Azobenzene isomerization on a reactive copper surface by efficient decoupling with bulky side groups

Surface Science, vol. 744, pp. 122468

Abstract

Azobenzene derivatives, an important class of molecular switches that undergo isomerization between trans and cis states, have been studied on various coinage metal surfaces in the past. However, on reactive copper surfaces switching turned out to be difficult. Here, we show that the use of bulky 2,6-dimethylphenyl side groups enables switching on a Cu(111) surface as studied by scanning tunneling microscopy. By applying voltage pulses from the STM tip, irreversible trans → cis isomerization of individual molecules can be induced where exactly one molecule within each unit cell is isomerized. The absence of backward cis → trans switching illustrates the importance of the adsorption structure on the potential energy landscape of azobenzene. Isomerization, which is activated by inelastic scattering of single tunneling electrons, happens in a very localized fashion, thus allowing to ‘write’ patterns of individual cis isomers into the homogeneous molecular layer. Our study demonstrates how the bulky spacer groups direct adsorption and self-assembly into close-packed structures, which are similar to three-dimensional molecular crystals, on the surface. In addition, they modulate the electronic coupling to the underlying substrate to maintain successful switching behavior even on the most reactive coinage metal surfaces.

Authors 5

1. Simon Jaekel

   University of Graz

   Affiliation as printed

   Department of Physical Chemistry, Karl-Franzens-Universität Graz, Heinrichstrasse 28, 8010 Graz, Austria

2. Ragnar S. Stoll

   Humboldt-Universität zu Berlin

   Affiliation as printed

   Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489, Berlin, Germany

3. Fabian Berger

   University of Cambridge · Humboldt-Universität zu Berlin

   Affiliation as printed

   Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489, Berlin, Germany

   Yusuf Hamied Department of Chemistry, University of Cambridge, CB2 1EW Cambridge, UK

4. Stefan Hecht corresponding Aachen DWI - Leibniz Institute for Interactive Materials

   Humboldt-Universität zu Berlin · DWI – Leibniz Institute for Interactive Materials

   Affiliation as printed

   DWI - Leibniz Institute for Interactive Materials, Forckenbeckstr. 50, 52074 Aachen, Germany

   Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489, Berlin, Germany

   IRIS Adlershof & CSMB, Humboldt-Universität zu Berlin, Zum Großen Windkanal 2, 12489, Berlin, Germany

5. Leonhard Grill corresponding

   University of Graz

   Affiliation as printed

   Department of Physical Chemistry, Karl-Franzens-Universität Graz, Heinrichstrasse 28, 8010 Graz, Austria