TY - JOUR A1 - Awad, Duha Jawad A1 - Schilde, Uwe A1 - Strauch, Peter T1 - 4,4 '-Bis(tert-butyl)-2,2 '-bipyridinedichlorometal(II) - Synthesis, structure and EPR spectroscopy JF - Inorganica chimica acta : the international inorganic chemistry journal N2 - Due to the better solubility of the 4,4'-substituted bipyridine ligand a series of 4,4'0-bis(tert-butyl)-2,2'-bipyridinedichlorometal(II) complexes, [M(tbbpy)Cl(2)], with M = Cu, Ni, Zn, Pd, Pt was synthesised and characterised. The blue copper complex 4,4'-bis(tert-butyl)-2,2'-bipyridinedichlorocopper(II) was isolated in two different polymorphic forms, as prisms 1 with a solvent inclusion and solvent-free as needles 2. Both structures were determined by X-ray structure analysis. They crystallise in the monoclinic space group P2(1)/c with four molecules in the unit cell, but with different unit cells and packing motifs. Whereas in the prisms 1, with the unit cell parameters a = 12.1613(12), b = 10.6363(7), c = 16.3074(15) angstrom, eta = 94.446(8)degrees, the packing is dominated by intra-and intermolecular hydrogen bonds, in the needles 2, with a = 7.738(1), b = 18. 333(2), c = 13.291(3) angstrom, beta = 97.512(15)degrees, only intramolecular hydrogen bonds appear and the complex molecules are arranged in columns which are stabilised by p-p-stacking interactions. In both complexes the copper has a tetrahedrally distorted coordination sphere. These copper complexes were also studied by EPR spectroscopy in solution, as frozen glass and diamagnetically diluted powder with the analogue [Pd(tbbpy)Cl(2)] as host lattice. KW - 4,4 '-Bis(tert-butyl)-2,2 '-bipyridine KW - X-ray structure KW - EPR KW - Copper(II) KW - Transition metals Y1 - 2011 U6 - https://doi.org/10.1016/j.ica.2010.08.035 SN - 0020-1693 VL - 365 IS - 1 SP - 127 EP - 132 PB - Elsevier CY - Lausanne ER - TY - JOUR A1 - Schreiber, Ulrike A1 - Hosemann, Benjamin A1 - Beuermann, Sabine T1 - 1H,1H,2H,2H-Perfluorodecyl-Acrylate-Containing block copolymers from ARGET ATRP JF - Macromolecular chemistry and physics N2 - Block copolymers of 1H,1H,2H,2H-perfluorodecyl acrylate (AC8) were obtained from ARGET ATRP. To obtain block copolymers of low dispersity the PAC8 block was synthesized in anisole with a CuBr(2)/PMDETA catalyst in the presence of tin(II) 2-ethylhexanoate as a reducing agent. The PAC8 block was subsequently used as macroinitiator for copolymerization with butyl and tert-butyl acrylate carried out in scCO(2). To achieve catalyst solubility in CO(2) two fluorinated ligands were employed. The formation of block copolymers was confirmed by size exclusion chromatography and DSC. KW - atom transfer radical polymerization (ATRP) KW - block copolymers KW - fluoropolymers KW - supercritical carbon dioxide Y1 - 2011 U6 - https://doi.org/10.1002/macp.201000307 SN - 1022-1352 VL - 212 IS - 2 SP - 168 EP - 179 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Prevost, Sylvain A1 - Wattebled, Laurent A1 - Laschewsky, André A1 - Gradzielski, Michael T1 - Formation of monodisperse charged vesicles in mixtures of cationic gemini surfactants and anionic SDS JF - Langmuir N2 - The aggregation behavior of catanionics formed by the mixture of cationic geminis derived from dodecyltrimethylammonium chloride (DTAC) and anionic sodium dodecylsulfate (SDS) was studied by means of phase studies and comprehensive small-angle neutron scattering (SANS) experiments at 25 degrees C and 50 mM overall concentration. The results are compared to those for the previously studied SDS + DTAC system. Various gemini spacers of different natures and geometries were used, but all of them had similar lengths: an ethoxy bridge, a double bond, and an aromatic ring binding the two DTACs in three different substitutions (ortho, meta, and para). SANS and SAXS data analysis indicates that the spacer has no large effect on the spheroidal micelles of pure surfactants formed at low concentration in water; however, specific effects appear with the addition of electrolytes. Microstructures formed in the catanionic mixtures are rather strongly dependent on the nature of the spacer. The most important finding is that for the hydrophilic, flexible ethoxy bridge, monodisperse vesicles with a fixed anionic/cationic charge ratio (depending only on the surfactant in excess) are formed. Furthermore, the composition of these vesicles shows that strongly charged aggregates are formed. This study therefore provides new opportunities for developing tailor-made gemini surfactants that allow for the fine tuning of catanionic structures. Y1 - 2011 U6 - https://doi.org/10.1021/la103976p SN - 0743-7463 VL - 27 IS - 2 SP - 582 EP - 591 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Glatzel, Stefan A1 - Laschewsky, André A1 - Lutz, Jean-Francois T1 - Well-Defined uncharged polymers with a sharp UCST in water and in physiological milieu JF - Macromolecules : a publication of the American Chemical Society Y1 - 2011 U6 - https://doi.org/10.1021/ma102677k SN - 0024-9297 VL - 44 IS - 2 SP - 413 EP - 415 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Tremblay, Jean Christophe A1 - Klinkusch, Stefan A1 - Klamroth, Tillmann A1 - Saalfrank, Peter T1 - Dissipative many-electron dynamics of ionizing systems JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - In this paper, we perform many-electron dynamics using the time-dependent configuration-interaction method in its reduced density matrix formulation (rho-TDCI). Dissipation is treated implicitly using the Lindblad formalism. To include the effect of ionization on the state-resolved dynamics, we extend a recently introduced heuristic model for ionizing states to the rho-TDCI method, which leads to a reduced density matrix evolution that is not norm-preserving. We apply the new method to the laser-driven excitation of H(2) in a strongly dissipative environment, for which the state-resolve lifetimes are tuned to a few femtoseconds, typical for dynamics of adsorbate at metallic surfaces. Further testing is made on the laser-induced intramolecular charge transfer in a quinone derivative as a model for a molecular switch. A modified scheme to treat ionizing states is proposed to reduce the computational burden associated with the density matrix propagation, and it is thoroughly tested and compared to the results obtained with the former model. The new approach scales favorably (similar to N(2)) with the number of configurations N used to represent the reduced density matrix in the rho-TDCI method, as compared to a N(3) scaling for the model in its original form. Y1 - 2011 U6 - https://doi.org/10.1063/1.3532410 SN - 0021-9606 VL - 134 IS - 4 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Piluso, Susanna A1 - Hiebl, Bernhard A1 - Gorb, Stanislav N. A1 - Kovalev, Alexander A1 - Lendlein, Andreas A1 - Neffe, Axel T. T1 - Hyaluronic acid-based hydrogels crosslinked by copper-catalyzed azide-alkyne cycloaddition with tailorable mechanical properties JF - The international journal of artificial organs N2 - Biopolymers of the extracellular matrix are attractive starting materials for providing degradable and biocompatible biomaterials. In this study, hyaluronic acid-based hydrogels with tunable mechanical properties were prepared by the use of copper-catalyzed azide-alkyne cycloaddition (known as "click chemistry"). Alkyne-functionalized hyaluronic acid was crosslinked with linkers having two terminal azide functionalities, varying crosslinker density as well as the lengths and rigidity of the linker molecules. By variation of the crosslinker density and crosslinker type, hydrogels with elastic moduli in the range of 0.5-4 kPa were prepared. The washed materials contained a maximum of 6.8 mg copper per kg dry weight and the eluate of the gel crosslinked with diazidostilbene did not show toxic effects on L929 cells. The hyaluronic acid-based hydrogels have potential as biomaterials for cell culture or soft tissue regeneration applications. KW - Biomaterial KW - Hydrogel KW - Hyaluronic acid KW - Microindentation KW - Rheology Y1 - 2011 U6 - https://doi.org/10.5301/IJAO.2011.6394 SN - 0391-3988 VL - 34 IS - 2 SP - 192 EP - 197 PB - Wichtig CY - Milano ER - TY - JOUR A1 - Graf, Philipp A1 - Mantion, Alexandre A1 - Haase, Andrea A1 - Thuenemann, Andreas F. A1 - Masic, Admir A1 - Meier, Wolfgang P. A1 - Luch, Andreas A1 - Taubert, Andreas T1 - Silicification of peptide-coated silver nanoparticles-A biomimetic soft chemistry approach toward chiral hybrid core-shell materials JF - ACS nano N2 - Silica and silver nanoparticles are relevant materials for new applications in optics, medicine, and analytical chemistry. We have previously reported the synthesis of pH responsive, peptide-templated, chiral silver nanoparticles. The current report shows that peptide-stabilized nanoparticles can easily be coated with a silica shell by exploiting the ability of the peptide coating to hydrolyze silica precursors such as TEOS or TMOS. The resulting silica layer protects the nanoparticles from chemical etching, allows their inclusion in other materials, and renders them biocompatible. Using electron and atomic force microscopy, we show that the silica shell thickness and the particle aggregation can be controlled simply by the reaction time. Small-angle X ray scattering confirms the Ag/peptide@silica core-shell structure. UV-vis and circular dichroism spectroscopy prove the conservation of the silver nanoparticle chirality upon silicification. Biological tests show that the biocompatibility in simple bacterial systems is significantly improved once a silica layer is deposited on the silver particles. KW - peptide-templated materials KW - silver nanoparticles KW - chiral nanoparticles KW - Ag/peptide@SiO(2) nanostructures KW - core-shell structures Y1 - 2011 U6 - https://doi.org/10.1021/nn102969p SN - 1936-0851 VL - 5 IS - 2 SP - 820 EP - 833 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Zaupa, Alessandro A1 - Neffe, Axel T. A1 - Pierce, Benjamin F. A1 - Lendlein, Andreas A1 - Hofmann, Dieter T1 - A molecular dynamic analysis of gelatin as an amorphous material Prediction of mechanical properties of gelatin systems JF - The international journal of artificial organs N2 - Biomaterials are used in regenerative medicine for induced autoregeneration and tissue engineering. This is often challenging, however, due to difficulties in tailoring and controlling the respective material properties. Since functionalization is expected to offer better control, in this study gelatin chains were modified with physically interacting groups based on tyrosine with the aim of causing the formation of physical crosslinks. This method permits application-specific properties like swelling and better tailoring of mechanical properties. The design of the crosslink strategy was supported by molecular dynamic (MD) simulations of amorphous bulk models for gelatin and functionalized gelatins at different water contents (0.8 and 25 wt.-%). The results permitted predictions to be formulated about the expected crosslink density and its influence on equilibrium swelling behavior and on elastic material properties. The models of pure gelatin were used to validate the strategy by comparison between simulated and experimental data such as density, backbone conformation angle distribution, and X-ray scattering spectra. A key result of the simulations was the prediction that increasing the number of aromatic functions attached to the gelatin chain leads to an increase in the number of physical netpoints observed in the simulated bulk packing models. By comparison with the Flory-Rehner model, this suggested reduced equilibrium swelling of the functionalized materials in water, a prediction that was subsequently confirmed by our experimental work. The reduction and control of the equilibrium degree of swelling in water is a key criterion for the applicability of functionalized gelatins when used, for example, as matrices for induced autoregeneration of tissues. KW - Physical Network KW - Biopolymer material KW - Molecular modeling KW - Gelatin Y1 - 2011 U6 - https://doi.org/10.5301/IJAO.2010.6083 SN - 0391-3988 VL - 34 IS - 2 SP - 139 EP - 151 PB - Wichtig CY - Milano ER - TY - JOUR A1 - Havelius, Kajsa G. V. A1 - Reschke, Stefan A1 - Horn, Sebastian A1 - Doerlng, Alexander A1 - Niks, Dimitri A1 - Hille, Russ A1 - Schulzke, Carola A1 - Leimkühler, Silke A1 - Haumann, Michael T1 - Structure of the molybdenum site in YedY, a sulfite oxidase homologue from escherichia coli JF - Inorganic chemistry N2 - YedY from Escherichia coil is a new member of the sulfite oxidase family of molybdenum cofactor (Moco)-containing oxidoreductases. We investigated the atomic structure of the molybdenum site in YedY by X-ray absorption spectroscopy, in comparison to human sulfite oxidase (hSO) and to a Mo(IV) model complex. The K-edge energy was indicative of Mo(V) in YedY, in agreement with X- and Q-band electron paramagnetic resonance results, whereas the hSO protein contained Mo(VI). In YedY and hSO, molybdenum is coordinated by two sulfur ligands from the molybdopterin ligand of the Moco, one thiolate sulfur of a cysteine (average Mo-S bond length of similar to 2.4 angstrom), and one (axial) oxo ligand (Mo=O, similar to 1.7 angstrom). hSO contained a second oxo group at Mo as expected, but in YedY, two species in about a 1:1 ratio were found at the active site, corresponding to an equatorial Mo-OH bond (similar to 2.1 angstrom) or possibly to a shorter M-O(-) bond. Yet another oxygen (or nitrogen) at a similar to 2.6 angstrom distance to Mo in YedY was identified, which could originate from a water molecule in the substrate binding cavity or from an amino acid residue close to the molybdenum site, i.e., Glu104, that is replaced by a glycine in hSO, or Asn45. The addition of the poor substrate dimethyl sulfoxide to YedY left the molybdenum coordination unchanged at high pH. In contrast, we found indications that the better substrate trimethylamine N-oxide and the substrate analogue acetone were bound at a similar to 2.6 angstrom distance to the molybdenum, presumably replacing the equatorial oxygen ligand. These findings were used to interpret the recent crystal structure of YedY and bear implications for its catalytic mechanism. Y1 - 2011 U6 - https://doi.org/10.1021/ic101291j SN - 0020-1669 VL - 50 IS - 3 SP - 741 EP - 748 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Huber, Christian A1 - Klamroth, Tillmann T1 - Explicitly time-dependent coupled cluster singles doubles calculations of laser-driven many-electron dynamics JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - We report explicitly time-dependent coupled cluster singles doubles (TD-CCSD) calculations, which simulate the laser-driven correlated many-electron dynamics in molecular systems. Small molecules, i.e., HF, H(2)O, NH(3), and CH(4), are treated mostly with polarized valence double zeta basis sets. We determine the coupled cluster ground states by imaginary time propagation for these molecules. Excited state energies are obtained from the Fourier transform of the time-dependent dipole moment after an ultrashort, broadband laser excitation. The time-dependent expectation values are calculated from the complex cluster amplitudes using the corresponding configuration interaction singles doubles wave functions. Also resonant laser excitations of these excited states are simulated, in order to explore the limits for the numerical stability of our current TD-CCSD implementation, which uses time-independent molecular orbitals to form excited configurations. Y1 - 2011 U6 - https://doi.org/10.1063/1.3530807 SN - 0021-9606 VL - 134 IS - 5 PB - American Institute of Physics CY - Melville ER -