Dresden 2020 – wissenschaftliches Programm
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O 41.6: Vortrag
Dienstag, 17. März 2020, 12:15–12:30, TRE Ma
Quantum Tunneling in Intramolecular Hydrogen Transfer: The Case of Porphycene on Metal Surfaces — •Yair Litman1 and Mariana Rossi1,2 — 1Fritz Haber Institute of the Max Planck Society, Berlin, Germany. — 2MPI for Structure and Dynamics of Matter, Hamburg, Germany
The intramolecular hydrogen transfer (IHT) of porphycene represents a paradigmatic process where nuclear quantum effects and anharmonicity result in unconventional hydrogen dynamics. Here, we study the IHT of porphycene adsorbed on Cu and Ag surfaces at different temperatures. We couple density functional theory calculations including dispersion corrections with the ring-polymer instanton method. This combination gives us access to unprecedented full-dimensional quantum mechanical reaction rates for porphycene on Cu(110) and Ag(110) in the deep tunneling regime. We predict rates in excellent agreement with experiments [3,4] and show the importance of heavy-atom tunneling in the reaction. We address the thus-far unexplained temperature dependence of the IHT and reveal that the observed activation energy is related to the energy difference between reactant and product, rather than reactant and transition state. Finally, we unequivocally identify the IHT mechanism as stepwise for Cu(110) and show the existence of a sharp transition between concerted and stepwise mechanisms on Ag(110) surface.  Y. Litman, et al., J. Am. Chem. Soc. 141, 2526 (2019);  J. O. Richardson and S. Althorpe, J. Chem. Phys. 131, 214106 (2009);  T. Kumagai, et al., Phys. Rev. Lett. 111, 246101 (2013);  M. Koch, et al., J. Am. Chem. Soc. 139, 12681 (2017).