Direct Observation of Double Hydrogen Transfer via Quantum Tunneling in a Single Porphycene Molecule on a Ag(110) Surface

Koch, Matthias, Pagan, Mark, Persson, Mats ORCID: 0000-0002-1443-9490, Gawinkowski, Sylwester, Waluk, Jacek and Kumagai, Takashi (2017) Direct Observation of Double Hydrogen Transfer via Quantum Tunneling in a Single Porphycene Molecule on a Ag(110) Surface. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 139 (36). pp. 12681-12687.

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Abstract

Quantum tunneling of hydrogen atoms (or protons) plays a crucial role in many chemical and biological reactions. Although tunneling of a single particle has been examined extensively in various one-dimensional potentials, many-particle tunneling in high-dimensional potential energy surfaces remains poorly understood. Here we present a direct observation of a double hydrogen atom transfer (tautomerization) within a single porphycene molecule on a Ag(110) surface using a cryogenic scanning tunneling microscope (STM). The tautomerization rates are temperature independent below ∼10 K, and a large kinetic isotope effect (KIE) is observed upon substituting the transferred hydrogen atoms by deuterium, indicating that the process is governed by tunneling. The observed KIE for three isotopologues and density functional theory calculations reveal that a stepwise transfer mechanism is dominant in the tautomerization. It is also found that the tautomerization rate is increased by vibrational excitation via an inelastic electron tunneling process. Moreover, the STM tip can be used to manipulate the tunneling dynamics through modification of the potential landscape.

Item Type:	Article
Depositing User:	Symplectic Admin
Date Deposited:	13 Nov 2017 12:13
Last Modified:	19 Jan 2023 06:50
DOI:	10.1021/jacs.7b06905
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3012068