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971.
972.
Pacchioni G Sicolo S Valentin CD Chiesa M Giamello E 《Journal of the American Chemical Society》2008,130(27):8690-8695
On the basis of experimental evidence and DFT calculations, we propose a simple yet viable way to stabilize and chemically activate gold nanoclusters on MgO. First the MgO surface is functionalized by creation of trapped electrons, (H (+))(e (-)) centers (exposure to atomic H or to H 2 under UV light, deposition of low amounts of alkali metals on partially hydroxylated surfaces, etc.); the second step consists in the self-aggregation of gold clusters deposited from the gas phase. The calculations show that the (H (+))(e (-)) centers act both as nucleation and activation sites. The process can lead to thermally stable gold cluster anions whose catalytic activity is enhanced by the presence of an excess electron. 相似文献
973.
A. G. B. Azebaze B. M. W. Ouahouo J. C. Vardamides A. Valentin V. Kuete L. Acebey V. P. Beng A. E. Nkengfack M. Meyer 《Chemistry of Natural Compounds》2008,44(5):582-587
The phytochemical study of the stem bark of Allanblackia gabonensis has resulted in the isolation and characterization of one new xanthone derivative, named allanxanthone D, together with ten
known compounds, including six xanthone derivatives, allanxanthone A, 1,5-dihydroxyxanthone, 1,7-dihydroxyxanthone and 1,3,6,7-tetrahydroxy-2-(3-methylbut-2-enyl)xanthone,
forbexanthone, 6-deoxyisojacareubin, one polyisoprenylated benzophenone, guttiferone F, one flavanol, epicathechin, two phytosterols,
β-sitosterol, and campesterol. The structures of these compounds were established on the basis of one- and two-dimensional
NMR homo- and heteronuclear evidence. These compounds were evaluated for their activity against Leishmania amazonensis in vitro and antimicrobial activities against a range of Gram-negative and Gram-positive bacteria.
Published in Khimiya Prirodnykh Soedinenii, No. 5, pp. 471–475, September-October, 2008. 相似文献
974.
Annika Krusenbaum Jonathan Geisler Fabien Joel Leon Kraus Sven Grätz Mark Valentin Höfler Torsten Gutmann Lars Borchardt 《Journal of polymer science. Part A, Polymer chemistry》2022,60(1):62-71
Herein we report the mechanochemical Friedel-Crafts alkylation of 1,3,5-triphenylbenzene (TPB) with two organochloride cross-linking agents, dichloromethane (DCM) and chloroform (CHCl3), respectively. During a thorough milling parameter evaluation, the DCM-linked polymers were found to be flexible and extremely sensitive toward parameter changes, which even enables the synthesis of a polymer with a SSABET of 1670 m2/g, on par with the solution-based reference. Contrary, CHCl3-linked polymers are exhibiting a rigid structure, with a high porosity that is widely unaffected by parameter changes. As a result, a polymer with a SSABET of 1280 m2/g could be generated in as little as 30 minutes, outperforming the reported literature analogue in terms of synthesis time and SSABET. To underline the environmental benefits of our fast and solvent-free synthesis approach, the green metrics are discussed, revealing an enhancement of the mass intensity, mass productivity and the E-factor, as well as of synthesis time and the work-up in comparison to the classical synthesis. Therefore, the mechanochemical polymerization is presented as a versatile tool, enabling the generation of highly porous polymers within short reaction times, with a minimal use of chlorinated cross-linker and with the possibility of a post polymerization modification. 相似文献
975.
Maude Aelterman Tony Biremond Prof. Dr. Philippe Jubault Prof. Dr. Thomas Poisson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(66):e202202194
The electrochemical synthesis of fluorinated allyl silanes and boronates was disclosed. The addition of electrogenerated boryl or silyl radicals onto many α-trifluoromethyl or α-difluoromethylstyrenes in an undivided cell allowed the formation of a large panel of synthetically useful gem-difluoro and γ-fluoroallyl boronates and silanes (64 examples, from 31 % to 95 % yield). In addition, a scale up of the reactions under continuous flow was showcased using an electrochemical reactor with promising volumetric productivity (688 g.L−1.h−1 and 496 g.L−1.h−1). Moreover, the synthetic utility of these building blocks was highlighted through versatile transformations. Finally, plausible reaction mechanisms were suggested to explain the formation of the products. 相似文献
976.
Azebaze AG Ouahouo BM Vardamides JC Valentin A Kuete V Acebey L Beng VP Nkengfack AE Meyer M 《Natural product research》2008,22(4):333-341
The phytochemical study of stem bark of Allanblackia gabonensis has resulted in the isolation and characterisation of one new xanthone derivative, named allanxanthone D, together with 10 known compounds, including 6 xanthones derivatives, allanxanthone A, 1,5-dihydroxyxanthone, 1,7-dihydroxyxanthone and 1,3,6,7-tetrahydroxy-2-(3-methylbut-2-enyl)xanthone, forbexanthone, 6-deoxyisojacareubin, one polyisoprenylated benzophenone, guttiferone F, one flavanol, epicathechin, two phytosterols, beta-sitosterol and campesterol. The structures of these compounds were established on the basis of one- and two-dimensional NMR homo- and hetero-nuclear evidence. These compounds were evaluated for their activity against Leishmania amazonensis in vitro and antimicrobial activities against a range of Gram negative and Gram positive bacteria. 相似文献
977.
François Quentel Valentin Mirčeski Maurice L’Her 《Journal of Solid State Electrochemistry》2008,12(1):31-39
Thermodynamics and kinetics of hydrophilic ion transfers across water|n-octanol (W|OCT) interface have been electrochemically studied by means of novel three-phase and thin-film electrodes. Three-phase
electrodes used for thermodynamics measurements comprise edge plane pyrolytic graphite, the surface of which was partly modified
with an ultrathin film of OCT, containing hydrophobic lutetium bis(tetra-tert-butylphthalocyaninato) (Lu[tBu4Pc]2) as a redox probe. The transfers of anions and cations from W to OCT were electrochemically driven by reversible redox transformations
of Lu[tBu4Pc]2 to chemically stable lipophilic monovalent cation and anion , respectively. Upon reduction of Lu[tBu4Pc]2, the transfers of alkali metal cations from W to OCT have been studied for the first time, enabling estimation of their Gibbs
transfer energies. For kinetic measurements, a thin-film electrode configuration has been used, consisting of the same electrode
covered completely with a thin layer of OCT that contained the redox probe and a suitable electrolyte. Combining the fast
and sensitive square-wave voltammetry with thin-film electrodes, the kinetics of , , and Cl− transfers have been estimated.
Dedicated to Professor Dr. Yakov I. Tur’yan on the occasion of his 85th birthday. 相似文献
978.
Valentin Paul Nicu Johannes Neugebauer Stephen K. Wolff Evert Jan Baerends 《Theoretical chemistry accounts》2008,119(1-3):245-263
We describe the implementation of the rotational strengths for vibrational circular dichroism (VCD) in the Slater-type orbital
based Amsterdam Density Functional (ADF) package. We show that our implementation, which makes use of analytical derivative
techniques and London atomic orbitals, yields origin independent rotational strengths. The basis set dependence in the particular
case of Slater-type basis functions is also discussed. It turns out that the triple zeta STO basis sets with one set of polarization
functions (TZP) are adequate for VCD calculations. The origin- dependence of the atomic axial tensors is checked by a distributed
origin gauge implementation. The distributed and common origin gauge implementations yield virtually identical atomic axial
tensors with the Slater-type basis sets employed here, proving that our implementation yields origin independent rotational
strengths. We verify the implementation for a set of benchmark molecules, for which the dependence of the VCD spectra on the
particular choice of the exchange–correlation functional is studied. The pure functionals BP86 and OLYP show a particularly
good performance. Then, we apply this approach to study the VCD spectra of hexa- and hepta- helicenes. In particular we focus
on relationships between the sign of the rotational strengths of the two helicenes.
Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. 相似文献
979.
The integral enthalpies of solution of glycylglycine and diglycylglycine in water–ethanol, water–n-propanol and water–i-propanol mixtures were measured at 298.15 K and alcohol mole fraction concentrations (x2) ranging up to 0.3 by calorimetry. The ΔsolH° and ΔtrH° vs. x2 were found to have extrema. Enthalpic coefficients of pairwise interactions (hxy) between peptide and alcohol molecules were positive and increased in the series ethanol, n-propanol, i-propanol. 相似文献
980.
Abhishek Baral Aromal Asokan Valentin Bauer Bruno Kieffer Vladimir Torbeev 《Tetrahedron》2019,75(6):703-708
Chemical composition of tumor suppressor protein p53 is altered via multiple post-translational modifications which modulate its cellular lifetime and interactions with other biomolecules. Here we report total chemical synthesis of a 61-residue form of transactivation domain (TAD) of p53 based on native chemical ligation of three peptide segments. The experiments to characterize its binding to nuclear co-activator binding domain (NCBD) of CREB-binding protein confirmed native-like induced folding upon binding to NCBD. Thus, the synthetic approach described herein can be useful for the preparation of various post-translationally modified analogues of TAD-p53 for further functional biochemical and biophysical studies. 相似文献