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Ligand Framework (ligand + framework)
Selected AbstractsNanoparticle-Structured Ligand Framework as Electrode InterfacesELECTROANALYSIS, Issue 1-2 2004Nancy Abstract Nanostructured thin film assemblies derived from metal or oxide nanocrystal cores and functionalized molecular shells provide large surface-to-volume ratio and three-dimensional ligand frameworks. In this article, we report results of an investigation of the nanostructured materials for electroanalysis. Monolayer-capped gold nanoparticles of 2-nm core diameter and carboxylic acid-functionalized alkyl thiols were assembled on electrode surfaces via an exchange-crosslinking-precipitation reaction route, and were studied as a model system. The network assemblies exhibit open frameworks in which the void space forms channels with the nanometer sized cores defining its size and the shell structures defining its chemical specificity. Such nanostructures were exploited to demonstrate the viability of responsive materials for interfacial incorporation and fluxes of ionic species. The nanomaterials were characterized by an array of techniques, including cyclic voltammetry, electrochemical quartz-crystal nanobalance, flow injection analysis, and surface infrared reflection spectroscopy. The current responses and mass loading as a result of the incorporation of ionic species into the nanostructure have been analyzed. The potential application of the nanostructured thin films for electrochemical detection in microfluidic systems is also discussed. [source] Synthetic Explorations Towards Sterically Crowded 1,2,3-Substituted Bis(indenyl)zirconium(IV) DichloridesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2005Andreas C. Möller Abstract The systematic synthesis of 1,3-dialkyl-substituted 2-silylindenes and their suitability as zirconocene ligands is discussed. Unexpected reactivities rendered a number of substitution patterns unfeasible, especially for alkyl groups other than methyl in 2-(trimethylsilyl)indene derivatives, and essentially for all derivatives of 2-(dimethylsilyl)indene. The syntheses of rac/meso -bis[1-methyl-2-(trimethylsilyl)indenyl]zirconium(IV) dichloride (12) and bis[1,3-dimethyl-2-(trimethylsilyl)indenyl]zirconium(IV) dichloride (13b) are described. The solid-state structure of the latter displays strong deformations within the ligand framework and an unusually large Cpcentroid -Zr,Cpcentroid angle. Both, 12/MAO and 13b/MAO, displayed ethene and ethene-co-1-hexene polymerization activity. Curiously, 13b/MAO shows an extraordinary monomer selectivity, which can be rationalized by means of DFT calculations on the active site. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Novel Chiral (Salen)MnIII Complexes Containing a Calix[4]arene Unit as Catalysts for Enantioselective Epoxidation Reactions of (Z)-Aryl AlkenesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 16 2005Maria E. Amato Abstract New asymmetric (salen)MnIII and UO2 complexes containing a calix[4]arene unit in the ligand framework were synthesized. The UO2 complexes were characterized by 1H-, 13C-, 2D TOCSY and T-ROESY NMR spectroscopy. Furthermore, the structure of one UO2 complex was determined by single-crystal X-ray analysis. The data showed that UO2 complexes, which can be considered in first approximation models of the Mn=O oxidant active species, possess a chiral pocket and adopt relevant conformations for the selectivity of the oxygen transfer process. Epoxidation data of model alkenes with the MnIII complexes showed moderate ee values and were not conclusive in indicating that the calix[4]arene unit might be able to influence the selectivity by a molecular recognition mechanism. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Alternating Copolymerization of Carbon Dioxide and Propylene Oxide Catalyzed by Cobalt Schiff Base ComplexMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 15 2009Yongsheng Niu Abstract Cobalt 2,4-dinitrophenolate (complex 1) based upon a N,N,O,O -tetradentate Schiff base ligand framework was prepared. X-ray diffraction analysis confirmed that complex 1 was triclinic species with a six-coordinated central cobalt octahedron in the solid. Asymmetric alternating copolymerization of carbon dioxide (CO2) with racemic propylene oxide (rac -PO) proceeded effectively by complex 1 in conjunction with (4-dimethylamino)pyridine (DMAP), yielding a perfectly alternating and bimodal molecular weight distribution PO/CO2 poly(propylene carbonate) (PPC) with a small amount of cyclic carbonate byproducts. [source] Characterisation via electrospray ionisation multistage mass spectrometry of three related series of nitrido technetium complexes containing phosphinothiolate and dithiocarbamate ligandsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2005Michela Tubaro Nine nitrido technetium compounds comprising bis-substituted Tc(N)(PS)2 (1,4) (PS,=,bidentate phosphinothiolate ligands) and Tc(N)(dtc)2 (5, 6) derivatives (dtc,=,bidentate dithiocarbamate), and mixed-ligand Tc(N)(PS)(dtc) (7,9) species, were subjected to electrospray ionisation mass spectrometry and MSn experiments. Bis-substituted phosphinothiolato complexes 1,4 lead to the straightforward formation of dinuclear species reasonably originating from proton bound dimers. These dinuclear species do not show, under collisionally induced fragmentation processes, the formation of monomeric units but cleavages related to the ligand framework, thereby proving the high stability of the [TcH+Tc] bond. Bis-dithiocarbamate compounds 5 and 6 show, instead, abundant [M+H]+, [M+Na]+ and [2M+Na]+ ions, and their collisionally induced fragmentations are highly favoured with cleavages related to the CN and CS bonds. During these processes, the coordination of a water molecule to [MH,L]+ product ions is observed, as proved by the collisionally induced H2O loss detected for this species. Mixed-ligand compounds 7 and 8 show the protonated molecules and Na+ -cationised ions with fragmentation processes related to the dithiocarbamate moiety. This behaviour indicates that coordination of ether- and ester-substituted dithiocarbamates to the [Tc,,N] group is weaker than that of phosphinothiolates. Conversely, diethyldithiocarbamate inserted in mixed complex 9 enhances both CN and TcS bonds, and fragmentation processes suggest that metal-phosphinothiolate and metal-dithiocarbamate show comparable strength. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||