Thermally and vibrationally induced tautomerization of single porphycene molecules on a Cu(110) surface.
We report the direct observation of intramolecular hydrogen atom transfer reactions (tautomerization) within a single porphycene molecule on a Cu(110) surface by scanning tunneling microscopy. It is found that the tautomerization can be induced via inelastic electron tunneling at 5 K. By measuring the bias-dependent tautomerization rate of isotope-substituted molecules, we can assign the scanning tunneling microscopy-induced tautomerization to the excitation of specific molecular vibrations. Furthermore, these vibrations appear as characteristic features in the dI/dV spectra measured over individual molecules. The vibrational modes that are associated with the tautomerization are identified by density functional theory calculations. At higher temperatures above ∼75  K, tautomerization is induced thermally and an activation barrier of about 168 meV is determined from an Arrhenius plot.
Department of Physical Chemistry, Fritz-Haber Institute of the Max-Planck Society, Faradayweg 4-6, 14195 Berlin, Germany.
Takashi
T
Kumagai
Surface Science Research Centre and Department of Chemistry, University of Liverpool, Liverpool L69 3BX, United Kingdom.
Felix
F
Hanke
Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.
Sylwester
S
Gawinkowski
Surface Science Research Centre and Department of Chemistry, University of Liverpool, Liverpool L69 3BX, United Kingdom.
John
J
Sharp
Surface Science Research Centre and Department of Chemistry, University of Liverpool, Liverpool L69 3BX, United Kingdom.
Konstantinos
K
Kotsis
Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.
Jacek
J
Waluk
Surface Science Research Centre and Department of Chemistry, University of Liverpool, Liverpool L69 3BX, United Kingdom and Department of Applied Physics, Chalmers University of Technology, 41296 Göteborg, Sweden.
Mats
M
Persson
Department of Physical Chemistry, Fritz-Haber Institute of the Max-Planck Society, Faradayweg 4-6, 14195 Berlin, Germany and Department of Physical Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria.
Leonhard
L
Grill
D003300:Copper / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D016252:Microscopy, Scanning Tunneling; D011166:Porphyrins / Q000737:chemistry*; D013499:Surface Properties; D014732:Vibration
D011166:Porphyrins; C051407:porphycene; D003300:Copper; D006859:Hydrogen