-
[show abstract]
[hide abstract]
ABSTRACT: The bonding and the temperature-driven metalation of 2H-tetraphenylporphyrin (2H-TPP) on the Cu(111) surface under ultrahigh vacuum conditions were investigated by a combination of x-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy with density functional theory calculations. Thin films were prepared by organic molecular beam epitaxy and subsequent annealing. Our systematic study provides an understanding of the changes of the spectroscopic signature during adsorption and metalation. Specifically, we achieved a detailed peak assignment of the 2H-TPP multilayer data of the C1s and the N1s region. After annealing to 420 K both XPS and NEXAFS show the signatures of a metalloporphyrin, which indicates self-metalation at the porphyrin-substrate interface, resulting in Cu-TPP. Furthermore, for 2H-TPP monolayer samples we show how the strong influence of the copper surface is reflected in the spectroscopic signatures. Adsorption results in a strongly deformed macrocycle and a quenching of the first NEXAFS resonance in the nitrogen edge suggesting electron transfer into the LUMO. For Cu-TPP the spectroscopic data indicate a reduced interaction of first-layer molecules with the substrate as demonstrated by the relaxed macrocycle geometry.
The Journal of chemical physics 01/2012; 136(1):014705. · 3.09 Impact Factor
-
F. Klappenberger,
D. Kühne, M. Marschall,
S. Neppl,
W. Krenner,
A. Nefedov,
T. Strunskus,
K. Fink,
Ch. Wöll,
S. Klyatskaya,
O. Fuhr,
M. Ruben,
J. V. Barth
Adv. Funct. Materials. 01/2011; 21:1631-1642.
-
J. V. Barth, M. Marschall,
J. Reichert,
K. Seufert,
W. Auwärter,
F. Klappenberger,
A. Weber-Bargioni,
S. Klyatskaya,
G. Zoppellaro,
A. Nefedov,
Th. Strunskus,
Ch. Wöll,
M. Ruben,
J. Barth
[show abstract]
[hide abstract]
ABSTRACT: The supramolecular organization and layer formation of the
non-linear, prochiral molecule [1, 1’;4’,1’’]-terphenyl-3,3“-dicarbonitrile
adsorbed on the Ag(111) surface is investigated by
scanning tunneling microscopy (STM) and near-edge X-ray absorption
fine-structure spectroscopy (NEXAFS). Upon two-dimensional
confinement the molecules are deconvoluted in
three stereoisomers, that is, two mirror-symmetric trans- and
one cis-species. STM measurements reveal large and regular islands
following room temperature deposition, whereby
NEXAFS confirms a flat adsorption geometry with the electronic
p-system parallel to the surface plane. The ordering within
the expressed supramolecular arrays reflects a substrate templating
effect, steric constraints and the operation of weak lateral
interactions mainly originating from the carbonitrile
endgroups. High-resolution data at room temperature reveal
enantiormorphic characteristics of the molecular packing
schemes in different domains of the arrays, indicative of chiral
resolution during the 2D molecular self-assembly process. At
submonolayer coverage supramolecular islands coexist with a
disordered fluid phase of highly mobile molecules. Following
thermal quenching (down to 6 K) we find extended supramolecular
ribbons stabilised again by attractive and directional
noncovalent interactions, the formation of which reflects a
chiral resolution of trans-species.
ChemPhysChem 02/2010; 2010(11):1446-1451. · 3.41 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We present a combined scanning tunneling microscopy (STM), near-edge x-ray-absorption fine-structure, and x-ray photoemission spectroscopy (XPS) study on the bonding and ordering of tetrapyridyl-porphyrin molecules on the Cu(111) surface in the 300-500 K temperature range. Following deposition at 300 K the molecules are adsorbed with a pronounced conformational adaptation of the anchored species featuring a saddle-shaped macrocycle and terminal groups pointing toward the substrate. Upon moderate annealing supramolecular chains evolve that are stabilized by metal-ligand interactions between the mesopyridyl substituents and copper adatoms resulting in twofold copper coordination. Annealing to temperatures exceeding 450 K strongly alters the molecular appearance in high-resolution STM data. This modification was also induced by controlled voltage pulses and related to a deprotonation of the molecule by XPS. Under appropriate conditions a novel binding motif leads to honeycomb structures coexisting with the chain segments. The conformation withstands annealing without large modification.
The Journal of chemical physics 01/2009; 129(21):214702. · 3.09 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We employed temperature-controlled fast-scanning tunneling microscopy to monitor the diffusion of tetrapyridylporphyrin molecules on the Cu(111) surface. The data reveal unidirectional thermal migration of conformationally adapted monomers in the 300-360 K temperature range. Surprisingly equally oriented molecules spontaneously form dimers that feature a drastically increased one-dimensional diffusivity. The analysis of the bonding and mobility characteristics indicates that this boost is driven by a collective transport mechanism of a metallosupramolecular complex.
Nano Letters 01/2009; 8(12):4608-13. · 13.20 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We employed temperature-controlled fast-scanning tunneling microscopy to monitor the diffusion of tetrapyridylporphyrin molecules on the Cu(111) surface. The data reveal unidirectional thermal migration of conformationally adapted monomers in the 300-360 K temperature range. Surprisingly equally oriented molecules spontaneously form dimers that feature a drastically increased one-dimensional diffusivity. The analysis of the bonding and mobility characteristics indicates that this boost is driven by a collective transport mechanism of a metallosupramolecular complex.
Nano Letters 12/2008; · 13.20 Impact Factor
-
J Reichert,
Augustin Schiffrin,
W. Auwarter,
A Weber-Bargioni, M Marschall,
M. Dell'Angela,
D. Cvetko,
G. Bavdek,
A. Cossaro,
A. Morgante,
J. V. Barth
ACS Nano, v.4, 1218-1226 (2010).
