TY  - JOUR
A1  - Utecht, Manuel Martin
A1  - Klamroth, Tillmann
A1  - Saalfrank, Peter
T1  - Optical absorption and excitonic coupling in azobenzenes forming self-assembled monolayers a study based on density functional theory
T2  - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2  - Based on the analysis of optical absorption spectra, it has recently been speculated that the excitonic coupling between individual azobenzene-functionalized alkanethiols arranged in a self-assembled monolayer (SAM) on a gold surface could be strong enough to hinder collective trans-cis isomerization-on top of steric hindrance [Gahl et al., J. Am. Chem. Soc., 2010, 132, 1831]. Using models of SAMs of increasing complexity (dimer, linear N-mers, and two-dimensionally arranged N-mers) and density functional theory on the (TD-) B3LYP/6-31G* level, we determine optical absorption spectra, the nature and magnitude of excitonic couplings, and the corresponding spectral shifts. It is found that at inter-monomer distances of about 20 angstrom and above, TD-B3LYP excitation frequencies (and signal intensities) can be well described by the frequently used point-dipole approximation. Further, calculated blue shifts in optical absorption spectra account for the experimental observations made for azobenzene/gold SAMs, and hint to the fact that they can indeed be responsible for reduced switching probability in densely packed self-assembled structures.
Y1  - 2011
UR  - https://publishup.uni-potsdam.de/frontdoor/index/index/docId/37233
SN  - 1463-9076
VL  - 13
IS  - 48
SP  - 21608
EP  - 21614
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  -