title: Imine derivatives on Au(111): evidence for "inverted" thermal isomerization.
abstract: Molecules that undergo reversible isomerization between trans and cis states, typically upon illumination with light at appropriate wavelengths, represent an important class of molecular switches. In this combined scanning tunneling microscopy (STM) and high-resolution electron energy loss spectroscopy (HREELS) study, we report on self-assembled arrays of imine derivatives on a Au(111) surface. Most of the molecules are found in the trans state after deposition at room temperature, but many of them change their conformation upon heating, which we assign to switching to the cis state. As for many molecular switches, the trans isomer is the energetically more stable compound in solution, resulting in thermal cis to trans relaxation upon sufficient heating. On the surface, however, the number of cis isomers increases with temperature, pointing toward an "inverted" thermal isomerization behavior. The reason for this surface-mediated effect could be a stronger coupling, as compared to the trans state, of the central imine part of the molecule to the gold surface, which is sterically only possible in the cis state.
authors.affiliation: Physics Department, Freie Universität Berlin, Arnimallee 14, Berlin, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Mielke
authors.forename: Felix
authors.initials: F
authors.lastname: Leyssner
authors.forename: Matthias
authors.initials: M
authors.lastname: Koch
authors.forename: Stephan
authors.initials: S
authors.lastname: Meyer
authors.forename: Ying
authors.initials: Y
authors.lastname: Luo
authors.forename: Sofia
authors.initials: S
authors.lastname: Selvanathan
authors.forename: Rainer
authors.initials: R
authors.lastname: Haag
authors.forename: Petra
authors.initials: P
authors.lastname: Tegeder
authors.forename: Leonhard
authors.initials: L
authors.lastname: Grill
mesh_terms: D000327:Adsorption; D006046:Gold / Q000737:chemistry*; D006358:Hot Temperature; D007097:Imines / Q000737:chemistry*; D007536:Isomerism; D008422:Materials Testing; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*
chemical_list: D007097:Imines; D006046:Gold