@article{GarnierLaschewsky2006, author = {Garnier, Sebastien and Laschewsky, Andre}, title = {Non-ionic amphiphilic block copolymers by RAFT-polymerization and their self-organization}, series = {Colloid and polymer science : official journal of the Kolloid-Gesellschaft}, volume = {284}, journal = {Colloid and polymer science : official journal of the Kolloid-Gesellschaft}, publisher = {Springer}, address = {Berlin}, issn = {0303-402X}, doi = {10.1007/s00396-006-1484-9}, pages = {1243 -- 1254}, year = {2006}, abstract = {Water-soluble, amphiphilic diblock copolymers were synthesized by reversible addition fragmentation chain transfer polymerization. They consist of poly(butyl acrylate) as hydrophobic block with a low glass transition temperature and three different nonionic water-soluble blocks, namely, the classical hydrophilic block poly(dimethylacrylamide), the strongly hydrophilic poly(acryloyloxyethyl methylsulfoxide), and the thermally sensitive poly(N-acryloylpyrrolidine). Aqueous micellar solutions of the block copolymers were prepared and characterized by static and dynamic light scattering analysis (DLS and SLS). No critical micelle concentration could be detected. The micellization was thermodynamically favored, although kinetically slow, exhibiting a marked dependence on the preparation conditions. The polymers formed micelles with a hydrodynamic diameter from 20 to 100 nm, which were stable upon dilution. The micellar size was correlated with the composition of the block copolymers and their overall molar mass. The micelles formed with the two most hydrophilic blocks were particularly stable upon temperature cycles, whereas the thermally sensitive poly(N-acryloylpyrrolidine) block showed a temperature-induced precipitation. According to combined SLS and DLS analysis, the micelles exhibited an elongated shape such as rods or worms. It should be noted that the block copolymers with the most hydrophilic poly(sulfoxide) block formed inverse micelles in certain organic solvents.}, language = {en} } @article{FuechselKlamrothDokicetal.2006, author = {F{\"u}chsel, Gernot and Klamroth, Tillmann and Dokic, Jadranka and Saalfrank, Peter}, title = {On the electronic structure of neutral and ionic azobenzenes and their possible role as surface mounted molecular switches}, series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, volume = {110}, journal = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, number = {33}, publisher = {Soc.}, address = {Washington}, issn = {1520-6106}, doi = {10.1021/jp060969v}, pages = {16337 -- 16345}, year = {2006}, abstract = {We report quantum chemical calculations, mostly based on density functional theory, on azobenzene and substituted azobenzenes as neutral molecules or ions, in ground and excited states. Both the cis and trans configurations are computed as well as the activation energies to transform one isomer into the other and the possible reaction paths and reaction surfaces along the torsion and inversion modes. All calculations are done for the isolated species, but results are discussed in light of recent experiments aiming at the switching of surface mounted azobenzenes by scanning tunneling microscopes.}, language = {en} } @misc{LutzKristenSkrabaniaetal.2006, author = {Lutz, Jean-Francois and Kristen, Juliane and Skrabania, Katja and Laschewsky, Andre}, title = {POLY 14-Synthetic strategies for preparing multicompartment micelles}, series = {Abstracts of papers / American Chemical Society}, volume = {232}, journal = {Abstracts of papers / American Chemical Society}, publisher = {American Chemical Society}, address = {Washington}, isbn = {0-8412-7426-6}, issn = {0065-7727}, pages = {1}, year = {2006}, abstract = {The fabrication of compartmented micellar systems is an exciting new area of research in the field of polymer self-assembly. Multicompartment micelles composed of a water-soluble shell and a segregated hydrophobic core can be obtained via direct aqueous self-assembly of preformed polymeric amphiphiles possessing one hydrophilic segment and two incompatible hydrophobic segments (e.g. hydrocarbon and fluorocarbon blocks). Such macromolecular building-blocks were prepared in the present work principally via reversible addition-fragmentation transfer polymerization (RAFT). Polysoaps or triblock macrosurfactants can be synthesized in high yields by RAFT under relatively straightforward experimental conditions.}, language = {en} } @article{SchmidtNave2006, author = {Schmidt, Bernd and Nave, Stefan}, title = {Stereoselective syntheses of enantiomerically pure 2,5-disubstituted dihydropyrans based on olefin metathesis}, series = {The journal of organic chemistry}, volume = {71}, journal = {The journal of organic chemistry}, number = {19}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/jo061190k}, pages = {7364 -- 7369}, year = {2006}, abstract = {A short synthesis of 2,5-disubstituted dihydropyrans starting from D-mannitol as a chiral building block is described. Our synthetic approach combines ruthenium-catalyzed ring closing olefin metathesis and palladium-catalyzed nucleophilic substitution.}, language = {en} } @article{KappBeissenhirtzGeyeretal.2006, author = {Kapp, A. and Beissenhirtz, Moritz Karl and Geyer, F. and Scheller, F. and Viezzoli, Maria Silvia and Lisdat, Fred}, title = {Electrochemical and sensorial behavior of SOD mutants immobilized on gold electrodes in aqueous/organic solvent mixtures}, series = {Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis}, volume = {18}, journal = {Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis}, publisher = {Wiley}, address = {Weinheim}, issn = {1040-0397}, doi = {10.1002/elan.200603620}, pages = {1909 -- 1915}, year = {2006}, abstract = {A cysteine mutant of a monomeric human Cu, Zn-SOD (Glycine 61, Serine 142) has been immobilized directly on gold electrodes using the thiol groups introduced. The electrochemical behavior of the surface confined protein was studied in mixtures of aqueous buffer and DMSO up to an organic solvent content of 60\%. The formal potential was found to be rather independent of the DMSO content. However, half peak width increased and the redoxactive amount clearly decreased with raising DMSO content. In addition, the kinetics of the heterogeneous electron transfer became slower; but still a quasireversible electrochemical conversion of the mutant SOD was feasible. Thus, the electrodes were applied for sensorial superoxide detection. At a potential of +220 mV vs. Ag/AgCl advantage was taken of the partial oxidation reaction of the enzyme. A defined superoxide signal was obtained in solutions up to 40\% DMSO. The sensitivity of the mutant electrodes decreased linearly with the organic solvent content in solution but was still higher compared to conventional cyt.c based sensors. At DMSO concentrations higher than 40\% no sensor response was detected.}, language = {en} } @article{Saalfrank2006, author = {Saalfrank, Peter}, title = {Quantum dynamical approach to ultrafast molecular desorption from surfaces}, series = {Chemical reviews}, volume = {106}, journal = {Chemical reviews}, number = {10}, publisher = {American Chemical Society}, address = {Washington}, issn = {0009-2665}, doi = {10.1021/cr0501691}, pages = {4116 -- 4159}, year = {2006}, language = {en} } @article{NoteKoetzKosmella2006, author = {Note, Carine and Koetz, Joachim and Kosmella, Sabine}, title = {Structural changes in poly(ethyleneimine) modified microemulsion}, series = {Journal of colloid and interface science}, volume = {302}, journal = {Journal of colloid and interface science}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0021-9797}, doi = {10.1016/j.jcis.2006.06.071}, pages = {662 -- 668}, year = {2006}, abstract = {The influence of branched poly(ethyleneimine) on the phase behavior of the system sodium dodecylsulfate/toluene-pentanol (1:1)/water has been studied. The isotropic microemulsions still exist when water is replaced with aqueous solutions of PEI (up to 30\% in weight), but their stability is significantly influenced. From a polymer concentration of 20 wt\%, the polymer enhances the solubilization of water in oil, changes the sign of the spontaneous curvature of the surfactant film, and induces an inversion of the microemulsion type from water-in-oil (L-2) to oil-in-water (L-1), by the formation of a bicontinuous channel. Further investigations show that the addition of polymer in the L-2 phase changes the droplet-droplet interactions as the conductivity drops and the percolation disappears. In the bicontinuous channel, higher viscosities can be detected, as well as a weak percolation followed by a steep increase of the conductivity, which can be related to evident structural changes in the system. DSC measurements allow then to follow the changes of the water properties in the system, from interfacial-water in the L-2 phase to free-water in the sponge-like phase. Finally, all the measurements performed permit to characterize the structural transitions in the system and to understand the role of the added polymer.}, language = {en} } @article{LangeWagnerZentel2006, author = {Lange, Birger and Wagner, J{\"u}rgen and Zentel, Rudolf}, title = {Fabrication of robust high-quality ORMOCER (R) inverse opals}, series = {Macromolecular rapid communications}, volume = {27}, journal = {Macromolecular rapid communications}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1336}, doi = {10.1002/marc.200600429}, pages = {1746 -- 1751}, year = {2006}, abstract = {The nanostructuring of ORMOCER (R) to form inverse opals is described. For this purpose a polymer opal is used as a template and infiltrated with liquid ORMOCER (R). After photopolymerization of the resin the host opal is dissolved in tetrahydrofuran and an ORMOCER (R) inverse opal is obtained. It shows excellent periodicity (by SEM) and optical properties to reveal a high degree of face centered cubic order. This replication process leads to a nanostructured photonic crystal with the outstanding mechanical properties of ORMOCER (R) and high temperature stability up to 350 degrees C.}, language = {en} } @article{TeixeiraBlanzatKoetzetal.2006, author = {Teixeira, C. V. and Blanzat, Muriel and Koetz, Joachim and Rico-Lattes, I. and Brezesinski, Gerald}, title = {In-plane miscibility and mixed bilayer microstructure in mixtures of catanionic glycolipids and zwitterionic phospholipids}, series = {Biochimica et biophysica acta : Biomembranes}, volume = {1758}, journal = {Biochimica et biophysica acta : Biomembranes}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0005-2736}, doi = {10.1016/j.bbamem.2006.05.025}, pages = {1797 -- 1808}, year = {2006}, abstract = {SAXS/WAXS studies were performed in combination with freeze fracture electron microscopy using mixtures of a new Gemini catanionic surfactant (Gem 16-12, formed by two sugar groups bound by a hydrocarbon spacer with 12 carbons and two 16-carbon chains) and the zwitterionic phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine(DPPC) to establish the phase diagram. Gem 16-12 in water forms bilayers with the same amount of hydration water as DPPC. A frozen interdigitated phase with a low hydration number is observed below room temperature. The kinetics of the formation of this crystalline phase is very slow. Above the chain melting temperature, multilayered vesicles are formed. Mixing with DPPC produces mixed bilayers above the corresponding chain melting temperature. At room temperature, partially lamellar aggregates with local nematic order are observed. Splitting of infinite lamellae into discs is linked to immiscibility in frozen state. The ordering process is always accompanied by dehydration of the system. As a consequence, an unusual order-disorder phase transition upon cooling is observed.}, language = {en} } @article{KozlevcarGolobicStrauch2006, author = {Kozlevcar, Bojan and Golobic, Amalija and Strauch, Peter}, title = {Dynamic pseudo Jahn-Teller distortion in a compressed octahedral CuO6 complex}, series = {Polyhedron : the international journal of inorganic and organometallic chemistry}, volume = {25}, journal = {Polyhedron : the international journal of inorganic and organometallic chemistry}, number = {15}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-5387}, doi = {10.1016/j.poly.2006.04.009}, pages = {2824 -- 2828}, year = {2006}, abstract = {The crystal structure of cis-[Cu(C8H7O3)(2)(H2O)(2)] (115 K data) reveals bidentate vanillinate ions coordinated via methoxy and deprotonated hydroxy oxygen atoms and water molecules in a distorted octahedral CuO6 chromophore. A cis orientation of the ligands enables two non-identical O(methoxy)-Cu-O(water) coordination axes (2.354(l) + 2.163(1); 2.151(1) + 2.020(1) angstrom), and the third shortest O(hydroxy)-Cu-O(hydroxy) axis (1.919(1) + 1.914(1) angstrom). This 115 K coordination sphere differs importantly to the one obtained from the 293 K data of the same compound, where two long 0(methoxy)-Cu-O(water) axes are of the same length, and only minor changes at the short 0(hydroxy)-Cu-O(hydroxy) axis are noticed. An axial symmetry of the complex with an inverse g(1.2)(g(perpendicular to)) > g(3)(g(parallel to)) pattern is observed in the temperature range from 298 to 180 K. A further decrease of temperature reveals gradual changes from axial to rhombic symmetry (g(1) > g(2) > g(3)) that is reversible. A mean-square displacement amplitude (MDSA) analysis reveals a disorder in the Cu-O(methoxy) bonds, but not in the other metal-ligand Cu-O(hydroxy) and Cu-O(water) bonds at 293 and 115 K. The disorder is significantly weaker in the 115 K structure. The MSDA analysis and the structural-EPR agreement show vibrational disorder in two coordination axes, due to the cis conformation of the complex with two 0(methoxy)-Cu-O(water) axes.}, language = {en} } @article{FudickarVomdranLinker2006, author = {Fudickar, Werner and Vomdran, Katja and Linker, Torsten}, title = {Auxiliary controlled singlet-oxygen ene reactions of cyclohexenes}, series = {Tetrahedron}, volume = {62}, journal = {Tetrahedron}, number = {46}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2006.07.104}, pages = {10639 -- 10646}, year = {2006}, abstract = {The photooxygenation of homochiral cyclohexene ketals, which are easily available from 2-cyclohexenone and L-tartrates, affords hydroperoxides and after reduction the corresponding allylic alcohols in good yields and high regioselectivities. This can be rationalized by electronic repulsions in a perepoxide intermediate and provides evidence for unfavorable 1,3 diaxial interactions with a dioxolane oxygen atom. Only low stereoselectivities were observed, due to the flexibility of the cyclohexene ring. However, the diastereomers could be separated and after cleavage of the auxiliary, 4-hydroxy-2-cyclohexen-1-one was isolated in enantiomerically pure form, which can serve as a building block for natural product synthesis.}, language = {en} } @article{NoteKosmellaKoetz2006, author = {Note, Carine and Kosmella, Sabine and Koetz, Joachim}, title = {Poly(ethyleneimine) as reducing and stabilizing agent for the formation of gold nanoparticles in w/o microemulsions}, series = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, volume = {290}, journal = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, number = {1-3}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0927-7757}, doi = {10.1016/j.colsurfa.2006.05.018}, pages = {150 -- 156}, year = {2006}, abstract = {This paper is focused on the use of branched poly(ethyleneimine) (PEI) as reducing as well as stabilizing agent for the formation of gold nanoparticles in different media. The process of nanoparticle formation was investigated, in the absence of any other reducing agents, in microemulsion template phase in comparison to the nucleation process in aqueous polymer solution. On the one hand, it was shown that the polyelectrolyte can be used for the controlled single-step synthesis and stabilization of gold nanoparticles via a nucleation reaction and particles with an average diameter of 7.1 nm can be produced. On the other hand, it was demonstrated that the polymer can also act as reducing and stabilizing agent in much more complex systems, i.e. in water-in-oil (w/o) microemulsion droplets. The reverse microemulsion droplets of the quaternary system sodium dodecylsulfate (SDS)/toluene-pentanol (1:1)/water were successfully used for the synthesis of gold nanoparticles. The polymer, incorporated in the droplets, exhibits reducing properties, adsorbs on the surface of the nanoparticles and prevents their aggregation. Consequently, nanoparticles of 8.6 nm can be redispersed after solvent evaporation without a change of their size. Nevertheless, the polymer acts already as a "template" during the formation of the nanoparticles in water and in microemulsion, so that an additional template effect of the microemulsion is not observed. The particle formation for both methods is checked by means of UV-vis spectroscopy and the particle size and size distribution are investigated via dynamic light scattering and transmission electron microscopy (TEM). (c) 2006 Elsevier B.V. All rights reserved.}, language = {en} } @article{MartinazzoNestSaalfranketal.2006, author = {Martinazzo, Rocco and Nest, Mathias and Saalfrank, Peter and Tantardini, Gian Franco}, title = {A local coherent-state approximation to system-bath quantum dynamics}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {125}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, number = {19}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.2362821}, pages = {16}, year = {2006}, abstract = {A novel quantum method to deal with typical system-bath dynamical problems is introduced. Subsystem discrete variable representation and bath coherent-state sets are used to write down a multiconfigurational expansion of the wave function of the whole system. With the help of the Dirac-Frenkel variational principle, simple equations of motion-a kind of Schrodinger-Langevin equation for the subsystem coupled to (pseudo) classical equations for the bath-are derived. True dissipative dynamics at all times is obtained by coupling the bath to a secondary, classical Ohmic bath, which is modeled by adding a friction coefficient in the derived pseudoclassical bath equations. The resulting equations are then solved for a number of model problems, ranging from tunneling to vibrational relaxation dynamics. Comparison of the results with those of exact, multiconfiguration time-dependent Hartree calculations in systems with up to 80 bath oscillators shows that the proposed method can be very accurate and might be of help in studying realistic problems with very large baths. To this end, its linear scaling behavior with respect to the number of bath degrees of freedom is shown in practice with model calculations using tens of thousands of bath oscillators.}, language = {en} } @article{SchmidtStaude2006, author = {Schmidt, Bernd and Staude, Lucia}, title = {Unexpected transfer hydrogenation of C-C-double bonds during Tandem-RCM-isomerization reactions}, series = {Journal of organometallic chemistry}, volume = {691}, journal = {Journal of organometallic chemistry}, number = {24-25}, publisher = {Elsevier}, address = {Lausanne}, issn = {0022-328X}, doi = {10.1016/j.jorganchem.2006.07.011}, pages = {5218 -- 5221}, year = {2006}, abstract = {Unexpected hydrogen transfer from 2-propanol to C-C-double bonds has been observed in the course of a Tandem RCM-isomerization reaction leading to sterically congested spirocycles.}, language = {en} } @article{FudickarLinker2006, author = {Fudickar, Werner and Linker, Torsten}, title = {Imaging by sensitized oxygenations of photochromic anthracene films}, series = {Chemistry - a European journal}, volume = {12}, journal = {Chemistry - a European journal}, publisher = {WILEY-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.200600387}, pages = {9276 -- 9283}, year = {2006}, abstract = {The aliphatic anthracene compound 1 and the oligomeric anthracene 2 were synthesized. Thin films of 1 and 2 mixed with the sensitizers tetraphenylporphyrin (TPP) and methylene blue (MB) were irradiated with visible light in air. Upon formation of singlet oxygen, the anthracene units were converted quantitatively to the corresponding endoperoxides. Heating of the irradiated samples afforded the parent anthracenes with high yields. Here, we demonstrate that the kinetics and reversibility of this reaction strongly depend on the microenvironment of the anthracene groups in the two compounds. The photooxidation of thin films of I is accompanied by interesting changes in the morphology of the film and allows the first application of 1 as a nondestructive negative-tone photo-resist for lithography and as an oxidizing ink. The morphology of 2 remained unchanged after photooxidation as a result of the stabilizing oligomer backbone. This stabilizing effect significantly improves the photochromic performance of 2. The reversibility of the photooxidation is very high (> 90\%) for oligomeric films of 2 after several cycles of irradiation and beating. Decomposition of the anthracene and a loss of the activity of the sensitizer diminish slightly the performance of the monomeric species.}, language = {en} } @article{AndrianovSaalfrank2006, author = {Andrianov, Ivan and Saalfrank, Peter}, title = {Free vibrational relaxation of H adsorbed on a Si(100) surface investigated with the multi-configurational time-dependent Hartree method}, series = {Chemical physics letters}, volume = {433}, journal = {Chemical physics letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0009-2614}, doi = {10.1016/j.cplett.2006.11.067}, pages = {91 -- 96}, year = {2006}, abstract = {The results of a quantum-mechanical study of vibrational relaxation of hydrogen adsorbed on a Si(100) surface with the multi-configurational time-dependent Hartree (MCTDH) method are presented. A two-dimensional subsystem is coupled non-linearly to a bath of harmonic oscillators (phonons of the Si bulk), and the relaxation of subsystem vibrations proceeds primarily via a two-phonon process. Characteristic times of the system evolution agree well with our previous perturbation theory study. The vibrational population decay is non-exponential, exhibiting pronounced recurrences due to finite bath size. The dependence of the lifetimes of the vibrational levels on the bath size and on the coupling details is investigated.}, language = {en} } @article{ZenSaphiannikovaNeheretal.2006, author = {Zen, Achmad and Saphiannikova, Marina and Neher, Dieter and Grenzer, J{\"o}rg and Grigorian, Souren A. and Pietsch, Ullrich and Asawapirom, Udom and Janietz, Silvia and Scherf, Ullrich and Lieberwirth, Ingo and Wegner, Gerhard}, title = {Effect of molecular weight on the structure and crystallinity of poly(3-hexylthiophene)}, doi = {10.1021/Ma0521349}, year = {2006}, abstract = {Recently, two different groups have reported independently that the mobility of field-effect transistors made from regioregular poly(3-hexylthiophene) (P3HT) increases strongly with molecular weight. Two different models were presented: one proposing carrier trapping at grain boundaries and the second putting emphasis on the conformation and packing of the polymer chains in the thin layers for different molecular weights. Here, we present the results of detailed investigations of powders and thin films of deuterated P3HT fractions with different molecular weight. For powder samples, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) were used to investigate the structure and crystallization behavior of the polymers. The GPC investigations show that all weight fractions possess a rather broad molecular weight distribution. DSC measurements reveal a strong decrease of the crystallization temperature and, most important, a significant decrease of the degree of crystallinity with decreasing molecular weight. To study the structure of thin layers in lateral and vertical directions, both transmission electron microscopy (TEM) and X-ray grazing incidence diffraction (GID) were utilized. These methods show that thin layers of the low molecular weight fraction consist of well-defined crystalline domains embedded in a disordered matrix. We propose that the transport properties of layers prepared from fractions of poly(3-hexylthiophene) with different molecular weight are largely determined by the crystallinity of the samples and not by the perfection of the packing of the chains in the individual crystallites}, language = {en} } @article{StrehmelLaschewskyStoesseretal.2006, author = {Strehmel, Veronika and Laschewsky, Andr{\´e} and Stoesser, Reinhard and Zehl, Andrea and Herrmann, Werner}, title = {Mobility of spin probes in ionic liquids}, doi = {10.1002/poc.1072}, year = {2006}, abstract = {The spin probes TEMPO, TEMPOL, and CAT-1 were used to investigate microviscosity and micropolarity of imidazolium based ionic liquids bearing either tetrafluoroborate or hexafluorophosphate as anions and a variation of the substitution at the imidazolium ion. The average rotational correlation times (r) obtained by complete simulation of the X-band ESR spectra of TEMPO, TEMPOL, and CAT-1 increase with increasing viscosity of the ionic liquid although no Stokes Einstein behavior is observed. This is caused by microviscosity effects of the ionic liquids shown by application of the Gierer-Wirtz theory. Interestingly, the jump of the probe molecule into the free volume of the ionic liquids is a nonactivated process. The hyperfine coupling constants (A(iso) (N-14)) of TEMPO and TEMPOL dissolved in the ionic liquids do not depend on the structure of the ionic liquids. The A(iso) (N-14) values show a micropolarity of the ionic liquids that is comparable with methylenchloride in case of TEMPO and with dimethylsulfoxide in case of TEMPOL. Micropolarity monitored by CAT-1 strongly depends on structural variation of the ionic liquid. CAT-1 dissolved in imidazolium salts substituted with shorter alkyl chains at the nitrogen atom exhibits a micropolarity comparable with dimethylsulfoxide. A significant lower micropolarity is found for imidazolium. salts bearing a longer alkyl substituent at the nitrogen atom or a methyl substituent at C-2. Copyright (c) 2006 John Wiley \& Sons, Ltd}, language = {en} } @article{SchmidtNave2006, author = {Schmidt, Bernd and Nave, Stefan}, title = {Control of ring size selectivity by substrate directable RCM}, doi = {10.1039/B604359c}, year = {2006}, abstract = {Hydroxy groups may exert strong catalyst-directing effects in olefin metathesis reactions, which are exploited for a ring size-selective RCM reaction}, language = {en} } @article{Schmidt2006, author = {Schmidt, Bernd}, title = {Olefin metathesis and isomerization : from undesired side reactions to useful synthetic methodology}, doi = {10.1016/j.molcata.2006.03.026}, year = {2006}, abstract = {Conversion of ruthenium carbene complexes to ruthenium hydride complexes by organometallic transformations in situ opens up interesting synthetic perspectives. In this account the use of Grubbs' catalyst to synthesize pent-4- enals selectively from diallyl- and allyl homoallyl ethers and scope and limitations of a Tandem RCM-isomerization sequence for the synthesis of cyclic enol ethers are discussed. (c) 2006 Elsevier B.V. All rights reserved}, language = {en} } @article{RullensVuillaumeMoussaetal.2006, author = {Rullens, F and Vuillaume, Pascal Y. and Moussa, Alain and Habib-Jiwan, Jean-Louis and Laschewsky, Andr{\´e}}, title = {Ordered polyelectrolyte "Multilayers". 7. Hybrid films self-assembled from fluorescent and smectogenic poly(diallylammonium) salts and delaminated clay}, doi = {10.1021/Cm060209x}, year = {2006}, abstract = {Homopolymers were prepared from diallylammonium monomers bearing 4-methylcoumarin and 4-cyanobiphenyl as fluorescent and mesogenic side groups, as well as their copolymers with diallyldimethylammonium chloride (DADMAC). Organic-inorganic hybrid films were electrostatically self-assembled via the layer-by-layer technique on silicon wafers and quartz plates from the chromophore-bearing polymers and an exfoliated synthetic hectorite. Photophysical studies performed in solution as well as in the self-assembled films demonstrated only a weak tendency for aggregation of the chromophores in the macromolecules. Moreover, assemblies made from the polymers carrying the cyanobiphenyl mesogen were found to exhibit a pronounced internal order}, language = {en} } @article{RullensLaschewskyDevillers2006, author = {Rullens, F and Laschewsky, Andr{\´e} and Devillers, M}, title = {Bulk and thin films of bismuth vanadates prepared from hybrid materials made from an organic polymer and inorganic salts}, doi = {10.1021/Cm051516q}, year = {2006}, abstract = {A new precursor route for the preparation of bulk oxides and thin films of bismuth vanadates is proposed. The method involves the thermal treatment under air and mild conditions of hybrid organic-inorganic precursors, made from a zwitterionic salt-free polymer matrix and selected inorganic species. Monoclinic BiVO4 was obtained in the form of bulk oxide by calcination of the powdered homogeneous hybrid materials at 600 degrees C, from precursors containing Bi and V in stoichiometric amounts. In the same way, thermodiffractometry studies performed on a hybrid material exhibiting a Bi/ V molar ratio of 2 revealed that the ionic conductor gamma-Bi4V2O11 phase can be stabilized under very soft thermal conditions (300 degrees C). Additionally, thin films of yellow monoclinic BiVO4 were for the first time fabricated, by thermal treatment of the same hybrid polymeric precursors deposited on quartz substrates by spin coating, using a layer- by-layer technique. The presence of the target phase at the surface of the plates was confirmed by X-ray diffraction as well as UV-vis measurements}, language = {en} } @article{KozlevcarOdlazekGolobicetal.2006, author = {Kozlevcar, Bojan and Odlazek, Darja and Golobic, Amalija and Pevec, Andrej and Strauch, Peter and Segedin, Primoz}, title = {Complexes with lignin model compound vanillic acid : two different carboxylate ligands in the same dinuclear tetracarboxylate complex [Cu-2(C8H7O4)(2)(O2CCH3)(2)(CH3OH)(2)]}, issn = {0277-5387}, doi = {10.1016/j.poly.2005.08.031}, year = {2006}, abstract = {Two copper(II) coordination compounds with vanillic acid C8H8O4 (1), namely [Cu- 2(C8H7O4)(2)(O2CCH3)(2)(CH3OH)(2)] (2) and [Cu-2(C8H7O4)(4)(H2O2)(2)] (3), were synthesized and characterized. Single crystals of 1-3 were obtained and their crystal structures determined. The structure of 2 shows dinuclear cage structure of copper acetate hydrate type, however with two different carboxylates, acetates and vanillic acid anions,. respectively. Both bridging anions are in pairs in trans orientation. Methanol molecules are apically coordinated (Cu-O7 2.160(2) angstrom), fulfilling square-pyramidal coordination sphere around both copper ions. The compound 2 decomposes outside mother-liquid (yielding [Cu-2(C8H7O4)(2)(O2CCH3)(2)(H2O)(2)] (2a)) with the removal of methanol, but without significant change of the dicopper tetracarboxylate cage structure, as noticed by mu(eff) 1.48 BM for 2a. Similar was found also in the X-band EPR spectra with three signals H-z1, H-perpendicular to 2 and H-z2 in the region from 0 to 600 mT. The structure of free vanillic acid 1 is composed of dimeric units of two molecules, connected by two parallel hydrogen bonds between carboxylate group of each other (O1-H(...)O2 2.642(3) angstrom), while the structure of 3 is of [Cu-2(O2CCH3)(4)(H2O)(2)] type. Interestingly, an additional signal in the EPR spectra of 3 is found at 80 mT (H- perpendicular to 1) at 298 and at 116 K, next to three signals H-z1, H-perpendicular to 2 and H-z2.}, language = {en} } @article{KoetzJagielskiKosmellaetal.2006, author = {Koetz, Joachim and Jagielski, Nicole and Kosmella, Sabine and Friedrich, Alwin and Kleinpeter, Erich}, title = {CdS nanocubes formed in phosphatidylcholin-based template phases}, volume = {288}, issn = {0927-7757}, doi = {10.1016/j.colsurfa.2006.01.013}, pages = {43 -- 1-3}, year = {2006}, abstract = {The paper is focused on the characterization and use of phosphatidylcholine (PC)-based inverse microemulsions as a template phase for the CdS nanoparticle formation. The optically clear, isotropic phase in the oil corner was identified as a "classical{\"o} water-in-oil microemulsion by means of NMR-diffusion measurements. Because of the very small dimensions of the water droplets, the isotropic phase shows a Newtonian-like flow behavior, and adequate amounts of bulk water cannot be detected by DSC. It is demonstrated that this w/o microemulsion can be used successfully as a nanoreactor for the formation of CdS nanoparticles with diameters of 4-5 nm. During the following process of solvent evaporation the individual small CdS nanoparticles aggregate to significant larger cubic nanoparticles, with an edge length of 2-40 nm, arranged in well-defined mosaic-like superstructures. In presence of SDS the nanocubes were stable up to 800 °C. It has to be stated here that polyelectrolytes prevent the formation of such well-ordered superstructures.}, language = {en} } @article{KleinpeterHolzberger2006, author = {Kleinpeter, Erich and Holzberger, Anja}, title = {Structure, intramolecular flexibility, and complexation of aza crown ethers to anions H2PO4- and HSO4- in nonprotic solvents}, series = {Tetrahedron}, volume = {62}, journal = {Tetrahedron}, number = {43}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0040-4020}, doi = {10.1016/j.tet.2006.07.074}, pages = {10237 -- 10247}, year = {2006}, abstract = {Both the structure and intramolecular flexibility of a series of aza crown ethers were studied by experimental NMR and theoretical molecular modeling. The stoichiometries of complexation to the anions H2PO4- and resulting complex stabilities were determined by experimental NMR (1H, 31P) titration and, in addition, the structure and mobility changes of the aza crown ethers upon complexation were also examined.}, language = {en} } @article{EngelhardKumkeLoehmannsroeben2006, author = {Engelhard, Sonja and Kumke, Michael Uwe and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Examples of the application of optical process and quality sensing (OPQS) to beer brewing and polyurethane foaming processes}, issn = {1618-2642}, doi = {10.1007/s00216-005-3364-4}, year = {2006}, abstract = {Optical methods play an important role in process analytical technologies (PAT). Four examples of optical process and quality sensing (OPQS) are presented, which are based on three important experimental techniques: near- infrared absorption, luminescence quenching, and a novel method, photon density wave (PDW) spectroscopy. These are used to evaluate four process and quality parameters related to beer brewing and polyurethane (PU) foaming processes: the ethanol content and the oxygen (O-2) content in beer, the biomass in a bioreactor, and the cellular structures of PU foam produced in a pilot production plant}, language = {en} } @article{DambacherKlieglHofmannetal.2006, author = {Dambacher, Michael and Kliegl, Reinhold and Hofmann, Markus and Jacobs, Arthur M.}, title = {Frequency and predictability effects on event-related potentials during reading}, issn = {0006-8993}, doi = {10.1016/j.brainres.2006.02.010}, year = {2006}, abstract = {Effects of frequency, predictability, and position of words on event-related potentials were assessed during word-by-word sentence reading in 48 subjects in an early and in a late time window corresponding to P200 and N400. Repeated measures multiple regression analyses revealed a P200 effect in the high-frequency range also the P200 was larger on words at the beginning and end of sentences than on words in the middle of sentences (i.e., a quadratic effect of word position). Predictability strongly affected the N400 component; the effect was stronger for low than for high- frequency words. The P200 frequency effect indicates that high-frequency words are lexically accessed very fast, independent of context information. Effects on the N400 suggest that predictability strongly moderates the late access especially of low-frequency words. Thus, contextual facilitation on the N400 appears to reflect both lexical and post- lexical stages of word recognition, questioning a strict classification into lexical and post-lexical processes.}, language = {en} } @article{BalciKochKleinpeter2006, author = {Balci, Kubilay and Koch, Andreas and Kleinpeter, Erich}, title = {A comparative vibrational spectroscopic investigation of free mn-12S(2)O(2) and fn-12S(2)O(2) dithiacrown ethers based on DFT calculations}, issn = {0022-2860}, doi = {10.1016/j.molstruc.2005.10.048}, year = {2006}, abstract = {A successful assignment for the fundamental bands observed in the experimental IR spectra of mn-12S(2)O(2) and fn-12S(2)O(2) dithiacrown ethers was achieved by the aid of the density functional theory (DFT) based quantum mechanical calculations carried out at the 133LYP/6-31G(d) and B3LYP/6-31 + G(d) level of theory. Two different scaling approaches, '(i) scaled quantum mechanics force field (SQM FF) methodology', and (ii) the 'scaling frequencies with dual empirical scale factors', were used in order to fit the calculated harmonic frequencies to the experimental ones. Potential energy distribution (PED) calculations were carried out to define the internal coordinate contributions to each normal mode and to define the corresponding normal modes of the molecules. The effects of the conformational differences onto the IR active normal modes of the two isomeric molecules and their corresponding experimental frequencies were discussed in the light of the calculated spectral data.}, language = {en} } @article{AndayiYenesewDereseetal.2006, author = {Andayi, Andrew W. and Yenesew, Abiy and Derese, Solomon and Midiwo, Jacob O. and Gitu, Peter M. and Jondiko, Ogoche J. I. and Akala, Hoseah M. and Liyala, Pamela and Wangui, Julia and Waters, Norman C. and Heydenreich, Matthias and Peter, Martin G.}, title = {Antiplasmodial flavonoids from Erythrina sacleuxii}, issn = {0032-0943}, doi = {10.1055/s-2005-873200}, year = {2006}, abstract = {The acetone extracts of the root bark and stem bark of Erythrina sacleuxii showed antiplasmodial activities against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum. Chromatographic separation of the acetone extract of the root bark afforded a new isoflavone, 7-hydroxy-4 -methoxy-3'- prenylisoflavone (trivial name 5-deoxy-3' - prenylbiochanin A) along with known isoflavonoids as the antiplasmodial principles. Flavonoids and isoflavonoids isolated from the stem bark of E. sucleuxii were also tested and showed antiplasmodial activities. The structures were determined on the basis of spectroscopic evidence}, language = {en} } @article{WattebledLaschewskyMoussaetal.2006, author = {Wattebled, Laurent and Laschewsky, Andr{\´e} and Moussa, Alain and Habib-Jiwan, Jean-Louis}, title = {Aggregation numbers of cationic oligomeric surfactants : A time-resolved fluorescence quenching study}, doi = {10.1021/La052414h}, year = {2006}, abstract = {The micelle aggregation numbers (N-agg) of several series of cationic oligomeric surfactants were determined by time-resolved fluorescence quenching (TRFQ) experiments, using advantageously 9,10-dimethylanthracene as fluorophore. The study comprises six dimeric ("gemini"), three trimeric, and two tetrameric surfactants, which are quaternary ammonium chlorides, with medium length spacer groups (C-3-C-6) separating the individual surfactant fragments. Two standard cationic surfactants served as references. The number of hydrophobic chains making up a micellar core is relatively low for the oligomeric surfactants, the spacer length playing an important role. For the dimers, the number decreases from 32 to 21 with increasing spacer length. These numbers decrease further with increasing degree of oligomerization down to values of about 15. As for many conventional ionic surfactants, the micelles of all oligomers studied grow only slightly with the concentration, and they remain in the regime of small micelles up to concentrations of at least 3 wt \%.}, language = {en} } @article{ShainyanUshakovKochetal.2006, author = {Shainyan, Bagrat A. and Ushakov, Igor A. and Koch, Andreas and Kleinpeter, Erich}, title = {Stereodynamics of 1-(methylsulfonyl)-3,5-bis(trifluoromethylsulfonyl)-1,3,5-triazinane: Experimental and theoretical analysis}, doi = {10.1021/Jo061112x}, year = {2006}, abstract = {Dynamic NMR of 1-(methylsulfonyl)-3,5-bis(trifluoromethylsulfonyl)-1,3,5-triazinane reveals the existence of three conformers and two dynamic processes: ring inversion and rotation about the N-S bond, both processes having Delta G(double dagger) = 13.5 kcal/mol. An unprecedented large reverse Perlin effect (J(CHax) > J(CHeq)) was found experimentally and calculated theoretically.}, language = {en} } @article{LaschewskyKirstenSkrabaniaetal.2006, author = {Laschewsky, Andr{\´e} and Kirsten, Juliane and Skrabania, Katja and Storsberg, Joachim}, title = {Designing functional macrosurfactants via triblock tercopolymers}, issn = {0065-7727}, year = {2006}, language = {en} } @article{SonnenburgAdelhelmAntoniettietal.2006, author = {Sonnenburg, Kirstin and Adelhelm, Philipp and Antonietti, Markus and Smarsly, Bernd and N{\"o}ske, Robert and Strauch, Peter}, title = {Synthesis and characterization of SiC materials with hierarchical porosity obtained by replication techniques}, doi = {10.1039/B604819F}, year = {2006}, abstract = {Porous silicon carbide monoliths were obtained using the infiltration of preformed SiO2 frameworks with appropriate carbon precursors such as mesophase pitch. The initial SiO2 monoliths possessed a hierarchical pore system, composed of an interpenetrating bicontinuous macropore structure and 13 nm mesopores confined in the macropore walls. After carbonization, further heat treatment at ca. 1400 degrees C resulted in the formation of a SiC-SiO2 composite, which was converted into a porous SiC monolith by post-treatment with ammonium fluoride solution. The resulting porous SiC featured high crystallinity, high chemical purity and showed a surface area of 280 m(2) g(-1) and a pore volume of 0.8 ml g(-1)}, language = {en} } @article{KumkeDoscheFlehretal.2006, author = {Kumke, Michael Uwe and Dosche, Carsten and Flehr, Roman and Trowitzsch-Kienast, Wolfram and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Spectroscopic characterization of the artificial siderophore pyridinochelin}, issn = {0939-5075}, year = {2006}, language = {en} } @article{GroboschSchildeTiersch2006, author = {Grobosch, Thomas and Schilde, Uwe and Tiersch, Brigitte}, title = {Abtrennung von Arsen und anderer Schwermetalle mit impr{\"a}gnierten Adsorberpolymeren - teil 2: Abtrennung von Blei, Kupfer, Nickel und Zink}, issn = {0009-286X}, doi = {10.1002/cite.200500171}, year = {2006}, language = {de} } @article{SchmidtNave2006, author = {Schmidt, Bernd and Nave, Stefan}, title = {Palladium-catalyzed O-allylation of alpha-hydroxy carbonyl compounds}, doi = {10.1002/adsc.200505361}, year = {2006}, abstract = {alpha-Hydroxy carbonyl compounds undergo smooth O-allylation using allylic carbonates and Pd(0) catalysts. This method has significant advantages over other O-allylation methods as it provides a solution to several problems previously observed for this synthetic transformation}, language = {en} } @article{SzatmariTothKochetal.2006, author = {Szatmari, Istvan and Toth, Diana and Koch, Andreas and Heydenreich, Matthias and Kleinpeter, Erich and Fulop, Ferenc}, title = {Study of the substituent-influenced anomeric effect in the ring-chain tautomerism of 1-alkyl-3-aryl-naphth[1,2- e][1,3]oxazines}, doi = {10.1002/ejoc.200600563}, year = {2006}, abstract = {The stabilities of the trans (B) and cis (C) tautomeric ring forms that are experimentally observed in the ring- chain tautomeric interconversion of 1-alkyl-3-aryl-2,3-dihydro-1H-naphth[1,2-e][1,3]oxazines has been investigated. Stability differences are explained by the analysis of the natural bond orbital results for the lone pairs of electrons that are on the heteroatoms in the oxazine ring system and by regression analysis of the calculated 13C NMR chemical shift values.}, language = {en} } @article{StrehmelLaschewskyWetzeletal.2006, author = {Strehmel, Veronika and Laschewsky, Andr{\´e} and Wetzel, Hendrik and Gornitz, Eckhard}, title = {Free radical polymerization of n-butyl methacrylate in ionic liquids}, doi = {10.1021/Ma0516945}, year = {2006}, abstract = {Ionic liquids based on imidazolium, pyridinium, and alkylammonium salts were investigated as solvents in free radical polymerization of the model monomer n-butyl methacrylate. The properties of the ionic liquids were systematically varied by changing the length of the alkyl substituents on the cations, and by employing different anions such as tetrafluoroborate, hexafluorophosphate, tosylate, triflate, alkyl sulfates and dimethyl phosphate. Results were compared to analogous polymerizations in toluene and in bulk. The solvents have no detectable influence on polymer tacticity. However, the molar masses obtained and the degree of polymerization, respectively, are very sensitive to the choice of the solvent. The degrees of polymerization are significantly higher when polymerizations were carried out in ionic liquids compared to polymerization in toluene, and can even exceed the values obtained by bulk polymerization. Imidazolium salts unsubstituted at C-2 result in an increase in the degree of polymerization of the poly(butyl methacrylate) with increasing viscosity of these ionic liquids. Methyl substitution at C-2 of the imidazolium ion results in an increase in the viscosity of the ionic liquid and in a viscosity independent degree of polymerization of the poly(butyl methacrylate). Ionic liquids based on imidazolium salts seem preferable over pyridinium and alkylammonium salts because of the higher degree of polymerization of the poly(butyl methacrylate)s obtained in the imidazolium salts. The glass transition temperatures and thermal stabilities are higher for poly(butyl methacrylate)s synthesized in the ionic liquids compared to the polymer made in toluene}, language = {en} } @article{KlinkaBalentovaBernatetal.2006, author = {Klinka, Karel D. and Balentova, Eva and Bern{\´a}t, Juraj and Imrich, J{\´a}n and Vavrusov{\´a}, Martina and Pihlaja, Kalevi and Koch, Andreas and Kleinpeter, Erich and Kelling, Alexandra and Schilde, Uwe}, title = {Structural revision of products resulting from the reaction of methylhydrazine with acridin-9-yl isothiocyanate due to unexpected acridinyl migration And further reactions}, issn = {1551-7004}, year = {2006}, abstract = {The reaction of methyl acridin-9-ylthiosemicarbazide under basic conditions with methyl bromoacetate resulted in a 1,3-thiazolin-4-one structure as provided by X-ray crystallography. The structure forced a re-evaluation of the reactant methyl acridin-9-ylthiosemicarbazide, originally thought to be 2-methyl 4-acridin-9-ylthiosemicarbazide based on synthetic expectations, but which when examined by X-ray crystallography was found to be in fact the isomeric 2- methyl 1-acridin-9-ylthiosemicarbazide resulting from rearrangement via a spiro form which it is in equilibrium with in solution. The product resulting from reaction with methyl iodide was also studied and the previously reported semicarbazide produced by reaction with MNO was re-examined. In both cases, the 1,2 isomer rather than the 2,4 isomer was found to be present based on the sign of the 3JCH3,N11 coupling. Full characterization of the compounds was rendered by 1H, 13C, and 15N solution-state NMR, and in the solid state, by both 13C and 15N NMR.}, language = {en} } @article{GroboschMicklerFeisteletal.2006, author = {Grobosch, Thomas and Mickler, Wulfhard and Feistel, Lothar and Schilde, Uwe}, title = {Separation of arsenic and other heavy metals with impregnated adsorber polymers : chapter 1: synthesis of the impregnation medium and separation of arsenic}, issn = {0009-286X}, doi = {10.1002/cite.200500170}, year = {2006}, language = {en} } @article{Kleinpeter2006, author = {Kleinpeter, Erich}, title = {Push-pull alkenes : structure and pi-electron distribution}, doi = {10.2298/Jsc0601001k}, year = {2006}, abstract = {Push-pull alkenes are substituted alkenes with one or two electron-donating substituents on one end of C=C double bond and with one or two electron-accepting substituents at the other end. Allowance for pi-electron delocalization leads to the central C=C double bond becoming ever more polarized and with rising push-pull character, the pi-bond order of this double bond is reduced and, conversely, the corresponding pi-bond orders of the C-Don and C- Ace bonds are accordingly increased. This push-pull effect is of decisive influence on both the dynamic behavior and the chemical reactivity of this class of compounds and thus it is Of Considerable interest to both determine and to quantify the inherent push-pull effect. previously, the barriers to rotation about the C=C, C-Don and/or C-Acc partial double bonds (Delta G(not equal), as determined by dynamic NMR spectroscopy) or the C-13 chemical shift difference of the polarized C=C partial double bond (Delta delta(C=C)) were employed for this purpose, However, these parameters can have serious limitations, viz. the barriers can be immeasurable on the NMR timescale (either by being too high or too low-, heavily-biased conformers are present, etc.) or Delta delta(C=C) behaves in a non-additive manner with respect to the combination of the four substituents. Hence, a general parameter to quantify the push-pull effect is not yet available. Ab initio MO calculations on a collection of compounds, together with NBO analysis, provided valuable information on the structure, bond energies, electron occupancies and bonding/antibonding interactions. In addition to Delta G(C=C)(not equal) (either experimentally determined or theoretically calculated) and Delta delta(C=C), the bond length of the C=C partial double bond was also examined and it proved to be a reliable parameter to quantify the push-pull effect. Equally so, the quotient of the occupation numbers of the antibonding and bonding pi orbitals of the central C=C partial double bond ( pi*(C=C)/pi(C=C) ) could also be employed for this purpose}, language = {en} } @phdthesis{Koehler2006, author = {K{\"o}hler, Karen}, title = {Temperature-induced rearrangements of polyelectrolyte multilayer capsules : mechanisms and applications}, address = {Potsdam}, pages = {XV, 118, B S. : Ill., graph. Darst.}, year = {2006}, language = {en} } @article{GorfmanTsirelsonPucheretal.2006, author = {Gorfman, Semen and Tsirelson, Vladimir and Pucher, Andreas and Morgenroth, Wolfgang and Pietsch, Ullrich}, title = {X-ray diffraction by a crystal in a permanent external electric field : electric-field-induced structural response in alpha-GaPO4}, issn = {0108-7673}, doi = {10.1107/S0108767305036111}, year = {2006}, abstract = {For the first time, site-selective distortion has been investigated for two different structural units in the ternary compound alpha-GaPO4 under the influence of a permanent external electric field. Based on 54 measured reflection intensities, the electric-field-induced distortion of PO4 and GaO4 tetrahedra in alpha-GaPO4 crystals is evaluated using a model of pseudoatomic displacements introduced recently [Gorfman, Tsirelson \& Pietsch (2005). Acta Cryst. A61, 387- 396]. A stronger variation of the P-O bond lengths in the PO4 tetrahedron was found compared to the bonds in the GaO4 tetrahedron. The different distortions of the tetrahedra owing to the electric field were analysed in terms of the valence charge density of alpha-GaPO4 and its topological characteristics. The larger charge of the P pseudoatom compared to the Ga atom was recognized as the main reason for the higher sensitivity of the PO4 tetrahedron to a permanent external electric field}, language = {en} } @article{KietzkeEgbeHoerholdetal.2006, author = {Kietzke, Thomas and Egbe, Daniel A. M. and H{\"o}rhold, Hans-Heinrich and Neher, Dieter}, title = {Comparative study of M3EH-PPV-based bilayer photovoltaic devices}, issn = {4018-4022}, doi = {10.1021/Ma0601991}, year = {2006}, abstract = {We have recently shown that efficient polymer solar cells can be fabricated by using a weakly soluble derivative of poly-p-vinylene (M3EH-PPV) as the electron donor. Here we present studies on bilayer devices using organic electron acceptors with varying LUMO levels and M3EH-PPV. It is found that the open-circuit voltage scales linearly with the LUMO level of the acceptor, reaching values as high as 1.5 V when cyano-substituted poly(p-phenyleneethynylene)-alt- poly(p-phenylenevinylene) copolymers are used. Further, we discovered that for an increasing number of triple bonds in the repeat unit of the acceptor polymer the device performance decreases with increasing thickness of the acceptor layer. Also, the quantum efficiency was smaller when using polymers with higher LUMO levels. Thus, further effort is needed to design optimum acceptor polymers for devices exhibiting large open-circuit voltage and high quantum efficiency}, language = {en} } @article{SchmidtHermanns2006, author = {Schmidt, Bernd and Hermanns, Jolanda}, title = {Ring closing metathesis of substrates containing more than two C-C-double bonds : rapid access to functionalized heterocycles}, year = {2006}, abstract = {In most cases where ring closing metathesis is applied to the synthesis of heterocycles, alpha,omega-dienes are used as precursors. If substrates containing more than two double bonds are subjected to a metathesis reaction, carba- or heterocycles bearing additional exocyclic alkene functionality result, or multiple ring closing processes occur. This offers interesting and potentially very useful synthetic perspectives. On the other hand, selectivity problems need to be addressed as the cyclization of substrates with more than two double bonds available for olefin metathesis may result in constitutional isomers or stereoisomers. This review highlights problems and opportunities evolving from ring closing metathesis of tri-, tetra-, and polyenes as a strategy for the selective synthesis of functionalized heterocycles. The chapter on RCM of trienes is subdivided according to the symmetry of the metathesis precursor. The following two chapters deal with the double or multiple RCM of tetra- or polyenes. These processes are further classified according to the preferred cyclization mode. Finally, the application of cascade or domino metathesis reactions to the synthesis of heterocycles will be discussed. These processes can be classified into those where exclusively C-C-double bonds take part in the metathesis reaction, and those where one or more C-C-triple bonds are involved}, language = {en} } @phdthesis{Kim2006, author = {Kim, Boo Geun}, title = {Radikalische Additionen an unges{\"a}ttigte Kohlenhydrate als Schl{\"u}sselschritt in der Synthese von Kohlenhydrat-C-Analoga}, address = {Potsdam}, pages = {113 Bl. : graph. Darst.}, year = {2006}, language = {de} } @article{Stoecklein2006, author = {St{\"o}cklein, Walter F. M.}, title = {Molecule-detective}, year = {2006}, abstract = {Biosensors are analytical devices incorporating biological material (receptor) intimately associated with or integrated within a physicochernical transducer. Advantages are the high selectivity for analyte detection. Examples given comprise the very successful commercial blood glucose biosensors made for the self-control by the diabetic patients. Other biosensors are part of an analytic system, including the sensor chips Of surface plasmon resonance or interferometry based devices, piezoelectric or reflectometric sensors capable of direct measurement of mass changes, and thermometric and other reagentless sensors. The development of nanotubes-based devices allows for significant enhancment of the signal-to-noise ratio of the biosensors. A milestone on the way towards miniaturization and parallelization of biosensors is the recently developed and prize-winning electronic DNA chip}, language = {en} } @article{YenesewKiplagatDereseetal.2006, author = {Yenesew, Abiy and Kiplagat, John T. and Derese, Solomon and Midiwo, Jacob O. and Kabaru, Jacques M. and Heydenreich, Matthias and Peter, Martin G.}, title = {Two unusual rotenoid derivatives, 7a-O-methyl-12a-hydroxydeguelol and spiro-13-homo-13-oxaelliptone, from the seeds of Derris trifoliata}, doi = {10.1016/j.phytochem.2006.01.002}, year = {2006}, abstract = {The crude methanol extract of the seeds of Derris trifoliata showed potent and dose dependent larvicidal activity against the 2nd instar larvae of Aedes aegypti. From this extract two unusual rotenoid derivatives, a rotenoloid (named 7a-O-methyl-12a-hydroxydeguelol) and a spirohomooxarotenoid (named spiro-13-homo-13-oxaelliptone), were isolated and characterised. In addition a rare natural chromanone (6,7-dimethoxy-4-chromanone) and the known rotenoids rotenone, tephrosin and dehydrodeguelin were identified. The structures were assigned on the basis of spectroscopic evidence. The larvicidal activity of the crude extract is mainly due to rotenone. (c) 2006 Elsevier Ltd. All rights reserved}, language = {en} } @article{HoldtMuellerKellingetal.2006, author = {Holdt, Hans-J{\"u}rgen and M{\"u}ller, Holger and Kelling, Alexandra and Drexler, Hans-Joachim and M{\"u}ller, Thomas and Schwarze, Thomas and Schilde, Uwe and Starke, Ines}, title = {Mercury(II) chloride and iodide complexes of dithia- and tetrathiacrown ethers}, issn = {0044-2313}, doi = {10.1002/zaac.200500281}, year = {2006}, abstract = {The complexes [(HgCl2)(2)((ch)(2)30S(4)O(6))] (1), [HgCl,(mn21S(2)O(5))] (2), [HgCl2(ch18S(2)O(4))] (3) and [HgI(meb12S(2)O(2))](2)[Hg2I6] (4) have been synthesized, characterized and their crystal structures were determined. In [(HgCl2)(2)((ch)(2)3OS(4)O(6))] two HgCl2 units are discretely bonded within the ligand cavity of the 30-membered dichinoxaline-tetrathia-30-crown-10 ((ch)(2)30S(4)O(6)) forming a binuclear complex. HgCl2 forms I : I "in-cavity" complexes with the 21-membered maleonitrile-dithia-21-crown-7(mn21S(2)O(5)) ligand and the 18-membered chinoxaline- dithia-18-crown-6 (ch18S(2)O(4)) ligand, respectively. The 12-membered 4-methyl-benzo-dithia-12-crown-4 (meb12S(2)O(2)) ligand gave with two equivalents HgI2 the compound [HgI(meb12S(2)O(2))](2)[Hg2I6]. In the cation [HgI(meb12S(2)O(2))](+) meb12S(2)O(2) forms with the cation HgI+ a half-sandwich complex}, language = {en} } @phdthesis{Klamroth2006, author = {Klamroth, Tillmann}, title = {Quantum mechanical simulations for correlated many-electron dynamics and electron induced processes at surfaces}, address = {Potsdam}, pages = {206 S. : graph. Darst.}, year = {2006}, language = {en} } @phdthesis{Kohlmeier2006, author = {Kohlmeier, Alexandra}, title = {Synthese und Eigenschaften supramolekularer polyphiler Blockmesogene}, address = {Potsdam}, pages = {116 S. : graph. Darst.}, year = {2006}, language = {de} } @phdthesis{Bellin2006, author = {Bellin, Ingo}, title = {Thermosensitive Polymer Networks with Two Different Shapes in Memory}, address = {Potsdam}, pages = {117 S. : graph. Darst.}, year = {2006}, language = {en} } @article{KammerMuellerGrunwaldetal.2006, author = {Kammer, Stefan and M{\"u}ller, Holger and Grunwald, Nicolas and Bellin, Anja and Kelling, Alexandra and Schilde, Uwe and Mickler, Wulfhard and Dosche, Carsten and Holdt, Hans-J{\"u}rgen}, title = {Supramolecular assemblies with honeycomb structures by pi-pi stacking of octahedral metal complexes of 1,12- diazaperylene}, issn = {1343-1948}, doi = {10.1002/ejic.200600092}, year = {2006}, abstract = {Homoleptic Ni-II and Fe-II complexes of the "large-surface" phenanthroline-type ligand 1,12-diazaperylene (dap), [Ni(dap)(3)](BF4)(2) (1) and [Fe(dap)(3)](PF6)(2) (2), respectively, were synthesized. In the crystal structure the complex cation [M(dap)(3)](2+) (M = Ni, Fe) exhibits C-3 symmetry and interacts with three other cations by pi-pi stacking. It forms a new metalla-supramolecular assembly with a honeycomb structure containing nanochannels running parallel to the crystallographic c axis. Aggregation by pi-pi stacking between metal complexes of "large-surface" ligands should give new perspectives for inorganic supramolecular chemistry.}, language = {en} } @article{KatterleHolzwarthJesorka2006, author = {Katterle, Martin and Holzwarth, Alfred R. and Jesorka, Aldo}, title = {A Heck-type coupling for the synthesis of novel bridged metallochlorin-fullerene C-60 dyads}, issn = {1434-193X}, doi = {10.1002/ejoc.200500494}, year = {2006}, abstract = {A short and convenient synthesis of metallochlorin-C-60 dyads based on a Heck-type hetero coupling at the 3(2) position of a chlorin is described. p-Bromobenzaldehyde was treated with Zn-metalated 13(2)- demethoxycarbonylmethylpheophorbide a, using a palladium acetate/LiCl catalyst mixture under phase-transfer conditions in DMF at 70 degrees C. The resulting asymmetric olefin was obtained in a high trans/cis ratio. The desired trans isomer was separated and subsequently transformed into a donor-acceptor dyad by a 1,3-dipolar cycloaddition to C-60 in the presence of sarcosine in refluxing toluene. The resulting dyads are expected to undergo efficient photoinduced electron transfer and can potentially be utilized in solar energy conversion devices.}, language = {en} } @article{HoldtMuellerPotteretal.2006, author = {Holdt, Hans-J{\"u}rgen and M{\"u}ller, Holger and Potter, Matthias and Kelling, Alexandra and Schilde, Uwe and Starke, Ines and Heydenreich, Matthias and Kleinpeter, Erich}, title = {The first sandwich complex with an octa(thioether) coordination sphere : Bis(maleonitrile-tetrathia-12-crown- 4)silver(I)}, issn = {1434-1948}, doi = {10.1002/ejic.200501109}, year = {2006}, abstract = {The new tetrathiacrown ethers maleonitrile-tetrathia-12-crown-4 (mn12S(4)) and maleonitrile-tetrathia-13-crown- 4 (mn13S(4)) have been prepared and characterised by X-ray crystallographic analysis. These crown ethers form 2:1, 3:2 and 1: 1 complexes with AgY (Y = BF4, PF6). The crystal structures of [Ag(mn12S(4))(2)]BF4 (3a), [Ag(mn13S(4))(2)]BF4 (4a) and [Ag-2(mn13S(4))(3)](PF6)(2) (6b) have been determined. Compound 3a contains the centrosymmetric sandwich complex cation [Ag(mn12S(4))(2)](+) where each mn12S(4) ligand is coordinated to the Ag centre in an endo manner through all four S atoms. The 2:1 complex [Ag(mn12S(4))(2)](+) is the first sandwich complex with a tetrathiacrown ether and the first complex with an octa(thioether) coordination sphere. The crystal structure of compound 4a also reveals a 2:1 complex. This complex, [Ag(mnl3S(4))(2)](+), exhibits a half-sandwich structure. One mn13S(4) ligand coordinates to Ag+ by all four S donor atoms and the other 13S(4) crown by only one S atom. Compound 6b contains a dinuclear Ag complex. The Ag complexes 3a,b-8a,b were also studied by electrospray ionisation mass spectrometry. Collision-induced dissociation (CID) was used to compare the relative stability of 2:1 complexes [AgL2]+ and 1:1 complexes [AgL](+) (L = mn12S(4), mn13S(4)). The C-13 NMR chemical shifts of 2:1 and 1:1 Ag complexes and their corresponding free ligands were also estimated and compared. The free energy of the barrier of ring inversion (Delta G(double dagger)) for [Ag(mn12S(4))(2)](+) was determined to be 64 kJmol(-1).}, language = {en} } @article{HeydenreichKochKlodetal.2006, author = {Heydenreich, Matthias and Koch, Andreas and Klod, Sabrina and Szatmari, Istvan and Fulop, Ferenc and Kleinpeter, Erich}, title = {Synthesis and conformational analysis of naphth[1', 2':5,6][1,3]oxazino[3,2-c][1,3]benzoxazine and naphth[1', 2':5,6][1,3]oxazino[3,4-c][1,3]benzoxazine derivatives}, series = {Tetrahedron}, volume = {62}, journal = {Tetrahedron}, number = {48}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0040-4020}, doi = {10.1016/j.tet.2006.09.037}, pages = {11081 -- 11089}, year = {2006}, abstract = {A new functional group, the hydroxy group, was inserted into a Betti base by reaction with salicylaldehyde, and the naphthoxazine derivatives thus obtained were converted by ring-closure reactions with formaldehyde, acetaldehyde, propionaldehyde or phosgene to the corresponding naphth[1',2':5,6][1,3]oxazino[3,2-c][1,3]benzoxazine derivatives. Further, the conformational analysis of these polycyclic compounds by NMR spectroscopy and an accompanying molecular modelling are reported; especially, both quantitative anisotropic ring current effects of the aromatic moieties in these compounds and steric substituent effects were employed to determine the stereochemistry of the naphthoxazinobenzoxazine derivatives.}, language = {en} } @article{StrehmelLaschewskyWetzel2006, author = {Strehmel, Veronika and Laschewsky, Andr{\´e} and Wetzel, Hendrik}, title = {Homopolymerization of a highly polar zwitterionic methacrylate in ionic liquids and its copolymerization with a non-polar methacrylate}, year = {2006}, abstract = {Free radical homo- and copolymerization of the highly polar 3-(N-[2-methacryloyloxyethyl]-N,N-dimethylammonio) propane sulfonate with the nonpolar n-butylmethacrylate was investigated in the ionic liquids 1-butyl-3-methyl imidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium hexafluoro phosphate, and compared to analogous polymerizations in standard solvents. Higher molar masses are obtained for the zwitterionic homopolymer when the polymerization is carried out in an ionic liquid compared to the classical reaction in water. Although homopolymerization of the sulfobetain monomer as well as of n-butylmethacrylate results in phase separation during the polymerization process, copolymerization of a stoichiometric ratio of the two monomers in the ionic liquids produced transparent gels indicating that no macrophase separation occurs. The use of ionic liquids as reaction medium improved the copolymerization behavior of the two methacrylates significantly. Whereas only minor amounts of n-butyl methacrylate were incorporated in the copolymer when synthesized in acetonitrile, the content of the non-polar monomer units in the zwitterionic copolymer approached increasingly its content in the polymerization mixture when ionic liquids were employed as solvents}, language = {en} } @article{HayerdeHalleuxKoehleretal.2006, author = {Hayer, Anna and de Halleux, Veronique and K{\"o}hler, Anna and El-Garoughy, Abdel and Meijer, E. W. and Barbera, Joaquin and Tant, Julien and Levin, Jeremy and Lehmann, Matthias and Gierschner, Johannes and Cornil, Jerome and Geerts, Yves Henri}, title = {Highly fluorescent crystalline and liquid crystalline columnar phases of pyrene-based structures}, issn = {1520-6106}, doi = {10.1021/Jp0573689}, year = {2006}, abstract = {A concept for highly ordered solid-state structures with bright fluorescence is proposed: liquid crystals based on tetraethynylpyrene chromophores, where the rigid core is functionalized with flexible, promesogenic alkoxy chains. The synthesis of this novel material is presented. The therniotropic properties are studied by means of differential scanning calorimetry (DSC), cross-polarized optical microscopy (POM), and X-ray diffraction. The mesogen possesses an enantiotropic Col(h) phase over a large temperature range before clearing. The material is highly fluorescent in solution and, most remarkably, in the condensed state, with a broad, strongly red shifted emission. Fluorescence quantum yields (Phi(F)) have been determined to be 70\% in dichloromethane solution and 62\% in the solid state. Concentration- and temperature-dependent absorption and emission studies as well as quantum-chemical calculations on isolated molecules and dimers are used to clarify the type of intermolecular interactions present as well as their influence on the fluorescence quantum yield and spectral properties of the material. The high luminescence efficiency in the solid state is ascribed to rotated chromophores, leading to an optically allowed lowest optical transition}, language = {en} } @article{KoetzAndresKosmellaetal.2006, author = {Koetz, Joachim and Andres, S. and Kosmella, Sabine and Tiersch, Brigitte}, title = {BaSO4 nanorods produced in polymer-modified bicontinuous microemulsions}, issn = {0927-6440}, doi = {10.1163/156855406777408629}, year = {2006}, abstract = {The influence of the water soluble polymer poly(ethylene glycol) (PEG) on structure formation in the quasiternary system sodium dodecylsulfate (SDS)/pentanol-xylene/water was checked by means of conductometry, rheology, and micro differential calorimetry. The polymer induces the formation of an isotropic phase channel between the o/w and w/o microemulsion. The transition from the normal as well as from the inverse micellar to the bicontinuous phase range can be detected by conductometry, rheology as well as micro-DSC. As a result of polymer-surfactant interactions, the spontaneous curvature of the surfactant film is changed and a sponge phase is formed. The bicontinuous phase is characterized by a moderate shear viscosity, a Newtonian flow behaviour, and the disappearence of interphasal water in the heating curve of the micro-DSC. When the polymer-modified bicontinuous phase is used as a template phase for the nanoparticle formation, spherical BaSO4 nanoparticles were formed. During the following solvent evaporation process the primarily formed spherical nanoparticles aggregate to nanorods and triangular structures due to the non-restriction of the bicontinuous template phase in longitudinal direction}, language = {en} } @article{StarkeFuerstenbergMuelleretal.2006, author = {Starke, Ines and F{\"u}rstenberg, Sylvia and M{\"u}ller, Holger and Holdt, Hans-J{\"u}rgen and Kleinpeter, Erich}, title = {Electrospray mass spectrometric studies of the complexational behavior of maleonitrile thiacrown ethers with various metals}, doi = {10.1002/Rcm.2384}, year = {2006}, abstract = {Electrospray ionization was employed to study the mass spectrometric behavior of the maleonitrile tetrathiacrown ethers mn12S(4) (1) and mn13S(4) (2) and maleonitrile pentathiacrown ether mn15S(5) (3) and of their complexes with various metal salts (MX2, M=Pd, Pt, Ni, Co, Fe; X=Cl, CrCl3, Ni(BF4)(2), TIPF6 or Cd(NO3)(2)) and Cu(SO3CF3)(2). Both singly charged, [MXL](+) and [MXL2]+, and doubly charged complexes, [MLn](2+) (n = 2-5), were observed. The formation of the different complexes consisting of the transition metal ion, the counterion and the various crown ethers and their subsequent dissociation was also studied by collision-induced dissociation measurements which were also used to evaluate the relative stabilities of the complexes. It was found that the collisional voltages for the dissociation of the complexes were generally greater in the [MXL](+) complexes than in the corresponding [MXL2]+ complexes. Copyright (c) 2006 John Wiley \& Sons, Ltd}, language = {en} } @article{KleinpeterSchulenburg2006, author = {Kleinpeter, Erich and Schulenburg, Anja}, title = {Quantification of the push-pull effect in tolanes and a revaluation of the factors affecting the C-13 chemical shifts of the carbon atoms of the C=C triple bond}, issn = {0022-3263}, doi = {10.1021/Jo060199j}, year = {2006}, abstract = {Variously substituted tolanes were employed to show that the push-pull effect is also active in C equivalent to C triple bonds by the successful correlation of the occupation quotient pi*/pi of the pi orbital in resonance with the substituted phenyl moieties of tolanes versus the bond length of the C equivalent to C triple bond. In addition, the influences of the ortho phenyl ring substituents on the C-13 chemical shifts of the triple bond carbon atoms, which were estimated by Rubin et al.(4) to be "inapplicable for describing triple bond polarization", were re-evaluated, leading to the conclusion that, while anisotropic effects of ortho substituents are negligible, the steric ortho-substituent effects do in fact dominate the deviations obtained. A detailed theoretical NBO/NCS study has been employed to illuminate the facts of this case}, language = {en} } @article{GarnierLaschewsky2006, author = {Garnier, Sebastien and Laschewsky, Andr{\´e}}, title = {New amphiphilic diblock copolymers : surfactant properties and solubilization in their micelles}, issn = {0743-7463}, doi = {10.1021/La0600595}, year = {2006}, abstract = {Several series of amphiphilic diblock copolymers are investigated as macrosurfactants in comparison to reference low-molar-mass and polymeric surfactants. The various copolymers share poly(butyl acrylate) as a common hydrophobic block but are distinguished by six different hydrophilic blocks (one anionic, one cationic, and four nonionic hydrophilic blocks) with various compositions. Dynamic light scattering experiments indicate the presence of micelles over the whole concentration range from 10(-4) to 10 g(.)L(-1). Accordingly, the critical micellization concentrations are very low. Still, the surface tension of aqueous solutions of block copolymers decreases slowly but continuously with increasing concentration, without exhibiting a plateau. The longer the hydrophobic block, the shorter the hydrophilic block, and the less hydrophilic the monomer of the hydrophilic block is, the lower the surface tension is. However, the effects are small, and the copolymers reduce the surface tension much less than standard low-molar-mass surfactants. Also, the copolymers foam much less and even act as anti-foaming agents in classical foaming systems composed of standard surfactants. The copolymers stabilize O/W emulsions made of methyl palmitate as equally well as standard surfactants but are less efficient for O/W emulsions made of tributyrine. However, the copolymer micelles exhibit a high solubilization power for hydrophobic dyes, probably at their core-corona interface, in dependence on the initial geometry of the micelles and the composition of the block copolymers. Whereas micelles of copolymers with strongly hydrophilic blocks are stable upon solubilization, solubilization-induced micellar growth is observed for copolymers with moderately hydrophilic blocks}, language = {en} } @article{KlinkaBalentovaBernatetal.2006, author = {Klinka, Karel D. and Balentova, Eva and Bern{\´a}t, Juraj and Imrich, Jan and Vavrusova, Martina and Kleinpeter, Erich and Pihlaja, Kalevi and Koch, Andreas}, title = {Tautomerism, regioisomerism, and cyclization reactions of acridinyl thiosemicarbazides}, issn = {0022-152X}, doi = {10.1002/jhet.5570430317}, year = {2006}, abstract = {The regioselectivities of methyl- and phenylhydrazine with acridin-9-yl isothiocyanate (thus yielding thiosemicarbazides with acridine substituted on the urea-type side) were examined. Methythydrazine regioselectivity was high with the alpha-nitrogen atom overwhelmingly more nucleophilic than the beta-nitrogen atom; phenylhydrazine regioselectivity was poor but varied with the solvent and only in the case of ethanol was nucleophilic predominance of the alpha-nitrogen atom pronounced. Of note, whilst both phenyl thiosemicarbazides were present in solution only as spiro forms, the methyl product was present as an equilibrium mixture of open-chain and spiro thiosemicarbazides. Reactions on the NH2 blocked analogue of methyl acridin-9-ylthiosemicarbazide (1-isopropylidene-2- methylthiosemicarbazide) were also examined. Interestingly, present in the starting material itself was a structural motif of novelty wherein a triazolethione represented the major species of an equilibrium between cyclic and open-chain forms}, language = {en} } @article{SchildeErkKleinpeter2006, author = {Schilde, Uwe and Erk, {\c{C}}akil and Kleinpeter, Erich}, title = {The crystal and molecular structures of sodium and barium complexes of dibenzo-24-crown-8 ether}, doi = {10.1524/zkri.2006.221.3.231}, year = {2006}, abstract = {The sodium and barium isothiocyanate complexes of 6,7,9,10,12,13,20,21,23,24,26,27-dodecahydrodibenzo[b,n]- 1,4,7,10,13,16,19,22-octaoxacyclotetracosin (dibenzo-24-crown-8 ether = DB24C8) were synthesized and analyzed by X-ray diffraction. The sodium complex, [Na(DB24C8)(NCS)(H2O)] 1, crystallizes in the orthorhombic space group Fdd2 with 16 molecules in the unit cell. The coordination number of Na is 6 and the central ion is located in a distorted octahedric environment. Only four of the crown ether oxygen atoms are involved. The coordination polyhedron is completed by the isothiocanate anion and by a water molecule, which is stabilized by hydrogen bonds. The barium complex, [Ba(DB24C8)(NCS)(2)] 2, crystallizes in the trigonale space group P3(1)21 with 3 molecules in the unit cell. Crystallographic C-2 symmetry is observed for the complex. The coordination number of Ba is 10. Barium is coordinated with the eight oxygen atoms of the macrocyclic ligand and with two isothiocyanate anions. The absolute structure was estimated using the FLACK parameter}, language = {en} } @article{WalzBaumannKrachetal.2006, author = {Walz, Bernd and Baumann, Otto and Krach, Christian and Baumann, Arnd and Blenau, Wolfgang}, title = {The aminergic control of cockroach salivary glands}, year = {2006}, abstract = {The acinar salivary glands of cockroaches receive a dual innervation from the subesophageal ganglion and the stomatogastric nervous system. Acinar cells are surrounded by a plexus of dopaminergic and serotonergic varicose fibers. In addition, seroton-ergic terminals lie deep in the extracellulor spaces between acinar cells. Excitation-secretion coupling in cockroach salivary glands is stimulated by both dopamine and serotonin. These monoamines cause increases in the intracellular concentrations of cAMP and Ca2+. Stimulation of the glands by serotonin results in the production of a protein-rich saliva, whereas stimulation by dopamine results in saliva that is protein-free. Thus, two elementary secretary processes, namely electrolyte/water secretion and protein secretion, are triggered by different aminergic transmitters. Because of its simplicity and experimental accessibility, cockroach salivary glands have been used extensively as a model system to study the cellular actions of biogenic amines and to examine the pharmacological properties of biogenic amine receptors. In this review, we summarize current knowledge concerning the aminergic control of cockroach salivary glands and discuss our efforts to characterize Periplaneta biogenic amine receptors molecularly}, language = {en} } @article{KammKammSchmidtetal.2006, author = {Kamm, Birgit and Kamm, Michael and Schmidt, Matthias and Starke, Ines and Kleinpeter, Erich}, title = {Chemical and biochemical generation of carbohydrates from lignocellulose-feedstock (Lupinus nootkatensis) : quantification of glucose}, issn = {0045-6535}, doi = {10.1016/j.chemosphere.2005.03.073}, year = {2006}, abstract = {Different chemical and enzymatic methods were applied for the hydrolysis of main stems from Lupinus nootkatensis (harvest November 2002). The whole process (all steps) is based on the lignocellulose-feedstock biorefinery regime. The acid hydrolysis of L. was performed with concentrated hydrochloric acid; advantages in this process are exothermic hydrolysis and the possibility of acid recovery. Enzymatic hydrolysis achieved high yields of fermentable carbohydrates (regarding to input cellulose) with high selectivity. However, this way requires the generation of cellulose from L. by chemical pulping. Monosaccharide derivatives thus obtained were identified by their GC retention times and the corresponding MS fragmentation. Hexamethyldisilazane was used as derivatization reagent to prepare the trimethylsilyl derivatives of the carbohydrates and of the degradations products of cellulose from the different fractions. The glucose content was quantified by GC peak integration with respect to an internal standard.}, language = {en} } @article{DelormeDuboisGarnieretal.2006, author = {Delorme, Nicolas and Dubois, Monique and Garnier, Sebastien and Laschewsky, Andr{\´e} and Weinkamer, Richard and Zemb, Thomas and Fery, Andreas}, title = {Surface immobilization and mechanical properties of catanionic hollow faceted polyhedrons}, issn = {1520-1758}, doi = {10.1021/Jp054473+}, year = {2006}, abstract = {We report here for the first time on surface immobilization of hollow faceted polyhedrons formed from catanionic surfactant mixtures. We find that electrostatic interaction with the substrate dominates their adhesion behavior. Using polyelectrolyte coated surfaces with tailored charge densities, polyhedrons can thus be immobilized without complete spreading, which allows for further study of their mechanical properties using AFM force measurements. The elastic response of individual polyhedrons can be locally resolved, showing pronounced differences in stiffness between faces and vertexes of the structure, which makes these systems interesting as models for structurally similar colloidal scale objects such as viruses, where such effects are predicted but cannot be directly observed due to the smaller dimensions. Elastic constants of the wall material are estimated using shell and plate deformation models and are found to be a factor of 5 larger than those for neutral lipidic bilayers in the gel state. We discuss the molecular origins of this high stiffness}, language = {en} } @article{BeitzLaudienLoehmannsroebenetal.2006, author = {Beitz, Toralf and Laudien, Robert and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Kallies, Bernd}, title = {Ion mobility spectrometric investigation of aromatic cations in the gas phase}, issn = {1089-5639}, doi = {10.1021/Jp055335n}, year = {2006}, abstract = {In this work, ion mobility (IM) spectra of more than 50 aromatic compounds were recorded with a laser-based IM spectrometer at atmospheric pressure. IM spectra of PAH in the laser desorption experiment show a high complexity resulting from the occurrence of monomeric, dimeric, and oligomeric cluster ions. The mobilities of all compounds were determined in helium as drift gas. This allows the calculation of the diffusion cross sections (Omega(calc)) on the basis of the exact hard sphere scattering model and their comparison with the experimentally determined diffusion cross sections (Omega(exp)). Extended Omega(exp)/Omega(calc) and Omega(exp/)mass correlations were performed in order to gain insight into conformational properties of cationic alkyl benzenes and internal rotation of phenyl rings in aromatic ions. This is demonstrated with some examples, such as the evaluation of the dihedral angle of the ions of 9,10- diphenylanthracene, o- and m-terphenyl, and 1,2,3- and 1,3,5-triphenylbenzene. Furthermore, sandwich and T-structures of dimeric PAH cations are discussed. The analysis was extended to oligomeric ions with up to nine monomer units. Experimental evidence is presented suggesting the formation of pi-stacks with a transition toward modified pi-stacks with increasing cluster size. The distance between monomeric units in dimeric and oligomeric ions was obtained}, language = {en} } @article{KleinpeterRollaKochetal.2006, author = {Kleinpeter, Erich and Rolla, Nadja and Koch, Andreas and Taddei, Fernando}, title = {Hyperconjugation and the increasing bulk of OCOCX3 substituents in trans-1,4-disubstituted cyclohexanes destabilize the diequatorial conformer}, issn = {4393-4399}, doi = {10.1021/Jo0600858}, year = {2006}, abstract = {The trans diesters of 1,4-cyclohexanediol with a number of acetic acid analogues, CX3COOH, of varying steric hindrance and polarity (CX3 = Me, Et, iso-Pr, tert-Bu, CF3, CH2Cl, CHCl2, CCl3, CH2Br, CHBr2, CBr3) were synthesized, and the axial, axial/equatorial, equatorial conformational equilibria were studied by low-temperature H-1 NMR spectroscopy in CD2Cl2. The structures and relative energies of the axial, axial and equatorial, equatorial conformers were calculated at both the MP2/6-311G* and the MP2/6-311+G* levels of theory, and it was only by including diffuse functions that a good correlation of Delta G degrees(calcd) vs Delta G(exptl) could be obtained. Both the structures and the energy differences of the axial, axial and equatorial, equatorial conformers are discussed with respect to the established models of conformational analysis, viz., steric 1,3-diaxial and hyperconjugative interactions. Interestingly, the hyperconjugative interactions sigma(C-C)/sigma(C-H)->sigma*(C-O), together with a steric effect which also destabilizes the equatorial, equatorial conformers on increasing bulk of the substituents, proved to dominate the position of the conformational equilibria. In addition, the preference of the axial, axial conformers with respect to their equatorial, equatorial analogues was greater than expected from the conformational energies of the corresponding substituents in the monosubstituted cyclohexyl esters. The reason for this very interesting and unexpected result is also discussed}, language = {en} } @phdthesis{Robertson2006, author = {Robertson, Daniela}, title = {Polymermodifizierte Phospholipid : Vesikel als neuartige Templat-Phase}, address = {Potsdam}, pages = {129 Bl. : Ill., graph. Darst.}, year = {2006}, language = {de} } @phdthesis{Holzberger2006, author = {Holzberger, Anja}, title = {Bestimmung der Konformationen und der Komplexbildungstendenzen von Kronenverbindungen in L{\"o}sung unter kombiniertem Einsatz von Kernmagnetischer Resonanzspektriskopie und Molecular Modelling}, address = {Potsdam}, pages = {90 S. : graph. Darst.}, year = {2006}, language = {de} } @article{LaschewskyGarnierKirstenetal.2006, author = {Laschewsky, Andr{\´e} and Garnier, Sebastien and Kirsten, Juliane and Mertoglu, Murat and Skrabania, Katja and Lutz, Jean-Francois}, title = {Comb-like polymeric surfactants by combining block and graft copolymer architectures}, issn = {0065-7727}, year = {2006}, language = {en} } @phdthesis{Wattebled2006, author = {Wattebled, Laurent}, title = {Oligomeric surfactants as novel type of amphiphiles : structure - property relationships and behaviour with additives}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-12855}, school = {Universit{\"a}t Potsdam}, year = {2006}, abstract = {The properties of a series of well-defined new surfactant oligomers (dimers to tetramers)were examined. From a molecular point of view, these oligomeric surfactants consist of simple monomeric cationic surfactant fragments coupled via the hydrophilic ammonium chloride head groups by spacer groups (different in nature and length). Properties of these cationic surfactant oligomers in aqueous solution such as solubility, micellization and surface activity, micellar size and aggregation number were discussed with respect to the two new molecular variables introduced, i.e. degree of oligomerization and spacer group, in order to establish structure - property relationships. Thus, increasing the degree of oligomerization results in a pronounced decrease of the critical micellization concentration (CMC). Both reduced spacer length and increased spacer hydrophobicity lead to a decrease of the CMC, but to a lesser extent. For these particular compounds, the formed micelles are relatively small and their aggregation number decreases with increasing the degree of oligomerization, increasing spacer length and sterical hindrance. In addition, pseudo-phase diagrams were established for the dimeric surfactants in more complex systems, namely inverse microemulsions, demonstrating again the important influence of the spacer group on the surfactant behaviour. Furthermore, the influence of additives on the property profile of the dimeric compounds was examined, in order to see if the solution properties can be improved while using less material. Strong synergistic effects were observed by adding special organic salts (e.g. sodium salicylate, sodium vinyl benzoate, etc.) to the surfactant dimers in stoichiometric amounts. For such mixtures, the critical aggregation concentration is strongly shifted to lower concentration, the effect being more pronounced for dimers than for analogous monomers. A sharp decrease of the surface tension can also be attained. Many of the organic anions produce viscoelastic solutions when added to the relatively short-chain dimers in aqueous solution, as evidenced by rheological measurements. This behaviour reflects the formation of entangled wormlike micelles due to strong interactions of the anions with the cationic surfactants, decreasing the curvature of the micellar aggregates. It is found that the associative behaviour is enhanced by dimerization. For a given counterion, the spacer group may also induce a stronger viscosifying effect depending on its length and hydrophobicity. Oppositely charged surfactants were combined with the cationic dimers, too. First, some mixtures with the conventional anionic surfactant SDS revealed vesicular aggregates in solution. Also, in view of these catanionic mixtures, a novel anionic dimeric surfactant based on EDTA was synthesized and studied. The synthesis route is relatively simple and the compound exhibits particularly appealing properties such as low CMC and σCMC values, good solubilization capacity of hydrophobic probes and high tolerance to hard water. Noteworthy, mixtures with particular cationic dimers gave rise to viscous solutions, reflecting the micelle growth.}, language = {en} } @phdthesis{Hildebrandt2006, author = {Hildebrandt, Niko}, title = {Lanthanides and quantum dots : time-resolved laser spectroscopy of biochemical F{\"o}rster Resonance Energy Transfer (FRET) systems}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-12686}, school = {Universit{\"a}t Potsdam}, year = {2006}, abstract = {F{\"o}rster Resonance Energy Transfer (FRET) plays an important role for biochemical applications such as DNA sequencing, intracellular protein-protein interactions, molecular binding studies, in vitro diagnostics and many others. For qualitative and quantitative analysis, FRET systems are usually assembled through molecular recognition of biomolecules conjugated with donor and acceptor luminophores. Lanthanide (Ln) complexes, as well as semiconductor quantum dot nanocrystals (QD), possess unique photophysical properties that make them especially suitable for applied FRET. In this work the possibility of using QD as very efficient FRET acceptors in combination with Ln complexes as donors in biochemical systems is demonstrated. The necessary theoretical and practical background of FRET, Ln complexes, QD and the applied biochemical models is outlined. In addition, scientific as well as commercial applications are presented. FRET can be used to measure structural changes or dynamics at distances ranging from approximately 1 to 10 nm. The very strong and well characterized binding process between streptavidin (Strep) and biotin (Biot) is used as a biomolecular model system. A FRET system is established by Strep conjugation with the Ln complexes and QD biotinylation. Three Ln complexes (one with Tb3+ and two with Eu3+ as central ion) are used as FRET donors. Besides the QD two further acceptors, the luminescent crosslinked protein allophycocyanin (APC) and a commercial fluorescence dye (DY633), are investigated for direct comparison. FRET is demonstrated for all donor-acceptor pairs by acceptor emission sensitization and a more than 1000-fold increase of the luminescence decay time in the case of QD reaching the hundred microsecond regime. Detailed photophysical characterization of donors and acceptors permits analysis of the bioconjugates and calculation of the FRET parameters. Extremely large F{\"o}rster radii of more than 100 {\AA} are achieved for QD as acceptors, considerably larger than for APC and DY633 (ca. 80 and 60 {\AA}). Special attention is paid to interactions with different additives in aqueous solutions, namely borate buffer, bovine serum albumin (BSA), sodium azide and potassium fluoride (KF). A more than 10-fold limit of detection (LOD) decrease compared to the extensively characterized and frequently used donor-acceptor pair of Europium tris(bipyridine) (Eu-TBP) and APC is demonstrated for the FRET system, consisting of the Tb complex and QD. A sub-picomolar LOD for QD is achieved with this system in azide free borate buffer (pH 8.3) containing 2 \% BSA and 0.5 M KF. In order to transfer the Strep-Biot model system to a real-life in vitro diagnostic application, two kinds of imunnoassays are investigated using human chorionic gonadotropin (HCG) as analyte. HCG itself, as well as two monoclonal anti-HCG mouse-IgG (immunoglobulin G) antibodies are labeled with the Tb complex and QD, respectively. Although no sufficient evidence for FRET can be found for a sandwich assay, FRET becomes obvious in a direct HCG-IgG assay showing the feasibility of using the Ln-QD donor-acceptor pair as highly sensitive analytical tool for in vitro diagnostics.}, language = {en} } @phdthesis{Mauser2006, author = {Mauser, Tatjana}, title = {Multilayer capsules with stimuli-sensitive properties : pH-response and carbohydrate-sensing}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-12529}, school = {Universit{\"a}t Potsdam}, year = {2006}, abstract = {Polyelectrolyte microcapsules containing stimuli-responsive polymers have potential applications in the fields of sensors or actuators, stimulable microcontainers and controlled drug delivery. Such capsules were prepared, with the focus on pH-sensitivity and carbohydrate-sensing. First, pH-responsive polyelectrolyte capsules were produced by means of electrostatic layer-by-layer assembly of oppositely charged weak polyelectrolytes onto colloidal templates that were subsequently removed. The capsules were composed of poly(allylamine hydrochloride) (PAH) and poly(methacrylic acid) (PMA) or poly(4-vinylpyridine) (P4VP) and PMA and varied considerably in their hydrophobicity and the influence of secondary interactions. These polymers were assembled onto CaCO3 and SiO2 particles with diameters of ~ 5 µm, and a new method for the removal of the silica template under mild conditions was proposed. The pH-dependent stability of PAH/PMA and P4VP/PMA capsules was studied by confocal laser scanning microscopy (CLSM). They were stable over a wide pH-range and exhibited a pronounced swelling at the edges of stability, which was attributed to uncompensated positive or negative charges within the multilayers. The swollen state could be stabilized when the electrostatic repulsion was counteracted by hydrogen-bonding, hydrophobic interactions or polymeric entanglement. This stabilization made it possible to reversibly swell and shrink the capsules by tuning the pH of the solution. The pH-dependent ionization degree of PMA was used to modulate the binding of calcium ions. In addition to the pH-sensitivity, the stability and the swelling degree of these capsules at a given pH could be modified, when the ionic strength of the medium was altered. The reversible swelling was accompanied by reversible permeability changes for low and high molecular weight substances. The permeability for glucose was evaluated by studying the time-dependence of the buckling of the capsule walls in glucose solutions and the reversible permeability modulation was used for the encapsulation of polymeric material. A theoretical model was proposed to explain the pH-dependent size variations that took into account an osmotic expanding force and an elastic restoring force to evaluate the pH-dependent size changes of weak polyelectrolyte capsules. Second, sugar-sensitive multilayers were assembled using the reversible covalent ester formation between the polysaccharide mannan and phenylboronic acid moieties that were grafted onto poly(acrylic acid) (PAA). The resulting multilayer films were sensitive to several carbohydrates, showing the highest sensitivity to fructose. The response to carbohydrates resulted from the competitive binding of small molecular weight sugars and mannan to the boronic acid groups within the film, and was observed as a fast dissolution of the multilayers, when they were brought into contact with the sugar-containing solution above a critical concentration. It was also possible to prepare carbohydrate-sensitive multilayer capsules, and their sugar-dependent stability was investigated by following the release of encapsulated rhodamine-labeled bovine serum albumin (TRITC-BSA).}, language = {en} } @misc{EngelbrechtLauSalffneretal.2006, author = {Engelbrecht, Rainer and Lau, Steffen and Salffner, Katharina and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Fasergekoppelte NIR-Diodenlaser-Spektrometer zur simultanen und isotopen-aufgel{\"o}sten Messung von CO und CO2 : Anwendungen in Plasma-Diagnostik und Bodengasanalyse}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-12348}, year = {2006}, abstract = {Die Anwendung zweier {\"a}hnlicher fasergekoppelte Diodenlaser-Spektrometer-Systeme werden vorgestellt. Basis sind handels{\"u}bliche DFB-Laserdioden der optischen Kommunikationstechnik. Der faseroptische Aufbau, das Detektionsverfahren (2f Wellenl{\"a}ngenmodulations-Spektroskopie mit Balanced Receiver), Rauschverhalten und Detektionslimit werden diskutiert. Zur in-situ Plasma-Diagnostik von CO- und CO2-Konzentrationen in industriellen CO2-Lasern der Materialbearbeitung wurde eine Wellenl{\"a}nge von 1582 nm verwendet. Bei einem Gasdruck von 100 hPa und einer Absorptionswegl{\"a}nge von 14,9 cm wurden mit einer Laserdiode simultan CO- und CO2-Konzentrationen von 0\% bis 11\% im Gasgef{\"a}ß bei laufender Hochfrequenzgasentladung des CO2-Lasers zeitaufgel{\"o}st gemessen. Vorgestellt und diskutiert werden Aufbau und Eigenschaften des Spektrometers sowie die Ergebnisse der dynamischen Gasanalysen, die zu einer Verbesserung der Katalysator-Technik im CO2-Laser beigetragen haben.Mit isotopenaufgel{\"o}ster CO- und CO2-Spektroskopie k{\"o}nnen biologische Gasaustauschprozesse, z.B. in Gasen aus dem Erdboden untersucht werden. Hierzu wurde ein fasergekoppeltes feldtaugliches Diodenlaser-Spektrometer bei Wellenl{\"a}ngen um 1605 nm zur Messungder Isotopologe 12C16O, 13C16O, 12C18O und 12C16O2, 13C16O2, 12C18O16O aufgebaut. Die Messung erfolgt extraktiv in Langwegzellen mit unterschiedlichen Absorptionswegl{\"a}ngen von 100.9 m und 29.9 m. Es werden Kalibrationsmessungen zur Linearit{\"a}t und zur Pr{\"a}zision der Bestimmung der Isotopenverh{\"a}ltnisse sowie Wiederholungsmessungen zur Stabilit{\"a}t vorgestellt. Nachweisgrenzen von wenigen ppm konnten f{\"u}r die CO- und CO2-Isotopologen erhalten werden.}, language = {de} } @phdthesis{Note2006, author = {Note, Carine}, title = {Influence of hydrophobically modified polyelectrolytes on nanoparticle synthesis in self-organized systems and in water}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-11670}, school = {Universit{\"a}t Potsdam}, year = {2006}, abstract = {The formation of colloids by the controlled reduction, nucleation, and growth of inorganic precursor salts in different media has been investigated for more than a century. Recently, the preparation of ultrafine particles has received much attention since they can offer highly promising and novel options for a wide range of technical applications (nanotechnology, electrooptical devices, pharmaceutics, etc). The interest derives from the well-known fact that properties of advanced materials are critically dependent on the microstructure of the sample. Control of size, size distribution and morphology of the individual grains or crystallites is of the utmost importance in order to obtain the material characteristics desired. Several methods can be employed for the synthesis of nanoparticles. On the one hand, the reduction can occur in diluted aqueous or alcoholic solutions. On the other hand, the reduction process can be realized in a template phase, e.g. in well-defined microemulsion droplets. However, the stability of the nanoparticles formed mainly depends on their surface charge and it can be influenced with some added protective components. Quite different types of polymers, including polyelectrolytes and amphiphilic block copolymers, can for instance be used as protecting agents. The reduction and stabilization of metal colloids in aqueous solution by adding self-synthesized hydrophobically modified polyelectrolytes were studied in much more details. The polymers used are hydrophobically modified derivatives of poly(sodium acrylate) and of maleamic acid copolymers as well as the commercially available branched poly(ethyleneimine). The first notable result is that the polyelectrolytes used can act alone as both reducing and stabilizing agent for the preparation of gold nanoparticles. The investigation was then focused on the influence of the hydrophobic substitution of the polymer backbone on the reduction and stabilization processes. First of all, the polymers were added at room temperature and the reduction process was investigated over a longer time period (up to 8 days). In comparison, the reduction process was realized faster at higher temperature, i.e. 100°C. In both cases metal nanoparticles of colloidal dimensions can be produced. However, the size and shape of the individual nanoparticles mainly depends on the polymer added and the temperature procedure used. In a second part, the influence of the prior mentioned polyelectrolytes was investigated on the phase behaviour as well as on the properties of the inverse micellar region (L2 phase) of quaternary systems consisting of a surfactant, toluene-pentanol (1:1) and water. The majority of the present work has been made with the anionic surfactant sodium dodecylsulfate (SDS) and the cationic surfactant cetyltrimethylammonium bromide (CTAB) since they can interact with the oppositely charged polyelectrolytes and the microemulsions formed using these surfactants present a large water-in-oil region. Subsequently, the polymer-modified microemulsions were used as new templates for the synthesis of inorganic particles, ranging from metals to complex crystallites, of very small size. The water droplets can indeed act as nanoreactors for the nucleation and growth of the particles, and the added polymer can influence the droplet size, the droplet-droplet interactions, as well as the stability of the surfactant film by the formation of polymer-surfactant complexes. One further advantage of the polymer-modified microemulsions is the possibility to stabilize the primary formed nanoparticles via a polymer adsorption (steric and/or electrostatic stabilization). Thus, the polyelectrolyte-modified nanoparticles formed can be redispersed without flocculation after solvent evaporation.}, subject = {Mikroemulsion}, language = {en} } @phdthesis{Peikow2006, author = {Peikow, Dirk}, title = {Synthese und Glycosidasehemmung von Thio-analogen Kohlenhydraten}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-11192}, school = {Universit{\"a}t Potsdam}, year = {2006}, abstract = {Chitin ist ein Polysaccharid, welches aus N-Acetylglucosamin (GlcNAc) aufgebaut ist. Das Biopolymer kommt in der Natur in Invertebraten, Algen, Pilzen und Einzellern vor. Chitinasen hydrolysieren Chitin. Diese Enzyme sind essentiell f{\"u}r die Regulierung und Entwicklung von Arthropoden und Mikroorganismen. Sie fungieren in Pflanzen als Phytoalexine. Das verst{\"a}rkt das Interesse am Design neuer nat{\"u}rlicher und synthetischer Chitinase-inhibitoren, die als potentielle Insektizide, Fungizide, Antimalaria bzw. Antiasthmatika eingesetzt werden k{\"o}nnen. Ziel dieser Arbeit war die Synthese von neuen Thioglycosidanaloga von N-Acetyl-chitooligosacchariden und deren Untersuchung als Enzyminhibitoren. Die gesch{\"u}tzten 4-O-Tf-galactopyranosylthioglycoside wurden aus den korrespondierenden p-Methoxyphenylglycosiden von GlcNAc nach einer neuen Methode in einer Stufe hergestellt. Die Reaktion der galacto-Triflate mit 2-Acetamido-3,4,6-tri-O-acetyl-2-desoxy-1-thio-ß-D-glucopyranose in Gegenwart von Natriumhydrid und 15-Krone-5 in THF lieferte die Pseudo-Trisaccharide. Die Herstellung der Glycosyl-Thiazoline aus den entsprechenden p-Methoxyphenyl-glycosiden mit Lawesson's Reagenz ist nach einem neuen Reaktionsweg beschrieben wie auch die Synthese der Thioacetamide von GlcNAc-Oligomeren. Die Pseudo-Oligosaccharide wurden als Inhibitoren der Chitinasen von Serratia marcescens, Chironomus tentans, Acanthocheilonema viteae und Hevaea brasiliensis sowie der N-Acetyl-glucosaminidase von Chironomus tentans getestet. In einigen F{\"a}llen ergab sich eine Hemmung (IC50) im µM-Bereich.}, language = {de} } @phdthesis{Meyer2006, author = {Meyer, Matthias}, title = {PIPOX-PEP : kontrollierte Synthese und Aggregationsverhalten von Blockcopolymeren mit schaltbarer Hydrophilie}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-10832}, school = {Universit{\"a}t Potsdam}, year = {2006}, abstract = {Es wurden Poly(2-isopropyl-2-oxazolin)-Makroinitiatoren mit terminaler Ammoniumtrifluoracetat-Endgruppe synthetisiert, die anschließend f{\"u}r die Ammonium vermittelte NCA Polymerisation in NMP eingesetzt wurden. Die hierbei synthetisierten Poly(2-isopropyl-2-oxazolin)-block-poly(L-glutamat) (PIPOX-PEP) Blockcopolymere hatten eine Molekulargewichtsverteilung von 1,2 (UZ). Es wurde beobachtet, dass Poly(2-isopropyl-2-oxazolin) bei langen Zeiten oberhalb der LCST irreversibel sph{\"a}rische Strukturen bildet, die eine hierarchische Struktur besitzen und bei denen es sich m{\"o}glicherweise um "large compound micelles" handelt. PIPOX-PEP kann in w{\"a}sseriger L{\"o}sung bei langen Zeiten oberhalb der LCST "cottonball" Strukturen bilden. Die Aggregate wurden mittels Lichtstreuung, NMR und TEM charakterisiert. Im Rahmen der Arbeit wurden Strukturbildungsmodelle entwickelt.}, subject = {Polymer}, language = {de} } @phdthesis{Rettig2006, author = {Rettig, Hartmut Arnim}, title = {Methoden zur Synthese von definierten bioorganisch-synthetischen Blockcopolymeren}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-10293}, school = {Universit{\"a}t Potsdam}, year = {2006}, abstract = {Bioorganisch-synthetische Blockcopolymere sind sowohl f{\"u}r die Materialwissenschaft als auch f{\"u}r die Medizin hochinteressant. Diese Arbeit besch{\"a}ftigte sich mit neuen Synthesewegen f{\"u}r die Herstellung dieser Blockcopolymere. Zun{\"a}chst wurde der klassische Ansatz zur Herstellung eines Blockcopolymers {\"u}ber die Kupplung der beiden Segmente aufgegriffen. Hierzu wurde eine Methode zur Synthese von selektiv s{\"a}ureendfunktionalisierten Polyacrylaten mittels einer terminalen Benzylesterschutzgruppe vorgestellt. F{\"u}r die Herstellung von bioorganisch-synthetischen Blockcopolymeren mit einem gr{\"o}ßeren Polymersegment wurde daher ein anderer Syntheseansatz entwickelt. Dieser geht von einem funktionalisierten Oligopeptid aus, an dem durch Polymerisation das synthetische Segment aufgebaut wird. Der Aufbau erfolgte durch kontrolliert radikalische Polymerisation, um ein m{\"o}glichst definiertes Segment zu erhalten. Zun{\"a}chst wurde eine Synthese von Oligopeptid-Makroinitiatoren f{\"u}r die ATRP-Polymerisation durchgef{\"u}hrt. Es konnte gezeigt werden, dass in geeigneten polaren L{\"o}sungsmitteln (DMSO, DMF) eine Polymerisation mit dem ATRP-Oligopeptid-Makroinitiator erfolgreich ist. Allerdings treten w{\"a}hrend der Polymerisation Wechselwirkungen zwischen dem Katalysator und dem Oligopeptid auf. Eine Alternative bietet die RAFT-Polymerisation, da sie ohne einen Katalysator durchgef{\"u}hrt wird. Es gelang ausgehend von dem Oligopeptid-ATRP-Makroinitiator den {\"U}bertr{\"a}ger herzustellen. Die RAFT-Polymerisation mit einem Oligopeptid{\"u}bertr{\"a}ger stellt eine wichtige Methode f{\"u}r die Herstellung von bioorganisch-synthetischen Blockcopolymeren dar. Sie besitzt eine hohe Toleranz gegen{\"u}ber funktionellen Gruppen. Die so hergestellten Blockcopolymere sind frei von Verunreinigungen, wie z.B. {\"U}bergangsmetallen. Dabei l{\"a}ßt sich das Molekulargewicht des synthetischen Blocks bei einer Polydispersit{\"a}t um 1,2 gut kontrollieren.}, subject = {ATRP}, language = {de} } @phdthesis{Ba2006, author = {Ba, Jianhua}, title = {Nonaqueous synthesis of metal oxide nanoparticles and their assembly into mesoporous materials}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-10173}, school = {Universit{\"a}t Potsdam}, year = {2006}, abstract = {This thesis mainly consist of two parts, the synthesis of several kinds of technologically interesting crystalline metal oxide nanoparticles via nonaqueous sol-gel process and the formation of mesoporous metal oxides using some of these nanoparticles as building blocks via evaporation induced self-assembly (EISA) technique. In the first part, the experimental procedures and characterization results of successful syntheses of crystalline tin oxide and tin doped indium oxide (ITO) nanoparticles are reported. SnO2 nanoparticles exhibit monodisperse particle size (3.5 nm in average), high crystallinity and particularly high dispersibility in THF, which enable them to become the ideal particulate precursor for the formation of mesoporous SnO2. ITO nanoparticles possess uniform particle morphology, narrow particle size distribution (5-10 nm), high crystallinity as well as high electrical conductivity. The synthesis approaches and characterization of various mesoporous metal oxides, including TiO2, SnO2, mixture of CeO2 and TiO2, mixture of BaTiO3 and SnO2, are reported in the second part of this thesis. Mesoporous TiO2 and SnO2 are presented as highlights of this part. Mesoporous TiO2 was produced in the forms of both films and bulk material. In the case of mesoporous SnO2, the study was focused on the high order of the porous structure. All these mesoporous metal oxides show high crystallinity, high surface area and rather monodisperse pore sizes, which demonstrate the validity of EISA process and the usage of preformed crystalline nanoparticles as nanobuilding blocks (NBBs) to produce mesoporous metal oxides.}, subject = {Nanopartikel}, language = {en} } @phdthesis{Bhattacharryya2006, author = {Bhattacharryya, Saroj Kumar}, title = {Development of detector for analytical ultracentrifuge. - [korr. Fassung]}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-8215}, school = {Universit{\"a}t Potsdam}, year = {2006}, abstract = {In this work approaches for new detection system development for an Analytical Ultracentrifuge (AUC) were explored. Unlike its counterpart in chromatography fractionation techniques, the use of a Multidetection system for AUC has not yet been implemented to full extent despite its potential benefit. In this study we tried to couple existing fundamental spectroscopic and scattering techniques that are used in day to day science as tool for extracting analyte information. Trials were performed for adapting Raman, Light scattering and UV/Vis (with possibility to work with the whole range of wavelengths) to AUC. Conclusions were drawn for Raman and Light scattering to be a possible detection system for AUC, while the development for a fast fiber optics based multiwavelength detector was completed. The multiwavelength detector demonstrated the capability of data generation matching the literature and reference measurement data and faster data collection than that of the commercial instrument. It became obvious that with the generation of data in 3-D space in the UV/Vis detection system, the user can select the wavelength for the evaluation of experimental results as the data set contains the whole range of information from UV/Vis wavelength. The detector showed the data generation with much faster speed unlike the commercial instruments. The advantage of fast data generation was exemplified with the evaluation of data for a mixture of three colloids. These data were in conformity with measurement results from normal radial experiments and without significant diffusion broadening. Thus conclusions were drawn that with our designed Multiwavelength detector, meaningful data in 3-D space can be collected with much faster speed of data generation.}, subject = {Ultrazentrifuge}, language = {en} } @phdthesis{Gehrke2006, author = {Gehrke, Nicole}, title = {Retrosynthese von Perlmutt}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-7971}, school = {Universit{\"a}t Potsdam}, year = {2006}, abstract = {In dieser Arbeit ist es gelungen, die Bedeutung physikalisch-chemischer Mechanismen in der Biomineralisation gegen{\"u}ber der bisher angenommenen Dominanz spezifischer biomolekularer Erkennungsmechanismen aufzuzeigen. Dazu wurden drei Ans{\"a}tze verfolgt: Zum einen wurden Studien zur Calciumcarbonatkristallisation durchgef{\"u}hrt. Zum anderen wurde das Biomineral Perlmutt intensiv untersucht. Als drittes wurde ein Modellsystem entwickelt, mit dem k{\"u}nstliches Perlmutt synthetisiert und ein Mechanismus f{\"u}r die Perlmuttmineralisation vorgeschlagen werden konnte. Im ersten Schritt wurden in einem simplen Kristallisationsansatz komplexe Calciumcarbonat{\"u}berstrukturen ohne die Verwendung von Additiven synthetisiert. Es wurde gezeigt, daß diese durch orientierte Anlagerung von Nanopartikeln gebildet werden, bei der dipolare Felder eine wichtige Rolle zu spielen scheinen. Dieser Mechansimus war bislang f{\"u}r Calciumcarbonat unbekannt und erm{\"o}glicht die Synthese komplexer Kristallmorphologien, wodurch die Frage aufgeworfen wird, ob er bei der Biomineralbildung von Bedeutung sein kann. Durch Einsatz minimaler Mengen eines einfachen, synthetischen Additivs bei der Kristallisation wurden zu {\"U}berstrukturen angeordnete Aragonitpl{\"a}ttchen synthetisiert, die von einer wenige nm dicken Schicht aus amorphen Calciumcarbonat umgeben sind. Eine solche Schicht wurde auch bei den Aragonitpl{\"a}ttchen Perlmutts entdeckt (s.u.) und bietet m{\"o}glicherweise in verschiedenen Systemen eine Erkl{\"a}rung f{\"u}r die Stabilisierung der sonst metastabilen Aragonitphase. Im zweiten Schritt wurden bei der Untersuchung von nat{\"u}rlichem Perlmutt zwei bislang unbekannte Strukturmerkmale entdeckt: Es gibt Bereiche, die nicht aus den charakteristischen Pl{\"a}ttchen bestehen, sondern wesentlich weniger stark mineralisert sind. Die Mineralphase besteht in diesen Bereichen aus Nanopartikeln. Es wurde weiterhin gezeigt, daß die Aragonitpl{\"a}ttchen von einer wenige nm dicken Schicht aus amorphem Calciumcarbonat umgeben ist. Die g{\"a}ngigen Modelle der Perlmuttbildung sind mit diesen Beobachtungen nicht zu vereinbaren und somit zu hinterfragen. Dagegen deuten diese Ergebnisse ein Wachstum von Perlmutt {\"u}ber ACC-Nanopartikel an. Unter der Annahme der Bedeutung physikalisch-chemischer Mechanismen in der Biomineralisation wurde schließlich als dritter Schritt ein Ansatz zur in vitro-Retrosynthese von Biomineralien ausgehend von ihrer unl{\"o}slichen Matrix entwickelt. Mit diesem Ansatz ist es erstmals gelungen, k{\"u}nstliches Perlmutt auf synthetischem Wege herzustellen, das morphologisch nicht vom Original zu unterscheiden ist. Die existierenden Unterschiede konnten zeigen, daß der Mineralisationsprozeß nicht auf ein spezifisches Mikroumgebungssystem beschr{\"a}nkt, sondern "allgemeiner g{\"u}ltig"' sein muß. Bei der Retrosynthese gibt es zwei Schl{\"u}sselfaktoren: Zum einen die demineralisierte unl{\"o}sliche Perlmuttmatrix als dreidimensionales Ger{\"u}st f{\"u}r das k{\"u}nstliche Perlmutt, zum anderen amorphe Precursorpartikel, die die Mineralphase bilden. Es werden keinerlei Proteine oder andere Biomolek{\"u}le verwendet. Dieser Ansatz bietet die M{\"o}glichkeit, den Mineralisationsprozeß an einem in vitro-Modellsystem zu verfolgen, was f{\"u}r das in vivo-System, wenn {\"u}berhaupt, nur unter starken Einschr{\"a}nkungen m{\"o}glich ist. Es wurde gezeigt, daß das k{\"u}nstliche Perlmutt {\"u}ber die Mesoskalentransformation von ACC-Precursorn innerhalb der Matrix gebildet wird und als m{\"o}glicher Mechanismus bei der Biomineralisation von nat{\"u}rlichem Perlmutt diskutiert. Es konnte in der vorliegenden Arbeit konsequent gezeigt werden, daß die Imitation von Biomineralisationsprozessen in in vitro-Ans{\"a}tzen m{\"o}glich ist, wobei chemisch-physikalische Parameter dominieren. In zuk{\"u}nftigen Studien sollten einerseits die mechanischen Eigenschaften des k{\"u}nstlichen Perlmutts untersucht werden, wof{\"u}r sich in Vorversuchen im Rahmen dieser Arbeit die Nanoindentierung als geeignet herausgestellt hat. Es sollte gepr{\"u}ft werden, ob das hier ermittelte Prinzip zur Mineralisierung in der Materialentwicklung angewendet werden kann. Andererseits sollte die Retrosynthese auf andere Systeme ausgeweitet und in vivo-Studien durchgef{\"u}hrt werden, um die G{\"u}ltigkeit der vorgeschlagenen Mechanismen zu {\"u}berpr{\"u}fen.}, subject = {Biomineralisation}, language = {de} } @phdthesis{Nolte2006, author = {Nolte, Marc}, title = {Integration of freestanding polyelectrolyte multilayer membranes in larger scale structures}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-7355}, school = {Universit{\"a}t Potsdam}, year = {2006}, abstract = {Ultrathin, semi-permeable membranes are not only essential in natural systems (membranes of cells or organelles) but they are also important for applications (separation, filtering) in miniaturized devices. Membranes, integrated as diffusion barriers or filters in micron scale devices need to fulfill equivalent requirements as the natural systems, in particular mechanical stability and functionality (e.g. permeability), while being only tens of nm in thickness to allow fast diffusion times. Promising candidates for such membranes are polyelectrolyte multilayers, which were found to be mechanically stable, and variable in functionality. In this thesis two concepts to integrate such membranes in larger scale structures were developed. The first is based on the directed adhesion of polyelectrolyte hollow microcapsules. As a result, arrays of capsules were created. These can be useful for combinatorial chemistry or sensing. This concept was expanded to couple encapsulated living cells to the surface. The second concept is the transfer of flat freestanding multilayer membranes to structured surfaces. We have developed a method that allows us to couple mm2 areas of defect free film with thicknesses down to 50 nm to structured surfaces and to avoid crumpling of the membrane. We could again use this technique to produce arrays of micron size. The freestanding membrane is a diffusion barrier for high molecular weight molecules, while small molecules can pass through the membrane and thus allows us to sense solution properties. We have shown also that osmotic pressures lead to membrane deflection. That could be described quantitatively.}, subject = {Polyelektrolyt}, language = {en} }