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11.
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Mark Eggink Maikel Wijtmans Ansgar Kretschmer Jeroen Kool Henk Lingeman Iwan J. P. de Esch Wilfried M. A. Niessen Hubertus Irth 《Analytical and bioanalytical chemistry》2010,397(2):665-675
Based on the template of a recently introduced derivatization reagent for aldehydes, 4-(2-(trimethylammonio)ethoxy)benzeneaminium
dibromide (4-APC), a new derivatization agent was designed with additional features for the analysis and screening of biomarkers
of lipid peroxidation. The new derivatization reagent, 4-(2-((4-bromophenethyl)dimethylammonio)ethoxy)benzenaminium dibromide
(4-APEBA) contains a bromophenethyl group to incorporate an isotopic signature to the derivatives and to add additional fragmentation
identifiers, collectively enhancing the abilities for detection and screening of unknown aldehydes. Derivatization can be
achieved under mild conditions (pH 5.7, 10 °C). By changing the secondary reagent (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide
instead of sodium cyanoborohydride), 4-APEBA is also applicable to the selective derivatization of carboxylic acids. Synthesis
of the new label, exploration of the derivatization conditions, characterization of the fragmentation of the aldehyde and
carboxylic acid derivatives in MS/MS, and preliminary applications of the labeling strategy for the analysis of aldehydes
in urine and plasma are described. 相似文献
13.
Hua-Hua Wang Yi-Yu Jiang Mian HR Mahmood Hai-Yang Liu Herman H.Y. Sung Ian D. Williams Chi K. Chang 《中国化学快报》2015,26(5):529-533
Tetrakis(alloxycarbonyl)porphyrin and its β-octafluoro-substituted derivatives were synthesized via Lindsey method and transformed to their zinc complexes.Single crystal X-ray structures of corresponding Zn(Ⅱ) porphyrins revealed that β-octafluorination will give more compactness of porphyrin moieties in the crystal structure owing to the hydrogen bonding interactions involving β-fluorine atoms.An unusual six-coordinated Zn(Ⅱ) was found via intramolecular coordination of oxygen atom of meso-substituents with central Zn(Ⅱ). 相似文献
14.
Wang ZC Weiske T Kretschmer R Schlangen M Kaupp M Schwarz H 《Journal of the American Chemical Society》2011,133(42):16930-16937
The oxygen-rich cluster Al(2)O(7)(+) is generated in the gas phase and investigated with respect to both its structure and its reactivity toward small, inert molecules using Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry and DFT-based calculations. Al(2)O(7)(+) reacts with CH(4) under ambient conditions via hydrogen atom transfer (HAT), and with H(2)O a ligand exchange occurs which gives rise to the evaporation of two O(2) molecules. The resulting product ion Al(2)O(4)H(2)(+) is also capable of abstracting a hydrogen atom from both H(2)O and CH(4). As indicated in the H(2)O/2O(2) ligand exchange and supported by collision-induced dissociation (CID) experiments, two O(2) units constitute structural elements of Al(2)O(7)(+). Further insight is provided by DFT calculations, performed at the unrestricted B3LYP/TZVP level, and reaction mechanisms are suggested on the basis of both the experimental and theoretical results. 相似文献
15.
16.
Smrati Gupta Dirk Kuckling Katja Kretschmer Veena Choudhary Hans‐Jürgen Adler 《Journal of polymer science. Part A, Polymer chemistry》2007,45(4):669-679
The aim of this work was the development of a versatile route for the preparation of temperature‐ and pH‐responsive hydrogels with small dimensions. The copolymerization of N,N‐dimethylaminoethyl methacrylate with various amounts (5 and 10 mol %) of dimethylmaleimidoethyl methacrylate in solution with 2,2′‐azobisisobutyronitrile as an initiator is described. The structural and molecular characterization of the copolymers was performed with proton nuclear magnetic resonance, Fourier transform infrared, and ultraviolet spectroscopy, as well as size exclusion chromatography. Differential scanning calorimetry and thermogravimetry were used for the thermal characterization of the copolymers. Micro‐ and nanohydrogels of the copolymers were prepared by photocrosslinking. The gels obtained by photocrosslinking were characterized with a combination of surface plasmon resonance and optical waveguide spectroscopy, dynamic light scattering, and scanning electron microscopy. The hydrogels showed temperature‐ and pH‐responsive behavior. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 669–679, 2007 相似文献
17.
18.
Alexander Goller Dr. Johannes Obenauf Dr. Winfried P. Kretschmer Prof. Dr. Rhett Kempe 《Angewandte Chemie (International ed. in English)》2023,62(8):e202216464
The highly controlled and efficient polymerization of ethylene is a very attractive but challenging target. Herein we report on a Coordinative Chain Transfer Polymerization catalyst, which combines a high degree of control and very high activity in ethylene oligo- or polymerization with extremely high chain transfer agent (triethylaluminum) to catalyst ratios (catalyst economy). Our Zr catalyst is long living and temperature stable. The chain length of the polyethylene products increases over time under constant ethylene feed or until a certain volume of ethylene is completely consumed to reach the expected molecular weight. Very high activities are observed if the catalyst elongates 60 000 or more alkyl chains and the polydispersity of the strictly linear polyethylene materials obtained are very low. The key for the combination of high control and efficiency seems to be a catalyst stabilized by only one strongly bound monoanionic N-ligand. 相似文献
19.
20.
Winfried P. Kretschmer Bart Hessen Natalie M. Scott 《Journal of organometallic chemistry》2007,692(21):4569-4579
This paper describes a substantial enhancement of the aminopyridinato ligand stabilized early transition metal chemistry by introducing the sterically very demanding 2,6-dialkylphenyl substituted aminopyridinato ligands derived from (2,6-diisopropylphenyl)-[6-(2,6-dimethylphenyl)-pyridin-2-yl]-amine (1a-H, ApH) and (2,6-diisopropylphenyl)-[6-(2,4,6-triisopropylphenyl)-pyridin-2-yl]- amine (1b-H, Ap∗H). The corresponding bis aminopyridinato zirconium dichloro complexes, [Ap2ZrCl2] (3a) and [Ap2∗ZrCl2] (3b) and the dimethyl analogues, [Ap2ZrMe2] (4a) and [Ap2∗ZrMe2] (4b) (Me = methyl) were synthesized, using standard salt metathesis routes. Single-crystal X-ray diffraction was carried out for the dichloro derivatives. Both zirconium metal centers have a distorted octahedral environment with a cis-orientation of the chloride ligands in 3a and a closer to trans-arrangement in 3b. The dimethyl derivatives are proven to be highly active ethylene polymerization catalysts after activation with [R2N(Me)H][B(C6F5)4] (R = C16H33-C18H37). During attempted co-polymerizations of α-olefins (propylene) and ethylene high activity and selectivity for ethylene and nearly no co-monomer incorporation was observed. Increasing the steric bulk of the ligand going from (2,6-dimethylphenyl) to (2,4,6-triisopropylphenyl) substituted pyridines, switches the catalyst system from producing long chain α-olefins to polymerization of ethylene in a living fashion. In contrast to the dimethyl complexes only [Ap2∗ZrCl2] in the presence of MAO at elevated temperature gave decent polymerization activity. NMR investigations of the reaction of dichloro complexes with 25 equiv. of MAO or AlMe3 at room temperature revealed, that [Ap2ZrCl2] decomposes under ligand transfer to aluminum and formation of [ApAlMe2], while [Ap2∗ZrCl2] remains almost unreacted under the same conditions. The aminopyridinato dimethyl aluminum complexes, [ApAlMe2] (5a) and [Ap∗AlMe2] (5b) were synthesized independently and structurally characterized. The aluminum complexes 5a and b show no catalytic activity towards ethylene, when “activated” with[R2N(Me)H][B(C6F5)4]. 相似文献