Trans to cis isomerization of an azobenzene derivative on a Cu(100) surface

This article reports the observation of two stable configurations of an azobenzene derivative on a Cu(100) surface, which resemble the trans and the cis isomers of the free molecule. Whereas the trans form is the only one observed upon adsorption, the cis isomer could be produced by manipulation of individual molecules using a low temperature scanning tunneling microscope. Density functional theory substantiates the observation of the two forms and explains that the cis-like configuration is the most stable on Cu(100) due to the formation of two chemical bonds between nitrogen and copper atoms. This cis isomer shows a less perturbed configuration due to its three-dimensional shape, suggesting that anchoring molecular switches to surfaces through the central azo group is a feasible approach to functionalize metal surfaces with photochromic azobenzene molecules.