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Related Ligands (relate + ligand)
Selected AbstractsComparative Solution Equilibrium Study of the Interactions of Copper(II), Iron(II) and Zinc(II) with Triapine (3-Aminopyridine-2-carbaldehyde Thiosemicarbazone) and Related LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2010Éva A. Enyedy Abstract The interactions of CuII, ZnII and FeII with Triapine (3-aminopyridine-2-carbaldehyde thiosemicarbazone), which is currently undergoing phase II clinical trials as a chemotherapeutic antitumour agent, were investigated in a water/DMSO mixture. The proton-dissociation constants of the ligands, the stability constants and the coordination modes of the metal complexes formed were determined by pH-potentiometric, UV/Vis spectrophotometric, EPR, 1H NMR spectroscopic and ESI-MS methods. Two N-terminally dimethylated derivatives of Triapine were also studied. Mono- and bis-ligand complexes in different protonation states were identified. Furthermore, the formation of the dinuclear species [Cu2L3]+ was confirmed for all ligands by EPR spectroscopy and ESI-MS measurements. The results showed that the N-terminally dimethylated ligands are much more potent chelators than Triapine for the divalent metal ions studied. All three ligands formed the least stable complexes with ZnII, whereas the FeII complexes were somewhat more stable than the corresponding CuII species. [source] Facile Synthesis of Flexible Bis(pyrazol-1-yl)alkane and Related Ligands in a Superbasic MediumEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 30 2007Andrei S. Potapov Abstract Flexible ligands 1,3-bis(pyrazol-1-yl)propanes, bis[2-(pyrazol-1-yl)ethyl] ethers, and bis[2-(3,5-dimethylpyrazol-1-yl)ethyl]amine were prepared by a facile procedure involving the reaction of pyrazoles with 1,3-dibromopropane, bis(2-chloroethyl) ether or bis(2-chloroethyl)amine hydrochloride in a superbasic medium (dimethyl sulfoxide/potassium hydroxide). Reaction of bis(2-chloroethyl)amine and pyrazole unexpectedly led to 1,4-bis[2-(pyrazol-1-yl)ethyl]piperazine. The corresponding 4,4,-diiodo-substituted bis(pyrazole) derivatives were prepared by oxidative iodination with I2/HIO3/H2SO4 in acetic acid. Vilsmeier,Haak formylation of some of the prepared compounds yielded the corresponding dialdehydes.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Methoxycarbonylation of Vinyl Acetate Catalyzed by Palladium Complexes of Bis(ditertiarybutylphosphinomethyl)benzene and Related Ligands.CHEMINFORM, Issue 29 2005Adam J. Rucklidge Abstract For Abstract see ChemInform Abstract in Full Text. [source] Quest for Environmentally Benign Ligands for Actinide Separations: Thermodynamic, Spectroscopic, and Structural Characterization of UVI Complexes with Oxa-Diamide and Related LigandsCHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2009Guoxin Tian Dr. Abstract Complexation of UVI with N,N,N,,N, -tetramethyl-3-oxa-glutaramide (TMOGA) and N,N -dimethyl-3-oxa-glutaramic acid (DMOGA; see picture) was studied in comparison with their dicarboxylate analogue, oxydiacetic acid (ODA). The stability constants, enthalpy, and entropy of complexation all decrease in the order ODA> DMOGA>TMOGA, showing that the complexation is entropy driven and the substitution of a carboxylate group with an amide group reduces the strength of complexation with UVI due to the decrease in the entropy of complexation (see figure). Complexation of UVI with N,N,N,,N, -tetramethyl-3-oxa-glutaramide (TMOGA) and N,N -dimethyl-3-oxa-glutaramic acid (DMOGA) was studied in comparison with their dicarboxylate analogue, oxydiacetic acid (ODA). Thermodynamic parameters, including stability constants, enthalpy, and entropy of complexation, were determined by spectrophotometry, potentiometry, and calorimetry. Single-crystal X-ray diffraction, EXAFS spectroscopy, FT-IR absorption spectroscopy, and laser-induced luminescence spectroscopy were used to obtain structural information on the UVI complexes. Like ODA, TMOGA and DMOGA form tridentate UVI complexes, with three oxygen atoms (the amide, ether, and/or carboxylate oxygen) coordinating to the linear UO22+ ion through the equatorial plane. The stability constants, enthalpy, and entropy of complexation all decrease in the order ODA>DMOGA>TMOGA, showing that the complexation is entropy driven and the substitution of a carboxylate group with an amide group reduces the strength of complexation with UVI due to the decrease in the entropy of complexation. The trend in the thermodynamic stability of the complexes correlates very well with the structural and spectroscopic data obtained by single-crystal X-ray diffraction, FT-IR spectroscopy, and laser-induced luminescence spectroscopy. [source] Drosophila neuromuscular synapse assembly and function require the TGF-, type I receptor saxophone and the transcription factor MadDEVELOPMENTAL NEUROBIOLOGY, Issue 2 2003Joel M. Rawson Abstract Transforming growth factor-,s (TGF-,) comprise a superfamily of secreted proteins with diverse functions in patterning and cell division control. TGF-, signaling has been implicated in synapse assembly and plasticity in both vertebrate and invertebrate systems. Recently, wishful thinking, a Drosophila gene that encodes a protein related to BMP type II receptors, has been shown to be required for the normal function and development of the neuromuscular junction (NMJ). These findings suggest that a TGF-,-related ligand activates a signaling cascade involving type I and II receptors and the Smad family of transcription factors to orchestrate the assembly of the NMJ. Here we demonstrate that the TGF-, type I receptor Saxophone and the downstream transcription factor Mothers against dpp (Mad) are essential for the normal structural and functional development of the Drosophila NMJ, a synapse that displays activity-dependent plasticity. © 2003 Wiley Periodicals, Inc. J Neurobiol 55: 134,150, 2003 [source] Enantioselective Copper-Catalysed Allylic Alkylation of Cinnamyl Chlorides by Grignard Reagents using Chiral Phosphine-Phosphite LigandsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010Wibke Lölsberg Abstract The copper(I)-catalysed SN2,-type allylic substitution of E -3-aryl-allyl chlorides (cinnamyl chlorides) using Grignard reagents represents a powerful method for the synthesis of compounds carrying a benzylic stereocentre. By screening a small library of modular chiral phosphine-phosphite ligands a new copper(I)-based catalyst system was identified which allows the performance of such reactions with exceptional high degrees of regio- and enantioselectivity. Best results were obtained using TADDOL-derived ligands (3,mol%), copper(I) bromide,dimethyl sulfide (CuBr,SMe2) (2.5,mol%) and methyl tert -butyl ether (MTBE) as a solvent. Various (1-alkyl-allyl)benzene derivatives were prepared with up to 99% ee (GC) in isolated yields of up to 99%. In most cases the product contained less than 3% of the linear regioisomer (except for ortho -substituted substrates). Both electron-rich and electron-deficient cinnamyl chlorides were successfully employed. The absolute configuration of the products was assigned by comparison of experimental and calculated CD spectra. The substrates were prepared from the corresponding alcohols by reaction with thionyl chloride. Initially formed mixtures of regioisomeric allylic chlorides were homogenised by treatment with CuBr,SMe2 (2.5,mol%) in the presence of triphenyl phosphine (PPh3) (3,mol%) in MTBE at low temperature to give the pure linear isomers. In reactions with methylmagnesium bromide (MeMgBr) an ortho -diphenylphosphanyl-arylphosphite ligand with an additional phenyl substituent in ortho, -position at the aryl backbone proved to be superior. In contrast, best results were obtained in the case of higher alkyl Grignard reagents (such as ethyl-, n -butyl-, isopropyl-, and 3-butenylmagnesium bromides) with a related ligand carrying an isopropyl substituent in ortho, -position. The method was tested on a multi-mmol scale and is suited for application in natural product synthesis. [source] Fluorinated ,-Diketones for the Extraction of Lanthanide Ions: Photophysical Properties and Hydration Numbers of Their EuIII ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2006Anne-Sophie Chauvin Abstract Tris(,-diketonato)europium(III) with a series of variably fluorinated ligands derived from 3,5-heptanedione were synthesised with the aim of determining their hydration state under extraction conditions. The number of coordinated water molecules was determined by measuring the lifetime of the Eu(5D0) excited level in water and deuterated water. The hydration gain (,q = q , q0) after shaking chloroform solutions during 10 min with 0.1 M NaClO4 aqueous solutions depends on the fluorination extent of the diketonates: fluorination of one methyl group leads to a decrease in ,q of ca. 0.5 unit, while fluorination of one ethyl group results in a decrease of ca. 1.3 units. Highly fluorinated complexes (i.e with hexafluoroacetylacetonate and related ligands) display a hydration number close to one while poorly fluorinated compounds (or nonfluorinated ones, such as the acetylacetonate complex) have a hydration state close to two. Photophysical properties of the EuIII ,-diketonates are also described and the synthesis of the fluorinated ,-diketones is re-investigated and discussed in details. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Using cluster analysis to study transition-metal geometries: four-coordinate complexes with two salicylaldiminato or related ligandsACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2007Andrew Parkin Cluster analysis is shown to be an effective method to analyse and classify metal coordination geometry in a very large number of four-coordinate bis -salicylaldimato (or bis- ,-iminoketonate) transition-metal complexes available in the Cambridge Structural Database. The methods described require no prior knowledge of chemistry to be input; retrieved structures are automatically clustered into groups based purely on the geometric similarity of the fragments and these groupings can then be interpreted by the structural chemist. [source] Spiro Skeletons: A Class of Privileged Structure for Chiral Ligand DesignCHEMISTRY - AN ASIAN JOURNAL, Issue 1 2009Kuiling Ding Prof. Abstract This Focus Review highlights the exciting results obtained in the area of asymmetric catalysis using spirobiindane- or spirobifluorene-based chiral ligands. The spiro, mono, and bidentate ligands have been successfully applied in a wide range of transition-metal-catalyzed asymmetric reactions, including hydrogenations, carbon,carbon and carbon,heteroatom coupling reactions, with superior or comparable enantioselectivities to those obtained by using the related ligands bearing other backbones, thus proving that the spiro skeleton is a type of privileged structure for chiral ligand design. It is expected that the spiro concept for chiral ligand design will stimulate the future efforts to understand the features that account for their broad applicability and to apply this understanding to seek new privileged chiral ligands and catalysts. 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