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molecular nanostructures and self-assembly – structure and dynamics

Thomas Waldmann, Michael Roos, Achim Breitruck, Harry E. Hoster, R. Jürgen Behm

 

 

Physical background of the self assembly of large organic molecules:

 

molecule: 2-phenyl-4,6-bis(6(pyrid-2-yl)-4(pyrid-4-yl)pyrid-2-yl)pyrimidine oligopyridine (2,4’-BTP) (Ziener et al.)

Molecular nanostructuring plays an important role in today's research, due to the great possibilities arising from this powerful technique. The main advantage herein is the ability to steer the self-organization process into desired nanostructures by use of special designed molecular building blocks. A major goal of our group is a basic and comprehensive understanding of molecular self-assembly on well defined surfaces. Therefore, we investigate the influence of both, the molecule geometry and its chemical structure on the resulting self-assembled-monolayer (SAM), as well as the role of the substrate type. By additionally studying dynamic effects, e.g. the change of domain walls occurring during phase transformations, we are able to describe the self-organization process quantitatively. A second aim of our team is to use these SAM's as template for metal incorporation, in order to perform in a second step model catalytic reactions at these surfaces.

 

most stable hydrogen bonds of 2,4’-BTP

 

experimental setup

Experimental Setup

Our experiments are carried out in an ultra high vacuum (UHV) chamber, equipped with a LEED (low energy electron diffraction), an AES (Auger electron spectroscopy), a QMS (quadrupol mass spectrometry) and a homebuild STM (scanning tunneling microscopy) for analysis, as well as a sputter gun and several evaporators for sample preparation

hydrogen bonds visualized in a Monte-Carlo simulation

 

typical hydrogen bonded structures

 

 

High resolution STM pictures of two different phases formed by 2,4'-BTP on Ag(111); coverage dependent structures results from subtle balance of molecule-molecule and molecule-substrate interactions

molecule - substrate interactions are dominated by the nitrogen atoms

 

 

thermal desorption: dominance of the pre-exponential factor

 

Desorption from BTP monolayer films occurs at much higher temperatures than fro multilayers.
Surprisingly, the main reason for that is a decrease in the pre-exponential factor by 9 orders of magnitude,
whereas the energetic desorption barrier remains virtually unchanged

"Entropic stabilization of large adsorbates on weakly binding substrates – a thermal desorption and scanning tunneling microscopy study", PCCP communications, in press

 

dynamics: real time observation of a mobile phase boundary by Video-STM

 

phase boundary: low density quasi-hexagonal phase (partially mobile) and quasi quadratic network

 

see: T. Waldmann, R. Reichert, H. Hoster, ChemPhysChem, in press

 

 

 

Related Literature:

Substrate registry in disordered layers of large molecules”, T. Waldmann, R. Reichert, H.E. Hoster, ChemPhysChem, in press

"Entropic stabilization of large adsorbates on weakly binding substrates – a thermal desorption and scanning tunneling microscopy study", M. Roos, A. Breitruck, H.E. Hoster, R.J. Behm, PCCP 12, 818-822 (2010)

“Concentration and Coverage Dependent Adlayer Structures: From Two-dimensional Networks to Rotation in a Bearing”, C. Meier, M. Roos, D. Künzel, A. Breitruck, H. Hoster, K. Landfester, A. Gross, R.J. Behm, U. Ziener, J. Phys. Chem. C 114, 1268-1277 (2010)

Short-range order in a metal organic network”, A. Breitruck, H.E. Hoster, R.J. Behm, J. Phys. Chem. C 113 (2009) 21265

Structure Formation in Bis(terpyridine)Derivative Adlayers – Molecule-Substrate vs. Molecule-Molecule Interactions”, H.E. Hoster, M. Roos, A. Breitruck, C. Meier, K. Tonigold, T. Waldmann, U. Ziener, K. Landfester, R.J. Behm, Langmuir 23 (2007) 11570

Coverage dependent structures of oligopyridine adlayers on Ag(111) oriented films”, M. Roos, H.E. Hoster, A. Breitruck, R.J. Behm, PCCP 9 (2007) 5672

Interaction of Cu atoms with ordered 2D oligopyridine networks”, A. Breitruck, H.E. Hoster, C. Meier, U. Ziener, R.J. Behm, Surf. Sci. 601 (2007) 4200

 

Hierarchically Self-Assembled Host-Guest Network at the Solid-Liquid Interface for Single-Molecule Manipulation”, C. Meier, K. Landfester, D. Künzel, T. Markert, A. Groß, U. Ziener, Angew. Chemie Int. Ed. 2008

Weak Hydrogen Bonds as a Structural Motif for Two-Dimensional Assemblies of Oligopyridines on Highly Oriented Pyrolytic Graphite: An STM Investigation”, C. Meier, U. Ziener, K. Landfester, P. Weihrich, Journal of Physical Chemistry B 109 (2005) 21015

Supramolecular assemblies of a bis(terpyridine) ligand and of its [2x2] grid-type ZnII and CoII complexes on highly ordered pyrolytic graphite”, U. Ziener, J.-M. Hehn, A. Mourran, M. Möller; Chemistry-A European Journal  8 (2002) 951

 

 

 

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