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991.
Marta Espina Palanco Klaus Bo Mogensen Katrin Kneipp 《Journal of Raman spectroscopy : JRS》2016,47(2):156-161
We report surface‐enhanced Raman studies on intact plant material using onion layers as a biological target, and silver nanoaggregates and silver island films as enhancing plasmonic structures. Surface‐enhanced Raman scattering (SERS) enhancement allows the detection of strong Raman signatures of chemical constituents of the surface of the onion layer such as cellulose, proteins, and flavonols. Because of long‐time incubation, SERS sensors can access the extracellular space in the inner of the layer. The location of silver nanoparticles inside the onion layer has been monitored by the SERS images collected from chemicals present in the onion and/or reporter molecules attached to the nanoparticles. Our studies show a competitive adsorption of intrinsic bio molecules of the onion layer and reporter molecules. Different spectra from different places of the layer indicate the complex heterogeneous chemical structure of the plant material. The pH‐sensitive reporter molecule para mercapto benzoic acid attached to the nanoparticles allows us to infer pH values inside the extracellular matrix of the onion layer. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
992.
Chun Y. Chow Hélène Bolvin Victoria E. Campbell Régis Guillot Jeff W. Kampf Wolfgang Wernsdorfer Frédéric Gendron Jochen Autschbach Vincent L. Pecoraro Talal Mallah 《Chemical science》2015,6(7):4148-4159
We report here the synthesis and the investigation of the magnetic properties of a series of binuclear lanthanide complexes belonging to the metallacrown family. The isostructural complexes have a core structure with the general formula [Ga4Ln2(shi3–)4(Hshi2–)2(H2shi–)2(C5H5N)4(CH3OH)x(H2O)x]·xC5H5N·xCH3OH·xH2O (where H3shi = salicylhydroxamic acid and Ln = GdIII1; TbIII2; DyIII3; ErIII4; YIII5; YIII0.9DyIII0.16). Apart from the Er-containing complex, all complexes exhibit an antiferromagnetic exchange coupling leading to a diamagnetic ground state. Magnetic studies, below 2 K, on a single crystal of 3 using a micro-squid array reveal an opening of the magnetic hysteresis cycle at zero field. The dynamic susceptibility studies of 3 and of the diluted DyY 6 complexes reveal the presence of two relaxation processes for 3 that are due to the excited ferromagnetic state and to the uncoupled DyIII ions. The antiferromagnetic coupling in 3 was shown to be mainly due to an exchange mechanism, which accounts for about 2/3 of the energy gap between the antiferro- and the ferromagnetic states. The overlap integrals between the Natural Spin Orbitals (NSOs) of the mononuclear fragments, which are related to the magnitude of the antiferromagnetic exchange, are one order of magnitude larger for the Dy2 than for the Er2 complex. 相似文献
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996.
A Multi‐Addressable Switch Based on the Dimethyldihydropyrene Photochrome with Remarkable Proton‐Triggered Photo‐opening Efficiency 下载免费PDF全文
Dr. Diego Roldan Dr. Saioa Cobo Dr. Frédéric Lafolet Dr. Neus Vilà Dr. Constance Bochot Dr. Christophe Bucher Prof. Dr. Eric Saint‐Aman Dr. Martial Boggio‐Pasqua Dr. Marco Garavelli Prof. Dr. Guy Royal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):455-467
A series of photochromic derivatives based on the trans‐10b,10c‐dimethyl‐10b,10c‐dihydropyrene (DHP, “closed form”) skeleton has been synthesized and their photoisomerization leading to the corresponding cyclophanediene (CPD, “open form”) isomers has been investigated by UV/Vis and 1H NMR spectroscopies. Substitution of the DHP core with electron‐withdrawing pyridinium groups was found to have major effects on the photoisomerization efficiency, the most remarkable examples being to enhance the quantum yield of the opening reaction and to allow fast and quantitative conversions at much lower radiant energies. This effect was rationalized by theoretical calculations. We also show that the reverse reaction, that is, going from the open form to the closed form, can be electrochemically triggered by oxidation of the CPD unit and that the photo‐opening properties of pyridine‐substituted DHPs can be efficiently tuned by protonation, the system behaving as a multi‐addressable molecular switch. These multi‐addressable photochromes show promise for the development of responsive materials. 相似文献
997.
Structural and Functional Implications of the Interaction between Macrolide Antibiotics and Bile Acids 下载免费PDF全文
Simon Glanzer Sergio A. Pulido Sarah Tutz Dr. Gabriel E. Wagner Dr. Manfred Kriechbaum Nina Gubensäk Jovana Trifunovic Markus Dorn Prof. Dr. Walter M. F. Fabian Prof. Predrag Novak Prof. Dr. Joachim Reidl Prof. Dr. Klaus Zangger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(11):4350-4358
Macrolide antibiotics, such as azithromycin and erythromycin, are in widespread use for the treatment of bacterial infections. Macrolides are taken up and excreted mainly by bile. Additionally, they have been implicated in biliary system diseases and to modify the excretion of other drugs through bile. Despite mounting evidence for the interplay between macrolide antibiotics and bile acids, the molecular details of this interaction remain unknown. Herein, we show by NMR measurements that macrolides directly bind to bile acid micelles. The topology of this interaction has been determined by solvent paramagnetic relaxation enhancements (solvent PREs). The macrolides were found to be bound close to the surface of the micelle. Increasing hydrophobicity of both the macrolide and the bile acid strengthen this interaction. Both bile acid and macrolide molecules show similar solvent PREs across their whole structures, indicating that there are no preferred orientations of them in the bile micelle aggregates. The binding to bile aggregates does not impede macrolide antibiotics from targeting bacteria. In fact, the toxicity of azithromycin towards enterotoxic E. coli (ETEC) is even slightly increased in the presence of bile, as was shown by effective concentration (EC50) values. 相似文献
998.
Torands Revisited: Metal Sequestration and Self‐Assembly of Cyclo‐2,9‐tris‐1,10‐phenanthroline Hexaaza Macrocycles 下载免费PDF全文
Dr. Matthias Georg Schwab Dr. Masayoshi Takase Dr. Alexey Mavrinsky Dr. Wojciech Pisula Prof. Dr. Xinliang Feng Dr. José A. Gámez Prof. Dr. Walter Thiel Dr. Kunal S. Mali Prof. Dr. Steven de Feyter Prof. Dr. Klaus Müllen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(23):8426-8434
A series of novel toroidal cyclo‐2,9‐tris‐1,10‐phenanthroline macrocycles with an unusual hexaaza cavity are reported. Nickel‐mediated Yamamoto aryl–aryl coupling was found to be a versatile tool for the cyclotrimerization of functionalized 1,10‐phenathroline precursors. Due to the now improved processability, both liquid‐crystalline behavior in the bulk phase and two‐dimensional self‐assembly at the molecular level could be studied, for the first time, for a torand system. The macrocycles exhibited a strong affinity for the complexation of different metal cations, as evidenced by MALDI‐TOF analysis and spectroscopic methods. Experimental results were correlated to an extensive computational study of the cyclo‐2,9‐tris‐1,10‐phenanthroline cavity and its binding mode for metal cations. Due to the combination of several interesting features, toroidal macrocycles may find future applications in the field of ion and charge transport through molecular channels, as well as for chemical sensing and molecular writing in surface‐confined monolayers under STM conditions. 相似文献
999.
Different Complexation Behavior of P‐Functionalized Ferrocene Derivatives Towards SnCl2, SnCl4 and SnPh2Cl2: Auto‐ionization and Redox‐Type Reactions 下载免费PDF全文
Dipl.‐Chem. Matthias Gawron Dr. Christina Dietz Michael Lutter Dr. Andrew Duthie Prof. Dr. Viatcheslav Jouikov Prof. Dr. Klaus Jurkschat 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(46):16609-16622
The novel phosphonyl‐substituted ferrocene derivatives [Fe(η5‐Cp)(η5‐C5H3{P(O)(O‐iPr)2}2‐1,2)] ( Fc1,2 ) and [Fe{η5‐C5H4P(O)(O‐iPr)2}2] ( Fc1,1′ ) react with SnCl2, SnCl4, and SnPh2Cl2, giving the corresponding complexes [(Fc1,2)2SnCl][SnCl3] ( 1 ), [{(Fc1,1′)SnCl2}n] ( 2 ), [(Fc1,1′)SnCl4] ( 3 ), [{(Fc1,1′)SnPh2Cl2}n] ( 4 ), and [(Fc1,2)SnCl4] ( 5 ), respectively. The compounds are characterized by elemental analyses, 1H, 13C, 31P, 119Sn NMR and IR spectroscopy, 31P and 119Sn CP‐MAS NMR spectroscopy, cyclovoltammetry, electrospray ionization mass spectrometry, and single‐crystal as well as powder X‐ray diffraction analyses. The experimental work is accompanied by DFT calculations, which help to shed light on the origin for the different reaction behavior of Fc1,1′ and Fc1,2 towards tin(II) chloride. 相似文献
1000.