title: Structure and excitonic coupling in self-assembled monolayers of azobenzene-functionalized alkanethiols.
abstract: Optical properties and the geometric structure of self-assembled monolayers of azobenzene-functionalized alkanethiols have been investigated by UV/visible and near edge X-ray absorption fine structure spectroscopy in combination with density-functional theory. By attaching a trifluoro-methyl end group to the chromophore both the molecular tilt and twist angle of the azobenzene moiety are accessible. Based on this detailed structural analysis the energetic shifts observed in optical reflection spectroscopy can be qualitatively described within an extended dipole model. This substantiates sizable excitonic coupling among the azobenzene chromophores as an important mechanism that hinders trans to cis isomerization in densely packed self-assembled monolayers.
authors.affiliation: Max-Born-Institut, Max-Born-Str. 2A, 12489 Berlin, Germany. gahl@mbi-berlin.de
authors.forename: Cornelius
authors.initials: C
authors.lastname: Gahl
authors.forename: Roland
authors.initials: R
authors.lastname: Schmidt
authors.forename: Daniel
authors.initials: D
authors.lastname: Brete
authors.forename: Erik R
authors.initials: ER
authors.lastname: McNellis
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Freyer
authors.forename: Robert
authors.initials: R
authors.lastname: Carley
authors.forename: Karsten
authors.initials: K
authors.lastname: Reuter
authors.forename: Martin
authors.initials: M
authors.lastname: Weinelt