Isomerization of an Azobenzene Derivative on a Thin Insulating Layer by Inelastically Tunneling Electrons

Abstract

Scanning tunneling microscopy is used to investigate isomerization of amino-nitro-azobenzene on a thin NaCl layer on Ag(111) by inelastically tunneling electrons. A reversible isomerization between a planar trans and a three-dimensional cis form with two different thresholds is demonstrated. The isomerization characteristics are rationalized in terms of binding of the multipolar molecule to the ionic layer. This study shows the feasibility of a bistable single molecule switch on an insulator.

Surface photochemistry probed by two-photon photoemission spectroscopy

“…In addition, scanning tunnelling microscopy (STM) has also been utilized to study surface chemical reactions by exploiting its ability to probe changes in electronic structure and large geometric changes of species reacting at a surface. [15][16][17][18][19] These techniques have played key roles in the development of surface chemistry and catalysis research. In addition to the structural changes in surface chemical reactions, electronic structures near the reaction sites also change significantly, so electronic spectroscopic techniques such as ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron photoemission (XPS) have been widely used in experimental studies of surface chemistry and catalysis.…”

Electromechanical switching behavior of individual molecular complexes of Cu and Ni on NaCl-covered Cu(111) and Ag(111)

“…The d level splitting diagram of a transition metal ion in a tetrahedral and a square-planar ligand field shown in figure 9, is a standard textbook example [32,33] . Since for a neutral copper atom the d-shell is completely filled with 10 electrons ([Ar]3d 10 4s 1 ), the electronic configuration of the metallic ion in the Cu(II) complex is [Ar]3d 9 . It is then immediately clear from the diagrams of figure 9 that the square-planar symmetry should be favored relative to the tetrahedral one, mainly because of the large energy gain due to the presence of an electron hole in the very energetically unfavorable dx2-y2 orbital.…”

“…In fact, the structure is then governed by inter-ligands steric and electrostatic effects, which are not taken into account in CFT, and a tetrahedral geometry is adopted to minimize the repulsive interaction between the ligands. 9 ) should remain in the SP conformation because of the stabilizing effect of one or two holes in the dx2-y2 orbital. Then, it can be concluded that charging the Ni complex would not induce a change in the ligand symmetry.…”

“…Recently, a wide variety of molecular switches have been characterized by different techniques, in particular by STM [5][6][7][8][9][10][11][12][13][14]. Most of the reported work in this field can be coarsely organized around two families of switchable molecules [5].…”

“…In the first one, the structure of the molecule changes by isomerization [6]. One of the most prominent examples in that respect is provided by photoisomerizable molecules such as azobenzene and its derivatives [7][8][9]. In the second one, different charge states of a molecule (coupled to a more or less important conformation change) are used.…”