Structure and excitonic coupling in self-assembled monolayers of azobenzene-functionalized alkanethiols.
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.
Gahl
Cornelius
C
Max-Born-Institut, Max-Born-Str. 2A, 12489 Berlin, Germany. gahl@mbi-berlin.de
Schmidt
Roland
R
Brete
Daniel
D
McNellis
Erik R
ER
Freyer
Wolfgang
W
Carley
Robert
R
Reuter
Karsten
K
Weinelt
Martin
M