TY - JOUR A1 - Poghosyan, Armen H. A1 - Arsenyan, Levon H. A1 - Gharabekyan, Hrant H. A1 - Falkenhagen, Sandra A1 - Koetz, Joachim A1 - Shahinyan, Aram A. T1 - Molecular dynamics simulations of inverse sodium dodecyl sulfate (SDS) micelles in a mixed toluene/pentanol solvent in the absence and presence of poly(diallyldimethylammonium chloride) (PDADMAC) JF - Journal of colloid and interface science N2 - We have performed a 15 ns molecular dynamics simulation of inverse sodium dodecyl sulfate (SDS) micelles in a mixed toluene/pentanol solvent in the absence and presence of a cationic polyelectrolyte, i.e. poly(diallyldimethylammonium chloride) (PDADMAC). The NAMD code and CHARMM force field were used. During the simulation time, the radii of SOS inverse micelles changed and the radii of the water droplets have been calculated. The behavior of SDS hydrocarbon chains has been characterized by calculating the orientation order parameter and the chain average length. The water droplet properties (water flow, water molecules displacement) have been examined. In summary the MD simulations indicate a more rigid and ordered surfactant film due to the formation of a polyelectrolyte palisade layer in full agreement with the experimental findings, e.g. the viscosity increase and shift of the percolation boundary. KW - Surfactant micelles KW - Molecular dynamics simulations KW - SDS Y1 - 2011 U6 - https://doi.org/10.1016/j.jcis.2011.01.091 SN - 0021-9797 VL - 358 IS - 1 SP - 175 EP - 181 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Wellert, Stefan A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Richardt, Andre A1 - Lapp, Alain A1 - Holderer, Olaf A1 - Gaeb, Juergen A1 - Blum, Marc-Michael A1 - Schulreich, Christoph A1 - Stehle, Ralf A1 - Hellweg, Thomas T1 - The DFPase from Loligo vulgaris in sugar surfactant-based bicontinuous microemulsions structure, dynamics, and enzyme activity JF - European biophysics journal : with biophysics letters ; an international journal of biophysics N2 - The enzyme diisopropyl fluorophosphatase (DFPase) from the squid Loligo vulgaris is of great interest because of its ability to catalyze the hydrolysis of highly toxic organophosphates. In this work, the enzyme structure in solution (native state) was studied by use of different scattering methods. The results are compared with those from hydrodynamic model calculations based on the DFPase crystal structure. Bicontinuous microemulsions made of sugar surfactants are discussed as host systems for the DFPase. The microemulsion remains stable in the presence of the enzyme, which is shown by means of scattering experiments. Moreover, activity assays reveal that the DFPase still has high activity in this complex reaction medium. To complement the scattering experiments cryo-SEM was also employed to study the microemulsion structure. KW - Dynamic light scattering KW - Neutron spin echo KW - Microemulsion KW - Enzyme catalysis KW - SANS KW - Protein structure Y1 - 2011 U6 - https://doi.org/10.1007/s00249-011-0689-0 SN - 0175-7571 VL - 40 IS - 6 SP - 761 EP - 774 PB - Springer CY - New York ER - TY - JOUR A1 - Antoniou, Stella A1 - Pashalidis, Ioannis A1 - Gessner, Andre A1 - Kumke, Michael Uwe T1 - Spectroscopic investigations on the effect of humic acid on the formation and solubility of secondary solid phases of Ln(2)(CO3)(3) JF - Journal of rare earths N2 - The formation of secondary Ln(III) solid phases (e.g., Nd-2(CO3)(3) and Sm-2(CO3)(3)) was studied as a function of the humic acid concentration in 0.1 mol/L NaClO4 aqueous solution in the neutral pH range (5-6.5). The solid phases under investigation were prepared by alkaline precipitation under 100% CO2 atmosphere and characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), time-resolved laser fluorescence spectroscopy (TRLFS), diffuse reflectance ultraviolet-visible (DR-UV-Vis), Raman spectroscopy, and solubility measurements. The spectroscopic data obtained indicated that Nd-2(CO3)(3) and Sm-2(CO3)(3) were stable and remained the solubility limiting solid phases even in the presence of increased humic acid concentration (0.5 g/L) in solution. Upon base addition in the Ln(III)-HA system, decomplexation of the previously formed Ln(III)-humate complexes and precipitation of two distinct phases occurred, the inorganic (Ln(2)(CO3)(3)) and the organic phase (HA), which was adsorbed on the particle surface of the former. Nevertheless, humic acid affected the particle size of the solid phases. Increasing humic acid concentration resulted in decreasing crystallite size of the Nd-2(CO3)(3) and increasing crystallite size of the Sm-2(CO3)(3) solid phase, and affected inversely the solubility of the solid phases. However, this impact on the solid phase properties was expected to be of minor relevance regarding the chemical behavior and migration of trivalent lanthanides and actinides in the geosphere. KW - lanthanide ions KW - humic acid KW - solid phase KW - solubility KW - Raman KW - TRLFS KW - DR-UV-Vis KW - rare earths Y1 - 2011 U6 - https://doi.org/10.1016/S1002-0721(10)60490-5 SN - 1002-0721 VL - 29 IS - 6 SP - 516 EP - 521 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Schmidt, Bernd A1 - Berger, René A1 - Kelling, Alexandra A1 - Schilde, Uwe T1 - Pd-Catalyzed [2+2+1] coupling of alkynes and arenes phenol diazonium salts as mechanistic trapdoors JF - Chemistry - a European journal N2 - Alkynes and phenol diazonium salts undergo a Pd-catalyzed [2+2+1] cyclization reaction to spiro[4,5]decatetraene-7-ones. This structure was confirmed for one example by X-ray single-crystal structure analysis. The reaction is believed to proceed through oxidative addition of the phenol diazonium cation to Pd(0), subsequent insertion of two alkynes, followed by irreversible spirocyclization. KW - alkynes KW - diazo compounds KW - palladium KW - phenols KW - spirocycles Y1 - 2011 U6 - https://doi.org/10.1002/chem.201100609 SN - 0947-6539 VL - 17 IS - 25 SP - 7032 EP - 7040 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Shkilnyy, Andriy A1 - Schöne, Stefanie A1 - Rumplasch, Claudia A1 - Uhlmann, Annett A1 - Hedderich, Annett A1 - Günter, Christina A1 - Taubert, Andreas T1 - Calcium phosphate mineralization with linear poly(ethylene imine) a time-resolved study JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - We have earlier shown that linear poly(ethylene imine) (LPEI) is an efficient growth modifier for calcium phosphate mineralization from aqueous solution (Shkilnyy et al., Langmuir, 2008, 24 (5), 2102). The current study addresses the growth process and the reason why LPEI is such an effective additive. To that end, the solution pH and the calcium and phosphate concentrations were monitored vs. reaction time using potentiometric, complexometric, and photometric methods. The phase transformations in the precipitates and particle morphogenesis were analyzed by X-ray diffraction and transmission electron microscopy, respectively. All measurements reveal steep decreases of the pH, calcium, and phosphate concentrations along with a rapid precipitation of brushite nanoparticles early on in the reaction. Brushite transforms into hydroxyapatite (HAP) within the first 2 h, which is much faster than what is reported, for example, for calcium phosphate precipitated with poly(acrylic acid). We propose that poly(ethylene imine) acts as a proton acceptor (weak buffer), which accelerates the transformation from brushite to HAP by taking up the protons that are released from the calcium phosphate precipitate during the phase transformation. KW - Calcium phosphate KW - Polyethylene imine KW - Mineralization KW - Kinetics Y1 - 2011 U6 - https://doi.org/10.1007/s00396-011-2403-2 SN - 0303-402X VL - 289 IS - 8 SP - 881 EP - 888 PB - Springer CY - New York ER - TY - JOUR A1 - Lahn, Mattes A1 - Dosche, Carsten A1 - Hille, Carsten T1 - Two-photon microscopy and fluorescence lifetime imaging reveal stimulus-induced intracellular Na+ and Cl- changes in cockroach salivary acinar cells JF - American journal of physiology : Cell physiology N2 - Lahn M, Dosche C, Hille C. Two-photon microscopy and fluorescence lifetime imaging reveal stimulus-induced intracellular Na+ and Cl- changes in cockroach salivary acinar cells. Am J Physiol Cell Physiol 300: C1323-C1336, 2011. First published February 23, 2011; doi: 10.1152/ajpcell.00320.2010.-The intracellular ion homeostasis in cockroach salivary acinar cells during salivation is not satisfactorily understood. This is mainly due to technical problems regarding strong tissue autofluorescence and ineffective ion concentration quantification. For minimizing these problems, we describe the successful application of two-photon (2P) microscopy partly in combination with fluorescence lifetime imaging microscopy (FLIM) to record intracellular Na+ and Cl- concentrations ([Na+](i), [Cl-](i)) in cockroach salivary acinar cells. Quantitative 2P-FLIM Cl- measurements with the dye N-(ethoxycarbonylmethyl)-6-methoxy-quinolinium bromide indicate that the resting [Cl-](i) is 1.6 times above the Cl- electrochemical equilibrium but is not influenced by pharmacological inhibition of the Na+-K+-2Cl(-) cotransporter (NKCC) and anion exchanger using bumetanide and 4,4'-diisothiocyanatodihydrostilbene-2,2'-disulfonic acid disodium salt. In contrast, rapid Cl- reuptake after extracellular Cl- removal is almost totally NKCC mediated both in the absence and presence of dopamine. However, in physiological saline [Cl-](i) does not change during dopamine stimulation although dopamine stimulates fluid secretion in these glands. On the other hand, dopamine causes a decrease in the sodium-binding benzofuran isophthalate tetra-ammonium salt (SBFI) fluorescence and an increase in the Sodium Green fluorescence after 2P excitation. This opposite behavior of both dyes suggests a dopamine-induced [Na+](i) rise in the acinar cells, which is supported by the determined 2P-action cross sections of SBFI. The [Na+](i) rise is Cl- dependent and inhibited by bumetanide. The Ca2+-ionophore ionomycin also causes a bumetanide-sensitive [Na+](i) rise. We propose that a Ca2+-mediated NKCC activity in acinar peripheral cells attributable to dopamine stimulation serves for basolateral Na+ uptake during saliva secretion and that the concomitantly transported Cl- is recycled back to the bath. KW - epithelial ion transport KW - Na+-K+-2Cl(-) cotransporter KW - MQAE KW - SBFI KW - 2P cross section Y1 - 2011 U6 - https://doi.org/10.1152/ajpcell.00320.2010 SN - 0363-6143 VL - 300 IS - 6 SP - C1323 EP - C1336 PB - American Chemical Society CY - Bethesda ER - TY - JOUR A1 - Cockburn, Robert A. A1 - Siegmann, Rebekka A1 - Payne, Kevin A. A1 - Beuermann, Sabine A1 - McKenna, Timothy F. L. A1 - Hutchinson, Robin A. T1 - Free Radical Copolymerization Kinetics of gamma-Methyl-alpha-methylene-gamma-butyrolactone (MeMBL) JF - Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences N2 - The propagation kinetics and copolymerization behavior of the biorenewable monomer gamma-methyl-alpha-methylene-gamma-butyrolactone (MeMBL) are studied using the Pulsed laser polymerization (PLP)/size exclusion chromatography (SEC) technique. The propagation rate coefficent for MeMBL is 15% higher than that of its structural analogue, methyl methacrylate (MMA), with a similar activation energy of 21.8 kJ . mol(-1). When compared to MMA, MeMBL is preferentially incorporated into copolymers when reacted with styrene (ST), MMA, and n-butyl acrylate (BA); the monomer reactivity ratios fit from bulk MeMBL/ST, MeMBL/MMA, and MeMBL/BA copolymerizations are r(MeMBL) = 0.80 +/- 0.04 and r(ST) = 0.34 +/- 0.04, r(MeMBL), = 3.0 +/- 0.3 and r(MMA) = 0.33 +/- 0.01, and r(MeMBL) = 7.0 +/- 2.0 and r(BA) = 0.16 +/- 0.03, respectively. In all cases, no significant variation with temperature was found between 50 and 90 degrees C. The implicit penultimate unit effect (IPUE) model was found to adequately fit the composition-averaged copolymerization propagation rate coefficient, k(p,cop), for the three systems. Y1 - 2011 U6 - https://doi.org/10.1021/bm200400s SN - 1525-7797 VL - 12 IS - 6 SP - 2319 EP - 2326 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Kolocouris, Antonios A1 - Zervos, Nikolaos A1 - De Proft, Frank A1 - Koch, Andreas T1 - Improper Hydrogen Bonded Cyclohexane C-H-ax center dot center dot center dot Y-ax Contacts theoretical predictions and experimental Evidence from H-1 NMR Spectroscopy of Suitable Axial Cyclohexane Models JF - The journal of organic chemistry N2 - C-H-ax center dot center dot center dot Y-ax are a textbook prototype of steric hindrance in organic chemistry. The nature of these contacts is investigated in this work. MP2/6-31+G(d,p) calculations predicted the presence of improper hydrogen bonded C-H-ax center dot center dot center dot Y-ax of different strength in substituted cyclohexane rings. To support the theoretical predictions with experimental evidence, several synthetic 2-substituted adamantane analogues (1-24) with suitable improper H-bonded C-H-ax center dot center dot center dot Y-ax contacts of different strength were used as models of a substituted cyclohexane ring. The H-1 NMR signal separation, Delta delta(gamma-CH2), within the cyclohexane ring gamma-CH(2)s is raised when the MP2/6-31+G(d,p) calculated parameters, reflecting the strength of the H-bonded C-H-ax center dot center dot center dot Y-ax contact, are increased. In molecules with enhanced improper H-bonded contacts C-H-ax center dot center dot center dot Y-ax, like those having sterically crowded contacts (Y-ax = t-Bu) or contacts including considerable electrostatic attractions (Y-ax = O-C or O=C) the calculated DFT steric energies of the gamma-axial hydrogens are considerably reduced reflecting their electron cloud compression. The results suggest that the proton H-ax electron cloud compression, caused by the C-H-ax center dot center dot center dot Y-ax contacts, and the resulting increase in Delta delta(gamma-CH2) value can be effected not just from van der Waals spheres compression, but more generally from electrostatic attraction forces and van der Waals repulsion, both of which are improper H-bonding components. Y1 - 2011 U6 - https://doi.org/10.1021/jo102353f SN - 0022-3263 VL - 76 IS - 11 SP - 4432 EP - 4443 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Jelicic, Aleksandra A1 - Yasin, Muttaqin A1 - Beuermann, Sabine T1 - Toward the description and prediction of solvent induced variations in Methacrylate Propagation Rate Coefficients on the basis of Solvatochromic Parameters JF - Macromolecular reaction engineering N2 - Benzyl methacrylate (BzMA) propagation rate coefficients, k(p), were determined in ionic liquids and common organic solvents via pulsed-laser polymerizations with subsequent polymer analysis by size-exclusion chromatography (PLP-SEC). The aim of the work is to gain a deeper understanding of the solvent influence on k(p) and to develop a general correlation between solvent-induced variations in k(p) and solvent properties. Applying a linear solvation energy relationship (LSER), which correlates k(p) to solvent solvatochromic parameters, suggests that dipolarity/polarizability determines the solvent influence on k(p). To compare the solvent influence on BzMA k(p) with data for methyl methacrylate, hydroxypropyl methacrylate, and 2-ethoxyethyl methacrylate normalized k(p) data were treated by a single LSER, providing a universal treatment of the solvent influence on the propagation kinetics of the four monomers. Further, the predictive capabilities of this universal correlation were tested with additional monomers from the methacrylate family. KW - ionic liquid KW - kinetics (polym.) KW - radical polymerization KW - solvent influence Y1 - 2011 U6 - https://doi.org/10.1002/mren.201000058 SN - 1862-832X VL - 5 IS - 5-6 SP - 232 EP - 242 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Juma, Wanyama P. A1 - Akala, Hoseah M. A1 - Eyase, Fredrick L. A1 - Muiva, Lois M. A1 - Heydenreich, Matthias A1 - Okalebo, Faith A. A1 - Gitu, Peter M. A1 - Peter, Martin G. A1 - Walsh, Douglas S. A1 - Imbuga, Mabel A1 - Yenesew, Abiy T1 - Terpurinflavone an antiplasmodial flavone from the stem of Tephrosia Purpurea JF - Phytochemistry letters N2 - The stem extract of Tephrosia purpurea showed antiplasmodial activity against the D6 (chloroquine-sensitive) and W2 (chloroquine-resistant) strains of Plasmodium falciparum with IC(50) values of 10.47 +/- 2.22 mu g/ml and 12.06 +/- 2.54 mu g/ml, respectively. A new prenylated flavone, named terpurinflavone, along with the known compounds lanceolatin A, (-)-semiglabrin and lanceolatin B have been isolated from this extract. The new compound, terpurinflavone, showed the highest antiplasmodial activity with IC(50) values of 3.12 +/- 0.28 mu M (D6) and 6.26 +/- 2.66 mu M (W2). The structures were determined on the basis of spectroscopic evidence. KW - Tephrosia purpurea KW - Leguminosae KW - Stem KW - Flavone KW - Terpurinflavone KW - Antiplasmodial Y1 - 2011 U6 - https://doi.org/10.1016/j.phytol.2011.02.010 SN - 1874-3900 VL - 4 IS - 2 SP - 176 EP - 178 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Pihlaja, Kalevi A1 - Sinkkonen, Jari A1 - Stajer, Geza A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - 1-Oxo-1,3-dithiolanes - synthesis and stereochemistry JF - Magnetic resonance in chemistry N2 - 1-Oxo-1,3-dithiolane (4) and its cis- and trans-2-methyl (5,6), -4-methyl (7,8) and -5-methyl (9,10) derivatives were prepared by oxidizing the corresponding 1,3-dithiolanes (1-3) with NaIO(4) in water. The oxides were purified and their isomers separated using thin layer chromatography. The structural characterization was carried out with (1)H and (13)C NMR spectroscopy and molecular modelling. The sulfoxides 4-6 and 8-10 attain two S(1) type envelopes (sometimes slightly distorted) the S=O(ax) envelope greatly dominating. Cis-4-methyl-1-oxo-1,3-dithiolane is a special case exhibiting both two closely related S=O(ax) (30 and 27%) as well as S=O(eq) (21 and 22%) forms [S(1) and C(4) envelopes, respectively]. The relative energies of these conformations, the values of (1)H-(1)H coupling constants and (1)H and (13)C chemical shifts were estimated by computational methods and they support well the conclusions based on the experimental data. KW - NMR KW - (1)H NMR KW - (13)C NMR KW - sulfur heterocycles KW - conformational analysis KW - computational chemistry Y1 - 2011 U6 - https://doi.org/10.1002/mrc.2764 SN - 0749-1581 VL - 49 IS - 7 SP - 443 EP - 449 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Wessig, Pablo A1 - Pick, Charlotte T1 - Photochemical synthesis and properties of axially chiral naphthylpyridines JF - Journal of photochemistry and photobiology : A, Chemistry N2 - Five alkynyl pyridines were prepared and cyclized to naphthylpyridines as the main products in the course of a Photo-Dehydro-Diels-Alder reaction. Four of the final products are axially chiral and the determination of the rotational barrier by DFT calculations, dynamic NMR and H PLC experiments is demonstrated. (C) 2011 Elsevier B.V. All rights reserved. KW - Photochemistry KW - Axial chirality KW - Photo-Dehydro-Diels-Alder reaction KW - Dynamic NMR KW - Dynamic HPLC KW - Molecular modeling Y1 - 2011 U6 - https://doi.org/10.1016/j.jphotochem.2011.06.006 SN - 1010-6030 VL - 222 IS - 1 SP - 263 EP - 265 PB - Elsevier CY - Lausanne ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Suslova, Elena N. A1 - Kleinpeter, Erich T1 - Conformational analysis of N-phenyl- and N-trifyl-4,4-dimethyl-4-silathiane 1-sulfimides JF - Journal of physical organic chemistry N2 - N-Substituted 4,4-dimethyl-4-silathiane 1-sulfimides Me2Si(sic)S=NSO2R [R- Ph (1), CF3 (2)] were studied experimentally by variable temperature dynamic NMR spectroscopy. Low temperature 13 C NMR spectra of the two compounds revealed the frozen ring inversion process and approximately equal content of the axial and equatorial conformers. Calculations of the 4-silathiane derivatives 1, 2 and the model compound [R Me (3)] as well as their carbon analogs, the similarly N-substituted (sic)S=NSO2R thiane 1-sulfimides [R = Ph (4), CF3 (5), Me (6)] at the DFT/B3LYP/6-311G(d, p) level in the gas phase and in chloroform solution using the PCM model at the same level of theory showed a strong dependence of the relative stability of the conformer on the solvent. The electronegative trifluoromethyl group increases the relative stability of the axial conformer. KW - 4-silathianes KW - conformational analysis KW - dynamic NMR KW - quantum chemical calculations KW - sulfimides Y1 - 2011 U6 - https://doi.org/10.1002/poc.1811 SN - 0894-3230 VL - 24 IS - 8 SP - 698 EP - 704 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Kröner, Dominik A1 - Ehlert, Christopher A1 - Saalfrank, Peter A1 - Holländer, Andreas T1 - Ab initio calculations for XPS chemical shifts of poly(vinyl-trifluoroacetate) using trimer models JF - Surface science N2 - X-ray photoelectron spectra (XPS) of the polymer poly(vinyl-trifluoroacetate) show C(1s) binding energy shifts which are unusual because they are influenced by atoms which are several bonds away from the probed atom. In this work, the influence of the trifluoroacetate substituent on the 1s ionization potential of the carbon atoms of the polyethylene chain is investigated theoretically using mono-substituted, diad and triad models of trimers representing the polymer. Carbon 1s ionization energies are calculated by the Hartree-Fock theory employing Koopmans' theorem. The influence of the configuration and conformation of the functional groups as well as the degree of substitution are found to be important determinants of XPS spectra. It is further found that the 1s binding energy correlates in a linear fashion, with the total electrostatic potential at the position of the probe atom, and depends not only on nearest neighbor effects. This may have implications for the interpretation of high-resolution XP spectra. KW - Ab initio quantum chemical methods and calculations KW - X-ray photoelectron spectroscopy KW - Insulating films Y1 - 2011 U6 - https://doi.org/10.1016/j.susc.2011.05.021 SN - 0039-6028 VL - 605 IS - 15-16 SP - 1516 EP - 1524 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kozlevcar, Bojan A1 - Gamez, Patrick A1 - de Gelder, Rene A1 - Jaglicic, Zvonko A1 - Strauch, Peter A1 - Kitanovski, Nives A1 - Reedijk, Jan T1 - Counterion and solvent effects on the primary coordination sphere of copper(II) Bis(3,5-dimethylpyrazol-1-yl)acetic acid coordination compounds JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - Four copper(II) coordination compounds with the neutral ligand bis(3,5-dimethylpyrazol-1-yl)acetic acid (Hbdmpza, C(12)H(16)N(4)O(2)) and its anionic form (bdmpza(-)), namely [Cu(Hbdmpza)(2)](HSO(4))(2) (1), [Cu(Hbdmpza)(2)]Cl(2) (2), [Cu(bdmpza)(2)](CH(3)COOH)(H(2)O) (3), and [Cu(bdmpza)(2)][Cu(2)(O(2)CCH(3))(4)] (4) have been synthesized starting from different metal salts. All the compounds have been fully characterized by physical and analytical methods. In addition, a single-crystal XRD analysis revealed the 3D structure of 1, which exhibits tridentate, vicinal N,N,O-coordination of two symmetry-related Hbdmpza ligands in an elongated octahedral arrangement with four equatorial nitrogen atoms and two axial oxygen atoms. The neutral carboxylic moiety acts as a hydrogen-bond donor to a HSO(4)(-) counterion. The two hydrogensulfates form a unique hydrogen-bonded pair (HSO(4)(-))(2) with very short O center dot center dot center dot O distances (2.59 angstrom) bridged between adjacent [Cu(HL)(2)](2+) coordination units. Also a short O center dot center dot center dot O contact (2.54 angstrom) is present between the C-OH and an 0 of a hydrogensulfate. A characteristic IR C=O vibration is observed at 1700 cm(-1) for 1 and 2, whereas the v(as)(O(2)C) vibration is present at 1650 cm(-1) for 3 and 4. These IR data strongly suggest the presence of Hbdmpza ligands in 1 and 2 and the deprotonated form bdmpza- in 3 and 4. A mononuclear coordination unit [CuL(2)], as proven for 1 by X-ray diffraction, is also proposed for the other compounds 2-4. In compound 4, an additional dinuclear [Cu(2)(O(2)CCH(3))(4)] neutral coordination unit is present, as deduced from the vibration bands v(as)(O(2)C) at 1600 cm(-1) and v(s)(O(2)C) at 1420 cm(-1), which are typical of a carboxylate function, and from the two-species analysis of the chi(M)T(T) curve of the magnetic susceptibility data (2J = -322 cm(-1)). Also, the EPR spectra recorded at different temperatures agree with this structure. KW - Copper KW - Coordination modes KW - Hydrogen bonds KW - Counterions KW - Solvent effects Y1 - 2011 U6 - https://doi.org/10.1002/ejic.201100410 SN - 1434-1948 IS - 24 SP - 3650 EP - 3655 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Yuan, Jiayin A1 - ten Brummelhuis, Niels A1 - Junginger, Mathias A1 - Xie, Zailai A1 - Lu, Yan A1 - Taubert, Andreas A1 - Schlaad, Helmut T1 - Diversified applications of chemically modified 1,2-Polybutadiene JF - Macromolecular rapid communications N2 - Commercially available 1,2-PB was transformed into a well-defined reactive intermediate by quantitative bromination. The brominated polymer was used as a polyfunctional macroinitiator for the cationic ring-opening polymerization of 2-ethyl-2-oxazoline to yield a water-soluble brush polymer. Nucleophilic substitution of bromide by 1-methyl imidazole resulted in the formation of polyelectrolyte copolymers consisting of mixed units of imidazolium, bromo, and double bond. These copolymers, which were soluble in water without forming aggregates, were used as stabilizers in the heterophase polymerization of styrene and were also studied for their ionic conducting properties. KW - emulsion polymerization KW - polybutadiene KW - polyelectrolytes KW - polymer modification KW - ring-opening polymerization Y1 - 2011 U6 - https://doi.org/10.1002/marc.201100254 SN - 1022-1336 VL - 32 IS - 15 SP - 1157 EP - 1162 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Wessig, Pablo A1 - Pick, Charlotte A1 - Schilde, Uwe T1 - First example of an atropselective dehydro-Diels-Alder (ADDA) reaction JF - Tetrahedron letters N2 - A new concept of a stereoselective synthesis of axially chiral biaryls, formed in the course of the dehydro-Diels-Alder (DDA) reaction, has been disclosed. It is based on asymmetric induction of the newly formed chirality axis by a chirality center, which is present in the two synthesized DDA reactants. Depending on the different length of the linkers joining the alkyne moieties the DDA reaction may be triggered photochemically or thermally, where only the thermal variant was stereoselective. KW - Cycloaddition KW - Atropselecrivity KW - Biaryls KW - Alkynes KW - Photochemistry Y1 - 2011 U6 - https://doi.org/10.1016/j.tetlet.2011.06.024 SN - 0040-4039 VL - 52 IS - 32 SP - 4221 EP - 4223 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - The anisotropic effect of functional groups in H-1 NMR spectra is the molecular response property of spatial NICS-the frozen conformational equilibria of 9-arylfluorenes JF - Tetrahedron N2 - Rotation about the single bond adjoining the aryl and fluorene moieties in 9-arylfluorenes can be frozen out on the NMR timescale if methyl groups are located at either one or both of the ortho positions of the aryl substituent. In the ground-state of these rotamers, the planes of the aryl and fluorene moieties are perpendicular to each other and the methyl substituents are consequently positioned either above the fluorene moiety or in-plane with it; thus, the methyl protons are either shielded or deshielded, respectively, due to the ring current effect of the fluorene moiety. This anisotropic effect on the H-1 chemical shifts of the methyl protons has been quantified on the basis of through-space NMR shieldings (TSNMRS) and subsequently Delta delta(calcd) compared with the experimentally observed chemical shift differences, Delta delta(exp). In this context, the experimental anisotropic effects of functional groups in the H-1 NMR have proven to quantitatively be the molecular response property of theoretical spatial nucleus independent chemical shieldings (NICS). Differences between Delta delta(calcd) and Delta delta(exp) were, for the first time, also quantified as arising from steric compression. KW - Through-space NMR shieldings (TSNMRS) KW - Spatial NICS KW - Anisotropic effect KW - Iso-chemical-shielding surfaces (ICSS) KW - 9-Arylfluorenes Y1 - 2011 U6 - https://doi.org/10.1016/j.tet.2011.06.005 SN - 0040-4020 VL - 67 IS - 32 SP - 5740 EP - 5743 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Luo, Ying A1 - Utecht, Manuel Martin A1 - Dokic, Jadranka A1 - Korchak, Sergey A1 - Vieth, Hans-Martin A1 - Haag, Rainer A1 - Saalfrank, Peter T1 - Cis-trans isomerisation of substituted aromatic imines a comparative experimental and theoretical study JF - ChemPhysChem : a European journal of chemical physics and physical chemistry N2 - The cis-trans isomerisation of N-benzylideneaniline (NBA) and derivatives containing a central C=N bond has been investigated experimentally and theoretically. Eight different NBA molecules in three different solvents were irradiated to enforce a photochemical trans (hv) -> cis isomerisation and the kinetics of the thermal backreaction cis (Delta)-> trans were determined by NMR spectroscopy measurements in the temperature range between 193 and 288 K. Theoretical calculations using density functional theory and Eyring transition-state theory were carried out for 12 different NBA species in the gas phase and three different solvents to compute thermal isomerisation rates of the thermal back reaction. While the computed absolute rates are too large, they reveal and explain experimental trends. Time-dependent density functional theory provides optical spectra for vertical transitions and excitation energy differences between trans and cis forms. Together with isomerisation rates, the latter can be used to identify "optimal switches" with good photochromicity and reasonable thermal stability. KW - density functional calculations KW - imines KW - isomerization KW - photochemistry KW - thermochemistry Y1 - 2011 U6 - https://doi.org/10.1002/cphc.201100179 SN - 1439-4235 VL - 12 IS - 12 SP - 2311 EP - 2321 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Bleger, David A1 - Dokic, Jadranka A1 - Peters, Maike V. A1 - Grubert, Lutz A1 - Saalfrank, Peter A1 - Hecht, Stefan T1 - Electronic decoupling approach to quantitative photoswitching in linear multiazobenzene architectures JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry N2 - A strategy to optimize the photoswitching efficiency of rigid, linear multiazobenzene constructs is presented. It consists of introducing large dihedral angles between azobenzene moieties linked via aryl-aryl connections in their para positions. Four bisazobenzenes exhibiting different dihedral angles as well as three single azobenzene reference compounds have been synthesized, and their switching behavior has been studied as well as experimentally and theoretically analyzed. As the dihedral angle between the two azobenzene units increases and consequently the electronic conjugation decreases, the photochromic characteristics improve, finally leading to individual azobenzene switches operating independently in the case of the perpendicular ortho,ortho,ortho',ortho'-tetramethyl biphenyl linker. The electronic decoupling leads to efficient separation of the absorption spectra of the involved switching states and hence by choosing the appropriate irradiation wavelength, an almost quantitative E -> Z photoisomerization up to 97% overall Z-content can be achieved. In addition, thermal Z -> E isomerization processes become independent of each other with increasing decoupling. The electronic decoupling could furthermore be proven by electrochemistry. The experimental data are supported by theory, and calculations additionally provide mechanistic insight into the preferred pathway for the thermal Z,Z -> Z,E -> E,E isomerization via inversion on the inner N-atoms. Our decoupling approach outlined herein provides the basis for constructing rigid rod architectures composed of multiple azobenzene photochromes, which display practically quantitative photoswitching properties, a necessary prerequisite to achieve highly efficient transduction of light energy directly into motion. Y1 - 2011 U6 - https://doi.org/10.1021/jp2044114 SN - 1520-6106 VL - 115 IS - 33 SP - 9930 EP - 9940 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Thuenemann, Andreas F. A1 - Klobes, Peter A1 - Wieland, Christoph A1 - Bruzzano, Stefano T1 - On the nanostructure of micrometer-sized cellulose beads JF - Analytical & bioanalytical chemistry N2 - The analysis of the porosity of materials is an important and challenging field in analytical chemistry. The gas adsorption and mercury intrusion methods are the most established techniques for quantification of specific surface areas, but unfortunately, dry materials are mandatory for their applicability. All porous materials that contain water and other solvents in their functional state must be dried before analysis. In this process, care has to be taken since the removal of solvent bears the risk of an incalculable alteration of the pore structure, especially for soft materials. In the present paper, we report on the use of small-angle X-ray scattering (SAXS) as an alternative analysis method for the investigation of the micro and mesopores within cellulose beads in their native, i.e., water-swollen state; in this context, they represent a typical soft material. We show that even gentle removal of the bound water reduces the specific surface area dramatically from 161 to 109 m(2) g(-1) in cellulose bead sample type MT50 and from 417 to 220 m(2) g(-1) in MT100. Simulation of the SAXS curves with a bimodal pore size distribution model reveals that the smallest pores with radii up to 10 nm are greatly affected by drying, whereas pores with sizes in the range of 10 to 70 nm are barely affected. The SAXS results were compared with Brunauer-Emmett-Teller results from nitrogen sorption measurements and with mercury intrusion experiments. KW - Small-angle X-ray scattering KW - Cellulose KW - Mesopores KW - Micropores KW - Porosimetry Y1 - 2011 U6 - https://doi.org/10.1007/s00216-011-5176-z SN - 1618-2642 VL - 401 IS - 4 SP - 1101 EP - 1108 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Kramer, Markus A1 - Kleinpeter, Erich T1 - A conformational study of N-acetyl glucosamine derivatives utilizing residual dipolar couplings JF - Journal of magnetic resonance N2 - The conformational analyses of six non-rigid N-acetyl glucosamine (NAG) derivatives employing residual dipolar couplings (RDCs) and NOEs together with molecular dynamics (MD) simulations are presented. Due to internal dynamics we had to consider different conformer ratios existing in solution. The good quality of the correlation between theoretically and experimentally obtained RDCs show the correctness of the calculated conformers even if the ratios derived from the MD simulations do not exactly meet the experimental data. If possible, the results were compared to former published data and commented. KW - NMR KW - Residual dipolar couplings KW - Molecular dynamics KW - N-acetyl glucosamine derivatives KW - Carbohydrates Y1 - 2011 U6 - https://doi.org/10.1016/j.jmr.2011.06.029 SN - 1090-7807 VL - 212 IS - 1 SP - 174 EP - 185 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Kienzler, Andrea A1 - Flehr, Roman A1 - Kramer, Rolf A. A1 - Gehne, Soeren A1 - Kumke, Michael Uwe A1 - Bannwarth, Willi T1 - Novel Three-Color FRET Tool Box for Advanced Protein and DNA Analysis JF - Bioconjugate chemistry N2 - We report on a new three-color FRET system which we were able to verify in peptides as well as in synthetic DNA. All three chromophores could be introduced by a building block approach avoiding postsynthetic labeling. Additional features are robustness, matching spectroscopic properties, high-energy transfer, and sensitivity. The system was investigated in detail on a set of peptides as well as an array of tailored oligonucleotides. The detailed analysis of the experimental data and comparison with theoretical considerations were in excellent agreement. It is shown that in the case of polypeptides specific interaction with the fluorescence probes has to be considered. In contrast with DNA, the fluorescence probes did not show any indications of such interactions. The novel three-color FRET toolbox revealed the potential for applications studying fundamental processes of three interacting molecules in life science applications. Y1 - 2011 U6 - https://doi.org/10.1021/bc2002659 SN - 1043-1802 VL - 22 IS - 9 SP - 1852 EP - 1863 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Kreye, Oliver A1 - Toth, Tommy A1 - Meier, Michael A. R. T1 - Copolymers derived from rapeseed derivatives via ADMET and thiol-ene addition JF - European polymer journal N2 - Novel (co)polymers were synthesized from substances obtained from rapeseed via ADMET and thiol-ene additions. alpha,omega-Dienes derived from oleic and erucic acid were copolymerized with a ferulic acid derivative, a representative phenolic acid (p-hydroxycinnamic acid) present, for instance, in rapeseed cake. Copolymers with different ratios of these monomers were prepared via two different routes (ADMET and thiol-ene) and studied in detail. Both monomer and polymer synthesis were optimized in order to achieve high yielding synthetic procedures that meet the requirements of green chemistry. Some thermal properties of the resulting copolymer series were then studied and correlated to the co-monomer composition. KW - Rapeseed oil KW - Rapeseed cake KW - p-Hydroxycinnamic acids KW - alpha,omega-Dienes KW - ADMET polymerization KW - Thiol-ene addition Y1 - 2011 U6 - https://doi.org/10.1016/j.eurpolymj.2011.06.012 SN - 0014-3057 VL - 47 IS - 9 SP - 1804 EP - 1816 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Schmidt, Bernd A1 - Geissler, Diana T1 - Ru- and Pd-Catalysed Synthesis of 2-Arylfurans by One-Flask Heck Arylation/Oxidation JF - European journal of organic chemistry N2 - 2,5-Disubstituted furans were synthesized by one-flask Heck arylation/oxidation sequences. The starting materials are 2-substituted 2,3-dihydrofurans, conveniently available by RCM/isomerization sequences, and arenediazonium salts. These react in ligand-free Heck reactions to afford 2,5-disub-stituted 2,5-dihydrofurans, which are oxidized to the corresponding furans without isolation or intermediate workup. The oxidation is conveniently achieved with chloranil or DDQ, depending on the substrate. KW - Diazonium salts KW - Palladium KW - C-C coupling KW - Heck coupling KW - Furans KW - Oxidation KW - Oxygen heterocycles Y1 - 2011 U6 - https://doi.org/10.1002/ejoc.201100549 SN - 1434-193X IS - 25 SP - 4814 EP - 4822 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Moskalik, Mikail Yu. A1 - Shainyan, Bagrat A. A1 - Schilde, Uwe T1 - Reaction of trifluoromethanesulfonamide with alkenes and cycloocta-1,5-diene under oxidative conditions direct assembly of 9-heterobicyclo[4.2.1]nonanes JF - Russian journal of organic chemistry N2 - Reactions of trifluoromethanesulfonamide with alpha-methylstyrene, 2-methylpent-1-ene, and cycloocta-1,5-diene in the system t-BuOCl-NaI were studied. In the reaction with alpha-methylstyrene 1-iodo-2-phenylpropan-2-ol was the only isolated product. The reaction with 2-methylpent-1-ene gave a mixture of N,N'-(2-methylpentane-1,2-diyl)bis(trifluoromethanesulfonamide), trifluoro-N-(2-hydroxy-2-methylpentyl)-methanesulfonamide, and N,N'-[oxybis(2-methylpentan-2,1-diyl)]bis(trifluoromethanesulfonamide). Trifluoromethanesulfonamide reacted with cycloocta-1,5-diene to produce a mixture of 2,5-diiodo-9-(trifluoromethylsulfonyl)-9-azabicyclo[4.2.1]nonane and 2,5-diiodo-9-oxabicyclo[4.2.1]nonane; this reaction may be regarded as the first example of direct assembly of bicyclononane skeleton. Y1 - 2011 U6 - https://doi.org/10.1134/S1070428011090016 SN - 1070-4280 VL - 47 IS - 9 SP - 1271 EP - 1277 PB - Pleiades Publ. CY - New York ER - TY - JOUR A1 - Löbbicke, Ruben A1 - Chanana, Munish A1 - Schlaad, Helmut A1 - Pilz-Allen, Christine A1 - Günter, Christina A1 - Möhwald, Helmuth A1 - Taubert, Andreas T1 - Polymer Brush Controlled Bioinspired Calcium Phosphate Mineralization and Bone Cell Growth JF - Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences N2 - Polymer brushes on thiol-modified gold surfaces were synthesized by using terminal thiol groups for the surface initiated free radical polymerization of methacrylic acid and dimethylaminotheyl methacrylate, respectively. Atomic force microscopy shows that the resulting poly(methacrylic acid (PMAA) and poly(dimethylaminothyl methacrylate) (PDM- AEMA) brushes are homogeneous. Contact angle measurements show that the brushes are pH responsive and can reversibly be protonated and deprotonated. Mineralization of the brushes with calcium phosphate at different pH yields homogeneously mineralized surfaces, and preosteoblastic cells proliferate-on be number of living cells on the mineralized hybrid surface is ca. 3 times (P corresponding nonmineralized brushes. Y1 - 2011 U6 - https://doi.org/10.1021/bm200991b SN - 1525-7797 VL - 12 IS - 10 SP - 3753 EP - 3760 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Riebe, Daniel A1 - Zühlke, Martin A1 - Zenichowski, Karl A1 - Beitz, Toralf A1 - Dosche, Carsten A1 - Löhmannsröben, Hans-Gerd T1 - Characterization of rhodamine 6G release in electrospray ionization by means of spatially resolved fluorescence spectroscopy JF - Zeitschrift für physikalische Chemie : international journal of research in physical chemistry and chemical physics N2 - In the present work, the density distribution of rhodamine 6G ions (R6G) in the gas phase and the droplets of an electrospray plume was studied by spatial and spectral imaging. The intention is to contribute to the fundamental understanding of the release mechanism of gaseous R6G in the electrospray ionization (ESI) process. Furthermore, the influence of ESI-parameters on the release efficiency of R6G, e. g. solvent flow, R6G and salt concentration were examined via direct fluorescence imaging of R6G. A solvent-shift of the fluorescence maximum,lambda(max) = 555 nm in methanolic solution and lambda(max) = 505 nm in gas phase, allows the discrimination between solvated and gaseous R6G. Two experimental setups were used for our measurements. In the first experiment, the R6G fluorescence and the light scattered from the spray plume were imaged in two spatial dimensions using a tunable wavelength filter. The second experiment was designed for obtaining 1-dimensional spatially resolved emission spectra of the spray. Here, the intensity distribution of solvated and gaseous R6G as well as scattered light (lambda = 355 nm) were measured simultaneously. The results show the distribution of gaseous R6G in the plane, orthogonal to the ESI capillary, decreasing slightly towards the spray center and showing maxima at the cone margins. The distribution of gaseous R6G confirms the preferred release of gaseous ions from nano-droplets, indicating the ion evaporation model (IEM) to be the dominating release mechanism. Up to now, only a few fluorescence spectra of ionic compounds in the gas phase were published because the measurement of emission spectra of mass-selected ions in an ion trap is experimentally challenging. The fluorescence spectrum of gaseous lucigenin at atmospheric pressure is reported for the first time. This spectrum of lucigenin in the gas phase exhibits a blue shift of about Delta lambda = 10 nm in comparison to the corresponding spectrum in methanol. KW - Fluorescence KW - Electrospray Ionization KW - Rhodamine 6G KW - Gaseous Ions KW - Lucigenin Y1 - 2011 U6 - https://doi.org/10.1524/zpch.2011.0149 SN - 0942-9352 VL - 225 IS - 9-10 SP - 1055 EP - 1072 PB - De Gruyter Oldenbourg CY - München ER - TY - JOUR A1 - Hass, Roland A1 - Reich, Oliver T1 - Photon density wave spectroscopy for dilution-free sizing of highly concentrated nanoparticles during starved-feed polymerization JF - ChemPhysChem : a European journal of chemical physics and physical chemistry KW - analytical methods KW - fiber-optical spectroscopy KW - nanoparticles KW - photon density wave spectroscopy KW - polymerization Y1 - 2011 U6 - https://doi.org/10.1002/cphc.201100323 SN - 1439-4235 VL - 12 IS - 14 SP - 2572 EP - 2575 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Köpf, Michael H. A1 - Harder, Heiko A1 - Reiche, Jürgen A1 - Santer, Svetlana T1 - Impact of temperature on the LB patterning of DPPC on Mica JF - Langmuir N2 - The influence of the subphase temperature on the stripe pattern formation during Langmuir-Blodgett transfer (LB patterning) is investigated in a combined experimental and theoretical study. According to our experiments on the LB transfer of dipalmitoylphosphatidylcholine (DPPC) on planar mica substrates, even small temperature changes between 21.5 and 24.5 degrees C lead to significant changes in the monolayer patterns. For a constant surface pressure and dipper speed, the width of the stripes and the overall spatial period of the patterns increase with increasing subphase temperature. Because the stripe patterns are ascribed to alternating monolayer domains in the liquid-expanded and the liquid-condensed phases, the working regime for the formation of stripes is found to depend strongly on the respective surface pressure-area isotherm. These experimental findings are in accordance with the results of a theoretical investigation based on a model that takes hydrodynamics and the monolayer thermodynamics into account. Y1 - 2011 U6 - https://doi.org/10.1021/la202728t SN - 0743-7463 VL - 27 IS - 20 SP - 12354 EP - 12360 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Licausi, Francesco A1 - Giorgi, Federico Manuel A1 - Schmaelzlin, Elmar A1 - Usadel, Björn A1 - Perata, Pierdomenico A1 - van Dongen, Joost Thomas A1 - Geigenberger, Peter T1 - HRE-Type Genes are regulated by Growth-Related Changes in internal Oxygen Concentrations During the normal development of Potato (Solanum tuberosum) Tubers JF - Plant & cell physiology N2 - The occurrence of hypoxic conditions in plants not only represents a stress condition but is also associated with the normal development and growth of many organs, leading to adaptive changes in metabolism and growth to prevent internal anoxia. Internal oxygen concentrations decrease inside growing potato tubers, due to their active metabolism and increased resistance to gas diffusion as tubers grow. In the present work, we identified three hypoxia-responsive ERF (StHRE) genes whose expression is regulated by the gradual decrease in oxygen tensions that occur when potato tubers grow larger. Increasing the external oxygen concentration counteracted the modification of StHRE expression during tuber growth, supporting the idea that the actual oxygen levels inside the organs, rather than development itself, are responsible for the regulation of StHRE genes. We identified several sugar metabolism-related genes co-regulated with StHRE genes during tuber development and possibly involved in starch accumulation. All together, our data suggest a possible role for low oxygen in the regulation of sugar metabolism in the potato tuber, similar to what happens in storage tissues during seed development. KW - Co-expression KW - ERF KW - Hypoxia KW - Potato KW - Solanum tuberosum KW - Tuber Y1 - 2011 U6 - https://doi.org/10.1093/pcp/pcr128 SN - 0032-0781 VL - 52 IS - 11 SP - 1957 EP - 1972 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Senge, Mathias O. A1 - Ryppa, Claudia A1 - Fazekas, Marijana A1 - Zawadzka, Monika A1 - Dahms, Katja T1 - 5,10-A2B2-Type meso-Substituted PorphyrinsuA Unique Class of Porphyrins with a Realigned Dipole Moment JF - Chemistry - a European journal N2 - Current applications in porphyrin chemistry require the use of unsymmetrically substituted porphyrins. Many current industrial interests in optics and biomedicine require systems with either pushpull (electron-donating and -withdrawing groups) or amphiphilic systems (hydrophobic and hydrophilic groups). In this context we present the class of 5,10-A2B2-type porphyrins for which two different substituents are positioned in diagonally opposite meso positions. Thus, the intramolecular dipole moment in these tetrapyrroles is positioned along a beta-beta vector passing through two pyrrole rings. This is opposite to the situation of the frequently used 5,15-A2BC porphyrins for which the dipole moment is oriented along a mesomeso axis. We have elaborated syntheses of the 5,10-A2B2 porphyrins by using transition-metal-catalyzed transformations of 5,10-A2 porphyrins or direct substitutions reactions thereof; this gives the target molecules in 2277% overall yields. The compounds exhibit interesting structural, spectroscopic, and optical features and can serve as building blocks for new porphyrin arrays and applications. KW - macrocycles KW - nitrogen heterocycles KW - nonlinear optics KW - porphyrinoids KW - tetrapyrroles Y1 - 2011 U6 - https://doi.org/10.1002/chem.201101934 SN - 0947-6539 VL - 17 IS - 48 SP - 13562 EP - 13573 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Kröner, Dominik A1 - Krüger, Hartmut A1 - Thesen, Manuel W. T1 - Electronic structure calculations for Hole-Transporting Triphenylamine Derivatives in Polymer Light-Emitting Diodes JF - Macromolecular theory and simulations N2 - Hole-transporting polymers based on polyethene-triphenylamine derivatives are investigated with respect to their UV/Vis spectra. Two substituents, N-phenyl-1-naphthylamine and carbazole, are examined as their respective polymer light-emitting diodes (PLEDs) show very different luminous efficiencies. In order to identify the origin of these phenomena electronic structure calculations based on TD-DFT were performed using monomer models of the hole-transporting polymers. In experiment these hole-transporting polymers show very specific differences in their absorption and emission (fluorescence and phosphorescence) spectra. The analysis of the simulated absorption and emission spectra, the MOs as well as the ground and excited state geometries give explanations for the different optical performances of the corresponding PLEDs. KW - charge transport KW - luminescence KW - organic light-emitting diodes KW - polystyrenes KW - quantum chemistry Y1 - 2011 U6 - https://doi.org/10.1002/mats.201100016 SN - 1022-1344 VL - 20 IS - 9 SP - 790 EP - 805 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Csuetoertoeki, Renata A1 - Szatmari, Istvan A1 - Koch, Andreas A1 - Heydenreich, Matthias A1 - Kleinpeter, Erich A1 - Fueloep, Ferenc T1 - Synthesis and conformational analysis of new naphth[1,2-e][1,3]oxazino[3,4-c]quinazoline derivatives JF - Tetrahedron N2 - A new highly functionalized aminonaphthol derivative, 1-(amino(2-aminophenyl)methyl)-2-naphthol (4), was synthesized by the reaction of 2-naphthol, 2-nitrobenzaldehyde and tert-butyl carbamate or benzyl carbamate, followed by reduction and/or removal of the protecting group. The aminonaphthol derivative thus obtained was converted in ring-closure reactions with formaldehyde. benzaldehyde and/or phosgene to the corresponding naphth[1,2-e][1,3]oxazino[3,4-c]quinazoline derivatives. The conformational analysis of some derivatives by NMR spectroscopy and accompanying molecular modelling are also reported. KW - Naphthoxazinoquinazolines KW - NMR KW - Conformational analysis KW - DFT calculations KW - Hammett-Brown plots Y1 - 2011 U6 - https://doi.org/10.1016/j.tet.2011.08.074 SN - 0040-4020 VL - 67 IS - 44 SP - 8564 EP - 8571 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Wessig, Pablo A1 - Wawrzinek, Robert A1 - Moellnitz, Kristian A1 - Feldbusch, Elvira A1 - Schilde, Uwe T1 - A new class of fluorescent dyes based on 1,3-benzodioxole and [1,3]-dioxolo[4.5-f]benzodioxole JF - Tetrahedron letters N2 - We report on synthesis and photophysical properties of a new class of fluorescent dyes. They are characterized by large Stokes-shifts, long fluorescence lifetimes in organic solvents and a pronounced dependency of the fluorescence lifetime on the solvent polarity. Also worthy of note is the high bleaching stability. To provide access to biochemical and medical applications a series of derivatives were prepared, which exhibit specific reactivity towards different biologically relevant functional groups (carboxylic acids, amines, maleimides, N-hydroxysuccinimide esters). Furthermore, two alkynes were prepared, which could be used in 'Click' chemistry. KW - Fluorescent dyes KW - Fluorescence lifetime KW - Large Stokes-shifts KW - Heterocycles Y1 - 2011 U6 - https://doi.org/10.1016/j.tetlet.2011.09.058 SN - 0040-4039 VL - 52 IS - 46 SP - 6192 EP - 6195 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Nikolaus, Jörg A1 - Czapla, Sylvia A1 - Möllnitz, Kristian A1 - Höfer, Chris T. A1 - Herrmann, Andreas A1 - Wessig, Pablo A1 - Müller, Peter T1 - New molecular rods - Characterization of their interaction with membranes JF - Biochimica et biophysica acta : Biomembranes N2 - Molecular rods are synthetical molecules consisting of a hydrophobic backbone which are functionalized with varying terminal groups. Here, we report on the interaction of a recently described new class of molecular rods with lipid and biological membranes. In order to characterize this interaction, different fluorescently labeled rods were synthesized allowing for the application of fluorescence spectroscopy and microscopy based approaches. Our data show that the rods are incorporated into membranes with a perpendicular orientation to the membrane surface and enrich preferentially in liquid-disordered lipid domains. These characteristics underline that rods can be applied as stable membrane-associated anchors for functionalizing membrane surfaces. KW - Molecular rod KW - Phospholipid KW - Lipid domain KW - Spiro compound Y1 - 2011 U6 - https://doi.org/10.1016/j.bbamem.2011.08.008 SN - 0005-2736 VL - 1808 IS - 12 SP - 2781 EP - 2788 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Schmidt, Bernd A1 - Geissler, Diana T1 - Olefin-Metathesis-Based Synthesis of Furans by an RCM/Deprotonation/Phosphorylation Sequence and Their Diels-Alder Reactions JF - European journal of organic chemistry N2 - Butenolides, obtained by ring-closing metathesis (RCM) of acrylates, undergo quantitative deprotonation with amide bases. Trapping of the resulting anions with electrophiles, for example, chlorophosphates, give furans. Subsequent DielsAlder reaction and acid-catalysed rearrangement of the resulting oxabicyclonorbornadienes give substituted benzenes. KW - Lactones KW - Metathesis KW - Ruthenium KW - Oxygen heterocycles KW - Metalation Y1 - 2011 U6 - https://doi.org/10.1002/ejoc.201101078 SN - 1434-193X IS - 35 SP - 7140 EP - 7147 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Weber, Nancy A1 - Tiersch, Brigitte A1 - Unterlass, Miriam M. A1 - Heilig, Anneliese A1 - Tauer, Klaus T1 - "Schizomorphic" Emulsion Copolymerization Particles JF - Macromolecular rapid communications N2 - Cryo-electron microscopy, atomic force microscopy, and light microscopy investigations provide experimental evidence that amphiphilic emulsion copolymerization particles change their morphology in dependence on concentration. The shape of the particles is spherical at solids content above 1%, but it changes to rod-like, ring-like, and web-like structures at lower concentrations. In addition, the shape and morphology of these particles at low concentrations are not fixed but very flexible and vary with time between spheres, flexible pearlnecklace structures, and stretched rods. KW - amphiphilic particles KW - emulsion polymerization KW - morphology Y1 - 2011 U6 - https://doi.org/10.1002/marc.201100491 SN - 1022-1336 VL - 32 IS - 23 SP - 1925 EP - 1929 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Bland-Hawthorn, Joss A1 - Ellis, S. C. A1 - Leon-Saval, S. G. A1 - Haynes, R. A1 - Roth, Martin M. A1 - Löhmannsröben, Hans-Gerd A1 - Horton, A. J. A1 - Cuby, J. -G. A1 - Birks, T. A. A1 - Lawrence, J. S. A1 - Gillingham, P. A1 - Ryder, S. D. A1 - Trinh, C. T1 - A complex multi-notch astronomical filter to suppress the bright infrared sky JF - Nature Communications N2 - A long-standing and profound problem in astronomy is the difficulty in obtaining deep near-infrared observations due to the extreme brightness and variability of the night sky at these wavelengths. A solution to this problem is crucial if we are to obtain the deepest possible observations of the early Universe, as redshifted starlight from distant galaxies appears at these wavelengths. The atmospheric emission between 1,000 and 1,800 nm arises almost entirely from a forest of extremely bright, very narrow hydroxyl emission lines that varies on timescales of minutes. The astronomical community has long envisaged the prospect of selectively removing these lines, while retaining high throughput between them. Here we demonstrate such a filter for the first time, presenting results from the first on-sky tests. Its use on current 8 m telescopes and future 30 m telescopes will open up many new research avenues in the years to come. Y1 - 2011 U6 - https://doi.org/10.1038/ncomms1584 SN - 2041-1723 VL - 2 IS - 50 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Fudickar, Werner A1 - Linker, Torsten T1 - Reversible Photooxygenation of Alkynylanthracenes chemical generation of singlet oxygen under very mild conditions JF - Chemistry - a European journal KW - anthracenes KW - oxidation KW - peroxides KW - reversibility KW - singlet oxygen Y1 - 2011 U6 - https://doi.org/10.1002/chem.201102230 SN - 0947-6539 VL - 17 IS - 49 SP - 13661 EP - 13664 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Radziuk, Darya A1 - Skirtach, Andre A1 - Gessner, Andre A1 - Kumke, Michael Uwe A1 - Zhang, Wei A1 - Möhwald, Helmuth A1 - Shchukin, Dmitry T1 - Ultrasonic Approach for Formation of Erbium Oxide Nanoparticles with Variable Geometries JF - Langmuir N2 - Ultrasound (20 kHz, 29 W. cm(-2)) is employed to form three types of erbium oxide nanoparticles in the presence of multiwalled carbon nanotubes as a template material in water. The nanoparticles are (i) erbium carboxioxide nanoparticles deposited on the external walls of multiwalled carbon nanotubes and Er(2)O(3) in the bulk with (ii) hexagonal and (iii) spherical geometries. Each type of ultrasonically formed nanoparticle reveals Er(3+) photoluminescence from crystal lattice. The main advantage of the erbium carboxioxide nanoparticles on the carbon nanotubes is the electromagnetic emission in the visible region, which is new and not examined up to the present date. On the other hand, the photoluminescence of hexagonal erbium oxide nanoparticles is long-lived (mu s) and enables the higher energy transition ((4)S(3/2)-(4)I(15/2)), which is not observed for spherical nanoparticles. Our work is unique because it combines for the first time spectroscopy of Er(3+) electronic transitions in the host crystal lattices of nanoparticles with the geometry established by ultrasound in aqueous solution of carbon nanotubes employed as a template material. The work can be of great interest for "green" chemistry synthesis of photoluminescent nanoparticles in water. Y1 - 2011 U6 - https://doi.org/10.1021/la203622u SN - 0743-7463 VL - 27 IS - 23 SP - 14472 EP - 14480 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Stojanovic, Milovan A1 - Markovic, Rade A1 - Kleinpeter, Erich A1 - Baranac-Stojanovic, Marija T1 - Endo-Mode cyclizations of vinylogous N-acyliminium ions as a route to the synthesis of condensed thiazolidines JF - Tetrahedron N2 - endo-Mode cyclizations of vinylogous N-acyliminium ions incorporating heteroatom-based nucleophiles have been examined as a route to the synthesis of condensed thiazolidines. The scope of these reactions and stereochemical outcome are discussed and explained using quantum chemical calculations. KW - Vinylogous N-acyliminium ion KW - endo-Mode cyclization KW - Condensed thiazolidines KW - Quantum chemical calculations Y1 - 2011 U6 - https://doi.org/10.1016/j.tet.2011.10.011 SN - 0040-4020 VL - 67 IS - 49 SP - 9541 EP - 9554 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kristen-Hochrein, Nora A1 - Laschewsky, André A1 - Miller, Reinhard A1 - von Klitzing, Regine T1 - Stability of foam Films of oppositely charged polyelectrolyte/surfactant mixtures - effect of isoelectric point JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry N2 - In the present paper, the influence of the surfactant concentration and the degree of charge of a polymer on foam film properties of oppositely charged polyelectrolyte/surfactant mixtures has been investigated. To verify the assumption that the position of the isoelectric point (IEP) does not change the character of the foam film stabilities, the position of the IEP of the polyelectrolyte/surfactant mixtures has been shifted in two different ways. Within the first series of experiments, the foam. film properties were studied using a fixed surfactant concentration of 3 x 10(-5) M in the mixture. Due to the low surfactant concentration, this is a rather dilute system. In the second approach, a copolymer of nonionic and ionic monomer units was Used to lower the charge density of the polymer. This gave rise to additional interactions between the polyelectrolyte and the surfactant, which makes the description of the foam film behavior more complex. In both systems, the same characteristics of the foam film stabilities were found: The foam film stability is reduced toward the IEP of the system, followed by a destabilization around the IEP., At polyelectrolyte concentrations above the IEP, foam films are very stable. However, the concentration range where unstable films were formed was rather broad, and the mechanisms leading to the destabilization had different origins. The results were compared with former findings on PAMPS/C(14)TAB mixtures with an IEP of 10(-4)M.(1) Y1 - 2011 U6 - https://doi.org/10.1021/jp206964k SN - 1520-6106 VL - 115 IS - 49 SP - 14475 EP - 14483 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Fechner, Mabya A1 - Koetz, Joachim T1 - Potentiometric behavior of Polyampholytes based on N,N'-diallyl-N,N'-dimethylammonium chloride and maleamic acid derivatives JF - Macromolecular chemistry and physics N2 - Strongly alternating copolymers (PalH, PalPh, PalPhBisCarb) composed of N,N'-diallyl-N,N'-dimethyl-ammonium chloride (DADMAC) and maleamic acid derivatives (MAD) are synthesized by a water-based free radical copolymerization using 4,4-azobis(4-cyanovaleric acid) (V501) as the initiator. The structure of the copolymers is verified by 1H-NMR, elemental analysis, and thermogravimetric measurements, and the physicochemical properties are investigated by viscometric and potentiometric techniques. Potentiometric titration curves show that the acidity of the carboxylic groups strongly depends on the degree of dissociation and the ionic strength. Since all copolymers behave as polycations at low degree of dissociation, a transition from an extended chain to a coil conformation can be identified by reaching the isoelectric point (IEP). KW - acidity constants KW - radical polymerization KW - polyampholytes KW - viscosity KW - conformational transitions Y1 - 2011 U6 - https://doi.org/10.1002/macp.201100532 SN - 1022-1352 VL - 212 IS - 24 SP - 2691 EP - 2699 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Kröner, Dominik T1 - Chiral distinction by ultrashort laser pulses electron wavepacket dynamics incorporating magnetic interactions JF - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory N2 - The qualitative and quantitative distinction of enantiomers is one of the key issues in chemical analysis. In the last years, circular dichroism (CD) has been combined with laser ionization mass spectrometry (LIMS), applying resonance enhanced multiphoton ionization (REMPI) with ultrashort laser pulses. We present theoretical investigations on the CD in the populations of the first electronic excited state of the REMPI process, caused by the interaction of 3-methylcyclopentanone with either left or right circular polarized fs-laser pulses. For this we performed multistate laser driven many electron dynamics based on ab initio electronic structure calculations, namely, TD-CIS(D)/6-311++(2d,2p). For a theoretical description of these experiments, a complete description of the field-dipole correlation is mandatory, including both electric field electric dipole and magnetic field magnetic dipole interactions. The effect of various pulse parameters on the CD are analyzed and compared with experimental results to gain further understanding of the key elements for an optimal distinction of enantiomers. Y1 - 2011 U6 - https://doi.org/10.1021/jp207270s SN - 1089-5639 VL - 115 IS - 50 SP - 14510 EP - 14518 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Zehm, Daniel A1 - Laschewsky, André A1 - Liang, Hua A1 - Rabe, Jürgen P. T1 - Straightforward access to amphiphilic dual bottle brushes by combining RAFT, ATRP, and NMP polymerization in one sequence JF - Macromolecules : a publication of the American Chemical Society N2 - Molecular brush diblock copolymers were synthesized by the orthogonal overlay of the RAFT (reversible addition-fragmentation chain transfer), the ATRP (atom transfer radical polymerization), and the NMP (nitroxide-mediated polymerization) techniques. This unique combination enabled the synthesis of the complex amphiphilic polymers without the need of postpolymerization modifications, using a diblock copolymer intermediate made from two selectively addressable inimers and applying a sequence of four controlled free radical polymerization steps in total. The resulting polymers are composed of a thermosensitive poly(N-isopropylacrylamide) brush as hydrophilic block and a polystyrene brush as hydrophobic block, thus translating the structure of the established amphiphilic diblock copolymers known as macro surfactants to the higher size level of "giant surfactants". The dual molecular brushes and the aggregates formed on ultra flat solid substrates were visualized by scanning force microscopy (SFM). Y1 - 2011 U6 - https://doi.org/10.1021/ma2015613 SN - 0024-9297 VL - 44 IS - 24 SP - 9635 EP - 9641 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Stojanovic, Milovan A1 - Markovic, Rade A1 - Kleinpeter, Erich A1 - Baranac-Stojanovic, Marija T1 - endo-Mode cyclizations of vinylogous N-acyliminium ions as a route to the synthesis of condensed thiazolidines Y1 - 2011 SN - 0040-4020 ER - TY - JOUR A1 - Csütörtöki, Renáta A1 - Szatmári, István A1 - Koch, Andreas A1 - Heydenreich, Matthias A1 - Kleinpeter, Erich A1 - Fulop, Ferenc T1 - Synthesis and conformational analysis of new naphth[1,2-e][1,3]oxazino[3,4-c]quinazoline derivatives Y1 - 2011 SN - 0040-4020 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Chelatoaromaticity-existing: yes or no? An answer given by spatial magnetic properties (through space NMR shieldings-TSNMRS) Y1 - 2011 SN - 1463-9076 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - The anisotropic effect of functional groups in 1H NMR spectra is the molecular response property of spatial NICS-the frozen conformational equilibria of 9-arylfluorenes N2 - Rotation about the single bond adjoining the aryl and fluorene moieties in 9-arylfluorenes can be frozen out on the NMR timescale if methyl groups are located at either one or both of the ortho positions of the aryl substituent. In the ground-state of these rotamers, the planes of the aryl and fluorene moieties are perpendicular to each other and the methyl protons are either shielded or deshielded, respectively, due to the ringe current effect of the fluorene moiety. This anisotropic effect on the 1H chemical shifts of the methyl protons has been quantified on the basis of through- space NMR shieldings (TSNMRS) and subsequently _______ compared with the experimentally observed chemical shift differences _____. In this context, the experimental anisotropic effects of functional groups in the !H NMR have proven to quantitatively be the molecular response property of theoretical spatial nucleus independent chemical shieldings (NICS). Differences between _______ and _____ were, for the first time, also quantified as arising from steric compression. Y1 - 2011 UR - http://www.sciencedirect.com/science/article/pii/S0040402011008507 (13.9.13) SN - 0040-4020 ER -