Einfluss der Photoionisation auf intermolekulare Bindungsmotive aromatischer Moleküle
Zusammenfassung der Projektergebnisse
In this project, we characterized the energetics and dynamics of simple solvent migration reactions in aromatic clusters to improve our knowledge of solvation dynamics at the single molecular level. Although solvation plays an important role in chemical reactions and bio-molecular recognition, its dynamics remains poorly characterized at the single molecular level, because most experimental approaches in the condensed phase cannot address the motion of individual solvent molecules. To overcome this problem, we studied solvation dynamics in molecular aromatic clusters isolated in the gas phase, because they can be prepared under well-defined conditions in a molecular beam by carefully selecting the composition, size, structure and energy content. We applied state-of-the-art static and time-resolved laser spectroscopic techniques and quantum chemical calculations to such clusters to probe solvation dynamics of single solvent molecules for the first time in real time and to unravel precise details of such migration reactions as a function of several adjustable parameters. In a strongly collaborative and international effort, we combined the world-wide unique expertise and equipment of several groups, including those in Berlin (Dopfer, infrared spectroscopy of aromatic cation clusters), Tokyo (Fujii, time-resolved spectroscopy), Manchester (Müller-Dethlefs, photoionization spectroscopy), and Würzburg (Mitric, molecular dynamics simulation). The experimental strategy involves resonant photoionization of the cluster, which triggers the solvent migration in the cation state that is then probed by time-resolved spectroscopy. The investigated systems include phenol solvated by rare gas atoms or methane, and a number of monohydrated aromatic biomolecules, which serve as models for peptides (alkyl-anilides) and neurotransmitters (hydroxyindole, tryptamine). The combined approach gave detailed insight into salient properties of the solvent migration reactions, such as the reaction mechanism (competing pathways, time constants, reaction yields, intermediates) and the role of energy dissipation. It turned out that the reaction mechanism strongly depends on number (one or more) and nature of the ligands (atomic or polyatomic, nonpolar or polar), details of the intermolecular potential (well depths, barrier heights), the number and type of functional groups (acceptor or donor of hydrogen bonds), and the internal energy available for the reaction. For example, water shuttling reaction time constants can vary by three orders of magnitude (ps-ns time scale) in monohydrated aromatic dimers. Significantly, our experimental spectra served as precise benchmark for developing and testing sophisticated and reliable approaches based on molecular dynamics simulations, which in turn provided many more details of the reaction properties than the experimental data alone. It is stressed that only this concerted international experimental and computational effort allowed for the quantum jump achieved in our understanding of single solvent migration reactions in clusters. To prepare studies of the effects of solvent-solvent interactions on the solute-solvent dynamics, we also determined the static micro-hydration structure for a number of aromatic cations solvated by up to five water ligands. In the near future, the important role of solvent-solvent (water-water) interactions will be revealed in a quantitative fashion by challenging time-resolved studies.
Projektbezogene Publikationen (Auswahl)
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Dissociation energetics of the phenol+...Ar2 cluster ion: The role of π → H isomerization. J. Chem. Phys. 133, 154308 (2010)
X. Tong, A. Armentano, M. Riese, M.B. Yezzar, S. Pimblott, K. Müller-Dethlefs, S. Ishiuchi, M. Sakai, A. Takeda, M. Fujii, O. Dopfer
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Ionization-induced site switching dynamics in solvated aromatic clusters: Phenol-(rare gas)n clusters as prototypical example. Int. Rev. Phys. Chem. 31, 131-173 (2012)
M. Fujii and O. Dopfer
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Watching Water Migration around a Peptide Bond. Angew. Chem. Int. Ed. 51, 6604-6607 (2012)
K. Tanabe, M. Miyazaki, M. Schmies, A. Patzer, H. Sekiya, M. Sakai, O. Dopfer, M. Fuji
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Microhydrated aromatic cluster cations: Binding motifs of 4-aminobenzonitrile-(H2O)n cluster cations with n≤4. J. Chem. Phys. 141, 214301 (2014)
M. Schmies, M. Miyazaki, M. Fujii, O. Dopfer
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Single Water Solvation Dynamics Probed by Infrared Spectra - Theory Meets Experiment. Angew. Chem. Int. Ed. 53, 14601-14604 (2014)
M. Wohlgemuth, M. Miyazaki, M. Weiler, M. Sakai, O. Dopfer, M. Fujii, R. Mitric
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Mass Analyzed Threshold Ionization Detected Infrared Spectroscopy: Isomerization Activity of the Phenol–Ar Cluster near the Ionization Threshold. Phys. Chem. Chem. Phys. 17, 2494-2503 (2015)
M. Miyazaki, S. Yoshikawa, F. Michels, K. Misawa, S. Ishiuchi, M. Sakai, O. Dopfer, K. Müller-Dethlefs, M. Fujii
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Probing solvation dynamics around aromatic and biological molecules at the single molecular level. Chem. Rev. 116, 5432-5463 (2016)
O. Dopfer and M. Fujii
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Deciphering environment effects in peptide bond solvation dynamics by experiment and theory. Phys. Chem. Chem. Phys. 19, 22564-22572 (2017)
M. Wohlgenuth, M. Miyazaki, K. Tsukuda, M. Weiler, O. Dopfer, M. Fujii, R. Mitric
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Microhydration of PAH+ Cations: Evolution of Hydration Network in Naphthalene+ -(H2O)n Clusters (n≤5). Chem. Sci. 9, 2301-2318 (2018)
K. Chatterjee and O. Dopfer
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Real-time observation of the photoionization induced water rearrangement dynamics in the 5-hydroxyindole– water cluster by time-resolved IR spectroscopy. Phys. Chem. Chem. Phys. 20, 3079-3091 (2018)
M. Miyazaki, A. Naito, T. Ikeda, J. Klyne, K. Sakota, H. Sekiya, O. Dopfer, M. Fujii
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Stepwise Microhydration of Aromatic Amide Cations: Solvation Networks Revealed by Infrared Spectra of Acetanilide+ -(H2O)n Clusters (n≤3). Phys. Chem. Chem. Phys. 20, 3148-3164 (2018)
J. Klyne, M. Schmies, M. Miyazaki, M. Fujii, O. Dopfer
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Aromatic Charge Resonance Interaction Probed by Infrared Spectroscopy. Angew. Chem. Int. Ed. 58, 3351-3355 (2019)
K. Chatterjee, Y. Matsumoto, O. Dopfer
