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101.
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Dr. Priyabrata Ghana Dr. Franziska D. van Krüchten Dr. Thomas P. Spaniol Prof. Dr. Jun Okuda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(45):10718-10723
Protonolysis of the titanium alkyl complex [Ti(CH2SiMe3)(Xy-N3N)] (Xy-N3N=[{(3,5-Me2C6H3)NCH2CH2}3N]3−) supported by a triamidoamine ligand, with [NEt3H][B(3,5-Cl2C6H3)4] or [PhNMe2H][B(C6F5)4] afforded the cations [Ti(Xy-N3N)][A] (A−=[B(3,5-Cl2C6H3)4]− ( 1[B(ArCl)4] ; B(ArCl)4=tetrakis(3,5-dichlorophenyl)borate); A−=[B(C6F5)4]− ( 1[B(ArF)4] ; B(ArF)4=tetrakis[3,5-bis(trifluoromethyl)phenyl]borate). These Lewis acidic cations were reacted with coordinating solvents to afford the cations [Ti(L)(Xy-N3N)][B(C6F5)4] ( 2-L ; L=Et2O, pyridine and THF). XRD analysis revealed a trigonal monopyramidal (TMP) geometry for the tetracoordinate cations in 1[B(ArX)4] and trigonal bipyramidal (TBP) geometry for the pentacoordinate cations in 2-L . Variable-temperature NMR spectroscopy showed a dynamic equilibrium for 2-Et2O in solution, involving the dissociation of Et2O. Coordination to the titanium(IV) center activated the THF molecule, which, in the presence of NEt3, underwent ring-opening to give the titanium alkoxide [Ti(O(CH2)4NEt3)(Xy-N3N)][B(3,5-Cl2C6H3)4] ( 3 ). Hydride abstraction from Cβ,eq of the triamidoamine ligand arm in [Ti(CH2SiMe3)(Xy-N3N)] or [Ti(NMe2)(Xy-N3N)] with [Ph3C][B(3,5-Cl2C6H3)4] led to the diamidoamine–imine complex [Ti(R){(Xy-N=CHCH2)(Xy-NCH2CH2)2N}][B(3,5-Cl2C6H3)4] (R=CH2SiMe3 ( 4 a ); R=NMe2 ( 4 b )). Hydride addition to 4 b with [Li(THF)][HBPh3] gave [Ti(NMe2)(Xy-N3N)], whereas KH deprotonated further to give [Ti(NMe2){(Xy-NCH=CH)(Xy-NCH2CH2)2N}] ( 5 ). XRD on single crystals of 3 and 4 b confirmed the proposed structures. 相似文献
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Markus Gellesch Franziska Hammerath Vicky Süß Marcel Haft Silke Hampel Sabine Wurmehl Bernd Büchner 《Journal of nanoparticle research》2017,19(9):307
The increasing interest in nanoscale materials goes hand in hand with the challenge to reliably characterize the chemical compositions and structural features of nanosized objects in order to relate those to their physical properties. Despite efforts, the analysis of the chemical composition of individual multi-element nanoparticles remains challenging—from the technical point of view as well as from the point of view of measurement statistics. Here, we demonstrate that zero-field solid-state nuclear magnetic resonance (NMR) complements local, single particle transmission electron microscopy (TEM) studies with information on a large assembly of chemically complex nanoparticles. The combination of both experimental techniques gives information on the local composition and structure and provides an excellent measurement statistic through the corresponding NMR ensemble measurement. This analytical approach is applicable to many kinds of magnetic materials and therefore may prove very versatile in the future research of particulate magnetic nanomaterials. 相似文献
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Schäfer-Bung B Bonacić-Koutecký V Sauer F Weber SM Wöste L Lindinger A 《The Journal of chemical physics》2006,125(21):214310
We present a joint theoretical and experimental study of the maximization of the isotopomer ratio (23)Na(39)K(23)Na(41)K using tailored phase-only as well as amplitude and phase modulated femtosecond laser fields obtained in the framework of optimal control theory and closed loop learning (CLL) technique. A good agreement between theoretically and experimentally optimized pulse shapes is achieved which allows to assign the optimized processes directly to the pulse shapes obtained by the experimental isotopomer selective CLL approach. By analyzing the dynamics induced by the optimized pulses we show that the mechanism involving the dephasing of the wave packets between the isotopomers (23)Na (39)K and (23)Na (41)K on the first excited state is responsible for high isotope selective ionization. Amplitude and phase modulated pulses, moreover, allow to establish the connection between the spectral components of the pulse and corresponding occupied vibronic states. It will be also shown that the leading features of the theoretically shaped pulses are independent from the initial conditions. Since the underlying processes can be assigned to the individual features of the shaped pulses, we show that optimal control can be used as a tool for analysis. 相似文献
108.
Aleksandra Jeličić Franziska Köhler Alette Winter Sabine Beuermann 《Journal of polymer science. Part A, Polymer chemistry》2010,48(14):3188-3199
Pulsed laser polymerizations were used to study the propagation kinetics of hydroxypropyl methacrylate (HPMA) in ionic liquids (ILs) and common organic solvents. The functional monomer was chosen to investigate the complex interplay of all interactions between monomer molecules and between monomer and solvent molecules and to obtain a deeper understanding of the impact of these interactions. The solvent effect on the HPMA propagation rate coefficient (kp) was examined using a linear solvation energy relationship (LSER) based on Kamlet‐Taft solvatochromic parameters π*, α, and β. The results suggest that dipolarity/polarizability, associated with π*, and hydrogen bond–donating ability of the solvents, accounted for by α, majorly contribute to variations in kp. Hydrogen bond–accepting (electron pair donating) ability of the solvents (β parameter) is of much lesser importance. In addition, LSER enables the prediction of HPMA kp based on solvatochromic parameters of the solvents. The results suggest that interactions between the hydroxyl group of the monomer and the anion are dominant compared with classical hydrogen bonding between carbonyl and hydroxyl groups of the monomer units. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3188–3199, 2010 相似文献
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Franziska Debatin Arne Thomas Prof. Dr. Alexandra Kelling Niklas Hedin Dr. Zoltan Bacsik Dr. Irena Senkovska Dr. Stefan Kaskel Prof. Dr. Matthias Junginger Holger Müller Uwe Schilde Prof. Dr. Christian Jäger Prof. Dr. Alwin Friedrich Dr. Hans‐Jürgen Holdt Prof. Dr. 《Angewandte Chemie (International ed. in English)》2010,49(7):1258-1262
110.
Juri Skotnitzki Alexander Kremsmair Daniel Keefer Franziska Schüppel Brieuc Le Cacher de Bonneville Regina de Vivie-Riedle Paul Knochel 《Chemical science》2020,11(20):5328
The diastereoselective SN2′-substitution of secondary alkylcopper reagents with propargylic phosphates enables the preparation of stereodefined alkylallenes. By using enantiomerically enriched alkylcopper reagents and enantioenriched propargylic phosphates as electrophiles anti-SN2′-substitutions were performend leading to α-chiral allenes in good yields with excellent regioselectivity and retention of configuration. DFT-calculations were performed to rationalize the structure of these alkylcopper reagents in various solvents, emphasizing their configurational stability in THF.The diastereoselective SN2′-substitution of secondary alkylcopper reagents with propargylic phosphates enables the preparation of stereodefined alkylallenes. 相似文献