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21.
Patrick Maestro Gerard Demazeau Michel Pouchard 《Journal of solid state chemistry》1981,40(1):101-108
A new solid solution Cr1?xIrxO2 (0 ≤ x ≤ 1) has been prepared using oxidizing agents under pressure. The magnetic study shows the importance of the spin-orbit coupling and the weakening of the ferromagnetic interactions with increasing iridium content. 相似文献
22.
Biswajit Pradhan Christopher Engelhard Sebastiaan Van Mulken Xueyan Miao Gerard W. Canters Michel Orrit 《Chemical science》2020,11(3):763
Monitoring the fluorescence of single-dye-labeled azurin molecules, we observed the reaction of azurin with hexacyanoferrate under controlled redox potential yielding data on the timing of individual (forward and backward) electron transfer (ET) events. Change-point analysis of the time traces demonstrates significant fluctuations of ET rates and of mid-point potential E0. These fluctuations are a signature of dynamical heterogeneity, here observed on a 14 kDa protein, the smallest to date. By correlating changes in forward and backward reaction rates we found that 6% of the observed change events could be explained by a change in midpoint potential, while for 25% a change of the donor–acceptor coupling could explain the data. The remaining 69% are driven by variations in complex association constants or structural changes that cause forward and back ET rates to vary independently. Thus, the observed spread in individual ET rates could be related in a unique way to variations in molecular parameters. The relevance for the understanding of metabolic processes is briefly discussed.Observing electron transfer events in individual azurin molecules, we relate the spread in transfer rates in a unique way to variations in molecular parameters. 相似文献
23.
24.
Janak KE Tanski JM Churchill DG Parkin G 《Journal of the American Chemical Society》2002,124(16):4182-4183
Mo(PMe3)6 reacts with thiophene to give the eta5-thiophene complex (eta5-C4H4S)Mo(PMe3)3 and the eta5-butadiene-thiolate complex (eta5-C4H5S)Mo(PMe3)2(eta2-CH2PMe2), which are the first examples of (i) eta5-thiophene coordination and (ii) C-S cleavage and hydrogenation by a molybdenum compound. Deuterium labeling studies suggest that the hydrogenation of thiophene may involve an alkylidene intermediate, an observation that has ramifications for the mechanisms of hydrodesulfurization. 相似文献
25.
Highly efficient capillary electrochromatographic separations of cardiac glycosides and other steroids are presented. Employing butyl-derivatized silica particles as stationary phase resulted in a nearly three times faster electroosmotic flow (EOF) compared to capillary electrochromatography (CEC) with octadecyl silica particles. On-column focusing with a preconcentration factor of 180 was performed and separation efficiencies of up to 240,000 plates per meter were obtained. Using label-free standard UV absorbance, detection limits of 10-80 nM were reached for all steroids tested. For screening of cardiac glycosides, e.g., digoxin and digitoxin in mixtures of steroids, CEC was combined with immunoaffinity extraction using immobilized polyclonal anti-digoxigenin antibodies and F(ab) fragments. Simply adding small amounts of antibody carrying particles to the samples and comparing chromatograms before and after antibody addition allowed screening for high affinity antigens in mixtures with moderate numbers of compounds. Under conditions of competing antigens, affinity fingerprints of immobilized anti-digoxigenin and anti-digitoxin antibodies were obtained, reflecting the cross-reactivity of eleven steroids. The method provides high selectivity due to the combination of bioaffinity interaction with highly efficient CEC separation and UV detection at several wavelengths in parallel. This selectivity was exploited for the detection of four cardiac glycosides in submicromolar concentrations in an untreated urine sample. 相似文献
26.
Karin Barthelet Didier Riou Gerard Frey 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(4):m264-m265
Crystals of caesium molybdenomethylenediphosphonate, [CsMoO2(CH3O6P2)], were hydrothermally synthesized at 473 K. The monoclinic structure, as determined from single‐crystal X‐ray diffraction, is two‐dimensional and consists of stacked mixed layers of corner‐sharing tetrahedral diphosphonate groups and MoO6 octahedra, between which Cs+ cations are intercalated. 相似文献
27.
This review will describe the ongoing efforts being made to incorporate organometallic fragments into the framework of dendrimers. While purely dendritic organic molecules are well known and well studied, species incorporating organometallic moieties potentially offer many benefits that are not available to only organic containing dendrimers. For example, catalytic or redox active organometallic functions can be included in the dendritic framework and impart these characteristics onto the dendrimer. This report will give an overview of the latest developments in this field by highlighting selected examples that detail novel synthetic strategies or dendrimer construction methodologies, interesting practical applications or address specific problems associated with organometallic dendrimers. 相似文献
28.
A ligand known to form a fluorescent complex with aluminum ion was immobilized on silica gel. The immobilization sequence was verified by cross-polarization magicangle spinning n.m.r. spectroscopy and diffuse reflectance u.v. spectroscopy. The solid-state fluorescence of the immobilized ligand complexed with aluminum ion was similar to the fluorescence of a solvated complex of a model ligand. The potential to eliminate possible interfering species by isolating the complex from solution was demonstrated. 相似文献
29.
Jockusch RA Kroemer RT Talbot FO Snoek LC Carçabal P Simons JP Havenith M Bakker JM Compagnon I Meijer G von Helden G 《Journal of the American Chemical Society》2004,126(18):5709-5714
The beta(1-->4) glycosidic linkage found in lactose is a prevalent structural motif in many carbohydrates and glycoconjugates. Using UV and IR ion-dip spectroscopies to probe benzyl lactoside isolated in the gas phase, we find that the disaccharide unit adopts only a single, rigid structure. Its fully resolved infrared ion-dip spectrum is in excellent agreement with that of the global minimum structure computed ab initio. This has glycosidic torsion angles of phi(H) (H1-C1-O-C4') approximately 180 degrees and psi(H) (C1-O-C4'-H4') approximately 0 degrees which correspond to a rotation of approximately 150 degrees about the glycosidic bond compared to the accepted solution-phase conformation. We discuss the biological implications of this discovery and the generality of the strategies employed in making it. 相似文献
30.
Richard W.M. Ten Hoedt Gerard van Koten Jan G. Noltes 《Journal of organometallic chemistry》1980,201(1):327-342
Thermal decomposition of configurationally pure 1,2-diarylpropenylcopper compounds Z-Vi2CU4Br2 and Z-Vi2Cu4R2 [Vi (2-Me2NC6H4)CC(Me)-(C6H4Me-4), R 2-Me2NC6H4 or 4-MeC6H4CC] predominantly results in the formation of ViH. In contrast, only dimers (ViVi) were formed on thermolysis of (Z-ViCu2OTf)η which is a further illustration of the influence of the counter anion on the reactivity of organocopper cluster compounds. However, in both cases partial inversion of configuration, giving mixtures of isomers, was observed. The thermolysis of (Z-ViCu2OTf)η is discussed in terms of OTf-enhanced intraaggregate electron-transfer processes. The formation of incipient vinyl cations which are η2-coordinated to the copper cluster can explain the observed isomerization.Also in the hydrolysis reaction of Z-Vi2Cu4Br2 mixtures of isomeric ViH compounds were obtained, the E/Z ratio being dependent on the type of reagent used. Mixtures of isomeric ViX compounds (X Br, Cl, I) were formed in the reaction of Z-Vi2Cu4Br2 with I2 and CuCl2. An explanation for the occurrence of isomerization is presented.Dimers (ViVi) were almost absent in the product mixture resulting from the reaction of Z-Vi2Cu4Br2 with CuCl2. In contrast, ViVi is obtained in about 50% yield from the reaction of ViLi with CuCl2 which is in accord with earlier observations for the reaction of aryllithium compounds with cupric halides.Highly selective E-ViBr formation was observed in the reaction of E-ViLi with AgBr. This reaction probably proceeds via a thermally unstable Z-ViAg2Br intermediate. 相似文献