TY  - JOUR
A1  - Coy, Ericsson D.
A1  - Jovanovic, Ljubisa
A1  - Sefkow, Michael
T1  - One-pot, Pd-catalyzed synthesis of trans-dihydrobenzofurans from o-aminophenols
N2  - An efficient and facile synthesis of trans-dihydrobenzofurans has been accomplished from o-aminophenols and phenylpropenes via a novel (one-pot) diastereoselective Pd-catalyzed oxyarylation reaction. The development and optimization of this method is described.
Y1  - 2010
UR  - http://pubs.acs.org/journal/orlef7
U6  - https://doi.org/10.1021/Ol100433z
SN  - 1523-7060
ER  - 
TY  - JOUR
A1  - Cywinski, Piotr J.
A1  - Idzik, Krzysztof R.
A1  - Cranfield, Charles G.
A1  - Beckert, Rainer
A1  - Mohr, Gerhard J.
T1  - Synthesis and sensing properties of a new carbazole fluorosensor for detection of abacavir
N2  - An abacavir-targeted fluorosensor based on the carbazole moiety has been synthesised and characterised. Recognition of abacavir is by base pairing between a uracil moiety present in the fluorosensor and the guanine moiety of abacavir. The fluorosensor exhibits five-fold quenching in the presence of 50M abacavir. Its sensitivity to abacavir is superior to that of other reverse transcriptase inhibitors: zidovudine, lamivudine and didanosine. Due to its high sensitivity, this fluorosensor has the potential to be used in multi-analyte array-based detection platforms as well as in microfluidics systems.
Y1  - 2010
UR  - http://www.informaworld.com/openurl?genre=journal&issn=1061-0278
U6  - https://doi.org/10.1080/10610278.2010.506541
SN  - 1061-0278
ER  - 
TY  - JOUR
A1  - de Araujo, Martha T.
A1  - Chacon, Eluzir P.
A1  - Carneiro, José W. de M.
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
T1  - Analysis of anisotropic effects in trinuclear metal carbonyl compounds by visualization of through-space NMR shielding
N2  - Through-space NMR shieldings were calculated for trinuclear metal-carbonyl compounds [M-3(CO)(12)] (M = Fe, Ru, Os), employing the nucleus-independent chemical shift approach. The through-space shieldings were visualized as a contour plot of iso-chemical shielding surfaces, and were applied to quantify the overall anisotropic effect of the carbonyl groups, as well as to identify the influence of the transition metal on the scopes of the corresponding anisotropy cones. The shielding surfaces show that the anisotropic effect of the carbonyl groups at equatorial positions changes depending on the metal. This effect was associated with pi-backdonation from the metal to the carbonyl groups in that position, in agreement with geometric data as well as calculated NMR parameters. Therefore, visualization of the through-space NMR shieldings of trinuclear metal-carbonyl compounds of group 8 is able to reflect the distinct arrangements of the carbonyl groups in these organometallic compounds.
Y1  - 2010
UR  - http://www.springerlink.com/content/100529
U6  - https://doi.org/10.1007/s00894-010-0662-3
SN  - 1610-2940
ER  - 
TY  - JOUR
A1  - de Espinosa, Lucas Montero
A1  - Meier, Michael A. R.
A1  - Ronda, Juan C.
A1  - Galiß, Marina
A1  - Cßdiz, Virginia
T1  - Phosphorus-containing renewable polyester-polyols via ADMET polymerization : synthesis, functionalization, and radical crosslinking
N2  - An alpha,omega-diene containing hydroxyl groups was prepared from plant oil-derived platform chemicals. The acyclic diene metathesis copolymerization (ADMET) of this monomer with a phosphorus-containing alpha,omega-cliene (DOPO II), also plant oil derived, afforded a series of phosphorus containing linear polyesters, which have been fully characterized. The backbone hydroxyls of these polyesters have been acrylated and radically polymerized to produce crosslinked polymers. The thermomechanical and mechanical properties, the thermal stability, and the flame retardancy of these phosphorus-based thermosets have been studied. Moreover, methyl 10-undecenoate has been used as chain stopper in selected ADMET polymerizations to study the effect of the prepolymers' molecular weights on the different properties of the final materials.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/journal/117932467/tocgroup
U6  - https://doi.org/10.1002/Pola.23887
SN  - 0887-624X
ER  - 
TY  - JOUR
A1  - Debatin, Franziska
A1  - Thomas, Arne
A1  - Kelling, Alexandra
A1  - Hedin, Niklas
A1  - Bacsik, Zoltan
A1  - Senkovska, Irena
A1  - Kaskel, Stefan
A1  - Junginger, Matthias
A1  - Müller, Holger
A1  - Schilde, Uwe
A1  - Jäger, Christian
A1  - Friedrich, Alwin
A1  - Holdt, Hans-Jürgen
T1  - In situ synthesis of an imidazolate-4-amide-5-imidate ligand and formation of a microporous zinc-organic framework with H2-and CO2-storage ability
N2  - Narrow channels with polar walls are the structural and functional features responsible for the high capacity of a zinc-organic framework based on an imidazolate-amide-imidate ligand for the uptake of H2 and CO2 (see structure: orange Zn, blue N, red O, dark gray C, light gray H). The rigid and stable chelating ligand was synthesized in situ by partial hydrolysis of a dicyanoimidazole compound.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/26737/
U6  - https://doi.org/10.1002/anie.200906188
SN  - 1433-7851
ER  - 
TY  - JOUR
A1  - Diehl, Christina
A1  - Cernoch, Peter
A1  - Zenke, Ingrid
A1  - Runge, Heike
A1  - Pitschke, Rona
A1  - Hartmann, Juergen
A1  - Tiersch, Brigitte
A1  - Schlaad, Helmut
T1  - Mechanistic study of the phase separation/crystallization process of poly(2-isopropyl-2-oxazoline) in hot water
N2  - The kinetics of the crystallization of thermoresponsive poly(2-isopropyl-2-oxazoline) in water and the time- dependent evolution of the morphology were examined using wide-angle X-ray scattering and conventional and cryogenic scanning electron microscopy. Results indicate that a temperature-induced phase separation produces a bicontinuous polymer network-like structure, which with the onset of crystallization collapses into individual particles (1-2 mu m in diameter) composed of a porous fiber mesh. Nanofibers then preferentially form at the particle surface, thus wrapping the microspheres like a ball of wool. The particle morphology is severely affected by changes in temperature and less by the initial polymer concentration.
Y1  - 2010
UR  - http://www.rsc.org/Publishing/Journals/sm/index.asp
U6  - https://doi.org/10.1039/C0sm00114g
SN  - 1744-683X
ER  - 
TY  - JOUR
A1  - Fandrich, Nick
A1  - Falkenhagen, Jana
A1  - Weidner, Steffen M.
A1  - Pfeifer, Dietmar
A1  - Staal, Bastiaan
A1  - Thuenemann, Andreas F.
A1  - Laschewsky, André
T1  - Characterization of new amphiphilic block copolymers of N-vinyl pyrrolidone and vinyl acetate, 1-analysis of copolymer composition, end groups, molar masses and molar mass distributions
N2  - New amphiphilic block copolymers consisting of N-vinyl pyrrolidone and vinyl acetate were synthesized via controlled radical polymerization using a reversible addition/fragmentation chain transfer (RAFT)/macromolecular design via the interchange of xanthates (MADIX) system. The synthesis was carried out in 1,4-dioxane as process solvent. In order to get conclusions on the mechanism of the polymerization the molecular structure of formed copolymers was analysed by means of different analytical techniques. C-13 NMR spectroscopy was used for the determination of the monomer ratios. End groups were analysed by means of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. This technique was also used to determine possible fragmentations of the RAFT end groups. By means of a combination of size exclusion chromatography, C-13 NMR and static light scattering molar mass distributions and absolute molar masses could be analysed. The results clearly show a non-ideal RAFT mechanism.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/journal/10003495/home
U6  - https://doi.org/10.1002/macp.200900466
SN  - 1022-1352
ER  - 
TY  - JOUR
A1  - Fandrich, Nick
A1  - Falkenhagen, Jana
A1  - Weidner, Steffen M.
A1  - Staal, Bastiaan
A1  - Thuenemann, Andreas F.
A1  - Laschewsky, André
T1  - Characterization of new amphiphilic block copolymers of N-vinylpyrrolidone and vinyl acetate, 2-chromatographic separation and analysis by MALDI-TOF and FT-IR coupling
N2  - PVP-block-PVAc block copolymers were synthesized by controlled radical polymerization applying a RAFT/MADIX system and were investigated by HPLC and by coupling of chromatography to FT-IR spectroscopy and MALDI-TOF MS. Chromatographic methods (LACCC and gradient techniques) were developed that allowed a separation of block copolymers according to their repeating units. The results of the spectroscopic and spectrometric analysis clearly showed transfer between radicals and process solvent. With the use of hyphenated techniques differences between main and side products were detected. In agreement with previously published results, obtained by NMR, SEC, static light scattering and MALDI- TOF MS, our data proved a non-ideal RAFT polymerization.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/journal/10003495/home
U6  - https://doi.org/10.1002/macp.201000044
SN  - 1022-1352
ER  - 
TY  - JOUR
A1  - Fechner, Mabya
A1  - Kosmella, Sabine
A1  - Koetz, Joachim
T1  - pH-dependent polyampholyte SDS interactions
N2  - Aqueous solutions of sodium dodecylsulfate (SDS) and poly(N,N'-diallyl-N,N'-dimethyl-alt-maleamic carboxylate) (PalH), a synthetic pH-tuneable polyelectrolyte (PEL), have been investigated by various techniques at different pH-values in absence and presence of NaCl. Potentiometric measurements using a surfactant-selective electrode indicate a quite complex interaction mechanism, which can be subdivided into different regions, where non-cooperative, electrostatic and cooperative hydrophobic interactions are of relevance. It was concluded, that in dependence on pH, conformational changes are responsible for the different interaction behavior in the NaCl-free system. Isothermal titration calorimetry (ITC) suggests that early stage hydrophobic binding is an exothermic process followed by electrostatic interactions, which are endothermic in nature and entropy driven. After NaCl addition the interaction mechanism becomes independent of pH due to a screening of (i) attractive interactions between the surfactant head groups and oppositely charged binding sites and (ii) repulsive forces between the surfactant head groups. Furthermore, the ITC investigations have revealed that after salt-addition surfactant micelles interact with the polymer instead of separated SDS molecules due to a depression of the CMC.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/00219797
U6  - https://doi.org/10.1016/j.jcis.2010.01.092
SN  - 0021-9797
ER  - 
TY  - JOUR
A1  - Fettke, Anja
A1  - Kramer, Markus
A1  - Kleinpeter, Erich
T1  - Lectin-bound conformations and non-covalent interactions of glycomimetic analogs of thiochitobiose
N2  - The bound conformations of five S-glycoside analogs of N,N'-diacetylchitobiose as well as their non- covalent interactions with two lectins, Phytolacca americana lectin (PAL) and wheat germ agglutinin (WGA), are reported. The conformations of the ligands were examined by trNOESY experiments and compared with the free, solution-state conformations and molecular modeling data obtained by force field calculations. In the case of S-aryl, S-glycosides with exclusively S-glycosidic linkages, similar free and lectin-bound conformations and non-covalent interactions were found, whereas they differed for mixed glycosides and for a thiazoline derivative. In addition, STD (saturation transfer difference) NMR magnetization transfer efficiencies at three different temperatures were determined and assessed with respect to the structural differences of these pseudosaccharides. The binding epitopes of each substrate with PAL and WGA were also determined.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/00404020
U6  - https://doi.org/10.1016/j.tet.2010.04.012
SN  - 0040-4020
ER  - 
TY  - JOUR
A1  - Fokou, Patrice A.
A1  - Meier, Michael A. R.
T1  - Studying and suppressing olefin isomerization side reactions during ADMET polymerizations
N2  - Olefin isomerization side reactions that occur during ADMET polymerizations were studied by preparing polyesters via ADMET and subsequently degrading these polyesters via transesterification with methanol. The resulting diesters, representing the repeating units of the previously prepared polyesters, were then analyzed by GC-MS. This strategy allowed quantification of the amount of olefin isomerization that took place during ADMET polymerization with second generation ruthenium metathesis catalysts. In a second step, it was shown that the addition of benzoquinone to the polymerization mixture prevented the olefin isomerization. Therefore, second generation ruthenium metathesis catalysts may now be used for the preparation of well-defined polymers via ADMET with very little isomerization, which was not possible before.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/10003270
U6  - https://doi.org/10.1002/marc.200900678
SN  - 1022-1336
ER  - 
TY  - JOUR
A1  - Fudickar, Werner
A1  - Linker, Torsten
T1  - Novel anthracene materials for applications in lithography and reversible photoswitching by light and air
N2  - Herein we demonstrate how the photoreaction between anthracenes and singlet oxygen (O-1(2)) is employed for applications either as photoswitch or as photoresist. Thin Films of the diaryl-alkyl anthracene 1 and the analogous oligomeric species 2 were it-radiated under photomasks to generate pattern structures composed of 1/1-O-2 and 2/2-O-2. Kelvin probe force microscopy (KPFM) provided a powerful and nondestructive method to image the pattern information. The following studies based on AFM, KPFM and contact angle measurements unfold that the two species 1 and 2 underwent different progressions after the imaging step. Degrading is observed for the monomeric compound 1 and the pattern eventually becomes recognizable in topography. In the oxidized state (1-O-2) the monomeric species remains physically stable. In consequence, the unreacted portion is removable and the remaining oxygenated form 1-O-2 is sufficiently stable to protect in underlying substrate (e.g., silver) from etching. Thus, the system 1/1-O-2 operates as photoresist. Oil the other hand, both states of the oligomier 2 remain stable. The Film is stable up to temperatures > 120 degrees C required to erase the pattern within acceptable time by cycloreversion. Anthracene 2 therefore acts as erasable and rewritable photochromic switch. The different behavior between 1 and 2 is explained by phase transitions which cause crystallization and finally ablation. Such transitions affect only the monomeric system 1/1-O-2 and not the oligomeric system 2/2-O-2. In conclusion, we designed two very similar materials based on diarylanthracenes, which can act either as a photoresist or as a rewritable photochrornic switch.
Y1  - 2010
UR  - http://pubs.acs.org/journal/langd5
U6  - https://doi.org/10.1021/La904299n
SN  - 0743-7463
ER  - 
TY  - JOUR
A1  - Füchsel, Gernot
A1  - Klamroth, Tillmann
A1  - Tremblay, Jean Christophe
A1  - Saalfrank, Peter
T1  - Stochastic approach to laser-induced ultrafast dynamics : the desorption of H-2/D-2 from Ru(0001)
N2  - The desorption of molecular hydrogen and deuterium induced by femtosecond-laser pulses is studied theoretically for the so-called DIMET (Desorption Induced by Multiple Electronic Transitions) process. These investigations are based on nonadiabatic classical Monte Carlo trajectory (CMCT) simulations on a ground and an excited state potential energy surface, including up to all six adsorbate degrees of freedom. The focus is on the hot-electron mediated energy transfer from the surface to the molecule and back, and the energy partitioning between the different degrees of freedom of the desorbing molecules. We first validate for a two-mode model comprising the desorption mode and the internal vibrational coordinate, the classical Monte Carlo trajectory method by comparing with Monte Carlo wavepacket (MCWP) calculations arising from a fully quantum mechanical open-system density matrix treatment. We then proceed by extending the CMCT calculations to include all six nuclear degrees of freedom of the desorbing molecule. This allows for a detailed comparison between theory and experiment concerning isotope effects, energy partitioning (translational, vibrational, and rotational energies and their distributions), and the dependence of these properties on the laser fluence. The most important findings are as follows. (i) CMCT agrees qualitative with the MCWP scheme. (ii) The basic experimental features such as the large isotope effect, the non-linear increase of yield with laser fluence, translationally hot products (in the order of several 1000 K) and non-equipartitioning of translational and internal energies (E-trans > E- vib > E-rot) are well reproduced. (iii) Predictions concerning a strong angular dependence of translational energies at large observation angles are also made.
Y1  - 2010
UR  - http://xlink.rsc.org/jumptojournal.cfm?journal_code=CP
U6  - https://doi.org/10.1039/C0cp00895h
SN  - 1463-9076
ER  - 
TY  - JOUR
A1  - Glatzel, Stefan
A1  - Badi, Nezha
A1  - Paech, Michael
A1  - Laschewsky, André
A1  - Lutz, Jean-Francois
T1  - Well-defined synthetic polymers with a protein-like gelation behavior in water
N2  - Homopolymers of N-acryloyl glycinamide were prepared by reversible addition-fragmentation chain transfer polymerization in water. The formed macromolecules exhibit strong polymer-polymer interactions in aqueous milieu and therefore form thermoreversible physical hydrogels in pure water, physiological buffer or cell medium.
Y1  - 2010
UR  - http://xlink.rsc.org/jumptojournal.cfm?journal_code=CC
U6  - https://doi.org/10.1039/C0cc00038h
SN  - 1359-7345
ER  - 
TY  - JOUR
A1  - Haase, Martin F.
A1  - Grigoriev, Dmitry
A1  - Moehwald, Helmuth
A1  - Tiersch, Brigitte
A1  - Shchukin, Dmitry G.
T1  - Encapsulation of amphoteric substances in a pH-sensitive pickering emulsion
N2  - Oil-in-water (o/w) Pickering emulsions stabilized with silica nanoparticles were prepared. Droplets of diethyl phthalate (oil phase) act as reservoirs for 8-hydroxyquinoline (8-HQ), which is used as (a) the hydrophobizing agent for the silica particles and (b) an encapsulated corrosion inhibitor for application in active feedback coatings. The hydrophobization of silica nanoparticles with 8-HQ is determined by the amount of this agent adsorbed on the nanoparticle surface. The latter is governed by the 8-HQ concentration in the aqueous phase, which in turn depends on the degree of protonation and fir ally on the pH. We observe three ranges of 8-HQ adsorption value with respect to nanoparticle hydophobization: (I) insufficient, (2) sufficient, and (3) excessive adsorption by the formation of an 8-HQ bilayer, where only case 2 leads to the necessary nanoparticle hydrophobization. Hence emulsions stable in a narrow pH window between pH 5.5 and 4.4 follow. Here functional molecules are sufficiently charged to compensate for the charges on silica nanoparticles to make them interfacially active and thus able to stabilize an emulsion but they are still to a large extent uncharged and thereby remain in the oil phase. The emulsification is reversible upon changing the pH to a value beyond the stability region.
Y1  - 2010
UR  - http://pubs.acs.org/journal/jpccck
U6  - https://doi.org/10.1021/Jp104052s
SN  - 1932-7447
ER  - 
TY  - JOUR
A1  - Harms, Stephan
A1  - Raetzke, Klaus
A1  - Faupel, Franz
A1  - Egger, Werner
A1  - Ravello, Lori Boyd de
A1  - Laschewsky, André
A1  - Wang, Weinan
A1  - Müller-Buschbaum, Peter
T1  - Free volume and swelling in thin films of poly(n-isopropylacrylamide) end-capped with n-butyltrithiocarbonate
N2  - The free volume in thin films of poly(N-isopropylacrylamid) end-capped with n-butyltrio-carbonate (nbc-PNIPAM) is probed with positron annihilation lifetime spectroscopy (PALS). The PALS measurements are performed as function of energy to obtain depth profiles of the free volume of nbc-PNIPAM films. The range of nbc-PNIPAM films with thicknesses from 40 to 200 nm is focused. With decreasing film thickness the free volume increases in good agreement with an increase in the maximum swelling capability of the nbc-PNIPAM films. Thus in thin hydrogel films the sorption and swelling behavior is governed by free volume.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/10003270
U6  - https://doi.org/10.1002/marc.201000067
SN  - 1022-1336
ER  - 
TY  - JOUR
A1  - Hass, Roland
A1  - Munzke, Dorit
A1  - Reich, Oliver
T1  - Inline-Partikelgroeßenmesstechniken fuer Suspensionen und Emulsionen
N2  - Die Inline-Bestimmung von Teilchengroeßen in Emulsionen und Suspensionen stellt besondere Anforderungen an die Messtechnik, da auch bei sehr hohen Teilchenkonzentrationen im Prozess verduennungsfreie Analytik betrieben werden soll. Neben einer Klaerung der Begriffe atline, online und in-line gibt der Beitrag eine Einfuehrung in die mathematische Beschreibung von Groeßenverteilungen. Als Inline-Techniken werden Photonendichtewellen-Spektroskopie, Focused Beam Reflectance Measurement und Ultraschallextinktion-Spektroskopie diskutiert und ihre sehr unterschiedlichen physikalischen Messprinzipien erlaeutert. Auch wird kurz erklaert, wie Teilchengroeßen aus den Messresultaten erhalten werden. Die wesentlichen Charakteristika dieser drei Methoden werden abschließend im ueberblick dargestellt.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/60500203/
U6  - https://doi.org/10.1002/cite.200900172
SN  - 0009-286X
ER  - 
TY  - JOUR
A1  - Kihampa, Charles
A1  - Nkunya, Mayunga H. H.
A1  - Joseph, Cosam C.
A1  - Magesa, Stephen M.
A1  - Hassanali, Ahmed
A1  - Heydenreich, Matthias
A1  - Kleinpeter, Erich
T1  - Antimosquito and antimicrobial clerodanoids and a chlorobenzoid from Tessmannia species
N2  - The clerodane diterpenoids trans-kolavenolic acid, 18-oxocleroda-3,13(E)-dien-15-oic acid, ent-(18- hydroxycarbonyl)-cleroda- 3,13(E)-dien-15-oate, 2-oxo-ent-cleroda-3,13(Z)-dien-15-oic acid and trans-2-oxo-ent-cleroda- 13(Z)-en-15-oic acid, and the chlorobenzenoid O-(3-hydroxy-4-hydroxycarbonyl-5-pentylphenyl)-3-chloro-4-methoxy-6-pentyl- 2-oxybenzoic acid were isolated from Tessmannia martiniana var pauloi and T. martiniana var matiniana. Structures were established based on interpretation of spectroscopic data. Some of the compounds exhibited significant antimosquito, antifungal and antibacterial activities.
Y1  - 2010
UR  - http://www.naturalproduct.us/
SN  - 1934-578X
ER  - 
TY  - JOUR
A1  - Kirpichenko, Svetlana V.
A1  - Kleinpeter, Erich
A1  - Shainyan, Bagrat A.
T1  - Conformational analysis of 3,3-dimethyl-3-silathiane, 2,3,3-trimethyl-3-silathiane and 2-trimethylsilyl-3,3- dimethyl-3-silathianeùpreferred conformers, barriers to ring inversion and substituent effec
N2  - The first conformational analysis of 3-silathiane and its C-substituted derivatives, namely, 3,3-dimethyl-3- silathiane 1, 2,3,3-trimethyl-3-silathiane 2, and 2-trimethylsilyl-3,3-dimethyl-3-silathiane 3 was performed by using dynamic NMR spectroscopy and B3LYP/6-311G(d,p) quantum chemical calculations. From coalescence temperatures, ring inversion barriers ;G; for 1 and 2 were estimated to be 6.3 and 6.8;kcal/mol, respectively. These values are considerably lower than that of thiacyclohexane (9.4;kcal/mol) but slightly higher than the one of 1,1- dimethylsilacyclohexane (5.5;kcal/mol). The conformational free energy for the methyl group in 2 (;;G°;=;0.35;kcal/mol) derived from low-temperature 13C NMR data is fairly consistent with the calculated value. For compound 2, theoretical calculations give ;E value close to zero for the equilibrium between the 2-Meax and 2-Meeq conformers. The calculated equatorial preference of the trimethylsilyl group in 3 is much more pronounced (;;G°;=;1.8;kcal/mol) and the predominance of the 3-SiMe3 eq conformer at room temperature was confirmed by the simulated 1H NMR and 2D NOESY spectra. The effect of the 2-substituent on the structural parameters of 2 and 3 is discussed.
Y1  - 2010
SN  - 0894-3230
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Boelke, Ute
A1  - Koch, Andreas
T1  - Subtle Trade-off Existing between (Anti)Aromaticity, Push-Pull Interaction, Keto-Enol Tautomerism, and Steric Hindrance When Defining the Electronic Properties of Conjugated Structures
Y1  - 2010
SN  - 1089-5639
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Boelke, Ute
A1  - Kreicberga, Jana
T1  - Quantification of the push-pull character of azo dyes and a basis for their evaluation as potential nonlinear optical materials
N2  - The push-pull characters of a large series of donor-acceptor substituted azo dyesù71 structures in allùhave been quantified by the NN double bond lengths, dNN, the 15N NMR chemical shift differences, ;;15N, of the two nitrogen atoms and the quotient, ;*/;, of the occupations of the antibonding ;*, and bonding ; orbitals of this partial NN double bond. The excellent correlation of the occupation quotients with the bond lengths strongly infers that both ;*/; and dNN are excellent parameters for quantifying charge alternation in the push-pull chromophore and the molecular hyperpolarizability, ;0, of these compounds. By this approach, selected compounds can be appropriately considered as viable candidates for nonlinear optical (NLO) applications.
Y1  - 2010
SN  - 0040-4020
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Koch, Andreas
T1  - Probing the exohedral magnetic properties of C20 derivatives by through space NMR shieldings (TSNMRS)
N2  - The through space NMR shieldings (TSNMRS) of dodecahedrane C20H20, of the isomeric hydrocarbons C20H12, of the ions C20H122+ and C20H122- of the fluxional fullerene C20 and of its dication C202+ have been ab initio calculated employing the NICS concept on basis of MP2/6-31G* geometries and visualized as iso-chemical-shielding/deshielding surfaces (ICSSs). TSNMRS values were employed to study the exohedral magnetic properties of the compounds studied. Hereby, the curved It-conjugation in the compounds studied could be quantified.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/01661280
U6  - https://doi.org/10.1016/j.theochem.2009.09.018
SN  - 0166-1280
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Koch, Andreas
T1  - Identification of benzenoid and quinonoid structures by through-space NMR shieldings (TSNMRS)
Y1  - 2010
SN  - 1089-5639
ER  - 
TY  - JOUR
A1  - Kramer, Markus
A1  - Kleinpeter, Erich
T1  - STD-DOSY : a new NMR method to analyze multi-component enzyme/substrate systems
N2  - A new approach to analyze multi-component Saturation Transfer Difference (STD) NMR spectra by combining the STD and the DOSY experiment is proposed. The resulting pulse sequence was successfully used to simplify an exemplary multi- component protein/substrate system by means of standard DOSY processing methods. Furthermore, the same experiment could be applied to calculate the ratio of saturated substrate molecules and its saturation rate in the case of competitive interactions. This ratio depends on the strength of this interaction between the substrates and the protein, so that this kind of information could be extracted from the results of our experiment.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/10907807
U6  - https://doi.org/10.1016/j.jmr.2009.11.007
SN  - 1090-7807
ER  - 
TY  - JOUR
A1  - Kuke, S.
A1  - Marmodee, Bettina
A1  - Eidner, Sascha
A1  - Schilde, Uwe
A1  - Kumke, Michael Uwe
T1  - Intramolecular deactivation processes in complexes of salicylic acid or glycolic acid with Eu(III)
N2  - The complexation of Eu(III) by 2-hydroxy benzoic acid (2HB) or glycolic acid (GL) was investigated using steady- state and time-resolved laser spectroscopy. Experiments were carried out in H2O as well as in D2O in the temperature range of View the MathML source. The Eu(III) luminescence spectra and luminescence decay times were evaluated with respect to the temperature dependence of (i) the luminescence decay time ;, (ii) the energy of the View the MathML source transition, (iii) the width of the View the MathML source transition, and (iv) the asymmetry ratio calculated from the luminescence intensities of the View the MathML source and View the MathML source transition, respectively. The differences in ligand-related luminescence quenching are discussed. Based on the temperature dependence of the luminescence decay times an activation energy for the ligand-specific non-radiative deactivation in Eu(III)-2HB or Eu(III)-GL complexes was determined. It is stressed that ligand-specific quenching processes (other than OH quenching induced by water molecules) need to be determined and considered in detail, in order to extract speciation- relevant information from luminescence data (e.g., estimation of the number of water molecules nH2O in the first coordination sphere of Eu(III)). In case of 2HB, conclusions drawn from the evaluation of the Eu(III) luminescence are compared with results of a X-ray structure analysis.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/article/pii/S1386142510000144
SN  - 0584-8539
ER  - 
TY  - JOUR
A1  - Lazareva, Nataliya F.
A1  - Shainyan, Bagrat A.
A1  - Kleinpeter, Erich
T1  - 4-Alkyl-2,2,6,6-tetramethyl-1,4,2,6-oxaazadisilinanes : synthesis, structure, and conformational analysis
N2  - 4-Alkyl-2,2,6,6-tetramethyl-1,4,2,6-oxaazadisilinanes RN[CH2Si(Me)2]2O [R = Me (1), i-Pr (2)] were synthesized by two methods which provided good yields up to 84%. Low temperature NMR study of compounds (1) and (2) revealed a frozen ring inversion with the energy barriers of 8.5 and 7.7 kcal/mol at 163 and 143 K, respectively, which is substantially lower than that for their carbon analog, N-methylmorpholine. DFT calculations performed on the example of molecule (1) showed that N-Meax conformer to exist in the sofa conformation with the coplanar fragment C-Si-O-Si-C, and its N-Meeq conformer in a flattened chair conformation.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/4569
U6  - https://doi.org/10.1002/Poc.1605
SN  - 0894-3230
ER  - 
TY  - JOUR
A1  - Schmidt, Bernd
A1  - Werner, Frank
A1  - Kelling, Alexandra
A1  - Schilde, Uwe
T1  - The reaction of 3,4-dihydro-2H-pyran with oxalyl chloride : formation and crystal structure analysis of an unexpected bicyclic product
N2  - 3,4-Dihydro-2-H-pyran and oxalyl chloride react, depending on the conditions, to keto esters, a pyran-3- carboxylic acid or derivatives thereof, or to an hitherto unknown bicyclic acetal containing a vinyl chloride moiety. The structure of the latter product has been unambiguously elucidated by single-crystal X-ray structure analysis. A mechanism for its formation is proposed.
Y1  - 2010
UR  - 1960 = dx.doi.org/10.1002/jhet.456
SN  - 0022-152X
ER  - 
TY  - JOUR
A1  - Schmidt, Roland
A1  - Hagen, Sebastian
A1  - Brete, Daniel
A1  - Carley, Robert
A1  - Gahl, Cornelius
A1  - Dokic, Jadranka
A1  - Saalfrank, Peter
A1  - Hecht, Stefan
A1  - Tegeder, Petra
A1  - Weinelt, Martin
T1  - On the electronic and geometrical structure of the trans- and cis-isomer of tetra-tert-butyl-azobenzene on Au(111)
N2  - Near edge X-ray absorption. ne structure and X-ray photoelectron spectroscopy have been employed to follow the reversible trans to cis isomerization of tetra-tert-butyl-azobenzene (TBA) adsorbed on Au(111). For one monolayer the molecules adopt an adsorption geometry characteristic of the trans-TBA isomer. The azo-bridge (N = N) is aligned nearly parallel to the surface and the phenyl rings exhibit a planar orientation with a small tilt angle <= 4 degrees with respect to the surface normal. Illumination of the molecular layer at 455 nm triggers the trans to cis isomerization which is associated with a pronounced change of the geometrical and electronic structure. The N1s to pi* transition of the central azo-bridge shifts by 0.45 +/- 0.05 eV to higher photon energy and the transition dipole moment (TDM) is tilted by 59 +/- 5 degrees with respect to the surface normal. The pi-system of one phenyl ring is tilted by about 30 degrees with respect to the surface normal, while the second ring plane is oriented nearly perpendicular to the surface. This reorientation is supported by a shift and broadening of the C-H resonances associated with the tert-butyl legs of the molecule. These findings support a configuration of the photo-switched TBA molecule on Au(111) which is comparable to the cis-isomer of the free molecule. In the photo-stationary state 53 +/- 5% of the TBA molecules are switched to the cis configuration. Thermal activation induces the back reaction to trans-TBA.
Y1  - 2010
UR  - http://pubs.rsc.org/en/content/articlehtml/2010/cp/b924409c
U6  - https://doi.org/10.1039/B924409c
SN  - 1463-9076
ER  - 
TY  - JOUR
A1  - Schwarz, Guntram
A1  - Bodenthin, Yves
A1  - Geue, Thomas
A1  - Koetz, Joachim
A1  - Kurth, Dirk G.
T1  - Structure and properties of dynamic rigid rod-like metallo-supramolecular polyelectrolytes in solution
N2  - Metal-ion-induced self-assembly in aqueous solution of the rigid ligand 1,4-bis(2,2':6',2 ''-terpyridine-4'-yl)benzene (1) with Fe(OAc)(2) and Ni(OAc)(2) is investigated with viscosimetry, SANS, and AFM. Ligand 1 forms extended, rigid-rod like metallo-supramolecular coordination polyeectrolytes (MEPEs) with a molar mass of up to 200 000 g mol(-1) under the Current experimental conditions. The molar mass depends oil concentration, stoichiometry, and time. By spin-coating MEPEs oil a solid surface, we call image the MEPEs in real space by AFM. Both AFM and SANS confirm the extended rigid-rod-type structure of the MEPEs. As a control experiment, we also studied the flexible ligand 1,3-bis[4'-oxa(2,2':6',2 ''-terpyridinyl)]propane (2). Ligand 2 does not form extended macro-assemblies but likely ringlike structures with three 10 four repeat units. Finally, we present it protocol to control the stoichiometry during self-assembly using conductometry, which is of paramount importance to obtain meaningful and reproducible results.
Y1  - 2010
UR  - http://pubs.acs.org/doi/full/10.1021/ma902057f
U6  - https://doi.org/10.1021/Ma902057f
SN  - 0024-9297
ER  - 
TY  - JOUR
A1  - Schwarz, Guntram
A1  - Sievers, Torsten K.
A1  - Bodenthin, Yves
A1  - Hasslauer, Ires
A1  - Geue, Thomas
A1  - Koetz, Joachim
A1  - Kurth, Dirk G.
T1  - The structure of metallo-supramolecular polyelectrolytes in solution and on surfaces
N2  - Metal ion induced self-assembly of the rigid ligand 1,4-bis(2,2':6',2 ''-terpyridine- 4'-yl) benzene (1) with Fe(II), Co(II), Ni(II) and Zn(II) acetate in aqueous solution results in extended, rigid- rod like metallosupramolecular coordination polyelectrolytes (MEPE-1). Under the current experimental conditions the molar masses range from 1000 g mol(-1) up to 500 000 g mol(-1). The molar mass depends on concentration, stoichiometry, metal-ion and time. In addition, we present viscosity measurements, small angle neutron scattering and AFM data. We introduce a protocol to precisely control the stoichiometry during self-assembly using conductometry. The protocol can be used with different terpyridine ligands and the above-mentioned metal ions and is of paramount importance to obtain meaningful and reproducible results. As a control experiment we studied the mononuclear 4'- (phenyl)2,2':6',2 ''-terpyridine (3) complex with Ni(II) and Zn(II) and the flexible ligand 1,3- bis[4'-oxa(2,2': 6',2 ''-terpyridinyl)] propane (2) with Ni(II) acetate (Ni-MEPE-2). This ligand does not form extended macroassemblies but likely ring-like structures with 3 to 4 repeat units. Through spin- coating of Ni-MEPE-1 on a solid surface we can image the MEPEs in real space by AFM. SANS measurements of Fe-MEPE-1 verify the extended rigid-rod type structure of the MEPEs in aqueous solution.
Y1  - 2010
UR  - http://pubs.rsc.org/en/content/articlehtml/2010/jm/b926783b
U6  - https://doi.org/10.1039/B926783b
SN  - 0959-9428
ER  - 
TY  - JOUR
A1  - Schwarze, Thomas
A1  - Dosche, Carsten
A1  - Flehr, Roman
A1  - Klamroth, Tillmann
A1  - Löhmannsröben, Hans-Gerd
A1  - Saalfrank, Peter
A1  - Cleve, Ernst
A1  - Buschmann, Hans-Jürgen
A1  - Holdt, Hans-Jürgen
T1  - Combination of a CT modulated PET and an intramolecular excimer formation to quantify PdCl2 by large fluorescence enhancement
N2  - The [6.6](9,10)anthracenophane 1 (Scheme 1) is a selective fluoroionophore for the detection of PdCl2 with a large fluorescence enhancement factor (I/I-0 > 250).
Y1  - 2010
UR  - http://pubs.rsc.org/en/content/articlehtml/2010/cc/b919973j
U6  - https://doi.org/10.1039/B919973j
SN  - 1359-7345
ER  - 
TY  - JOUR
A1  - Schwarze, Thomas
A1  - Dosche, Carsten
A1  - Flehr, Roman
A1  - Klamroth, Tillmann
A1  - Löhmannsröben, Hans-Gerd
A1  - Saalfrank, Peter
A1  - Cleve, Ernst
A1  - Buschmann, Hans-Jürgen
A1  - Holdt, Hans-Jürgen
T1  - Combination of a CT modulated PET and an intramolecular excimer formation to quantify PdCl2 by large fluorescence enhancement
Y1  - 2010
UR  - http://www.rsc.org/ej/CC/2010/b919973j.pdf
SN  - 1359-7345
ER  - 
TY  - JOUR
A1  - Schwarze, Thomas
A1  - Mickler, Wulfhard
A1  - Dosche, Carsten
A1  - Flehr, Roman
A1  - Klamroth, Tillmann
A1  - Löhmannsröben, Hans-Gerd
A1  - Saalfrank, Peter
A1  - Holdt, Hans-Jürgen
T1  - Systematic investigation of photoinduced electron transfer controlled by internal charge transfer and its consequences for selective PdCl2 coordination
N2  - Fluoroionophores of fluorophore-spacer-receptor format were prepared for detection of PdCl2 by fluorescence enhancement. The fluorophore probes 1-13 consist of a fluorophore group, in alkyl spacer and a dithiomaleonitrile PdCl2 receptor. First, varying the length of the alkylene spacer (compounds 1-3) revealed, dominant through-space pathway for oxidative photoinduced electron transfer (PET) in CH2-bridged dithiomaleonitrile fluoroionophores. Second. fluorescent probes 4-9 containing two anthracene or pyrene fragments connected through CH2 bridges to the dithiomaleonitrile unit were synthesized. Modulation of the oxidation potential (E-Ox) through electron-withdrawing or -donating groups on the anthracene moiety regulates file thermodynamic driving force for oxidative PET (Delta G(PET)) in bis(anthrylmethylthio)maleonitriles and therefore the fluorescence quantum yields (Phi(f)), too. The new concept was confirmed and transferred to pyrenyl ligands, and fluorescence enhancements (FE) greater than 3.2 in the presence of PdCl2 were achieved by 7 and 8 (FE=5.4 and 5.2). Finally, for comparison, monofluorophore ligands 10-13 were synthesized.
Y1  - 2010
UR  - http://onlinelibrary.wiley.com/doi/10.1002/chem.200902281/pdf
U6  - https://doi.org/10.1002/chem.200902281
SN  - 0947-6539
ER  - 
TY  - JOUR
A1  - Schwarze, Thomas
A1  - Mickler, Wulfhard
A1  - Dosche, Carsten
A1  - Flehr, Roman
A1  - Klamroth, Tillmann
A1  - Löhmannsröben, Hans-Gerd
A1  - Saalfrank, Peter
A1  - Holdt, Hans-Jürgen
T1  - Systematic investigation of photoinduced electron transfer controlled by internal charge transfer and its consequences for selective PdCl2 coordination
N2  - Fluoroionophores of fluorophore-spacer-receptor format were prepared for detection of PdCl2 by fluorescence enhancement. The fluorescent probes 1-13 consist of a fluorophore group, an alkyl spacer and a dithiomaleonitrile PdCl2 receptor. First, varying the length of the alkylene spacer (compounds 1-3) revealed a dominant through-space pathway for oxidative photoinduced electron transfer (PET) in CH2-bridged dithiomaleonitrile fluoroionophores. Second, fluorescent probes 4-9 containing two anthracene or pyrene fragments connected through CH2 bridges to the dithiomaleonitrile unit were synthesized. Modulation of the oxidation potential (EOx) through electron-withdrawing or -donating groups on the anthracene moiety regulates the thermodynamic driving force for oxidative PET (GPET) in bis(anthrylmethylthio)maleonitriles and therefore the fluorescence quantum yields (f), too. The new concept was confirmed and transferred to pyrenyl ligands, and fluorescence enhancements (FE) greater than 3.2 in the presence of PdCl2 were achieved by 7 and 8 (FE=5.4 and 5.2). Finally, for comparison, monofluorophore ligands 10-13 were synthesized.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/journal/26293/home
SN  - 0947-6539
ER  - 
TY  - JOUR
A1  - Schweizer, S.
A1  - Schuster, T.
A1  - Junginger, Matthias
A1  - Siekmeyer, Gerd
A1  - Taubert, Andreas
T1  - Surface modification of ickel/Titanium Alloy and Titanium Surfaces via a Polyelectrolyte Multilayer/Calcium Phosphate Hybrid Coating
N2  - The report shows that simple LbL deposition of positively charged chitosan and negatively charged heparin can be used to efficiently modify the native surface of both NiTi and Ti without any previous treatments. Moreover, mineralization of the polymer multilayers with calcium phosphate leads to surfaces with low contact angles around 70 and 20 degrees for NiTi and Ti, respectively. This suggests that a polymer multilayer/calcium phosphate hybrid coating could be useful for making NiTi or Ti implants that are at the same time antibacterial (via the chitosan), suppress blood clot formation (via the heparin), and favor fast endothelialization (via the improved surface hydrophilicity compared to the respective neat material).
Y1  - 2010
UR  - http://onlinelibrary.wiley.com/doi/10.1002/mame.200900347/pdf
U6  - https://doi.org/10.1002/mame.200900347
SN  - 1438-7492
ER  - 
TY  - JOUR
A1  - Senge, Mathias O.
A1  - Shaker, Yasser M.
A1  - Pintea, Monica
A1  - Ryppa, Claudia
A1  - Hatscher, Sabine S.
A1  - Ryan, Aoife
A1  - Sergeeva, Yulia
T1  - Synthesis of meso-substituted ABCD-Type porphyrins by functionalization reactions
N2  - Considerable progress has been made in recent years in the search for synthetic methods leading to functionalized porphyrins, especially for modification of either the beta- or meso positions. For the latter, total synthesis based on condensation methods or partial synthesis through functionalization of preformed porphyrin have emerged as possible methods. The increasing number of possible technical and medicinal applications for unsymmetrically meso-substituted porphyrins requires straightforward methods for the preparation of the so-called ABCD-porphyrins, i.e., porphyrins with up to four different meso substituents. Here, we describe new strategies for the synthesis of ABCD-type porphyrins based on porphyrin reactions with organolithium reagents and the use of Pd-catalyzed coupling reactions. With the whole repertoire of contemporary functionalization methods, a comprehensive analysis and comparison of the various strategies for A-, AB-, A(2)B-, ABC-, A(2)BC- and ABCD-type porphyrins is given. In addition, we report on the synthesis of new functionalized derivatives for some of these porphyrin classes. In practical terms and taking an applied-science- oriented approach, the synthesis of unsymmetrically meso-substituted porphyrins is best accomplished by a combination of well-developed condensation methods with subsequent functionalization. by organolithium compounds or transition-metal- catalyzed coupling protocols. The methods described are suitable for the preparation of porphyrins for many divergent applications ranging over amphiphilic porphyrins for photodynamic therapy, push-pull systems for optical applications and chiral systems useful in catalysis to donor-acceptor systems suitable for electron-transfer studies.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/27380/
U6  - https://doi.org/10.1002/ejoc.200901113
SN  - 1434-193X
ER  - 
TY  - JOUR
A1  - Shainyan, Bagrat A.
A1  - Moskalik, Mikail Yu
A1  - Starke, Ines
A1  - Schilde, Uwe
T1  - Formation of unexpected products in the attempted aziridination of styrene with trifluoromethanesulfonyl nitrene
N2  - The reaction of styrene with trifluoromethanesulfonyl nitrene generated from trifluoromethanesulfonamide in the system (t-BuOCl+NaI) results in the formation of trifluoro-N-[2-phenyl-2-(trifluoromethylsulfonyl) aminoethyl]methanesulfonamide, 1-pheny1-2-iodo-ethanol, and 2,5-diphenyl-1,4-bis(trifluoromethyl sulfonyl)piperazine rather than the expected product of aziridination, 2-phenyl-1-(trifluoromethylsulfonyl) aziridine. The mechanism of the reaction is discussed.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/00404020
U6  - https://doi.org/10.1016/j.tet.2010.08.070
SN  - 0040-4020
ER  - 
TY  - JOUR
A1  - Siegmann, Rebekka
A1  - Beuermann, Sabine
T1  - Individual rate coefficients for 1H,1H,2H,2H-tridecafluorooctyl methacrylate radical polymerizations
N2  - Kinetic data for radical polymerizations of 1H,1H,2H,2H-tridecafluorooctyl methacrylate (TDFOMA) in bulk is reported. Pulsed laser initiated polymerizations yield propagation rate coefficients, k(p), which are by a factor of 1.9 higher than methyl methacrylate k(p). The activation energy of TDFOMA k(p) is not significantly different from that of alkyl methacrylates. Chain-length averaged termination rate coefficients were estimated from chemically initiated polymerizations with in-line FT-NIR spectroscopic monitoring of monomer conversion. Up to 30% of monomer conversion TDFOMA termination rate coefficients are only slightly below MMA low conversion values. The result is suggested to be due to less interactions between the macroradicals compared to nonfluorinated systems.
Y1  - 2010
UR  - http://pubs.acs.org/journal/mamobx
U6  - https://doi.org/10.1021/Ma902653b
SN  - 0024-9297
ER  - 
TY  - JOUR
A1  - Siegmann, Rebekka
A1  - Jelicic, Aleksandra
T1  - Propagation and termination kinetics of PEGylated methacrylate radical polymerizations
N2  - Propagation and chain-length averaged termination rate coefficients, k(p) and <k(t)>, for radical polymerizations of methacrylates carrying poly(ethylene glycol) (PEG) units are reported. kp derived from pulsed laser initiated polymerizations in bulk, in organic solvents, and in ionic liquids follows the methacrylate-type family behavior. Contrary, diffusion controlled k(t) values obtained from chemically initiated polymerizations with in-line FT- NIR monitoring of monomer conversion are strongly affected by the PEG units in the ester group. Compared to alkyl methacrylates <k(t)> is unexpectedly high. Moreover, <k(t)> of poly(ethylene glycol) ethyl ether methacrylate shows a significant reduction in k(t) already at 15% conversion, whereas dodecyl methacrylate <k(t)> is constant up to at least 70% conversion.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/journal/10003495/home
U6  - https://doi.org/10.1002/macp.200900527
SN  - 1022-1352
ER  - 
TY  - JOUR
A1  - Skrabania, Katja
A1  - von Berlepsch, Hans
A1  - Böttcher, Christoph
A1  - Laschewsky, André
T1  - Synthesis of ternary, hydrophilic-lipophilic-fluorophilic block copolymers by consecutive RAFT polymerizations and their self-assembly into multicompartment micelles
N2  - Linear amphiphilic diblock and ternary triblock copolymers were synthesized by the RAFT method in three Successive Steps, using oligo(ethylene oxide) monomethyl ether acrylate, butyl or 2-ethylhexyl acrylate, and 1H, 1H, 2H, 2H-perfluorodecyl acrylate. The diblock and the triblock copolymers, which consist of a hydrophilic, a lipophilic, and a fluorophilic block, self-assemble in water into spherical micellar aggregates. Imaging by cryogenic transmission electron microscopy (cryo-TEM) revealed that the cores of the micellar aggregates made from these "triphilic" copolymers undergo local phase separation to form various ultrastructures, which depend sensitivity on the given block sequence. While the sequence hydrophilic-lipophilic-fluorophilic resulted in multicompartment cores with core-shell-corona morphology, the sequence lipophilic-hydrophilic-fluorophilic provided new "patched double micelle" and larger "soccer ball" structures.
Y1  - 2010
UR  - http://pubs.acs.org/journal/mamobx
U6  - https://doi.org/10.1021/Ma901913f
SN  - 0024-9297
ER  - 
TY  - JOUR
A1  - Starke, Ines
A1  - Kammer, Stefan
A1  - Holdt, Hans-Jürgen
A1  - Kleinpeter, Erich
T1  - Stability of disubstituted copper complexes in the gas phase analyzed by electrospray ionization mass spectrometry
N2  - A series of nitrogen ligand (L)/copper complexes of the type [(CuL)-L-I](+), [(CuL)-L-II(X)](+) and [(CuL2)-L- I](+) (X = Cl-, BF4-, acac(-), CH3COO- and SO3CF3-) was studied in the gas phase by electrospray ionization mass spectrometry. The following ligands (L) were employed: 1,12-diazaperylene (dap), 1,1'-bisiso-quinoline (bis), 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), 2,11-disubstituted 1,12-diazaperylenes (dap), 3,3'- disubstituted 1,1'-bisisoquinoline (bis), 5,8-dimethoxy-substituted diazaperylene (meodap), 6,6'-dimethoxy- substituted bisisoquinoline (meobis) and 2,9-dimethyl-1,10-phenanthroline (dmphen). Collision-induced decomposition measurements were applied to evaluate the relative stabilities of the different copper complexes. The influence of the spatial arrangement of the ligands, of the type of substituents and of the counter ion of the copper salts employed for the complexation was examined. Correlations were found between the binding constants of the [ML2](+) complexes in solution and the relative stabilities of the analogous complexes in the gas phase. Furthermore, complexation with the ligands 2,11-dialkylated 1,12-diazaperylenes [alkyl = ethyl (dedap) and isopropyl (dipdap)] was studied in the solvents CH3OH and CH3CN.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/4849
U6  - https://doi.org/10.1002/Rcm.4519
SN  - 0951-4198
ER  - 
TY  - JOUR
A1  - Strehmel, Veronika
A1  - Lungwitz, Ralf
A1  - Rexhausen, Hans
A1  - Spange, Stefan
T1  - Relationship between hyperfine coupling constants of spin probes and empirical polarity parameters of some ionic liquids
N2  - The polarity of 1-alkyl-3-methylimidazolium-based ionic liquids containing hexafluorophosphate, tetrafluoroborate, dicyanoimide, or bis(trifluoromethanesulfonyl) imide as anions and a variation of the alkyl-chain length of the cation are investigated by both solvatochromic dyes and spin probes. Two different polarity scales are used for discussion of the polarity of these ionic liquids. These polarity scales are the empirical Kamlet-Taft parameters alpha, beta, and pi* and the hyperfine coupling constants A(iso)(N-14) obtained for spin probes substituted either with an ammonio or a sulfate group at 4-position. The results show that both polarity scales are valid for description of the ionic liquid polarity although differences are found between the two polarity scales. The most clear trend is found in all ionic liquids investigated for the hydrogen-bond accepting ability (beta) and the hyperfine- coupling constant of the anionic spin probe, where both parameters increase for all ionic liquids investigated until an alkyl chain length of eight carbon atoms and keep constant at longer alkyl chains.
Y1  - 2010
UR  - http://rsc.org/Publishing/Journals/nj/
U6  - https://doi.org/10.1039/C0nj00253d
SN  - 1144-0546
ER  - 
TY  - JOUR
A1  - Strehmel, Veronika
A1  - Rexhausen, Hans
A1  - Strauch, Peter
T1  - 2,2,6,6-Tetramethylpiperidine-1-yloxyl bound to the imidazolium ion by an acetamido group for investigation of ionic liquids
N2  - New spin probes bearing the 2,2,6,6-tetramethylpiperidine-1-yloxyl covalently bound to the imidazolium ion via a methylene spacer and an amide group are synthesized. If the anion is bis(trifluoromethylsulfonylimide) instead of iodide, the new spin probe has a similar structure as that of an ionic liquid. Nevertheless, the new spin probes are useful tools to investigate ionic liquids.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/00404039
U6  - https://doi.org/10.1016/j.tetlet.2009.11.124
SN  - 0040-4039
ER  - 
TY  - JOUR
A1  - Strehmel, Veronika
A1  - Rexhausen, Hans
A1  - Strauch, Peter
T1  - Influence of imidazolium bis(trifluoromethylsulfonylimide)s on the rotation of spin probes comprising ionic and hydrogen bonding groups
N2  - The influence of the alkyl chain length in 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonylimide)s is studied to explore the rotation of piperidine-1-yloxyl derivatives substituted with either hydrogen bonding hydroxy group or ionic substituents, such as the cationic trimethylammonium or the anionic sulfate group placed at the 4 position. Structural variation of the ionic liquids results in differences of their viscosity influencing the rotation of the spin probes. The size of the average rotational correlation times of the spin probes dissolved in the ionic liquids depends further on the additional substituent in 4-position at these spin probes. The rotational correlation time exhibits a linear dependence on the ionic liquid viscosity in the case of the spin probe forming hydrogen bonding with the ionic liquids. In contrast to this, a deviation from the Stokes-Einstein behavior is found in the case of rotation of the charged spin probes in the 1-alkyl-3-methylimidazolium bis( trifluoromethylsulfonylimide) s substituted with a longer alkyl chain. This effect may be explained by phase separation on a molecular level between the charged part of the ionic liquid and the longer alkyl chains bound at the imidazolium ion. Although the neutral and the cationic spin probes show only a slight dependence between ionic liquid structure variation and the hyperfine coupling constants, structural effects cause changes in the hyperfine coupling constants in the case of the anionic spin probes. These probes strongly interact with the imidazolium ion.
Y1  - 2010
UR  - http://www.rsc.org/Publishing/Journals/CP/index.asp
U6  - https://doi.org/10.1039/B920586a
SN  - 1463-9076
ER  - 
TY  - JOUR
A1  - Strehmel, Veronika
A1  - Rexhausen, Hans
A1  - Strauch, Peter
A1  - Strehmer, Bernd
T1  - Temperature dependence of interactions between stable piperidine-1-yloxyl derivatives and a semicrystalline ionic liquid
N2  - The stable 2,2,6,6-tetramethylpiperidine-1-yloxyl and its derivatives with hydrogen-bond-forming (-OH, -OSO3H), anionic (-OSO3- bearing K+ or [K(18-crown-6)](+) as counter ion), or cationic (-N+-(CH3)(3) bearing I-, BF4-, PF6- or N- (SO2CF3)(2) as counter ion) substituents are investigated in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide over a wide temperature range. The temperature dependence of the viscosity of the ionic liquid is well described by the Vogel-Fulcher-Tammann equation. Interestingly, the temperature dependence of the rotational correlation time of the spin probes substituted with either a hydrogen-bond-forming group or an ionic substituent can be described using the Stokes-Einstein equation. In contrast, the temperature dependence of the rotational correlation time of the spin probe without an additional substituent at the 4-position to the nitroxyl group does not follow this trend. The activation energy for the mobility of the unsubstituted spin probe, determined from an Arrhenius plot of the spin-probe mobility in the ionic liquid above the melting temperature, is comparable with the activation energy for the viscous flow of the ionic liquid, but is higher for spin probes bearing an additional substituent at the 4-position. Quantum chemical calculations of the spin probes using the 6-31G+d method give information about the rotational volume of the spin probes and the spin density at the nitrogen atom of the radical structure as a function of the substituent at the spin probes in the presence and absence of a counter ion. The results of these calculations help in understanding the effect of the additional substituent on the experimentally determined isotropic hyperfine coupling constant.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/72514732/
U6  - https://doi.org/10.1002/cphc.200900977
SN  - 1439-4235
ER  - 
TY  - JOUR
A1  - Tiseanu, Carmen
A1  - Parvulescu, Vasile Ion
A1  - Cojocaru, Bogdan
A1  - Lorenz-Fonfria, Victor A.
A1  - Kumke, Michael Uwe
A1  - Gessner, Andre
A1  - Enculescu, Ion
T1  - Polymer-microporous host interactions probed by photoluminescence spectroscopy
N2  - Zeolites NaY and ZSM-5 were used as hosts for styrene polymerization after ion-exchange with europium ions. The parent and hybrid, polystyrene coated Eu-NaY (Eu-NaY/PS) and Eu-ZSM-5 (Eu-ZSM-5/PS) zeolites were investigated by using thermal analysis, SEM, PXRD, FT-IR, DR-UV/Vis, steady state and time-resolved photoluminescence spectroscopy. FT-IR spectra evidenced for the interaction between the zeolitic hosts and polystyrene while the PXRD spectra supported for the presence of the polymer inside the channels/pores of Eu-NaY/PS and Eu-ZSM-5/PS materials. The optical properties of Eu-NaY/PS and Eu-ZSM-5/PS were significantly changed relative to those of the parent zeolites, giving further evidence for the presence of polymer inside zeolites. An interesting case is presented by NaY zeolite: following styrene polymerization, the polymer interacted selectively with one of the two main species co-existing inside zeolite while for ZSM-5 a similar effect was not observed.
Y1  - 2010
UR  - http://www.rsc.org/Publishing/Journals/CP/index.asp
U6  - https://doi.org/10.1039/B922591a
SN  - 1463-9076
ER  - 
TY  - JOUR
A1  - Tiseanu, Carmen
A1  - Parvulescu, Vasile
A1  - Parvulescu, Victoria
A1  - Cotoi, Elena
A1  - Gessner, Andre
A1  - Kumke, Michael Uwe
A1  - Simon, Simion
A1  - Vasiliu, Florin
T1  - Structural and photoluminescence characterization of mesoporous silicon-phosphates
N2  - Two different types of mesoporous silicon-phosphate supports using different surfactants (a mixture of (CH3)(3)C13H27NBr with an organophosphorus coupling molecule (HO-PO(i-C3H7)(2)) and with a co-surfactant ((C2H5)(3)(C6H5)PCl), respectively) were synthesized. Trivalent europium (Eu) ions were immobilized via ion-exchange on these supports. The resulting materials were characterized using nitrogen adsorption isotherms at -196 degrees C, thermogravimetric analysis, SEM, TEM, FT-IR, PXRD, CP/MAS. (HSi)-H-1-Si-29 and P-31 NMR, DR-UV-vis as well as steady- state and time-resolved photoluminescence spectroscopy. The results evidenced that the co-polymerization of silicon and phosphorous yielded a unique morphology in these materials. Following calcination at 450 and 900 degrees C europium- exchanged silicon-phosphates with great surface area (BET=600-705 m(2) g(-1)) and 3.4 nm sized mesopores were obtained. The differences among the optical properties of the non-calcined europium materials such as the emission lifetimes, local environment at the europium sites or the relative contribution of the upper excited levels to the total photoluminescence were assigned to the surfactants used in the synthesis. Calcination of the silicon-phosphates at higher temperatures than 450 degrees C did not induce major changes in the structural properties: in contrast, photoluminescence properties of europium were markedly improved in terms of intensity and average lifetime.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/10106030
U6  - https://doi.org/10.1016/j.jphotochem.2010.07.015
SN  - 1010-6030
ER  - 
TY  - JOUR
A1  - Tremblay, Jean Christophe
A1  - Krause, Pascal
A1  - Klamroth, Tillmann
A1  - Saalfrank, Peter
T1  - Time-dependent response of dissipative electron systems
N2  - We present a systematic study of the influence of energy and phase relaxation on dynamic polarizability simulations in the linear response regime. The nonperturbative approach is based on explicit electron dynamics using short laser pulses of low intensities. To include environmental effects on the property calculation, we use the time- dependent configuration-interaction method in its reduced density matrix formulation. Both energy dissipation and nonlocal pure dephasing are included. The explicit treatment of time-resolved electron dynamics gives access to the phase shift between the electric field and the induced dipole moment, which can be used to define a useful uncertainty measure for the dynamic polarizability. The nonperturbative treatment is compared to perturbation theory expressions, as applied to a simple model system, the rigid H-2 molecule. It is shown that both approaches are equivalent for low field intensities, but the time-dependent treatment provides complementary information on the phase of the induced dipole moment, which allows for the definition of an uncertainty associated with the computation of the dynamic polarizability in the linear response regime.
Y1  - 2010
UR  - http://pra.aps.org/
U6  - https://doi.org/10.1103/Physreva.81.063420
SN  - 1050-2947
ER  - 
TY  - JOUR
A1  - Tremblay, Jean Christophe
A1  - Monturet, Serge
A1  - Saalfrank, Peter
T1  - Electronic damping of anharmonic adsorbate vibrations at metallic surfaces
N2  - The nonadiabatic coupling of an adsorbate close to a metallic surface leads to electronic damping of adsorbate vibrations and line broadening in vibrational spectroscopy. Here, a perturbative treatment of the electronic contribution to the lifetime broadening serves as a building block for a new approach, in which anharmonic vibrational transition rates are calculated from a position-dependent coupling function. Different models for the coupling function will be tested, all related to embedding theory. The first two are models based on a scattering approach with (i) a jellium-type and (ii) a density functional theory based embedding density, respectively. In a third variant a further refined model is used for the embedding density, and a semiempirical approach is taken in which a scaling factor is chosen to match harmonic, single-site, first-principles transition rates, obtained from periodic density functional theory. For the example of hydrogen atoms on (adsorption) and below (subsurface absorption) a Pd(111) surface, lifetimes of and transition rates between vibrational levels are computed. The transition rates emerging from different models serve as input for the selective subsurface adsorption of hydrogen in palladium starting from an adsorption site, by using sequences of infrared laser pulses in a laser distillation scheme.
Y1  - 2010
UR  - http://prb.aps.org/
U6  - https://doi.org/10.1103/Physrevb.81.125408
SN  - 1098-0121
ER  - 
TY  - JOUR
A1  - Tronci, Giuseppe
A1  - Neffe, Axel T.
A1  - Pierce, Benjamin Franklin
A1  - Lendlein, Andreas
T1  - An entropy-elastic gelatin-based hydrogel system
N2  - Gelatin is a non-immunogenic and degradable biopolymer, which is widely applied in the biomedical field e. g. for drug capsules or as absorbable hemostats. However, gelatin materials present limited and hardly reproducible mechanical properties especially in aqueous systems, particularly caused by the uncontrollable partial renaturation of collagen-like triple helices. Therefore, mechanically demanding applications for gelatin-based materials, such as vascular patches, i.e. hydrogel films that seal large incisions in vessel walls, and for induced autoregeneration, are basically excluded if this challenge is not addressed. Through the synthesis of a defined chemical network of gelatin with hexamethylene diisocyanate (HDI) in DMSO, the self-organization of gelatin chains could be hindered and amorphous gelatin films were successfully prepared having Young's moduli of 60-530 kPa. Transferring the crosslinking reaction with HDI and, alternatively, ethyl lysine diisocyanate (LDI), to water as reaction medium allowed the tailoring of swelling behaviour and mechanical properties by variation of crosslinker content while suppressing the formation of helices. The hydrogels had Young's moduli of 70-740 kPa, compressive moduli of 16-48 kPa, and degrees of swelling of 300-800 vol%. Test reactions investigated by ESI mass spectrometry allowed the identification and quantification of reaction products of the crosslinking reaction. The HDI crosslinked networks were stabilized by direct covalent crosslinks (ca. 10 mol%), supported by grafting (50 mol%) and blending of hydrophobic oligomeric chains. For the LDI- based networks, less crosslinked (3 mol%) and grafted species (5 mol%) and much higher amounts of oligomers were observed. The adjustable hydrogel system enables the application of gelatin-based materials in physiological environments.
Y1  - 2010
UR  - http://www.rsc.org/Publishing/Journals/jm/index.asp
U6  - https://doi.org/10.1039/C0jm00883d
SN  - 0959-9428
ER  -