | 2021 |
| Předmět: |
Proton
Transition dipole moment Ensemble averaging FOS: Physical sciences 02 engineering and technology 010402 general chemistry 01 natural sciences Chemical reaction [SPI]Engineering Sciences [physics] Physics - Chemical Physics Molecule General Materials Science Physical and Theoretical Chemistry ComputingMilieux_MISCELLANEOUS [PHYS]Physics [physics] Chemical Physics (physics.chem-ph) Chemistry 021001 nanoscience & nanotechnology Tautomer 0104 chemical sciences Quinone Chemical physics Density functional theory 0210 nano-technology Physics - Optics Optics (physics.optics) |
| Zdroj: | Repositorio Institucional del Instituto Madrileño de Estudios Avanzados en Nanociencia instname Journal of Physical Chemistry Letters Journal of Physical Chemistry Letters, American Chemical Society, 2021, 12 (3), pp.1025-1031. ⟨10.1021/acs.jpclett.0c03459⟩ Journal of Physical Chemistry Letters, 2021, 12 (3), pp.1025-1031. ⟨10.1021/acs.jpclett.0c03459⟩ |
| ISSN: | 1948-7185 |
| DOI: | 10.1021/acs.jpclett.0c03459⟩ |
| Popis: | Tautomerization is a fast chemical reaction where structures of the reactants differ only in the position of a proton and a double bond. Tautomerization often occurs in natural substances and is a fundamental process in organic- and biochemistry. However, studying the optical properties of tautomeric species is challenging due to ensemble averaging. Many molecules, such as porphines, porphycenes or phenanthroperylene quinones, exhibit a reorientation of the transition dipole moment (TDM) during tautomerization, which can be directly observed in a single molecule experiment. A prominent phenanthroperylene quinone is hypericin showing antiviral, antidepressive, and photodynamical properties. Here, we study single hypericin molecules by using confocal microscopy combined with higher order laser modes. Observing abrupt flipping of the image pattern allows to draw conclusions about the coexistence of different tautomers and their conversion path. Time-dependent density functional theory calculations show that hypericin is cycling between the four most stable tautomers. This approach allows to unambiguously assign a TDM orientation to a specific tautomer and enables to determine the chemical structure in situ. Additionally, tautomerization can not only be observed by the image pattern orientation, but also as intermittency in the fluorescence emission of a single molecule. Time correlated single photon counting enables to determine the excited state lifetimes of the hypericin tautomers. Our approach is not only limited to hypericin, but can be applied to other molecules showing a TDM reorientation during tautomerization, helping to get a deeper understanding of this important process. |
| Databáze: | OpenAIRE |
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