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41.
Contributions to the Chemistry of Halosilane Adducts. XXII. Hydrogen Bonding and Ionization of Pentacoordinated Si-Compounds. Preparation, Properties, Crystal and Molecular Structure of 2,2-Dimethyl-2,3-dihydro-1H-[1,4,2]diazasilolo[4,5-α]pyridinium-chloride-Chloroform(1/1), The title compound ( 1 ) is obtained by the reaction of 2-trimethylsilylaminopyridine and Me2CH2ClSiCl in CHCl3. The SiCl bond is ionic (X-ray structure determination). 1 crystallizes monoclinic space group P21/c (Z = 8). The asymmetric unit contains two symmetrically nonequivalent molecular cations of 1 , two Cl anions and two CHCl3. Silicon is tetracoordinate with Si? N-bond distances of 1.766 Å and 1.777 Å. The shortest SiCl distances (3.908 and 4.110 Å) correspond to ionic interactions. Both Cl anions are hydrogen bonded to CHC13. Additionally one C1? is hydrogen bonded to the NH groups of two neighbouring cations. Structural comparison with related compounds suggests these interactions to be responsible for the transition from pentacoordination to tetracoordination at Si (ionization of the Sic1 bond). 1H- and 29Si-NMR investigations of 1 show this transition to be dependent on the combined effect of NH…?C1? and C13CH…?C1? interactions. 1 is completely ionized in CDCl3 in the temperature range ?80° to +80°C while in the weaker acceptor solvent benzonitrile a temperature dependent shift from the ionic tetracoordinate to the pentacoordinate structure is observed with increasing pentacoordination with increase of temperature. 相似文献
42.
Francesco Gentile Michael Fernandez Fuqiang Ban Anh-Tien Ton Hazem Mslati Carl F. Perez Eric Leblanc Jean Charle Yaacoub James Gleave Abraham Stern Bill Wong Franois Jean Natalie Strynadka Artem Cherkasov 《Chemical science》2021,12(48):15960
Recent explosive growth of ‘make-on-demand’ chemical libraries brought unprecedented opportunities but also significant challenges to the field of computer-aided drug discovery. To address this expansion of the accessible chemical universe, molecular docking needs to accurately rank billions of chemical structures, calling for the development of automated hit-selecting protocols to minimize human intervention and error. Herein, we report the development of an artificial intelligence-driven virtual screening pipeline that utilizes Deep Docking with Autodock GPU, Glide SP, FRED, ICM and QuickVina2 programs to screen 40 billion molecules against SARS-CoV-2 main protease (Mpro). This campaign returned a significant number of experimentally confirmed inhibitors of Mpro enzyme, and also enabled to benchmark the performance of twenty-eight hit-selecting strategies of various degrees of stringency and automation. These findings provide new starting scaffolds for hit-to-lead optimization campaigns against Mpro and encourage the development of fully automated end-to-end drug discovery protocols integrating machine learning and human expertise.Deep learning-accelerated docking coupled with computational hit selection strategies enable the identification of inhibitors for the SARS-CoV-2 main protease from a chemical library of 40 billion small molecules. 相似文献
43.
Eva Marie Freiberger Dr. Julien Steffen Natalie J. Waleska-Wellnhofer Anton Harrer Felix Hemauer Valentin Schwaab Prof. Dr. Andreas Görling Prof. Dr. Hans-Peter Steinrück Prof. Dr. Christian Papp 《Chemphyschem》2023,24(22):e202300510
This study addresses a fundamental question in surface science: the adsorption of halogens on metal surfaces. Using synchrotron radiation-based high-resolution X-ray photoelectron spectroscopy (XPS), temperature-programmed XPS, low-energy electron diffraction (LEED) and density functional theory (DFT) calculations, we investigated the adsorption and thermal stability of bromine on Rh(111) in detail. The adsorption of elemental bromine on Rh(111) at 170 K was followed in situ by XPS in the Br 3d region, revealing two individual, coverage-dependent species, which we assign to fcc hollow- and bridge-bound atomic bromine. In addition, we find a significant shift in binding energy upon increasing coverage due to adsorbate-adsorbate interactions. Subsequent heating shows a high thermal stability of bromine on Rh(111) up to above 1000 K, indicating strong covalent bonding. To complement the XPS data, LEED was used to study the long-range order of bromine on Rh(111): we observe a (√3×√3)R30° structure for low coverages (≤0.33 ML) and a star-shaped compression structure for higher coverages (0.33–0.43 ML). Combining LEED and DFT calculations, we were able to visualize bromine adsorption on Rh(111) in real space for varying coverages. 相似文献
44.
Timo Fuchs Valentín Briega-Martos Jakub Drnec Natalie Stubb Isaac Martens Federico Calle-Vallejo Prof. David A. Harrington Serhiy Cherevko Prof. Olaf M. Magnussen 《Angewandte Chemie (International ed. in English)》2023,62(34):e202304293
The degradation of Pt-containing oxygen reduction catalysts for fuel cell applications is strongly linked to the electrochemical surface oxidation and reduction of Pt. Here, we study the surface restructuring and Pt dissolution mechanisms during oxidation/reduction for the case of Pt(100) in 0.1 M HClO4 by combining operando high-energy surface X-ray diffraction, online mass spectrometry, and density functional theory. Our atomic-scale structural studies reveal that anodic dissolution, detected during oxidation, and cathodic dissolution, observed during the subsequent reduction, are linked to two different oxide phases. Anodic dissolution occurs predominantly during nucleation and growth of the first, stripe-like oxide. Cathodic dissolution is linked to a second, amorphous Pt oxide phase that resembles bulk PtO2 and starts to grow when the coverage of the stripe-like oxide saturates. In addition, we find the amount of surface restructuring after an oxidation/reduction cycle to be potential-independent after the stripe-like oxide has reached its saturation coverage. 相似文献
45.
Cholesteric polysiloxanes containing an azo dye were irradiated with linearly or circularly polarized laser light or with the unpolarized light from a HgXe lamp. Photoinduced rotational diffusion was observed leading to new textures with a completely different orientational distribution of the chromophoric and the mesogenic side chains. A broad variety of new structures was detected depending on the polarization state of the light, the helical arrangement of the azo dye and the optional application of an electrical d.c. field. The new structures were characterized by spectroscopy with polarized light. Co-operative reorientation of chromophoric and mesogenic side chains was proven. The formation of a Bragg grating upon short term irradiation with linearly polarized light was observed. Continued irradiation leads in most cases to a strongly birefringent texture with a high dichroic ratio of the azo dye resembling a planar nematic texture. With circularly polarized light or with unpolarized light, a uniaxial homeotropic texture appeared predominantly. The formation of the new textures occurred in the glassy state of the samples leading to new structures with good optical quality and an exceptionally good long-term stability. 相似文献
46.
Glycopeptides were isolated from functional units of two molluscan hemocyanins (Hcs). They were analyzed and localized in the sequences. A comparison with potential N-glycosylation sites of two other molluscan Hcs was made. An immunological cross-reactivity was observed between the beta-Hc and the alpha-macroglobulin of Helix pomotia. ELISA experiments with glycopeptide fractions indicated a competition. 相似文献
47.
Václav Štengl Snejana Bakardjieva Natalie Murafa Eva Večerníková Jan Šubrt Vladimír Balek 《Journal of nanoparticle research》2007,9(3):455-470
A new method for preparation of titania nanowires with diameter around 10 nm and length up to 2–3 μm is described. The precursor
was prepared from sodium titanate by adding ethylene glycole (EG) and heating at temperature of 198°C for 6 h under reflux.
The sodium titanate glycolate formed by this way aggregated into 1D nanostructures and was subsequently transformed into titania
glycolate during a chemical treatment with 98% sulfuric acid. Titania nanowires with variable amount of anatase and rutile
were prepared by heating to temperatures in the range 350–1000°C. The precursor as well as titania based samples were characterized
by X-ray diffraction, Infrared spectroscopy, Scanning electron microscopy, High resolution transmission microscopy, Thermogravimetry,
Differential thermal analysis, Evolved gas analysis and Emanation thermal analysis. The nitrogen adsorption/desorption was
used for surface area and porosity determination. The photoactivity of the prepared titania samples was assessed by the photocatalytic
decomposition of 4-chlorophenol in an aqueous slurry under UV irradiation of 365 nm wavelength. 相似文献
48.
The preparation of SiH-containing silylphosphines from SiH-containing chlorosilanes is successful by using an excess of chlorosilans. Chemical shift data and coupling constants of the compounds HxSi[P(C2H5)2]4?x and (CH3)xSi[P(C2H5)2]4?x are communicated and compared with those of HxSiX4?x and (CH3)xSiX4?x (X = halogen or H). 相似文献
49.
50.
A theoretical study of the solvation of ( R)- N-(3,5-dinitrobenzoyl)phenylglycine- and ( R)- N-(3,5-dinitrobenzoyl)leucine-derived chiral stationary phases (CSPs) is presented. Semiflexible models of the chiral selectors are prepared from B3LYP/6-311G** calculations, and these are used in the molecular dynamics simulations of the corresponding interface. The chiral interface is examined for four solvents: 100% hexane, 90:10 hexane:2-propanol, 80:20 hexane:2-propanol, and 100% 2-propanol. Despite the similarities between phenylglycine and leucine, the interfaces are distinct both in terms of the selector orientations at the surface and in the number of hydrogen bonds formed with 2-propanol. We also find that an increase in alcohol concentration alters the preferred orientations of the selectors. 相似文献