book of abstracts - IM2NP

A B S T R A C T S WEDNESDAY, JUNE 30 N A N O S E A 2 0 1 0
Our STM and LEED investigations reveal a specific adsorption behaviour of the metal-free phthalocyanine
molecules. At room temperature the adsorption of the molecules leads to the formation of double rows,
which run in the direction of the close-packed gold atom rows. Beneath these double rows, the reconstruction
of the supporting gold is changed from a (1x2) to a (1x3) structure by the adsorption of the phthalocyanine
molecules. An additional long range periodicity, perpendicular to the molecular rows, is observed at higher
coverage. Namely, one (1x3) trough filled with molecules is alternating with two (1x2) unit cells. The
coexistence of (1x2) and (1x3) troughs is confirmed by LEED observations.
This system can neither be described by the classical models of substrate induced structure formation nor by
molecular self assembly, but by a cooperative effect. The formation of double rows on the (1x3)
reconstructed Au(110) surface is triggered by both a strong molecule-molecule interaction and a strong
molecule-substrate interaction. In contrast only a weak interaction between adjacent dimers along the rows
could be observed, the closest distance between them equals six times the Au lattice constant.
9H40-10H00
Self-organized Porphyrin monolayers on halide-modified noble metal surfaces.
M. Schneider, T. Kosmala, K. Wandelt (Institute of Physical and Theoretical Chemistry, University
of Bonn - Wegelerstr. 12 D-53115, Bonn, Germany)schneider@pc.uni-bonn.de
In the field of template chemistry, new and interesting phenomena can be discovered at gold/electrolyte
interfaces in the presence of anions and supramolecules as function of electrode potentials. The phase
transitions of iodine adsorbate layers on gold surfaces allow us to study the influence of template effects of
first and second order on the self-organisation of porphyrins.
Halide-modified gold surfaces are desirable substrates due to their long range order. Iodide-modified
Au(111)-surfaces show phase transitions (from (√3x√3)R30° over c(px√3) to rotated-hexagonal) and
electrocompression dependent on the electrode potential.
Porphyrins are important organic compounds in the fields of biology and technology. They open a series of
potential applications in cancer therapy, or as catalysts and sensors. Specifically, Tetra(N-methyl-4-pyridyl)-
porphyrin molecules (TMPyP) form various rectangular structures on iodine-modified Au(111) and Cu(111)
surfaces.
Our studies with STM and cyclic voltammetry not only reproduce previous works about TMPyP on iodidemodified
Au(111)-surfaces, but provide an even more precise understanding. Namely, it is found that the
TMPyP layer exhibits a long-range periodic superstructure beyond the molecular arrangement.
This research complements one of our previous studies regarding adsorption of the same molecule on halide
modified copper surfaces, allowing comparisons between systems with the same molecule but different
substrates. Beyond the similarities in molecular arrangement, the long-range periodic superstructure found in
our recent works is a novelty.
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