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Tetradentate Ligand (tetradentate + ligand)
Selected AbstractsFacile Synthesis of Nitrogen Tetradentate Ligands and Their Applications in CuI -Catalyzed N-Arylation and Azide,Alkyne CycloadditionCHEMISTRY - A EUROPEAN JOURNAL, Issue 40 2009Fuwei Li Dr. Abstract Five new tetradentate ligands [NNNN] with benzimidazolyl-imine or amine nitrogen donors have been synthesized in good yields under mild conditions from easily available substrates. trans - N,N,-bis(1-Ethyl-2-benzimidazolylmethylene)cyclohexane-1,2-diimine is the best accelerating ligand in this series that supports the CuI -catalyzed Ullmann N-arylation and the direct three-component azide,alkyne cycloaddition reaction to give the corresponding substituted imidazole, pyrazole, and triazole in high yields. Single-crystal X-ray diffraction analysis of its complex with CuI reveals a novel one-dimensional coordination polymer of the metal chain bridged alternately by the [NNNN] ligand and diiodides. [source] Pentadentate Ligands for the 1:1 Coordination of Lanthanide(III) Salts,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2007Markus Albrecht Abstract Three hydrazone type ligands, namely 2 -H, 3, and 4, which were designed to form 1:1 complexes with lanthanoid(III) ions, are presented. Although the tetradentate ligand 2, leads to an interesting complex [(2)(2 -H)YCl2] with yttrium(III), a more general principle for the coordination of the metal ions by hydrazone-type ligands can be found with ligand 3, where 1:1 complexes are obtained with an effective coordination of the metal salts by the ligand. The stabledimer [{(3)Nd(CF3SO3)}2(,-CF3SO3)3]CF3SO3 was characterized by X-ray structure determination. Depending on the size of the metal ion, additional co-ligands can also be bound to the metal centers. This is observed in the molecular structures of [(3)Pr(NO3)2(MeOH)2](NO3), [(3)NdCl2(MeOH)(EtOH)]Cl, [(3)ErCl2(MeOH)]Cl, and [(3)LuCl2]Cl. The solid-state molecular structures of 4 and 4·HCl show the helicating ability of this ligand upon metal coordination. The corresponding lanthanide complexes of 4 are characterized by standard techniques such as NMR and CD spectroscopy and mass spectrometry.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] A Magnetostructural and Electrochemical Study of CuII and FeIII Complexes Containing a Tetradentate Aminebis(phenolate) Ligand with a Pendent Tetrahydrofuran GroupEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2007Elham Safaei Abstract Ligating properties of a tetradentate ligand 2-{bis[(3,5-di- tert -butyl-2-hydroxybenzyl)amino]methyl}tetrahydrofuran,H2L, with [O,O,N,O]-donor atoms towards CuII and FeIII are described. The ligand H2L yields both mononuclear LFeIII(acac) (1) and dinuclear [L2FeIII2(,-OCH3)-(,-OH)] (2), [L2FeIII2(,-C2O4)] (3) and [L2CuII2] (4) complexes, which were characterized by various physical techniques, including X-ray diffraction, Mössbauer, electrochemical and magnetic susceptibility (2,290 K) measurements. That the electrochemical oxidations are ligand-centered, i.e. formation of phenoxyl radicals from the coordinated phenolates, have been shown by voltammetric methods. Complexes 2,4 display antiferromagnetic exchange coupling of the neighbouring metal centers. Comparison of the evaluated weak exchange coupling constants (J) with the literature values leads to the conclusion that the angle Cu,O,Cu, is not the only determinant for the nature of the exchange coupling and the capability of the bridging ligands as mediators for spin coupling in case of FeIII follows the order phenoxide , methoxide > hydroxide. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Syntheses and crystal structures of triorganotin (IV) derivatives with 2,2,-bipyridine-4,4,-dicarboxylic acidHETEROATOM CHEMISTRY, Issue 1 2009Ru-Fen Zhang Four organotin complexes with 2,2,-bipyridine-4,4,-dicarboxylic acid, H2dcbp: (Ph3n)2(dcbp) 1, [(PhCH2)3n]2(dcbp) , 2CH3OH 2, [(Me3Sn)2(dcbp)]n3, [(Bu3Sn)2(dcbp)]n4 have been synthesized. The complexes 1,4 were characterized by elemental, IR, 1H, 13C, 119n NMR, and X-ray crystallographic analyses. Crystal structures show that complex 1 is a monomer with one ligand coordinated to two triorganotin moieties, and a 1D infinite polymeric chain generates via intermolecular CH,,,N hydrogen bond; complex 2 is also a monomer and forms a 2D network by intermolecular O,H,,,O weak interaction; both of complexes 3 and 4 form 2D network structures where 2,2,-bipyridine-4,4,-dicarboxylate acts as a tetradentate ligand coordinated to trimethyltin and tri-n-butyltin ions, respectively. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:19,28, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20506 [source] Synthesis and evaluation of two uncharged 99mTc-labeled derivatives of thioflavin-T as potential tracer agents for fibrillar brain amyloidJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 6 2009K. Serdons Abstract Thioflavin-T is a fluorescent dye for in vitro detection of fibrillar amyloid ,, a protein found in the brain of patients suffering from Alzheimer's disease. We synthesized and biologically evaluated two uncharged 99mTc-labeled derivatives of thioflavin-T. The precursors for labeling were synthesized by coupling an S,S, -bis-triphenylmethyl- N - tert -butoxycarbonyl bis-amino-bis-thiol tetradentate ligand via a propoxy spacer to 2-(4,-aminophenyl)-1,3-benzothiazole at the 6-position or the 2,-position. Deprotection and labeling with 99mTc were done via a one-pot procedure (15% yield) after which the labeled compound was isolated by high performance liquid chromatography (LC). LC in combination with mass spectrometry (MS) was used for identity confirmation of the labeled compounds. Results of electrophoresis and log,P determination supported the assumption that the radiolabeled compounds could cross the blood,brain barrier by passive diffusion. However, in normal mice both compounds showed a low brain uptake 2,min post injection. They were mainly excreted through the hepatobiliary system, with some accumulation in the stomach. Sixty minutes after intravenous injection, 37% of the 99mTc-activity in the blood corresponded to the original compound. In view of the low brain uptake, it is concluded that the studied 99mTc-labeled derivatives of thioflavin-T are not suitable as tracer agents for in vivo visualization of amyloid in brain. Copyright © 2009 John Wiley & Sons, Ltd. [source] A new tetradentate ligand for atom transfer radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2004Shijie Ding Abstract The properties of a ligand, including molecular structure and substituents, strongly affect the catalyst activity and control of the polymerization in atom transfer radical polymerization (ATRP). A new tetradentate ligand, N,N,-bis(pyridin-2-ylmethyl-3-hexoxo-3-oxopropyl)ethane-1,2-diamine (BPED) was synthesized and examined as the ligand of copper halide for ATRP of styrene (St), methyl acrylate (MA), and methyl methacrylate (MMA), and compared with other analogous linear tetrdendate ligands. The BPED ligand was found to significantly promote the activation reaction: the CuBr/BPED complex reacted with the initiators so fast that a large amount of Cu(II)Br2/BPED was produced and thus the polymerizations were slow for all the monomers. The reaction of CuCl/BPED with the initiator was also fast, but by reducing the catalyst concentration or adding CuCl2, the activation reaction could be slowed to establish the equilibrium of ATRP for a well-controlled living polymerization of MA. CuCl/BPED was found very active for the polymerization of MA. For example, 10 mol% of the catalyst relatively to the initiator was sufficient to mediate a living polymerization of MA. The CuCl/BPED, however, could not catalyze a living polymerization of MMA because the resulting CuCl2/BPED could not deactivate the growing radicals. The effects of the ligand structures on the catalysis of ATRP are also discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3553,3562, 2004 [source] Interactions between dimers of {1,1,-[o -phenylenebis(nitrilomethylidyne)]di-2-naphtholato-,4O,N,N,,O,}nickel(II)ACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2009Anita Blagus In the title compound, [Ni(C28H18N2O2)], the NiII centre has a square-planar coordination geometry in which the Schiff base ligand acts as a cis - O,N,N,,O,-tetradentate ligand. The crystal structure is built up of centrosymmetric dimer units stacked into chains along the [010] direction. Adjacent chains associate via C,H...O hydrogen bonding only, leading to a two-dimensional sheet-like structure consisting of layers parallel to (10). The cofacial dimeric complex contains an Ni...Ni contact of 3.291,(4),Å. [source] Betti base-derived tetradentate ligand: synthesis and application in copper-catalyzed N -arylation of imidazolesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 9 2009Bojie Weng Abstract Betti base-derived tetradentate ligand 2 has been successfully designed and synthesized through the condensation of Betti base with glyoxal. Its application in N -arylation of imidazoles has been investigated which opens a new field for application of Betti base derivatives in organic transformation. Copyright © 2009 John Wiley & Sons, Ltd. [source] Strong Circularly Polarized Luminescence from Highly Emissive Terbium Complexes in Aqueous SolutionEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2010Amanda P. S. Samuel Abstract Two luminescent terbium(III) complexes have been prepared from chiral ligands containing 2-hydroxyisophthalamide (IAM) antenna chromophores and their non-polarized and circularly-polarized luminescence properties have been studied. These tetradentate ligands, which form 2:1 ligand/TbIII complexes, utilize diaminocyclohexane (cyLI) and diphenylethylenediamine (dpenLI) backbones, which we reasoned would impart conformational rigidity and result in TbIII complexes that display both large luminescence quantum yield (,) values and strong circularly polarized luminescence (CPL) activities. Both TbIII complexes are highly emissive, with , values of 0.32 (dpenLI-Tb) and 0.60 (cyLI-Tb). Luminescence lifetime measurements in H2O and D2O indicate that while cyLI-Tb exists as a single species in solution, dpenLI-Tb exists as two species: a monohydrate complex with one H2O molecule directly bound to the TbIII ion and a complex with no water molecules in the inner coordination sphere. Both cyLI-Tb and dpenLI-Tb display increased CPL activity compared to previously reported TbIII complexes made with chiral IAM ligands. The CPL measurements also provide additional confirmation of the presence of a single emissive species in solution in the case of cyLI-Tb, and multiple emissive species in the case of dpenLI-Tb. [source] Investigation of reduction of Cu(II) complexes in positive-ion mode electrospray mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2001Luca Gianelli The electrospray ionization mass spectrometry (ESI-MS) behavior of seven Cu(II) complexes with tetradentate ligands has been studied. An unexpected reduction process, in positive ion mode, of the Cu oxidation state was observed, and shown to be due to charge transfer between the metal complex and the solvent molecules in the gas phase. Ion trap collision-induced dissociation experiments and deuterated solvents were used to support the proposed mechanism that is not a common electrochemical redox reaction at the ESI tip, but a gas-phase process. A series of solvents (acetonitrile, methanol, ethanol, propanol and iso -butanol) were tested, and a correlation between ionization energy (IE) and the amount of Cu(I) produced in ESI has been demonstrated for the alcohols, although some other solvent properties should also be taken into account. The electrochemical reduction potential of the complexes in solution is also an important parameter, since complexes more easily reduced in solution are also easier to reduce in the gas phase. Copyright © 2001 John Wiley & Sons, Ltd. [source] Facile Synthesis of Nitrogen Tetradentate Ligands and Their Applications in CuI -Catalyzed N-Arylation and Azide,Alkyne CycloadditionCHEMISTRY - A EUROPEAN JOURNAL, Issue 40 2009Fuwei Li Dr. Abstract Five new tetradentate ligands [NNNN] with benzimidazolyl-imine or amine nitrogen donors have been synthesized in good yields under mild conditions from easily available substrates. trans - N,N,-bis(1-Ethyl-2-benzimidazolylmethylene)cyclohexane-1,2-diimine is the best accelerating ligand in this series that supports the CuI -catalyzed Ullmann N-arylation and the direct three-component azide,alkyne cycloaddition reaction to give the corresponding substituted imidazole, pyrazole, and triazole in high yields. Single-crystal X-ray diffraction analysis of its complex with CuI reveals a novel one-dimensional coordination polymer of the metal chain bridged alternately by the [NNNN] ligand and diiodides. [source] | ||||||||||