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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 71: Organic Electronics and Photovoltaics - OLEDs and Molecular Excitations
CPP 71.10: Talk
Thursday, March 15, 2018, 17:30–17:45, C 243
Direct observation of double hydrogen transfer via quantum tunneling in a single porphycene molecule on Ag(110) — •Matthias Koch1, Mark Pagan2, Mats Persson2, Sylwester Gawinkowski3, Jacek Waluk3,4, and Takashi Kumagai1 — 1Fritz-Haber-Institut — 2University of Liverpool — 3Polish Academy of Sciences — 4Cardinal Stefan Wyszyński University
Quantum tunneling of hydrogen atoms plays a crucial role in many chemical and biological reactions. Although tunneling of a single particle has been studied extensively in one-dimensional potentials, many-particle tunneling in high-dimensional potential energy surface remains poorly understood. Recently tautomerization of a single molecules was observed in LT-STM experiments [1, 2]. Here we present a direct observation of double hydrogen atom transfer within a single porphycene molecule on Ag(110) using a low temperature STM [3]. We find that below ~10 K the tautomerization rate is temperature-independent and a large kinetic isotope effect (KIE) was observed upon substituting the hydrogen atoms by deuterium. Inelastic electron tunneling increases the tautomerization rate by a vibrational excitation. The observed KIE for three isotopologues and density functional theory calculations indicate that a stepwise transfer mechanism is dominant in the tautomerization. This is also in agreement with the observed third state in our time dependent tip height traces.
[1] L. J. Lauhon et al. Phys. Rev. Lett. 85, 4566 (2000)
[2] T. Kumagai et al. Phys. Rev. Lett. 100, 166101 (2008)
[3] M. Koch et al. J. Am. Chem. Soc. 139 (36), 12681 (2017)