TY  - JOUR
A1  - Machumi, Francis
A1  - Yenesew, Abiy
A1  - Midiwo, Jacob O.
A1  - Heydenreich, Matthias
A1  - Kleinpeter, Erich
A1  - Tekwani, Babu L.
A1  - Khan, Shabana I.
A1  - Walker, Larry A.
A1  - Muhammad, Ilias
T1  - Antiparasitic and anticancer carvotacetone derivatives of Sphaeranthus bullatus
JF  - Natural product communications : an international journal for communications and reviews
N2  - The CH2Cl2-MeOH (1:1) extract of the aerial parts of Sphaeranthus bullatus, an annual herb native to tropical East Africa, showed activity against chloroquine sensitive D6 (IC50 9.7 mu g/mL) and chloroquine resistant W2 (IC50 15.0 mu g/mL) strains of Plasmodium falciparum. Seventeen secondary metabolites were isolated from the extract through conventional chromatographic techniques and identified using various spectroscopic methods. The compounds were evaluated for their in vitro antiplasmodial, antileishmanial and anticancer activities revealing activity of four carvotacetone derivatives, namely 3-acetoxy-7-hydroxy-5-tigloyloxycarvotacetone (1) 3,7-dihydroxy-5-tigloyloxycarvotacetone (2), 3-acetoxy-5,7-dihydroxycarvotacetone (3) and 3,5,7-trihydroxycarvotacetone (4); with antiplasmodial IC50 values of 1.40, 0.79, 0.60 and 3.40 mu g/mL, respectively, against chloroquine sensitive D6 strains of P. falciparum; antiplasmodial activity of IC50 2.00, 0.90, 0.68 and 2.80 mu g/mL respectively, against chloroquine resistant W2 strains of P. falciparum, antileishmanial IC50, values of 0.70, 3.00, 0.70 and 17.00 mu g/mL, respectively, against the parasite L. donovanii promastigotes, and anticancer activity against human SK-MEL, KB, BT-549 and SK-OV-3 tumor cells, with IC50 values between <1.1 - 5.3 mu g/mL, for 1-3. In addition, cytotoxic effects of the active compounds were evaluated against monkey kidney fibroblasts (VERO) and pig kidney epithelial cells (LLC-PK11). The structures of carvotacetone derivatives were determined by ID and 2D NMR spectroscopy; the absolute stereochemical configuration of 3-acetoxy-7-hydroxy-5-tigloyloxycarvotacetone (I) was determined as 3R, 4R, 5S by circular dichroism, specific rotation, H-1 NMR and 2D NMR ROESY and NOESY experiments.
KW  - Sphaeranthus bullatus
KW  - Asteraceae
KW  - Antiplasmodial
KW  - Antileishmanial
KW  - Anticancer
KW  - Carvotacetones
Y1  - 2012
SN  - 1934-578X
VL  - 7
IS  - 9
SP  - 1123
EP  - 1126
PB  - NPC
CY  - Westerville
ER  - 
TY  - JOUR
A1  - Induli, Martha
A1  - Cheloti, Michael
A1  - Wasuna, Antonina
A1  - Wekesa, Ingrid
A1  - Wanjohi, John M.
A1  - Byamukama, Robert
A1  - Heydenrich, Matthias
A1  - Makayoto, Moses
A1  - Yenesew, Abiy
T1  - Naphthoquinones from the roots of Aloe secundiflora
JF  - Phytochemistry letters
N2  - Two new naphthoquinones, 5-hydroxy-3,6-dimethoxy-2-methylnaphthalene-1,4-dione and 5,8-dihydroxy-3-methoxy-2-methylnaphthalene-1,4-dione, were isolated from the roots of Aloe secundiflora together with the known compounds chrysophanol, helminthosporin, isoxanthorin, ancistroquinone C, aloesaponarins I and II, aloesaponols I and II, laccaic acid D methyl ester and asphodelin. The structures were elucidated based on spectroscopic evidence. This appears to be the first report on the occurrence of naphthoquinones in the genus Aloe. Aloesaponarin I and 5-hydroxy-3,6-dimethoxy-2-methylnaphthalene-1,4-dione showed anti-bacterial activity against Mycobacterium tuberculosis with MIC values of 21-23 mu g/mL in the Microplate Alamar Blue Assay (MABA) and Low Oxygen Recovery Assay (LORA); 5-hydroxy-3,6-dimethoxy-2-methylnaphthalene-1,4-dione also showed cytotoxicity against the Vero cell line (IC50 = 10.2 mu g/mL).
KW  - Aloe secundiflora
KW  - Asphodelaceae
KW  - Roots
KW  - Naphthoquinone
KW  - 5-Hydroxy-3,6-dimethoxy-2-methylnaphthalene-1,4-dione 5,8-Dihydroxy-3-methoxy-2-methylnaphthalene-1,4-dione
KW  - Anthraquinone
KW  - Aloesaponarin I
KW  - Mycobacterium tuberculosis
Y1  - 2012
U6  - https://doi.org/10.1016/j.phytol.2012.04.014
SN  - 1874-3900
VL  - 5
IS  - 3
SP  - 506
EP  - 509
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Gumula, Ivan
A1  - Heydenreich, Matthias
A1  - Derese, Solomon
A1  - Ndiege, Isaiah O.
A1  - Yenesew, Abiy
T1  - Four isoflavanones from the stem bark of Platycelphium voense
JF  - Phytochemistry letters
N2  - From the stem bark of Platycelphium voense (Leguminosae) four new isoflavanones were isolated and characterized as (S)-5,7-dihydroxy-2 ',4 '-dimethoxy-3 '-(3 ''-methylbut-2 ''-enyl)-isoflavanone (trivial name platyisoflavanone A), (+)-5,7,2 '-trihydroxy-4 '-methoxy-3 '-(3 ''-methylbut-2 ''-enyl)-isoflavanone (platyisoflavanone B), 5,7-dihydroxy-4 '-methoxy-2 ''-(2 '''-hydroxyisopropyl)-dihydrofurano-[4 '',5 '':3 ',2 ']-isoflavanone (platyisoflavanone C) and 5,7,2 ',3 ''-tetrahydroxy-2 '',2 ''-dimethyldihydropyrano-[5 '',6 '':3 ',4 ']-isoflavanone (platyisoflavanone D). In addition, the known isoflavanones, sophoraisoflavanone A and glyasperin F; the isoflavone, formononetin; two flavones, kumatakenin and isokaempferide; as well as two triterpenes, betulin and beta-amyrin were identified. The structures were elucidated on the basis of spectroscopic evidence. Platyisoflavanone A showed antibacterial activity against Mycobacterium tuberculosis in the microplate alamar blue assay (MABA) with MIC = 23.7 mu M, but also showed cytotoxicity (IC50 = 21.1 mu M) in the vero cell test.
KW  - Platycelphium voense
KW  - Stem bark
KW  - Leguminosae
KW  - Isoflavanones
KW  - Platyisoflavanone
KW  - Mycobacterium tuberculosis
Y1  - 2012
U6  - https://doi.org/10.1016/j.phytol.2011.11.012
SN  - 1874-3900
VL  - 5
IS  - 1
SP  - 150
EP  - 154
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Munzke, Dorit
A1  - Saunders, John
A1  - Omrani, Hengameh
A1  - Reich, Oliver
A1  - Loock, Hans-Peter
T1  - Modeling of fiber-optic fluorescence probes for strongly absorbing samples
JF  - Applied optics
N2  - The dynamic range of fiber-optic fluorescent probes such as single fibers and fiber bundles is calculated for strongly absorbing samples, such as process liquids, foodstuffs, and lubricants. The model assumes an excitation beam profile based on a Lambertian light source and uses analytical forms of the collection efficiency, followed by an Abel transformation and numerical integration. It is found that the effect of primary absorption of the excitation light and secondary absorption of the fluorescence is profound. For fiber bundles and bifurcated fiber probes, the upper accessible concentration limit is roughly given by the absorption length of the primary and secondary absorption. Fluorescence detectors that are placed at right angles to the excitation beam axis or collinear to the beam axis are equally strongly affected by secondary absorption. A probe in which the same fiber is used for excitation and for collection of the fluorescence emerges as the fiber probe with the largest accessible concentration range.
Y1  - 2012
U6  - https://doi.org/10.1364/AO.51.006343
SN  - 1559-128X
SN  - 2155-3165
VL  - 51
IS  - 26
SP  - 6343
EP  - 6351
PB  - Optical Society of America
CY  - Washington
ER  - 
TY  - JOUR
A1  - Ruiz, Salome Vargas
A1  - Hass, Roland
A1  - Reich, Oliver
T1  - Optical monitoring of milk fat phase transition within homogenized fresh milk by Photon Density Wave spectroscopy
JF  - International dairy journal
N2  - Photon Density Wave (PDW) spectroscopy was applied for temperature dependent monitoring of melting and crystallization of milk fat within homogenized fresh milk. As an in-line process analytical technique, PDW spectroscopy quantifies continuously the optical properties of turbid material, providing an insight into its structural processes. Here, the measured absorption coefficients reflect temperature as well as fat content of milk and the reduced scattering coefficients probe physical changes of the light scattering fat droplets and casein micelles. Thermal processing reveals breakpoints within the temperature trend of the reduced scattering coefficient of fat containing milk. Found at 16 degrees C and 24 degrees C while cooling and heating, respectively, they are associated to the phase transitions of milk fat. Continuous isothermal measurement of the optical coefficients showed that the crystallization process requires several hours. The strongly changing reduced scattering coefficient implies that the thermal history of milk will have a major impact on any method based on light scattering as quantitative analytical technique.
Y1  - 2012
U6  - https://doi.org/10.1016/j.idairyj.2012.03.012
SN  - 0958-6946
VL  - 26
IS  - 2
SP  - 120
EP  - 126
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Wöhl-Bruhn, Stefanie
A1  - Badar, Muhammad
A1  - Bertz, Andreas
A1  - Tiersch, Brigitte
A1  - Koetz, Joachim
A1  - Menzel, Henning
A1  - Müller, Peter P.
A1  - Bunjes, Heike
T1  - Comparison of in vitro and in vivo protein release from hydrogel systems
JF  - Journal of controlled release
N2  - Hydrogel systems based on hydroxyethyl starch-polyethylene glycol methacrylate (HES-P(EG)(6)MA) or hydroxyethyl starch methacrylate (HES-MA) were used to assess the protein release behavior. Here, we analyzed the in vitro release of FITC-anti-human antibodies incorporated in either HES-P(EG)(6)MA or HES-MA hydrogel delivery systems in PBS or human serum. In addition, hydrogel disks and microparticles prepared from the two polymers were subcutaneously implanted in BALB/c mice. The in vivo release of FITC-IgG was non-invasively monitored by an in vivo imaging system (IVIS 200) over a time period of up to 3 months. The imaging system allowed to asses individual animals over time, therefore only a small number of animals was required to obtain high quality data. The reduction in fluorescence intensity at the site of administration was compared to in vitro release profiles. These investigations demonstrated a sustained release from HES-MA hydrogel disks compared to rapidly degrading HES-P(EG)(6)MA disks and microparticles. The sustained release from HES-MA disks could be further optimized by using increased polymer concentrations. Human serum as in vitro release medium reflected better the in vivo release from HES-P(EG)(6)MA systems than PBS, suggesting that the presence of organic substances like proteins or lipids may play a significant role for the release kinetics.
KW  - In vivo imaging system (IVIS)
KW  - Hydrogel disks
KW  - Hydrogel microparticles
KW  - Release
KW  - In vivo-in vitro correlation
KW  - Hydroxyethyl starch (HES)
Y1  - 2012
U6  - https://doi.org/10.1016/j.jconrel.2012.05.049
SN  - 0168-3659
VL  - 162
IS  - 1
SP  - 127
EP  - 133
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Koeth, Anja
A1  - Tiersch, Brigitte
A1  - Appelhans, Dietmar
A1  - Gradzielski, Michael
A1  - Cölfen, Helmut
A1  - Koetz, Joachim
T1  - Synthesis of Core-Shell Gold Nanoparticles with Maltose-Modified Poly(Ethyleneimine)
JF  - Journal of dispersion science and technology
N2  - The synthesis of ultrafine gold nanoparticles in presence of maltose-modified hyperbranched poly(ethyleneimines) (PEI) is described. The polymer acted as both a reducing and stabilising agent in the particle formation process. The nanoparticles were characterized by means of dynamic light scattering (DLS), transmission electron microscopy (TEM), analytical ultracentrifugation (AUC), small-angle x-ray scattering (SAXS), and small-angle neutron scattering (SANS). The mechanism of nanoparticle formation can be described in two steps. The reduction process of the Au3+ ions located in the inner coil region of the hyperbranched PEI led to the formation of a compact gold core, and is accompanied by a collapse of the polymer coil. Therefore, in the subsequent reduction process a gold-polymer hybrid shell is formed. By using the PEI of higher molar mass, core-shell gold nanoparticles of about 3.6 nm size with a more narrow size distribution and special fluorescence behavior could be synthesized.
KW  - Gold nanoparticles
KW  - gold-polymer hybrid shell
KW  - maltose-modified poly(ethyleneimine)
Y1  - 2012
U6  - https://doi.org/10.1080/01932691.2010.530084
SN  - 0193-2691
VL  - 33
IS  - 1-3
SP  - 52
EP  - 60
PB  - Taylor & Francis Group
CY  - Philadelphia
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Shainyan, Bagrat A.
A1  - Kirpichenko, Svetlana V.
A1  - Shlykov, Sergei A.
T1  - Structure and Conformational Properties of 1,3,3-Trimethyl-1,3-Azasilinane : Gas Electron Diffraction, Dynamic NMR, and Theoretical Study.
Y1  - 2012
SN  - 1089-5639
ER  - 
TY  - JOUR
A1  - Shainyan, Bagrat A.
A1  - Suslova, Elena N.
A1  - Kleinpeter, Erich
T1  - Conformational analysis of 4,4-dimethyl-1-(trifluoromethylsulfonyl)-1,4-azasilinane and 2,2,6,6-tetramethyl-4- (trifluoromethylsulfonyl)-1,4,2,6-oxazadisilinane
N2  - 4,4-Dimethyl-1-(trifluoromethylsulfonyl)-1,4-azasilinane 1 and 2,2,6,6-tetramethyl-4-(trifluoromethylsulfonyl)- 1,4,2,6-oxazadisilinane 2 were studied by variable temperature dynamic 1H, 13C, 19F NMR spectroscopy and theoretical calculations at the DFT (density functional theory) and MP2 (Moller-Plesset 2) levels of theory. Both kinetic (barriers to ring inversion) and thermodynamic data (frozen conformational equilibria) could be obtained for the two compounds. The computations revealed two minima on the potential energy surface for molecules 1 and 2 corresponding to the rotamers with the CF3SO2 group directed inward and outward the ring, the latter being 0.20.4 kcal/mol (for 1) and 1.1 kcal/mol (for 2) more stable than the former. The vibrational calculations at the DFT and MP2 levels of theory give the values of the free energy difference Delta G degrees for the 'inward' reversible arrow 'outward' equilibrium consistent with those determined from the experimentally measured ratio of the rotamers. The structure of crystalline compound 2 was ascertained by X-ray diffraction analysis.
Y1  - 2012
ER  - 
TY  - JOUR
A1  - Lazareva, Nataliya F.
A1  - Albanov, Alexander I.
A1  - Shainyan, Bagrat A.
A1  - Kleinpeter, Erich
T1  - Synthesis and conformational properties of substituted 1,4,2-oxazasilinanes: low temperature NMR study and quantum chemical calculations
Y1  - 2012
UR  - http://www.sciencedirect.com/science/article/pii/S0040402011018321
U6  - https://doi.org/10.1016/j.tet.2011.11.077
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Stojanovic, Milovan
A1  - Markovic, Rade
A1  - Baranac-Stojanovic, Marija
T1  - Synthesis of thiazolidine-fused heterocycles via exo-mode cyclizations of vinylogous N-acyliminium ions
N2  - Syntheses of thiazolidine-fused heterocycles via exo-mode cyclizations of vinylogous N-acyliminium ions incorporating heteroatom-based nucleophiles have been examined and discussed. The formation of (5,6)-membered systems was feasible with all nucleophiles tried (O, S and N), while the closing of the five-membered ring was restricted to O- and S-nucleophiles. The closure of a four-membered ring failed. Instead, the bicyclic (5,6)-membered acetal derivative and the tricyclic system with an eight-membered central ring were obtained from the substrates containing O and S nucleophilic moieties, respectively. The reaction outcome and stereochemistry are rationalized using quantum chemical calculations at B3LYP/6-31G(d) level. The exclusive cis-stereoselectivity in the formation of (5,6)- and (5,5)-membered systems results from thermodynamic control, whereas the formation of the eight-membered ring was kinetically controlled.
Y1  - 2012
SN  - 1477-0520
ER  - 
TY  - JOUR
A1  - Shainyan, Bagrat A.
A1  - Kleinpeter, Erich
T1  - Conformational preferences of Si-Ph,H and Si-Ph,Me silacyclohexanes and 1,3-thiasilacyclohexanes : Additivity of conformational energies in 1,1-disubstituted heterocyclohexanes
N2  - The conformational equilibria of 1-phenyl-1-silacyclohexane 1, 3-phenyl-1,3-thiasilacyclohexane 2, 1-methyl-1- phenyl-1-silacyclohexane 3, and 3-methyl-3-phenyl-1,3-thiasilacyclohexane 4 have been studied for the first time by low temperature C-13 NMR spectroscopy at 103 K. Predominance of the equatorial conformer of compound 1 (Ph-eq/Ph-ax=78%:22%) is much less than in its carbon analog, phenylcyclohexane (nearly 100% of Ph-eq). And in contrast to 1-methyl-1- phenylcyclohexane, the conformers with the equatorial Ph group are predominant for compounds 3 and 4: at 103 K, Ph-eq/Ph- ax ratios are 63%:37% (3) and 68%:32% (4). As the Si-C bonds are elongated with respect to C-C bonds, the barriers to ring inversion are only between 5.2-6.0 (ax -> eq) and 5.4-6.0 (eq -> ax) kcal mol(-1). Parallel calculations at the DFT and MP2 level of theory (as well as the G2 calculations for compound 1) show qualitative agreement with the experiment. The additivity/nonadditivity of conformational energies of substituents on cyclohexane and silacyclohexane derivatives is analyzed. The geminally disubstituted cyclohexanes containing a phenyl group show large deviations from additivity, whereas in 1-methyl-1-phenyl-1-silacyclohexane and 3-methyl-3-phenyl-1,3-thiasilacyclohexane the effects of the methyl and phenyl groups are almost additive. The reasons for the different conformational preferences in carbocyclic and heterocyclic compounds are analyzed using the homodesmotic reactions approach.
Y1  - 2012
UR  - http://www.sciencedirect.com/science/article/pii/S0040402011016620 (25.11.2013)
SN  - 0040-4020
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Heydenreich, Matthias
A1  - Koch, Andreas
A1  - Linker, Torsten
T1  - Synthesis and NMR spectroscopic conformational analysis of esters of 4-hydroxy-cyclohexanone-the more polar the molecule the more stable the axial conformer
N2  - The esters of 4-hydroxy-cyclohexanone and a series of carboxylic acids R-COOH with R of different electronic and steric influence (R=Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, sec-Bu, t-Bu, CF3, CH2Cl, CHCl2, CCl3, CH2Br, CHBr2, and CBr3) were synthesized and the conformational equilibria studied by 1H and 13C NMR spectroscopy at 103 K and at 295 K, respectively. The geometry of optimized structures of the axial/equatorial chair conformers was computed at the ab initio MO and DFT levels of theory. Only one preferred conformation was obtained for the axial and the equatorial conformer as well. When comparing the conformational equilibria of the cyclohexanone esters with those of the corresponding cyclohexyl esters a certain polarity contribution of the cyclohexanone framework was revealed, which is independent of the substituent effects and increases the stability of the axial conformers by a constant amount.
Y1  - 2012
SN  - 0040-4020
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Neuvonen, Kari
A1  - Neuvonen, Helmi
A1  - Koch, Andreas
T1  - Taft equation in the light of NBO computations : Introduction of a novel polar computational substituent constant scale for alkyl groups
Y1  - 2012
SN  - 2210-271X
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Lazareva, Nataliya F.
A1  - Shainyan, Bagrat A.
A1  - Schilde, Uwe
A1  - Chipania, Nina N.
T1  - Synthesis, Molecular Structure, Conformational Analysis, and Chemical Properties of Silicon-Containing Derivatives of Quinolizidine
Y1  - 2012
SN  - 0022-3263
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Koch, Andreas
T1  - Spatial magnetic properties subject to lone pair and pi electron delocalization in benzenoid and quinoid structures : are quinoid tautomers really nonaromatic?
N2  - The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of benzenoid and quinoid tautomeric structures such as benzodifurantrione and phenazine-type molecules have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept of Paul von Rague Schleyer and visualized as iso- chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values were employed to quantify and visualize the partial aromaticity of the studied compounds. In the case of the surprisingly more stable quinoid tautomers, the aromaticity-synonymous with stability due to the conjugation of p electrons and lone pairs-was not found to be particularly reduced.
Y1  - 2012
SN  - 1551-7004
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Modarresi-Alam, Ali Reza
A1  - Inaloo, Iman Dindarloo
T1  - Synthesis of primary thiocarbamates by silica sulfuric acid as effective reagent under solid-state and solution conditions
N2  - A simple and efficient method for the conversion of alcohols and phenols to primary O-thiocarbamates and S- thiocarbamates in the absence of solvent (solvent-free condition) using silica sulfuric acid (SiO2OSO3H) as a solid acid is described. The products are easily distinguished by IR, NMR and X-ray data. X-ray data of the compounds reveal a planar trigonal orientation of the NH2 nitrogen atom with the partial C,N double-bond character and the CS or CO groups in synperiplanar position with CarylO and CalkylS moieties, respectively. Moreover, the OCSNH2 group which is perpendicular to the plane of the benzene ring in 1c and the central thiocarbamate SCONH2 group in 2b are essentially planar.
Y1  - 2012
SN  - 0022-2860
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
T1  - Are lithium and sodium salts of N-(2-hydroxyphenyl)-salicylaldimine aromatic metalla-hetero[10]annulenes? An answer given by spatial magnetic properties (through space NMR shieldings-TSNMRS)
N2  - The spatial magnetic properties (through space NMR shieldings-TSNMRS) of the enol tautomer of N-(2- hydroxyphenyl)-salicylaldimine, the lithium and sodium salts in comparison with cyclodecapentaene and pyrano[2,3- b]pyrrole were studied to answer this question.
Y1  - 2012
SN  - 1463-9076
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Branac-Stojanovi, Marija
A1  - Koch, Andreas
T1  - Is the Conventional Interpretation of the Anisotropic Effects of CC Double Bonds and Aromatic Rings in NMR Spectra in Terms of the -Electron Shielding/Deshielding Contributions Correct?
N2  - Based on the nucleus-independent chemical shift (NICS) concept, isotropic magnetic shielding values have been computed along the three Cartesian axes for ethene, cyclobutadiene, benzene, naphthalene, and benzocyclobutadiene, starting from the molecular/ring center up to 10;Å away. These through-space NMR spectroscopic shielding (TSNMRS) values, which reflect the anisotropic effects, have been broken down into contributions from localized- and canonical molecular orbitals (LMOs and CMOs); these contributions revealed that the proton NMR spectroscopic chemical shifts of nuclei that are spatially close to the C=C double bond or the aromatic ring should not be explained in terms of the conventionally accepted ;-electron shielding/deshielding effects. In fact, these effects followed the predictions only for the antiaromatic cyclobutadiene ring.
Y1  - 2012
SN  - 1521-3765
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Balci, Kubilay
A1  - Yapar, G.
A1  - Akkaya, S.
A1  - Akyuz, S.
A1  - Koch, Andreas
T1  - A conformational analysis and vibrational spectroscopic investigation on 1,2-bis(o-carboxyphenoxy) ethane molecule
N2  - The minima on the potential energy surface of 1,2-bis(o-carboxyphenoxy) ethane (CPE) molecule in its electronic ground state were searched by a molecular dynamics simulation performed with MM2 force field. For each of the found minimum-energy conformers, the corresponding equilibrium geometry, charge distribution, HOMO-LUMO energy gap, force field, vibrational normal modes and associated IR and Raman spectral data were determined by means of the density functional theory (DFT) based electronic structure calculations carried out by using B3LYP method and various Pople- style basis sets. The obtained theoretical data confirmed the significant effects of the intra- and inter-molecular hydrogen bonding interactions on the conformational structure, force field, and group vibrations of the molecule. The same data have also revealed that two of the determined stable conformers, both of which exhibit pseudo-crown structure, are considerably more favorable in energy to the others and accordingly provide the major c ntribution to the experimental spectra of CPE. In the light of the improved vibrational spectral data obtained within the "SQM FF" methodology and "Dual Scale Factors" approach for the monomer and dimer forms of these two conformers, a reliable assignment of the fundamental bands observed in the experimental room-temperature IR and Raman spectra of the molecule was given, and the sensitivities of its group vibratb20s to conformation, substitution and dimerization were discussed.
Y1  - 2012
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Schainyan, Bagrat A.
A1  - Kirpichenko, Svetlane V.
T1  - Synthesis and conformational properties of 1,3-dimethyl-3-phenyl-1,3-azasilinane : low temperature dynamic NMR and computational study
N2  - 1,3-Dimethyl-3-phenyl-1,3-azasilinane was synthesized and its conformational behavior was studied by the low temperature NMR spectroscopy and quantum chemical calculations. The compound was shown to exist as an equilibrium mixture of the PhaxMeeq and PheqMeax chair conformers with the N-methyl substituent in equatorial position. The barrier to ring inversion was also determined.
Y1  - 2012
SN  - 1551-7004
ER  - 
TY  - JOUR
A1  - Awad, Duha Jawad
A1  - Koch, Andreas
A1  - Mickler, Wulfhard
A1  - Schilde, Uwe
A1  - Strauch, Peter
T1  - EPR spectroscopy of 4, 4 '-Bis(tert-butyl)-2, 2 '-bipyridine-1, 2-dithiolatocuprates(II) in host lattices with different coordination geometries
JF  - Zeitschrift für anorganische und allgemeine Chemie
N2  - A series of new heteroleptic MN2S2 transition metal complexes with M = Cu2+ for EPR measurements and as diamagnetic hosts Ni2+, Zn2+, and Pd2+ were synthesized and characterized. The ligands are N2 = 4, 4'-bis(tert-butyl)-2, 2'-bipyridine (tBu2bpy) and S2 =1, 2-dithiooxalate, (dto), 1, 2-dithiosquarate, (dtsq), maleonitrile-1, 2-dithiolate, or 1, 2-dicyanoethene-1, 2-dithiolate, (mnt). The CuII complexes were studied by EPR in solution and as powders, diamagnetically diluted in the isostructural planar [NiII(tBu2bpy)(S2)] or[PdII(tBu2bpy)(S2)] as well as in tetrahedrally coordinated[ZnII(tBu2bpy)(S2)] host structures to put steric stress on the coordination geometry of the central CuN2S2 unit. The spin density contributions for different geometries calculated from experimental parameters are compared with the electronic situation in the frontier orbital, namely in the semi-occupied molecular orbital (SOMO) of the copper complex, derived from quantum chemical calculations on different levels (EHT and DFT). One of the hosts, [NiII(tBu2bpy)(mnt)], is characterized by X-ray structure analysis to prove the coordination geometry. The complex crystallizes in a square-planar coordination mode in the monoclinic space group P21/a with Z = 4 and the unit cell parameters a = 10.4508(10) angstrom, b = 18.266(2) angstrom, c = 12.6566(12) angstrom, beta = 112.095(7)degrees. Oxidation and reductions potentials of one of the host complexes, [Ni(tBu2bpy)(mnt)], were obtained by cyclovoltammetric measurements.
KW  - 1
KW  - 2-Dithiosquarate
KW  - 1
KW  - 2-Dithiooxalate
KW  - 1
KW  - 2-Dicyanoethene-1
KW  - 2-dithiolate
KW  - 4
KW  - 4'-Bis(tert-butyl)-2
KW  - 2'-bipyridine
KW  - X-ray structure
KW  - EPR
KW  - Copper
KW  - Nickel
KW  - Zinc
Y1  - 2012
U6  - https://doi.org/10.1002/zaac.201100517
SN  - 0044-2313
VL  - 638
IS  - 6
SP  - 965
EP  - 975
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Primus, Philipp-A.
A1  - Kumke, Michael Uwe
T1  - Flash photolysis study of complexes between salicylic acid and lanthanide ions in water
JF  - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory
N2  - In the natural environment humic substances (HS) represent a major factor determining the speciation of metal ions, e.g., in the context of radionuclide migration. Here, due to their intrinsic sensitivity and selectivity, spectroscopic methods are often applied, requiring a fundamental understanding of the photophysical processes present in such HS-metal complexes. Complexes with different metal ions were studied using 2-hydroxybenzoic acid (2HB) as a model compound representing an important part of the chelating substructures in HS. In flash photolysis experiments under direct excitation of 2HB in the absence and the presence of different lanthanide ions, the generation and the decay of the 2HB triplet state, of the phenoxy radical, and of the solvated electron were monitored. Depending on the lanthanide ion different intracomplex processes were observed for these transient species including energy migration to and photoreduction of the lanthanide ion. The complexity of the intracomplex photophysical processes even for small molecules such as 2HB underlines the necessity to step-by-step approach the photochemical reactivity of HS by using suitable model compounds.
Y1  - 2012
U6  - https://doi.org/10.1021/jp2043575
SN  - 1089-5639
VL  - 116
IS  - 4
SP  - 1176
EP  - 1182
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Shainyan, Bagrat A.
A1  - Tolstikova, Ljudmila L.
A1  - Schilde, Uwe
T1  - Simple methods for the preparation of N-triflyl guanidines and the structure of compounds with the CF3SO2N=C-N fragment
JF  - Journal of fluorine chemistry
N2  - Two novel and simple approaches to N-triflyl guanidines are elaborated. Owing to very strong conjugation the formally double C=N bond of TIN=C(NHR)(2) is longer than the formally single N-C bonds. Energetic effect of the triflylgroup on the conjugation in the N-C=N moiety is estimated to be >= 150 kcal/mol.
KW  - N-triflyl guanidines
KW  - Synthesis
KW  - Structure
KW  - X-ray
KW  - MP2 calculations
Y1  - 2012
U6  - https://doi.org/10.1016/j.fluchem.2011.12.004
SN  - 0022-1139
VL  - 135
IS  - 1
SP  - 261
EP  - 264
PB  - Elsevier
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Heydenreich, Matthias
A1  - Koch, Andreas
A1  - Linker, Torsten
T1  - Synthesis and NMR spectroscopic conformational analysis of esters of 4-hydroxy-cyclohexanone-the more polar the molecule the more stable the axial conformer
JF  - Tetrahedron
N2  - The esters of 4-hydroxy-cyclohexanone and a series of carboxylic acids R-COOH with R of different electronic and steric influence (R=Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, sec-Bu, t-Bu, CF3, CH2Cl, CHCl2, CCl3, CH2Br, CHBr2, and CBr3) were synthesized and the conformational equilibria studied by H-1 and C-13 NMR spectroscopy at 103 K and at 295 K, respectively. The geometry of optimized structures of the axial 'equatorial chair conformers was computed at the ab initio MO and DFT levels of theory. Only one preferred conformation was obtained for the axial and the equatorial conformer as well. When comparing the conformational equilibria of the cyclohexanone esters with those of the corresponding cyclohexyl esters a certain polarity contribution of the cyclohexanone framework was revealed, which is independent of the substituent effects and increases the stability of the axial conformers by a constant amount.
KW  - 4-Substituted cyclohexanones
KW  - Conformational analysis
KW  - Dynamic NMR
KW  - Simulation of H-1 NMR spectra
KW  - Quantum chemical calculations
KW  - ALTONA equation
Y1  - 2012
U6  - https://doi.org/10.1016/j.tet.2012.01.022
SN  - 0040-4020
VL  - 68
IS  - 10
SP  - 2363
EP  - 2373
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Seto, Jong
A1  - Ma, Yurong
A1  - Davis, Sean A.
A1  - Meldrum, Fiona
A1  - Gourrier, Aurelien
A1  - Kim, Yi-Yeoun
A1  - Schilde, Uwe
A1  - Sztucki, Michael
A1  - Burghammer, Manfred
A1  - Maltsev, Sergey
A1  - Jäger, Christian
A1  - Cölfen, Helmut
T1  - Structure-property relationships of a biological mesocrystal in the adult sea urchin spine
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - Structuring overmany length scales is a design strategy widely used in Nature to create materials with unique functional properties. We here present a comprehensive analysis of an adult sea urchin spine, and in revealing a complex, hierarchical structure, showhow Nature fabricates a material which diffracts as a single crystal of calcite and yet fractures as a glassy material. Each spine comprises a highly oriented array of Mg-calcite nanocrystals in which amorphous regions and macromolecules are embedded. It is postulated that this mesocrystalline structure forms via the crystallization of a dense array of amorphous calcium carbonate (ACC) precursor particles. A residual surface layer of ACC and/or macromolecules remains around the nanoparticle units which creates the mesocrystal structure and contributes to the conchoidal fracture behavior. Nature's demonstration of howcrystallization of an amorphous precursor phase can create a crystalline material with remarkable properties therefore provides inspiration for a novel approach to the design and synthesis of synthetic composite materials.
KW  - calcium carbonate biomineralization
KW  - echinoderm skeleton
KW  - hierarchical structuring
KW  - mesocrystal
KW  - skeletal elements
Y1  - 2012
U6  - https://doi.org/10.1073/pnas.1109243109
SN  - 0027-8424
VL  - 109
IS  - 10
SP  - 3699
EP  - 3704
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schmidt, Bernd
A1  - Krehl, Stefan
A1  - Kelling, Alexandra
A1  - Schilde, Uwe
T1  - Synthesis of 8-Aryl-Substituted Coumarins based on Ring-Closing Metathesis and Suzuki-Miyaura coupling - synthesis of a Furyl Coumarin natural product from Galipea panamensis
JF  - The journal of organic chemistry
N2  - The synthesis of 7-methoxy-8-(4-methyl-3-furyl)-2H-chromen-2-one, a natural product with antileishmanial activity recently isolated from the plant Galipea panamensis, is described. The key step is a Suzuki-Miyaura coupling of a furan-3-boronic acid and an 8-halocoumarin, which is advantageously synthesized using a ring-closing metathesis reaction. Several non-natural analogues are also available along these lines.
Y1  - 2012
U6  - https://doi.org/10.1021/jo2026564
SN  - 0022-3263
VL  - 77
IS  - 5
SP  - 2360
EP  - 2367
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Lazareva, Nataliya F.
A1  - Shainyan, Bagrat A.
A1  - Schilde, Uwe
A1  - Chipanina, Nina N.
A1  - Oznobikhina, Larisa P.
A1  - Albanov, Alexander I.
A1  - Kleinpeter, Erich
T1  - Synthesis, molecular structure, conformational analysis, and chemical properties of silicon-containing derivatives of quinolizidine
JF  - The journal of organic chemistry
N2  - A silicon analog of quinolizidine 3,3,7,7-tetramethylhexahydro-1H-[1,4,2]oxazasilino[4,5-d][1,4,2]oxazasilin-9a-yl)methanol 3 was synthesized. X-ray diffraction analysis confirmed the trans configuration and low temperature NMR spectroscopy both the flexibility (barrier of interconversion 5.8 kcal mol(-1)) and the conformational equilibrium (chair-chair and chair-twist conformers) of the compound. The relative stability of the different isomers/conformers of 3 was calculated also at the MP2/6-311G(d,p) level of theory. Intra- and intermolecular hydrogen bonding in 3 and the appropriate equilibrium between free and self-associated molecules was studied in solvents of different polarity. Both the N-methyl quaternary ammonium salt and the O-trimethylsilyl derivative of 3 could be obtained and their structure determined.
Y1  - 2012
U6  - https://doi.org/10.1021/jo202658n
SN  - 0022-3263
VL  - 77
IS  - 5
SP  - 2382
EP  - 2388
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Kreye, Oliver
A1  - Türünc, Oguz
A1  - Sehlinger, Ansgar
A1  - Rackwitz, Jenny
A1  - Meier, Michael A. R.
T1  - Structurally diverse polyamides obtained from monomers derived via the Ugi multicomponent reaction
JF  - Chemistry - a European journal
N2  - The combination of the Ugi four-component reaction (Ugi-4CR) with acyclic diene metathesis (ADMET) or thiolene polymerization led to the formation of poly-1-(alkylcarbamoyl) carboxamides, a new class of substituted polyamides with amide moieties in the polymer backbone, as well as its side chains. 10-Undecenoic acid, obtained by pyrolysis of ricinoleic acid, the main fatty acid of castor oil, was used as the key renewable building block. The use of different primary amines, as well as isonitriles (isocyanides) for the described Ugi reactions provided monomers with high structural diversity. Furthermore, the possibility of versatile post-modification of functional groups in the side chains of the corresponding polymers should be of considerable interest in materials science. The obtained monomers were polymerized by ADMET, as well as thiolene, chemistry and all polymers were fully characterized. Finally, ortho-nitrobenzylamide-containing polyamides obtained by this route were shown to be photoresponsive and exhibited a dramatic change of their properties upon irradiation with light.
KW  - metathesis
KW  - polyamides
KW  - polymerization
KW  - renewable resources
KW  - Ugi reaction
KW  - thiol-ene reactions
Y1  - 2012
U6  - https://doi.org/10.1002/chem.201103341
SN  - 0947-6539
VL  - 18
IS  - 18
SP  - 5767
EP  - 5776
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Zakrevskyy, Y.
A1  - Ritschel, T.
A1  - Dosche, C.
A1  - Löhmannsröben, Hans-Gerd
T1  - Quantitative calibration - and reference-free wavelength modulation spectroscopy
JF  - Infrared physics & technology
N2  - A unified model for quantitative description of harmonic spectra of gases obtained by wavelength modulation spectroscopy (WMS) technique is presented. In the model, both intensity modulation (IM) and frequency modulation (FM) of the laser emission are taken into account using minimum number of parameters. For the first time, the static behavior of a laser is described as a limiting case of its dynamic response. Laser and its driver are considered as a single device converting applied bias to laser emission. This allows application of the model to any type of laser and the introduced parameters can be assigned to the corresponding laser and/or driver properties. The approach was tested using a distributed feedback (DFB) laser spectrometer. Correctness of the proposed model is justified by very good agreement between the measured and modeled/fitted spectra, which allowed evaluation of the setup performance and assessment of modulation parameters of the DFB laser. An algorithm to minimize the time of numerical calculation of harmonic spectra using numerically approximated Voigt lineshape function was developed. Absolute values of the absorption line parameters (line strength and line width) were obtained from a single calibration- and reference-free spectrum scan with accuracy better than 0.1%.
KW  - Wavelength modulation gas spectroscopy
KW  - Diode laser
KW  - Isotope detection
Y1  - 2012
U6  - https://doi.org/10.1016/j.infrared.2011.12.001
SN  - 1350-4495
VL  - 55
IS  - 2-3
SP  - 183
EP  - 190
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Kienzler, Andrea Altevogt Nee
A1  - Flehr, Roman
A1  - Gehne, Sören
A1  - Kumke, Michael Uwe
A1  - Bannwarth, Willi
T1  - Verification and biophysical characterization of a New Three-Color Forster Resonance-Energy-Transfer (FRET) System in DNA
JF  - Helvetica chimica acta
N2  - We report on a new three-color FRET system consisting of three fluorescent dyes, i.e., of a carbostyril (=quinolin-2(1H)-one)-derived donor D, a (bathophenanthroline)ruthenium complex as a relay chromophore A1, and a Cy dye as A2 (FRET=Forster resonance-energy-transfer) (cf. Fig. 1). With their widely matching spectroscopic properties (cf. Fig. 2), the combination of these dyes yielded excellent FRET efficiencies. Furthermore, fluorescence lifetime measurements revealed that the long fluorescence lifetime of the Ru complex was transferred to the Cy dye offering the possibility to measure the whole system in a time-resolved mode. The FRET system was established on double-stranded DNA (cf. Fig. 3) but it should also be generally applicable to other biomolecules.
KW  - Forster resonance energy transfer (FRET) system
KW  - DNA
KW  - Fluorescence
KW  - Ruthenium complexes
Y1  - 2012
U6  - https://doi.org/10.1002/hlca.201100460
SN  - 0018-019X
VL  - 95
IS  - 4
SP  - 543
EP  - 555
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Schmidt, Bernd
A1  - Kunz, Oliver
T1  - alpha,beta-Unsaturated delta-Valerolactones through RCM-Isomerization Sequence
JF  - Synlett : accounts and rapid communications in synthetic organic chemistry
N2  - alpha,beta-Unsaturated d-lactones are accessible via a sequential ring-closing metathesis (RCM) double-bond migration reaction starting from butenoates of allyl alcohols. This approach proceeds efficiently with lower catalyst loadings and higher initial substrate concentrations compared to the alternative RCM of acrylates derived from homoallylic alcohols.
KW  - ruthenium
KW  - lactones
KW  - tandem reactions
KW  - metathesis
KW  - esters
Y1  - 2012
U6  - https://doi.org/10.1055/s-0031-1290488
SN  - 0936-5214
IS  - 6
SP  - 851
EP  - 854
PB  - Thieme
CY  - Stuttgart
ER  - 
TY  - JOUR
A1  - Strehmel, Veronika
A1  - Rexhausen, Hans
A1  - Strauch, Peter
T1  - New spin probes starting from 4-amino-2,2,6,6-tetramethylpiperidine-1-yloxyl
JF  - Tetrahedron letters
N2  - This Letter describes four new 4-trimethylammonio-2,2,6,6-tetramethylpiperidine-1-yloxyls bearing camphorsulfonate, triflate, tosylate, or lactate as counter ions. These spin probes were made by anion metathesis of 4-trimethylammonio-2,2,6,6-tetramethylpiperidine-1-yloxyl iodide using the corresponding silver salts. The latter is made by the alkylation of 4-amino-2,2,6,6-tetramethylpiperidine-1-yloxyl. Furthermore, the Letter gives an improved synthetic way to 4-sulfonamido-2,2,6,6-tetramethylpiperidine-1-yloxyl using chlorosulfuric acid trimethylsilylester and 4-amino-2,2,6,6-tetramethylpiperidine-1-yloxyl. All the spin probes are highly interesting for the investigation of ionic liquids.
KW  - Nitroxides
KW  - Spin probes
KW  - ESR spectroscopy
KW  - Ionic liquids
Y1  - 2012
U6  - https://doi.org/10.1016/j.tetlet.2012.01.063
SN  - 0040-4039
VL  - 53
IS  - 13
SP  - 1587
EP  - 1591
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Bramborg, Andrea
A1  - Linker, Torsten
T1  - Regioselective synthesis of alkylarenes by two-step ipso-substitution of aromatic dicarboxylic acids
JF  - European journal of organic chemistry
N2  - A strategy for the regioselective alkylation of arenes was developed, starting from commercially available and inexpensive terephthalic acid or naphthalene-1,4-dicarboxylic acid. The method entails a formal ipso-substitution of the carboxylate groups by a sequence of reductive alkylation under Birch conditions and subsequent acid-mediated rearomatization with loss of carbon monoxide and carbon dioxide. More than 20 different arenes with various side-chains were synthesized. With naphthalene-1,4-dicarboxylic acid as starting material, we were able to control the degree of alkylation by choosing the appropriate electrophile in the Birch reduction. Thus, bisalkylated naphthalenes and naphthoic acids became available chemoselectively. All reactions afforded a single regioisomer exclusively in high yields. Overall, aromatic dicarboxylic acids are suitable substrates for a two-step ipso-substitution that allows the selective synthesis of alkylated benzenes and naphthalenes.
KW  - Synthetic methods
KW  - Alkylation
KW  - Birch reduction
KW  - Arenes
KW  - Regioselectivity
Y1  - 2012
U6  - https://doi.org/10.1002/ejoc.201200823
SN  - 1434-193X
IS  - 28
SP  - 5552
EP  - 5563
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Weiss, Jan
A1  - Laschewsky, André
T1  - One-step synthesis of amphiphilic, double thermoresponsive diblock copolymers
JF  - Macromolecules : a publication of the American Chemical Society
N2  - The copolymerization of an excess of a functionalized styrene monomer, 4-vinylbenzyl methoxytetrakis(oxyethylene) ether, with various N-substituted maleimides yields tapered diblock copolymers in a one-step procedure, when applying reversible deactivation radical polymerization (RDRP) methods, such as ATRP and RAFT. The particular chemical structure of the diblock copolymers prepared results in reversible temperature-responsive two-step aggregation behavior in dilute aqueous solution. In this way, a double hydrophilic block copolymer is transformed step by step into an amphiphilic macrosurfactant, and finally into a double hydrophobic copolymer, as followed by turbidimetry and dynamic light scattering. Copolymers in which the maleimide repeat units bear short hydrophobic side chains are freely water-soluble at low temperature and form micellar aggregates above their cloud point. Further heating above the phase transition temperature of the second block results in secondary aggregation. Copolymers with maleimides that bear strongly hydrophobic substituents undergo two thermally induced aggregation steps upon heating, too, but show in addition intramolecular hydrophobic association in water already at low temperatures, similar to the behavior of polysoaps.
Y1  - 2012
U6  - https://doi.org/10.1021/ma300285y
SN  - 0024-9297
VL  - 45
IS  - 10
SP  - 4158
EP  - 4165
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Wessig, Pablo
A1  - Möllnitz, Kristian
T1  - Building blocks for oligospiroketal (OSK) rods and evaluation of their influence on rod rigidity
JF  - The journal of organic chemistry
N2  - We report on the synthesis of three new sleeves and their incorporation in OSK rods. The structures of these sleeves are based on neo-inositol, terephthalaldehyde diacetals, and indacene. To quantify the influence of the sleeves on rod rigidity, we applied the worm-like chain (WLC) model on the new rods and found that this approach is rather disappointing. As the chief cause of this result, we assume that the rigidity of typical molecular rods largely exceeds the rigidity of polymers, which were successfully described by the WLC model. Alternatively, we suggest quantifying the rigidity of molecular rods by fitting an empirical function on the end-to-end distance distribution curve obtained by MD simulations. After checking various function types, the Levy-Martin function proved to be most suitable for this purpose. On the basis of this function, we defined the Levy-Martin parameter and suggest using this parameter for the characterization of the rigidity of molecular rods.
Y1  - 2012
U6  - https://doi.org/10.1021/jo300266b
SN  - 0022-3263
VL  - 77
IS  - 8
SP  - 3907
EP  - 3920
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Kröner, Dominik
A1  - Götze, Jan Philipp
T1  - Modeling of a violaxanthin-chlorophyll b chromophore pair in its LHCII environment using CAM-B3LYP
JF  - Journal of photochemistry and photobiology : B, Biology
N2  - Collecting energy for photosystem II is facilitated by several pigments, xanthophylls and chlorophylls, embedded in the light harvesting complex II (LHCII). One xanthophyll, violaxanthin (Vio), is loosely bound at a site close to a chlorophyll b (Chl). No final answer has yet been found for the role of this specific xanthophyll. We study the electronic structure of Vio in the presence of Chl and under the influence of the LHCII environment, represented by a point charge field (PCF).
 We compare the capability of the long range corrected density functional theory (DFT) functional CAM-B3LYP to B3LYP for the modeling of the UV/vis spectrum of the Vio + Chl pair. CAM-B3LYP was reported to allow for a very realistic reproduction of bond length alternation of linear polyenes, which has considerable impact on the carotenoid structure and spectrum. To account for the influence of the LHCII environment, the chromophore geometries are optimized using an ONIOM(DFT/6-31G(d):PM6) scheme.
 Our calculations show that the energies of the locally excited states are almost unaffected by the presence of the partner chromophore or the PCF. There are, however, indications for excitonic coupling of the Chl Soret band and Vio. We propose that Vio may accept energy from blue-light excited Chl.
KW  - CAM-B3LYP
KW  - Density functional theory
KW  - Light-harvesting complex II
KW  - Photosynthesis
KW  - Violaxanthin
KW  - Chlorophyll b
Y1  - 2012
U6  - https://doi.org/10.1016/j.jphotobiol.2011.12.007
SN  - 1011-1344
VL  - 109
IS  - 2
SP  - 12
EP  - 19
PB  - Elsevier
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Pimpalpalle, Tukaram M.
A1  - Yin, Jian
A1  - Linker, Torsten
T1  - Barton radical reactions of 2-C-branched carbohydrates
JF  - Organic & biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry
N2  - Barton esters have been introduced into the side chain of carbohydrates with high yields in only a few steps from easily available glycals. Their radical reactions afford 2-C-methyl and 2-C-bromomethyl hexoses, pentoses and disaccharides in good yields in analytically pure form. Since the Barton esters have been synthesized by an oxidative radical addition and their transformations by reductive radical processes, our results demonstrate the power of such reactions in carbohydrate chemistry.
Y1  - 2012
U6  - https://doi.org/10.1039/c1ob06370g
SN  - 1477-0520
VL  - 10
IS  - 1
SP  - 103
EP  - 109
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Ali, Mostafa
A1  - Homann, Thomas
A1  - Kreisel, Janka
A1  - Khalil, Mahmoud
A1  - Puhlmann, Ralf
A1  - Kruse, Hans-Peter
A1  - Rawel, Harshadrai Manilal
T1  - Characterization and modeling of the interactions between coffee storage proteins and phenolic compounds
JF  - Journal of agricultural and food chemistry : a publication of the American Chemical Society
N2  - This study addresses the interactions of coffee storage proteins with coffee-specific phenolic compounds. Protein profiles, of Coffea arabica and Coffea canephora (var robusta) were compared. Major Phenolic compounds were extracted and analyzed with appropriate methods. The polyphenol-protein interactions during protein extraction have been addressed by different analytical setups [reversed-phase high-performance liquid chromatography (RP-HPLC), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS), and Trolox equivalent antioxidant capacity (TEAC) assays], with focus directed toward identification of covalent adduct formation. The results indicate that C. arabica proteins are more susceptible to these interactions and the polyphenol oxidase activity seems to be a crucial factor for the formation of these addition products. A tentative allocation of the modification type and site in the protein has been attempted. Thus, the first available in silico modeling of modified coffee proteins is reported. The extent of these modifications may contribute to the structure and function of "coffee melanoidins" and are discussed in the context of coffee flavor formation.
KW  - Coffee beans
KW  - storage proteins
KW  - phenolic compounds
KW  - antioxidants
KW  - protein-phenol interactions
KW  - modeling
Y1  - 2012
U6  - https://doi.org/10.1021/jf303372a
SN  - 0021-8561
VL  - 60
IS  - 46
SP  - 11601
EP  - 11608
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Koeth, Anja
A1  - Appelhans, Dietmar
A1  - Prietzel, Claudia Christina
A1  - Koetz, Joachim
T1  - Asymmetric gold nanoparticles synthesized in the presence of maltose-modified poly(ethyleneimine)
JF  - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects
N2  - A self-assembled tube-like network, spontaneously formed by adding maltose-modified poly(ethyleneimine) (mal-PEI5000) to mixed phospholipid vesicles, can be used as a template for the formation of gold nanoparticles. High resolution TEM indicates that the growing process leads not only to the formation of spherical gold nanoparticles with an absorption maximum at 520 nm, but also very flat triangles, hexagons, and long bent rods are formed, revealing an absorption maximum in the NIR at about 850 nm.
 One can conclude that nanorods, nanotriangles and nanohexagons are predominantly formed in the tubular network structure.
KW  - Gold triangles
KW  - Hexagons and nanorods
KW  - Tube-like template phase
KW  - Maltose-modified PEI
Y1  - 2012
U6  - https://doi.org/10.1016/j.colsurfa.2012.08.004
SN  - 0927-7757
VL  - 414
IS  - 21
SP  - 50
EP  - 56
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - de Molina, Paula Malo
A1  - Herfurth, Christoph
A1  - Laschewsky, André
A1  - Gradzielski, Michael
T1  - Structure and dynamics of networks in mixtures of hydrophobically modified telechelic multiarm polymers and oil in water microemulsions
JF  - Langmuir
N2  - The structural and dynamical properties of oil-in-water (O/W) microemulsions (MEs) modified with telechelic polymers of different functionality (e.g., number of hydrophobically modified arms, f) were studied by means of dynamic light scattering (DLS), small-angle neutron scattering (SANS), and high frequency rheology measurements as a function of the polymer architecture and the amount of added polymer. For this purpose, we employed tailor-made hydrophobically end-capped poly(N,N-dimethylacrylamide) star polymers of a variable number of endcaps, f, of different alkyl chain lengths, synthesized by the reversible addition-fragmentation chain transfer method. The addition of the different end-capped polymers to an uncharged ME of O/W droplets leads to a large enhancement of the viscosity of the systems. SANS experiments show that the O/W ME droplets are not changed upon the addition of the polymer, and its presence only changes the interdroplet interactions. The viscosity increases largely upon addition of a polymer, and this enhancement depends pronouncedly on the alkyl length of the hydrophobic sticker as it controls the residence time in a ME droplet. Similarly, the high frequency modulus G(0) depends on the amount of added polymer but not on the sticker length. G(0) was found to be directly proportional to f - 1. The onset of network formation is shifted to a lower number of stickers per ME droplet with increasing f, and the network formation becomes more effective. Thus, the dynamics of network formation are controlled by the polymer architecture. The effect on the dynamics seen by DLS is even more pronounced. Upon increasing the polymer concentration, slower relaxation modes appear that become especially pronounced with increasing number of arms. The relaxation dynamics are correlated to the rheological relaxation, and both are controlled by the polymer architecture.
Y1  - 2012
U6  - https://doi.org/10.1021/la303673a
SN  - 0743-7463
VL  - 28
IS  - 45
SP  - 15994
EP  - 16006
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Siegmann, Rebekka
A1  - Möller, Eleonore
A1  - Beuermann, Sabine
T1  - Propagation rate coefficients for homogeneous phase VDF-HFP copolymerization in supercritical CO2
JF  - Macromolecular rapid communications
N2  - For the first time, propagation rate coefficients, kp,COPO, for the copolymerizations of vinylidene fluoride and hexafluoropropene have been determined. The kinetic data was determined via pulsed-laser polymerization in conjunction with polymer analysis via size-exclusion chromatography, the PLP-SEC technique. The experiments were carried out in homogeneous phase with supercritical CO2 as solvent for temperatures ranging from 45 to 90 degrees C. Absolute polymer molecular weights were calculated on the basis of experimentally determined MarkHouwink constants. The Arrhenius parameters of kp,COPO vary significantly compared with ethene, which is explained by the high electronegativity of fluorine and less intra- and intermolecular interactions between the partially fluorinated macroradicals.
KW  - copolymerization
KW  - fluorinated olefins
KW  - kinetics (polym)
KW  - pulse laser initiated polymerization
KW  - radical polymerization
Y1  - 2012
U6  - https://doi.org/10.1002/marc.201200115
SN  - 1022-1336
VL  - 33
IS  - 14
SP  - 1208
EP  - 1213
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Miasnikova, Anna
A1  - Laschewsky, André
T1  - Influencing the phase transition temperature of poly(methoxy diethylene glycol acrylate) by molar mass, end groups, and polymer architecture
JF  - Journal of polymer science : A, Polymer chemistry
N2  - The easily accessible, but virtually overlooked monomer methoxy diethylene glycol acrylate was polymerized by the RAFT method using monofunctional, difunctional, and trifunctional trithiocarbonates to afford thermoresponsive polymers exhibiting lower critical solution temperature-type phase transitions in aqueous solution. The use of the appropriate RAFT agent allowed for the preparation and systematic variation of polymers with defined molar mass, end-groups, and architecture, including amphiphilic diblock, symmetrical triblock, and triarm star-block copolymers, containing polystyrene as permanently hydrophobic constituent. The cloud points (CPs) of the various polymers proved to be sensitive to all varied parameters, namely molar mass, nature, and number of the end-groups, and the architecture, up to relatively high molar masses. Thus, CPs of the polymers can be adjusted within the physiological interesting range of 2040 degrees C. Remarkably, CPs increased with the molar mass, even when hydrophilic end groups were attached to the polymers.
KW  - water-soluble polymers
KW  - diblock copolymers
KW  - triblock copolymers
KW  - star-block copolymers
KW  - reversible addition fragmentation chain transfer (RAFT)
KW  - LCST
KW  - stimuli-sensitive polymers
Y1  - 2012
U6  - https://doi.org/10.1002/pola.26116
SN  - 0887-624X
VL  - 50
IS  - 16
SP  - 3313
EP  - 3323
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Unuabonah, Emmanuel I.
A1  - El-Khaiary, Mohammad I.
A1  - Olu-Owolabi, Bamidele I.
A1  - Adebowale, Kayode O.
T1  - Predicting the dynamics and performance of a polymer-clay based composite in a fixed bed system for the removal of lead (II) ion
JF  - Chemical engineering research and design
N2  - A polymer-clay based composite adsorbent was prepared from locally obtained kaolinite clay and polyvinyl alcohol. The composite adsorbent was used to remove lead (II) ions from aqueous solution in a fixed bed mode. The increase in bed height and initial metal ion concentration increased the adsorption capacity of lead (II) and the volume of aqueous solution treated at 50% breakthrough. However, the adsorption capacity was reduced by almost 16.5% with the simultaneous presence of Ca2+/Pb2+ and Na+/Pb2+ in the aqueous solution. Regeneration of the adsorbent with 0.1 M of HCl also reduced its adsorption capacity to 75.1%. Adsorption of lead (II) ions onto the polymer-clay composite adsorbent in the presence of Na+ and Ca2+ electrolyte increased the rate of mass transfer, probably due to competition between cationic species in solution for adsorption sites. Regeneration further increased the rate of mass transfer as a result of reduced adsorption sites after the regeneration process. The length of the mass transfer zone was found to increase with increasing bed height but did not change with increasing the initial metal ion concentration. The models of Yoon-Nelson, Thomas, and Clark were found to give good fit to adsorption data. On the other hand, Bohart-Adams model was found to be a poor predictor for the column operation. The polymer-clay composite adsorbent has a good potential for the removal of lead (II) ions from highly polluted aqueous solutions.
KW  - Fixed bed
KW  - Adsorption models
KW  - Polymer-clay composite
KW  - Regeneration
KW  - Breakthrough
KW  - Mass transfer zone
Y1  - 2012
U6  - https://doi.org/10.1016/j.cherd.2011.11.009
SN  - 0263-8762
VL  - 90
IS  - 8
SP  - 1105
EP  - 1115
PB  - Inst. of Electr. and Electronics Engineers
CY  - Rugby
ER  - 
TY  - JOUR
A1  - Khare, Varsha
A1  - Ruby, Christian
A1  - Sonkaria, Sanjiv
T1  - A green and sustainable nanotechnology role of ionic liquids
JF  - International journal of precision engineering and manufacturing
N2  - In the present study, the effects of ionic liquids (ILs) on the stability of nanoparticles in several IL compositions were investigated. In this context, we examined the primary role of ILs in the synthesis of metal/metal oxide nanoparticles and their dispersions extensively. However, the focus of the discussion in this communication centers mainly on the effect of EMIM Ethyl Sulfate on growth and stability of nanoparticles. The dispersion properties of ILs based on their ability to aid the synthesis of uniformly dispersed nanoparticles have been further explored to produce nanoparticles of an effective catalyst useful in water purification, soil remediation and battery applications. Two independent protocols were developed for the synthesis of nanoparticles, namely (a) one pot process via chemical reduction (b) dispersion of the inorganic material in ILs. The protocols are simple, sustainable and environmentally friendly because the processes are conducted in ILs as harmless non-toxic green solvent materials. The catalysts were analyzed by x-ray diffraction, electron microscopy, UV visible spectroscopy and dynamic light scattering as the main methodologies.
KW  - Nanotechnology
KW  - Green synthesis
KW  - Ionic liquid
KW  - Green rust
KW  - Gold nanoparticles
Y1  - 2012
U6  - https://doi.org/10.1007/s12541-012-0160-x
SN  - 2234-7593
VL  - 13
IS  - 7
SP  - 1207
EP  - 1213
PB  - Korean Society of Precision Engineering
CY  - Seoul
ER  - 
TY  - JOUR
A1  - Coy-Barrera, Ericsson D.
A1  - Cuca-Suarez, Luis E.
A1  - Sefkow, Michael
A1  - Schilde, Uwe
T1  - Cinerin C: a macrophyllin-type bicyclo[3.2.1]octane neolignan from Pleurothyrium cinereum (Lauraceae)
JF  - Acta crystallographica : Section C, Crystal structure communications
N2  - The structure of naturally-occurring cinerin C [systematic name: (7S,8R,3'R,4'S,5'R)-Delta(8')-4'-hydroxy-5,5',3'-trimethoxy-3,4-methylenedioxy-2',3',4',5'-tetrahydro-2'-oxo-7.3',8.5'-neolignan], isolated from the ethanol extract of leaves of Pleurothyrium cinereum (Lauraceae), has previously been established by NMR and HRMS spectroscopy, and its absolute configuration established by circular dichroism measurements. For the first time, its crystal strucure has now been established by single-crystal X-ray analysis, as the monohydrate, C22H26O7 center dot H2O. The bicyclooctane moiety comprises fused cyclopentane and cyclohexenone rings which are almost coplanar. An intermolecular O-H center dot center dot center dot O hydrogen bond links the 4'-OH and 5'-OCH3 groups along the c axis.
Y1  - 2012
U6  - https://doi.org/10.1107/S0108270112030946
SN  - 0108-2701
VL  - 68
IS  - 2
SP  - O320
EP  - +
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Tiseanu, Carmen
A1  - Cojocaru, Bogdan
A1  - Parvulescu, Vasile I.
A1  - Sanchez-Dominguez, Margarita
A1  - Primus, Philipp A.
A1  - Boutonnet, Magali
T1  - Order and disorder effects in nano-ZrO2 investigated by micro-Raman and spectrally and temporarily resolved photoluminescence
JF  - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2  - Pure and europium (Eu3+) doped ZrO2 synthesized by an oil-in-water microemulsion reaction method were investigated by in situ and ex situ X-ray diffraction (XRD), ex situ Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), steady state and time-resolved photoluminescence (PL) spectroscopies. Based on the Raman spectra excited at three different wavelengths i.e. 488, 514 and 633 nm and measured in the spectral range of 150-4000 cm(-1) the correlation between the phonon spectra of ZrO2 and luminescence of europium is clearly evidenced. The PL investigations span a variety of steady-state and time resolved measurements recorded either after direct excitation of the Eu3+ f-f transitions or indirect excitation into UV charge-transfer bands. After annealing at 500 degrees C, the overall Eu3+ emission is dominated by Eu3+ located in tetragonal symmetry lattice sites with a crystal-field splitting of the D-5(0)-F-7(1) emission of 20 cm(-1). Annealing of ZrO2 at 1000 degrees C leads to a superposition of Eu3+ emissions from tetragonal and monoclinic lattice sites with monoclinic crystal-field splitting of 200 cm(-1) for the D-5(0)-F-7(1) transition. At all temperatures, a non-negligible amorphous/disordered content is also measured and determined to be of monoclinic nature. It was found that the evolutions with calcination temperature of the average PL lifetimes corresponding to europium emission in the tetragonal and monoclinic sites and the monoclinic phase content of the Eu3+ doped ZrO2 samples follow a similar trend. By use of specific excitation conditions, the distribution of europium on the amorphous/disordered surface or ordered/crystalline sites can be identified and related to the phase content of zirconia. The role of zirconia host as a sensitizer for the europium PL is also discussed in both tetragonal and monoclinic phases.
Y1  - 2012
U6  - https://doi.org/10.1039/c2cp41946g
SN  - 1463-9076
VL  - 14
IS  - 37
SP  - 12970
EP  - 12981
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Nagy, Zsuzsanna T.
A1  - Heinrich, Benoit
A1  - Guillon, Daniel
A1  - Tomczyk, Jaroslaw
A1  - Stumpe, Joachim
A1  - Donnio, Bertrand
T1  - Heterolithic azobenzene-containing supermolecular tripedal liquid crystals self-organizing into highly segregated bilayered smectic phases
JF  - Journal of materials chemistry
N2  - Synthesis, self-organization, and optical properties of supermolecular tripedal liquid crystals incorporating various prototypical mesogenic units such as alkoxy-azobenzene (AZB), alkoxy-biphenylene (BPH) or alkoxy-cyanobiphenyl (OCB) derivatives are reported. Different molecular systems were designed in order to sequentially incorporate the smectogenic-like alkoxy-azobenzene-based chromophore within the molecular structure, whose relative proportion is selectively varied by exchanging with the other mesogens. A divergent synthetic mode was elaborated for their synthesis, starting from the regioselective functionalization of the phloroglucinol-based (PG) inner core. This methodology allowed the preparation of several sets of unconventional tripedal oligomers with conjugated heterolithic structures (made of different blocks, e.g. PG(6)AZB(x)BPH(3-x) and PG(6)AZB(x)OCB(3-x), x = 1 or 2) along the homolithic parents (all identical blocks, e.g. PG(z)AZB(3), z = 6 or 11, z is the number of methylene in the spacer between PG and the protomesogen, PG(6)BPH(3), and PG(6)OCB(3)), respectively. Essentially all the synthesized systems behave as thermotropic liquid crystals and show various types of highly segregated multilayered smectic phases, or, in one case, a nematic phase, depending on the nature of the constitutive anisotropic blocks and on the molecular topology (homolithic versus heterolithic, mesogenic ratio x : 3 - x). The effects of these structural modifications on the mesomorphism (mesophase structures, temperature ranges, and thermodynamic stability) have been investigated by differential scanning calorimetry and small-angle X-ray diffraction experiments combined with dilatometric measurements. Models describing the various supramolecular organizations of these tripedes into such multilayered structures are proposed and discussed. Preliminary results of the investigations of their optical properties will also be presented.
Y1  - 2012
U6  - https://doi.org/10.1039/c2jm33751g
SN  - 0959-9428
VL  - 22
IS  - 35
SP  - 18614
EP  - 18622
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Lemke, Karina
A1  - Koetz, Joachim
T1  - Polycation-capped CdS quantum dots synthesized in reverse microemulsions
JF  - Journal of nanomaterials
N2  - This paper is focused on the formation and recovery of cadmium sulfide (CdS) nanoparticles in two different types of polycation-modified reverse microemulsions using low molecular weight poly(diallyldimethylammonium chloride) (PDADMAC) and poly(ethyleneimine) (PEI). Both polymers were incorporated in a quaternary w/o microemulsion consisting of water, toluene-pentanol (1 : 1), and sodium dodecyl sulfate (SDS), as well as in a ternary w/o microemulsion consisting of water, heptanol, and 3( N,N-dimethyl-dodecylammonio)-propanesulfonate (SB). UV-vis and fluorescence measurements in the microemulsion illustrate the capping effect of the polycations on the formation of the CdS quantum dots. The nanoparticles are redispersed in water and characterized by using UV-vis and fluorescence spectroscopy, in combination with dynamic light scattering. From the quaternary microemulsion, only nanoparticle aggregates of about 100 nm can be redispersed, but, from the ternary microemulsion, well-stabilized polycation-capped CdS quantum dots can be obtained. The results show that the electrostatic interactions between the polycation and the surfactant are of high relevance especially in the solvent evaporation and redispersion process. That means only that in the case of moderate polycation-surfactant interactions a redispersion of the polymer-capped CdS quantum dots without problems of aggregation is possible.
Y1  - 2012
U6  - https://doi.org/10.1155/2012/478153
SN  - 1687-4110
IS  - 4
PB  - Hindawi Publishing Corp.
CY  - New York
ER  - 
TY  - JOUR
A1  - Baumgartner, Jens
A1  - Lesevic, Paul
A1  - Kumari, Monika
A1  - Halbmair, Karin
A1  - Bennet, Mathieu
A1  - Koernig, Andre
A1  - Widdrat, Marc
A1  - Andert, Janet
A1  - Wollgarten, Markus
A1  - Bertinetti, Luca
A1  - Strauch, Peter
A1  - Hirt, Ann
A1  - Faivre, Damien
T1  - From magnetotactic bacteria to hollow spirilla-shaped silica containing a magnetic chain
JF  - RSC Advances
N2  - Magnetotactic bacteria produce chains of magnetite nanoparticles, which are called magnetosomes and are used for navigational purposes. We use these cells as a biological template to prepare a hollow hybrid material based on silica and magnetite, and show that the synthetic route is nondestructive as the material conserves the cell morphology as well as the alignment of the magnetic particles. The hybrid material can be resuspended in aqueous solution, and can be shown to orient itself in an external magnetic field. We anticipate that chemical modification of the silica can be used to functionalize the material surface in order to obtain multifunctional materials with specialized applications, e.g. targeted drug delivery.
Y1  - 2012
U6  - https://doi.org/10.1039/c2ra20911j
SN  - 2046-2069
VL  - 2
IS  - 21
SP  - 8007
EP  - 8009
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  -