TY - JOUR A1 - Träger, Juliane A1 - Klamroth, Tillmann A1 - Kelling, Alexandra A1 - Lubahn, Susanne A1 - Cleve, Ernst A1 - Mickler, Wulfhard A1 - Heydenreich, Matthias A1 - Müller, Holger A1 - Holdt, Hans-Jürgen T1 - Complexation of Palladium(II) with unsaturated Dithioethers a systematic development of highly selective ligands for solvent extraction JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - There is a demand for new and robust PdII extractants due to growing recycling rates. Chelating dithioethers are promising substances for solvent extraction as they form stable square-planar complexes with PdII. We have modified unsaturated dithioethers, which are known to coordinate PdII, and adapted them to the requirements of industrial practice. The ligands are analogues of 1,2-dithioethene with varying electron-withdrawing backbones and polar end-groups. The crystal structures of several ligands and their palladium complexes were determined as well as their electro- and photochemical properties, complex stability and behaviour in solution. Solvent extraction experiments showed the superiority of some of our ligands over conventionally used extractants in terms of their very fast reaction rates. With highly selective 1,2-bis(2-methoxyethylthio)benzene (4) it is possible to extract PdII from a highly acidic medium in the presence of other base and palladium-group metals. KW - Renewable resources KW - Palladium KW - Chelates KW - Ligand design KW - S li-gands Y1 - 2012 U6 - https://doi.org/10.1002/ejic.201101406 SN - 1434-1948 IS - 14 SP - 2341 EP - 2352 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schwarze, Thomas A1 - Kelling, Alexandra A1 - Müller, Holger A1 - Trautmann, Michael A1 - Klamroth, Tillmann A1 - Baumann, Otto A1 - Strauch, Peter A1 - Holdt, Hans-Jürgen T1 - N-2-Pyridinylmethyl-N '-arylmethyl-diaminomaleonitriles: New Highly Selective Chromogenic Chemodosimeters for Copper(II) JF - Chemistry - a European journal KW - amides KW - chemodosimeter KW - colorimetric detection KW - copper KW - sensors KW - UV KW - Vis spectroscopy Y1 - 2012 U6 - https://doi.org/10.1002/chem.201201731 SN - 0947-6539 VL - 18 IS - 34 SP - 10506 EP - 10510 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Zenichowski, Karl A1 - Dokic, Jadranka A1 - Klamroth, Tillmann A1 - Saalfrank, Peter T1 - Current versus temperature-induced switching of a single molecule - open-system density matrix theory for 1,5-cyclooctadiene on Si(100) JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - The switching of single cyclooctadiene molecules chemisorbed on a Si(100) surface between two stable conformations, can be achieved with a scanning tunneling microscope [Nacci , Phys. Rev. B 77, 121405(R) (2008)]. Recently, it was shown by quantum chemical and quantum dynamical simulations that major experimental facts can be explained by a single-mode model with switching enforced by inelastic electron tunneling (IET) excitations and perturbed by vibrational relaxation [Nacci , Nano Lett. 9, 2997 (2009)]. In the present paper, we extend the previous theoretical work in several respects: (1) The model is generalized to a two-mode description in which two C2H4 units of COD can move independently; (2) contributions of dipole and, in addition, (cation and anion) resonance-IET rates are considered; (3) the harmonic-linear vibrational relaxation model used previously is generalized to anharmonic vibrations. While the present models highlight generic aspects of IET-switching between two potential minima, they also rationalize specific experimental findings for COD/Si(100): (1) A single-electron excitation mechanism with a linear dependence of the switching rate on tunneling current I, (2) the capability to switch both at negative and positive sample biases, and (3) a crossover temperature around similar to 60 K from an IET-driven, T-independent atom tunneling regime, to classical over-the-barrier isomerization with exponential T-dependence at higher temperatures for a bias voltage of +1.5 V and an average tunneling current of 0.73 nA. Y1 - 2012 U6 - https://doi.org/10.1063/1.3692229 SN - 0021-9606 VL - 136 IS - 9 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Füchsel, Gernot A1 - Tremblay, Jean Christophe A1 - Klamroth, Tillmann A1 - Saalfrank, Peter T1 - Selective excitation of molecule-surface vibrations in H2 and D2 dissociatively adsorbed on Ru(0001) JF - Israel journal of chemistry N2 - In this contribution we report about the selective vibrational excitation of H2 and D2 on Ru(0001) as an example for nonadiabatic coupling of an open quantum system to a dissipative environment. We investigate the possibility of achieving state-selective vibrational excitations of H2 and D2 adsorbed on a Ru(0001) surface using picosecond infrared laser pulses. The systems behavior is explored using pulses that are rationally designed and others that are optimized using a time-local variant of Optimal Control Theory. The effects of dissipation on the laser-driven dynamics are studied using the reduced-density matrix formalism. The non-adiabatic couplings between adsorbate and surface are computed perturbatively, for which our recently introduced state-resolved anharmonic rate model is used. It is shown that mode- and state-selective excitation can be achieved in the absence of dissipation when using optimized laser pulses. The inclusion of dissipation in the model reduces the state selectivity and the population transfer yield to highly excited states. In this case, mode activation is most effectively realized by a rational pulse of carefully chosen duration rather than by a locally optimized pulse. KW - dissipative dynamics KW - photochemistry KW - quantum control KW - surface chemistry Y1 - 2012 U6 - https://doi.org/10.1002/ijch.201100097 SN - 0021-2148 VL - 52 IS - 5 SP - 438 EP - 451 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Zenichowski, Karl A1 - Nacci, Ch A1 - Fölsch, S. A1 - Dokic, Jadranka A1 - Klamroth, Tillmann A1 - Saalfrank, Peter T1 - STM-switching of organic molecules on semiconductor surfaces: an above threshold density matrix model for 1,5 cyclooctadiene on Si(100) JF - Journal of physics : Condensed matter N2 - The scanning tunnelling microscope (STM)-induced switching of a single cyclooctadiene molecule between two stable conformations chemisorbed on a Si(100) surface is investigated using an above threshold model including a neutral ground state and an ionic excited state potential. Switching was recently achieved experimentally with an STM operated at cryogenic temperatures (Nacci et al 2008 Phys. Rev. B 77 121405(R)) and rationalized by a below threshold model using just a single potential energy surface (Nacci et al 2009 Nano Lett. 9 2997). In the present paper, we show that experimental key findings on the inelastic electron tunnelling (IET) switching can also be rationalized using an above threshold density matrix model, which includes, in addition to the neutral ground state potential, an anionic or cationic excited potential. We use one and two-dimensional potential energy surfaces. Furthermore, the influence of two key parameters of the density matrix description, namely the electronic lifetime of the ionic resonance and the vibrational lifetimes, on the ground state potential are discussed. Y1 - 2012 U6 - https://doi.org/10.1088/0953-8984/24/39/394009 SN - 0953-8984 VL - 24 IS - 39 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Bronner, C. A1 - Leyssner, F. A1 - Stremlau, S. A1 - Utecht, Manuel Martin A1 - Saalfrank, Peter A1 - Klamroth, Tillmann A1 - Tegeder, P. T1 - Electronic structure of a subnanometer wide bottom-up fabricated graphene nanoribbon: End states, band gap, and dispersion JF - Physical review : B, Condensed matter and materials physics N2 - Angle-resolved two-photon photoemission and high-resolution electron energy loss spectroscopy are employed to derive the electronic structure of a subnanometer atomically precise quasi-one-dimensional graphene nanoribbon (GNR) on Au(111). We resolved occupied and unoccupied electronic bands including their dispersion and determined the band gap, which possesses an unexpectedly large value of 5.1 eV. Supported by density functional theory calculations for the idealized infinite polymer and finite size oligomers, an unoccupied nondispersive electronic state with an energetic position in the middle of the band gap of the GNR could be identified. This state resides at both ends of the ribbon (end state) and is only found in the finite sized systems, i.e., the oligomers. Y1 - 2012 U6 - https://doi.org/10.1103/PhysRevB.86.085444 SN - 1098-0121 VL - 86 IS - 8 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Füchsel, Gernot A1 - Tremblay, Jean Christophe A1 - Klamroth, Tillmann A1 - Saalfrank, Peter A1 - Frischkorn, C. T1 - Concept of a single temperature for highly nonequilibrium laser-induced hydrogen desorption from a ruthenium surface JF - Physical review letters N2 - Laser-induced condensed phase reactions are often interpreted as nonequilibrium phenomena that go beyond conventional thermodynamics. Here, we show by Langevin dynamics and for the example of femtosecond-laser desorption of hydrogen from a ruthenium surface that light adsorbates thermalize rapidly due to ultrafast energy redistribution after laser excitation. Despite the complex reaction mechanism involving hot electrons in the surface region, all desorption product properties are characterized by equilibrium distributions associated with a single, unique temperature. This represents an example of ultrahot chemistry on the subpicosecond time scale. Y1 - 2012 U6 - https://doi.org/10.1103/PhysRevLett.109.098303 SN - 0031-9007 VL - 109 IS - 9 PB - American Physical Society CY - College Park ER -