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991.
Stephan K. Pedersen Kristina Eriksen Nataliya N. Karaush‐Karmazin Boris Minaev Hans gren Gleb V. Baryshnikov Michael Pittelkow 《Angewandte Chemie (International ed. in English)》2020,59(13):5144-5150
We present a high‐yielding intramolecular oxidative coupling within a diazadioxa[10]helicene to give a dihydro‐diazatrioxa[9]circulene. This is the first [n]circulene containing more than eight ortho‐annulated rings (n>8). The single‐crystal X‐ray structure reveals a tight columnar packing, with a proton from a pendant naphthalene moiety centred directly above the central nine‐membered ring. This distinct environment induces a significant magnetic deshielding effect on that particular proton as determined by 1H NMR spectroscopy. The origin of the deshielding effect was investigated computationally in terms of the NICS values. It is established that the deshielding effect originates from an induced paratropic ring current from the seven aromatic rings of the [9]circulene structure, and is not due to the nine‐membered ring being antiaromatic. UV/Vis spectroscopy reveals more efficient conjugation in the prepared diazatrioxa[9]circulene compared to the parent helical azaoxa[10]helicenes, and DFT calculations, including energy levels, confirm the experimental observations. 相似文献
992.
Jonathan Mendy Dr. Anh Thy Bui Dr. Amandine Roux Jean-Christophe Mulatier Damien Curton Dr. Alain Duperray Dr. Alexei Grichine Dr. Yannick Guyot Dr. Sophie Brasselet Dr. François Riobé Dr. Chantal Andraud Dr. Boris Le Guennic Dr. Véronique Patinec Pr. Raphael Tripier Dr. Maryline Beyler Dr. Olivier Maury 《Chemphyschem》2020,21(10):1036-1043
Cationic lanthanide complexes are generally able to spontaneously internalize into living cells. Following our previous works based on a diMe-cyclen framework, a second generation of cationic water-soluble lanthanide complexes based on a constrained cross-bridged cyclam macrocycle functionalized with donor-π-conjugated picolinate antennas was prepared with europium(III) and ytterbium(III). Their spectroscopic properties were thoroughly investigated in various solvents and rationalized with the help of DFT calculations. A significant improvement was observed in the case of the Eu3+ complex, while the Yb3+ analogue conserved photophysical properties in aqueous solvent. Two-photon (2P) microscopy imaging experiments on living T24 human cancer cells confirmed the spontaneous internalization of the probes and images with good signal-to-noise ratio were obtained in the classic NIR-to-visible configuration with the Eu3+ luminescent bioprobe and in the NIR-to-NIR with the Yb3+ one. 相似文献
993.
Svetlana H. Lakićević Boris Pejin Aleksandra S. Djordjević Saša M. Matijašević Miodrag L. Lazić 《Natural product research》2020,34(11):1542-1546
AbstractAutochthonous variety 'Prokupac' (Vitis vinifera L.) red wines with the addition of selected aromatic herbs (Artemisia absinthium, Cinnamomum zeylanicum, Glycyrrhiza glabra and Pimpinella anisum L.) were evaluated for chemical composition and biological activity. Furthermore, their polyphenolic profiles were determined by HPLC-DAD. While total phenolic (TPC) and flavonoid (TFC) contents, along with antioxidant activity, were significantly higher in all examined wine samples, the content of total anthocyanins was decreased, compared to a pure 'Prokupac' wine, used as the control one. On the other hand, 'Prokupac' wines with the addition of cinnamon (S. zeylanicum) and wormwood (A. absinthium) displayed highest antioxidant (EC50, 0.021?±?0.001?mg/mL) and antibacterial (Enterococcus faecalis, MIC/MBC 15.63/62.50?μL/mL) activities, respectively. The study showed that 'Prokupac' wine with the addition of cinnamon was significantly enriched both with TPC and TFC, compared to control wine (p?<?0.05), which may contribute to its market potential. 相似文献
994.
Mark Levin Alexey Krisilov Boris Zon Gary Eiceman 《International Journal for Ion Mobility Spectrometry》2014,17(2):73-77
We present the study of expansion of an ion cloud in the process of its drift in the ion mobility spectrometer taking into account the influence of diffusion and electric field of the space charge of the ion cloud. Nonlinear integro-differential equation describing these effects was obtained and solved numerically in the one-dimensional case. We found a threshold value of the ion density, above which the nonlinear effects associated with the space-charge field become significant, which agrees well with the experimental data and the criterion of Spangler. These nonlinear effects lead to the fact that the spatial ion distribution ceases to be Gaussian, and with good accuracy are approximated by the distribution of Kohlrausch–Williams–Watts. 相似文献
995.
Maximiliano Díaz Nataly Silva Nicolás Yutronic Eduardo Peña Boris Chornik Paul Jara 《Journal of inclusion phenomena and macrocyclic chemistry》2014,80(1-2):133-138
In this work, we report the nanodecoration of microcrystals of inclusion compound (IC) of γ-cyclodextrin (γ-CD) that contain octanethiol, decanethiol and dodecanethiol. Crystals of these ICs provide a suitable environment for nucleation, growth and immobilization of gold nanoparticles that were obtained by the magnetron sputtering technique. The use of γ-CD IC substrates with a specific surface morphology (i.e., the functional group of the guest molecule faces outward preferentially from a crystal plane) is an efficient method for the preparation of AuNPs with low size dispersion, which is due to the high affinity between the functional group of the surfactant alkylthiol guest with the metal nanoparticles. 相似文献
996.
Phosphate‐Triggered Self‐Assembly of N‐[(Uracil‐5‐yl)methyl]urea: A Minimalistic Urea‐Derived Hydrogelator 下载免费PDF全文
Alexander J. Kleinsmann Nicole M. Weckenmann Prof. Boris J. Nachtsheim 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(31):9753-9761
N‐[(Uracil‐5‐yl)methyl]urea is reported as a minimalistic low‐molecular‐weight hydrogelator (LMWHG). The unusual phosphate‐induced assembly of this compound has been thoroughly investigated by IR, UV/Vis, and NMR spectroscopy, electron microscopy, and rheological experiments. This rare example of an anion‐triggered urea‐based LMWHG is the first example of a pyrimidine‐ and urea‐containing molecule that can be forced into self‐assembly in aqueous solution without additional aromatic or lipophilic groups. The gelator/phosphate ratio within the hydrogel was successfully determined by 31P MAS NMR spectroscopy. The hydrogel exhibits a very fast and repeatable self‐healing property, and remarkable G′ values. The viscoelastic properties of the hydrogel can easily be tuned by variation of the phosphate ratio. 相似文献
997.
Comparative Analysis of Conjugated Alkynyl Chromophore–Triazacyclononane Ligands for Sensitized Emission of Europium and Terbium 下载免费PDF全文
Marine Soulié Frédéric Latzko Emmanuel Bourrier Dr. Virginie Placide Dr. Stephen J. Butler Dr. Robert Pal Dr. James W. Walton Dr. Patrice L. Baldeck Dr. Boris Le Guennic Dr. Chantal Andraud Dr. Jurriaan M. Zwier Dr. Laurent Lamarque Prof. David Parker Dr. Olivier Maury 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(28):8636-8646
A series of europium and terbium complexes based on a functionalized triazacyclononane carboxylate or phosphinate macrocyclic ligand is described. The influence of the anionic group, that is, carboxylate, methylphosphinate, or phenylphosphinate, on the photophysical properties was studied and rationalized on the basis of DFT calculated structures. The nature, number, and position of electron‐donating or electron‐withdrawing aryl substituents were varied systematically within the same phenylethynyl scaffold in order to optimize the brightness of the corresponding europium complexes and investigate their two‐photon absorption properties. Finally, the europium complexes were examined in cell‐imaging applications, and selected terbium complexes were studied as potential oxygen sensors. 相似文献
998.
Assessment of bitter taste of pharmaceuticals with multisensor system employing 3 way PLS regression
Alisa Rudnitskaya Dmitry Kirsanov Yulia Blinova Evgeny Legin Boris Seleznev David Clapham Robert S. Ives Kenneth A. Saunders Andrey Legin 《Analytica chimica acta》2013
The application of the potentiometric multisensor system (electronic tongue, ET) for quantification of the bitter taste of structurally diverse active pharmaceutical ingredients (API) is reported. The measurements were performed using a set of bitter substances that had been assessed by a professional human sensory panel and the in vivo rat brief access taste aversion (BATA) model to produce bitterness intensity scores for each substance at different concentrations. The set consisted of eight substances, both inorganic and organic – azelastine, caffeine, chlorhexidine, potassium nitrate, naratriptan, paracetamol, quinine, and sumatriptan. With the aim of enhancing the response of the sensors to the studied APIs, measurements were carried out at different pH levels ranging from 2 to 10, thus promoting ionization of the compounds. This experiment yielded a 3 way data array (samples × sensors × pH levels) from which 3wayPLS regression models were constructed with both human panel and rat model reference data. These models revealed that artificial assessment of bitter taste with ET in the chosen set of API's is possible with average relative errors of 16% in terms of human panel bitterness score and 25% in terms of inhibition values from in vivo rat model data. Furthermore, these 3wayPLS models were applied for prediction of the bitterness in blind test samples of a further set of API's. The results of the prediction were compared with the inhibition values obtained from the in vivo rat model. 相似文献
999.
Samuel Lundqvist Alessandro Oneto Bruce Reznick Boris Shapiro 《Journal of Pure and Applied Algebra》2019,223(5):2062-2079
In what follows, we pose two general conjectures about decompositions of homogeneous polynomials as sums of powers. The first one (suggested by G. Ottaviani) deals with the generic k-rank of complex-valued forms of any degree divisible by k in any number of variables. The second one (by the fourth author) deals with the maximal k-rank of binary forms. We settle the first conjecture in the cases of two variables and the second in the first non-trivial case of the 3-rd powers of quadratic binary forms. 相似文献
1000.
We generalize the notion of involutivity to systems of differential equations of different orders and show that the classical
results relating involutivity, restrictions, characteristics and characteristicity, known for first order systems, extend
to the general context. This involves, in particular, a new definition of strong characteristicity. The proof exploits a spectral
sequence relating Spencer δ-cohomology of a symbolic system and its restriction to a non-characteristic subspace.
相似文献