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991.
Jocelyn C. Bruce Klaus R. Koch 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(1):m1-m4
The crystal and molecular structures of N‐benzoyl‐N′,N′‐dibutylselenourea (HL), C16H24N2OSe, and the corresponding complex bis(N‐benzoyl‐N′,N′‐dibutylselenoureato‐κ2Se,O)palladium(II), [Pd(C16H23N2OSe)2], are reported. The selenourea molecule is characterized by intermolecular hydrogen bonds between the selenoamidic H atom and the Se atom of a neighbouring molecule forming a dimer, presumably as a consequence of resonance‐assisted hydrogen bonding or π‐bonding co‐operativity. A second dimeric hydrogen bond is also described. In the palladium complex, the typical square‐planar coordination characteristic of such ligands results in a cis‐[Pd(L‐Se,O)2] complex. 相似文献
992.
García Cuesta I Sánchez Marín J Bondo Pedersen T Koch H Sánchez de Merás AM 《Physical chemistry chemical physics : PCCP》2008,10(3):361-365
Using correlated ab initio methods, the polarizability of large [4n+2]-annulenes is determined, showing that there exists an almost linear relation between the exaltation of magnetic susceptibility (a measure of aromaticity) and an equivalent enlargement of polarizability. 相似文献
993.
994.
We use (2)H NMR to investigate the segmental motion of poly(ethylene oxide) (PEO) in neat and nanocomposite materials that do and do not contain salt. Specifically, in addition to a neat low-molecular-weight PEO, we study mixtures of this polymer with TiO 2 nanoparticles and LiClO 4. To characterize the polymer dynamics over a wide range of time scales, we combine (2)H NMR spin-lattice relaxation, line-shape, and stimulated-echo analyses. The results consistently show that the presence of nanoparticles hardly affects the behavior of the polymer, while addition of salt leads to substantial changes; e.g., it reduces the crystallinity. For neat PEO and a PEO-TiO 2 mixture, stimulated-echo spectroscopy enables measurement of rotational correlation functions for the crystalline phase. Analysis of the decays allows us to determine correlation times, to demonstrate the existence of a nonexponential relaxation, which implies a high complexity of the polymer dynamics in the crystal, and to show that the reorientation can be described as a large-angle jump. For a PEO-TiO 2-LiClO 4 mixture, we use (2)H and (7)Li NMR to study the polymer and the lithium dynamics, respectively. Analysis of the (7)Li spin-lattice relaxation reveals a high lithium ionic mobility in this nanocomposite polymer electrolyte. The (7)Li stimulated-echo decay is well described by a stretched exponential extending over about 6 orders of magnitude, indicating that a broad and continuous distribution of correlation times characterizes the fluctuations of the local lithium ionic environments. 相似文献
995.
Iris Berg Dr. Luca Schio Justus Reitz Dr. Elena Molteni Linoy Lahav Carolina Gutiérrez Bolaños Dr. Andrea Goldoni Dr. Cesare Grazioli Prof. Guido Fratesi Prof. Max M. Hansmann Dr. Luca Floreano Prof. Elad Gross 《Angewandte Chemie (International ed. in English)》2023,62(46):e202311832
Self-assembled monolayers (SAMs) of N-heterocyclic olefins (NHOs) have been prepared on Au(111) and their thermal stability, adsorption geometry, and molecular order were characterized by X-ray photoelectron spectroscopy, polarized X-ray absorption spectroscopy, scanning tunneling microscopy (STM), and density functional theory (DFT) calculations. The strong σ-bond character of NHO anchoring to Au induced high geometrical flexibility that enabled a flat-lying adsorption geometry via coordination to a gold adatom. The flat-lying adsorption geometry was utilized to further increase the surface interaction of the NHO monolayer by backbone functionalization with methyl groups that induced high thermal stability and a large impact on work-function values, which outperformed that of N-heterocyclic carbenes. STM measurements, supported by DFT modeling, identified that the NHOs were self-assembled in dimers, trimers, and tetramers constructed of two, three, and four complexes of NHO−Au-adatom. This self-assembly pattern was correlated to strong NHO−Au interactions and steric hindrance between adsorbates, demonstrating the crucial influence of the carbon-metal σ-bond on monolayer properties. 相似文献
996.
Jonas Koch Daniel Scheps Matthias Gunne Oliver Boscheinen Christian Frech 《Journal of separation science》2023,46(9):2300031
In process development and characterization, the scale-up of chromatographic steps is a crucial part and brings a number of challenges. Usually, scale-down models are used to represent the process step, and constant column properties are assumed. The scaling is then typically based on the concept of linear scale-up. In this work, a mechanistic model describing an anti-Langmuirian to Langmuirian elution behavior of a polypeptide, calibrated with a pre-packed 1 ml column, is applied to demonstrate the scalability to larger column volumes up to 28.2 ml. Using individual column parameters for each column size, scaling to similar eluting salt concentrations, peak heights, and shapes is experimentally demonstrated by considering the model's relationship between the normalized gradient slope and the eluting salt concentration. Further scale-up simulations show improved model predictions when radial inhomogeneities in packing quality are considered. 相似文献
997.
Sørensen LM Nielsen KF Jacobsen T Koch AG Nielsen PV Frisvad JC 《Journal of chromatography. A》2008,1205(1-2):103-108
A method for determination of mycophenolic acid (MPA) in dry-cured ham, fermented sausage and liver paté is described. MPA was extracted from meat with bicarbonate-acetonitrile, further cleaned-up by mixed mode reversed phase-anion exchange and detected using a LC-MS system with electrospray ionisation-time-of-flight detection. The limit of detection was 4 microg/kg in sausage and 6 microg/kg in ham and paté. The method was successfully used for quantification of MPA in dry-cured ham and liver paté artificially inoculated with Penicillium brevicompactum. Levels ranged from 190 microg/kg in centre to 11 mg/kg in surface of ham and from 150 microg/kg in bottom to 14 mg/kg in surface of paté. 相似文献
998.
Uzra Diwan Virendra Kumar Rakesh K. Mishra Nishant Kumar Rana Biplob Koch Manish Kumar Singh K.K. Upadhyay 《Analytica chimica acta》2016
The present study deals with the photophysical property of a pyrene-benzthiazolium conjugate R1, as a strong intramolecular charge transfer (ICT) probe exhibiting long wavelength emission in the red region. Unlike traditional planar polyaromatic hydrocarbons whose aggregation generally quenches the light emission, the pyrene based R1 was found to display aggregation-induced emission (AIE) property along with simultaneous increase in its quantum yield upon increasing the water content of the medium. The R1 exhibits high specificity towards HSO3−/SO32− by interrupting its own ICT producing there upon a large ratiometric blue shift of ∼220 nm in its emission spectrum. The lowest detection limit for the above measurement was found to be 8.90 × 10−8 M. The fluorescent detection of HSO3− was also demonstrated excellently by test paper strip and silica coated TLC plate incorporating R1. The live cell imaging of HSO3─ through R1 in HeLa cells was studied using fluorescence microscopic studies. The particle size and morphological features of R1 and R1-HSO3− aggregates in aqueous solution were characterized by DLS along with SEM analysis. 相似文献
999.
Gaslonde T Michel S Koch M Pfeiffer B Léonce S Pierré A Tillequin F 《Chemical & pharmaceutical bulletin》2007,55(5):734-738
Coupling of 6-hydroxy-3,3-14-trimethyl-3,14-dihydro-7H-benzo[b]pyrano[3,2-h]acridin-7-one (6) with alpha,omega-diiodoalkanes of varying length under alkaline conditions gave dimers 7-10. Halogenated ethers 11-14, cyclization products 15-17, and compounds 18-22 were also isolated in small yield from the reaction mixtures. Compounds 7-10 were more potent than acronycine and benzo[b]acronycine in inhibiting L1210 cell proliferation. The length of the alkyl ether linkage between the two benzopyranoacridone units had a dramatic influence on the cytotoxic activity. Compound 9 (n=5) was the most active, with an IC(50) value against L1210 cells within the same range of magnitude as diacetate 5, currently under clinical development. 相似文献
1000.
Eugenie Geringer Dr. Marina Gerhard Prof. Dr. M. Koch Dr. Claudio K. Krug Prof. Dr. J. Michael Gottfried Prof. Dr. Stefanie Dehnen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(8):2734-2741
Herein, we present the synthesis of two pyrene-functionalized clusters, [(RpyrSn)4S6]⋅2 CH2Cl2 ( 4 ) and [(RpyrSn)4Sn2S10]⋅n CH2Cl2 (n=4, 5 a ; n=2, 5 b ; Rpyr=CMe2CH2C(Me)N-NC(H)C16H9), both of which form in reactions of the organotin sulfide cluster [(RNSn)4S6] ( C ; RN=CMe2CH2C(Me)N-NH2) with the well-known fluorescent dye 1-pyrenecarboxaldehyde ( B ). In contrast, reactions using an organotin sulfide cluster with another core structure, [(RNSn)3S4Cl] ( A ), leads to formation of small molecular fragments, [(RpyrCl2Sn)2S] ( 1 ), (pyren-1-ylmethylene)hydrazine ( 2 ), and 1,2-bis(pyren-1-ylmethylene)hydrazine ( 3 ). Besides synthesis and structures of the new compounds, we report the influence of the inorganic core on the optical properties of the dye, which was analyzed exemplarily for compound 5 a via absorption and fluorescence spectroscopy. This cluster was also used for exploring the potential of such non-volatile clusters for deposition on a metal surface under vacuum conditions. 相似文献