TY  - JOUR
A1  - Utecht, Manuel Martin
A1  - Pan, Tianluo
A1  - Klamroth, Tillmann
A1  - Palmer, Richard E.
T1  - Quantum chemical cluster models for chemi- and physisorption of chlorobenzene on Si(111)-7x7
JF  - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory
N2  - Motivated by recent atomic manipulation experiments, we report quantum chemical calculations for chemi- and physisorption minima of chlorobenzene on the Si(111)-7x7 surface. A density functional theory cluster approach is applied, using the B3LYP hybrid functional alongside Grimme's empirical dispersion corrections (D3). We were able to identify chemisorption sites of binding energies of 1.6 eV and physisorption energies of 0.6 eV, both in encouraging agreement with the trend of experimental data. The cluster approach opens up the possibility of a first-principles based dynamical description of STM manipulation experiments on this system, the interpretation of which involves both the chemi- and physisorbed states. However, we found that special care has to be taken regarding the choice of clusters, basis sets, and the evaluation of the dispersion corrections.
Y1  - 2014
U6  - https://doi.org/10.1021/jp504208d
SN  - 1089-5639
VL  - 118
IS  - 33
SP  - 6699
EP  - 6704
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Bronner, Christopher
A1  - Utecht, Manuel Martin
A1  - Haase, Anton
A1  - Saalfrank, Peter
A1  - Klamroth, Tillmann
A1  - Tegeder, Petra
T1  - Electronic structure changes during the surface-assisted formation of a graphene nanoribbon
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - High conductivity and a tunability of the band gap make quasi-one-dimensional graphene nanoribbons (GNRs) highly interesting materials for the use in field effect transistors. Especially bottom-up fabricated GNRs possess well-defined edges which is important for the electronic structure and accordingly the band gap. In this study we investigate the formation of a sub-nanometer wide armchair GNR generated on a Au(111) surface. The on-surface synthesis is thermally activated and involves an intermediate non-aromatic polymer in which the molecular precursor forms polyanthrylene chains. Employing angle-resolved two-photon photoemission in combination with density functional theory calculations we find that the polymer exhibits two dispersing states which we attribute to the valence and the conduction band, respectively. While the band gap of the non-aromatic polymer obtained in this way is relatively large, namely 5.25 +/- 0.06 eV, the gap of the corresponding aromatic GNR is strongly reduced which we attribute to the different degree of electron delocalization in the two systems.
Y1  - 2014
U6  - https://doi.org/10.1063/1.4858855
SN  - 0021-9606
SN  - 1089-7690
VL  - 140
IS  - 2
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Knie, Christopher
A1  - Utecht, Manuel Martin
A1  - Zhao, Fangli
A1  - Kulla, Hannes
A1  - Kovalenko, Sergey
A1  - Brouwer, Albert M.
A1  - Saalfrank, Peter
A1  - Hecht, Stefan
A1  - Bleger, David
T1  - ortho-Fluoroazobenzenes: visible light switches with very long-lived Z isomers
JF  - Chemistry - a European journal
N2  - Improving the photochemical properties of molecular photoswitches is crucial for the development of light-responsive systems in materials and life sciences. ortho-Fluoroazobenzenes are a new class of rationally designed photochromic azo compounds with optimized properties, such as the ability to isomerize with visible light only, high photoconversions, and unprecedented robust bistable character. Introducing sigma-electron-withdrawing F atoms ortho to the N=N unit leads to both an effective separation of the n -> pi* bands of the E and Z isomers, thus offering the possibility of using these two transitions for selectively inducing E/Z iso-merizations, and greatly enhanced thermal stability of the Z isomers. Additional para-electron-withdrawing groups (EWGs) work in concert with ortho-F atoms, giving rise to enhanced separation of the n -> pi* transitions. A comprehensive study of the effect of substitution on the key photochemical properties of ortho-fluoroazobenzenes is reported herein. In particular, the position, number, and nature of the EWGs have been varied, and the visible light photoconversions, quantum yields of isomerization, and thermal stabilities have been measured and rationalized by DFT calculations.
KW  - azobenzenes
KW  - photochromism
KW  - photoswitches
KW  - substituent effects
KW  - visible light
Y1  - 2014
U6  - https://doi.org/10.1002/chem.201404649
SN  - 0947-6539
SN  - 1521-3765
VL  - 20
IS  - 50
SP  - 16492
EP  - 16501
PB  - Wiley-VCH
CY  - Weinheim
ER  -