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Coordination Complexes (coordination + complex)

Distribution by Scientific Domains

Chemistry	83%

Selected Abstracts

ChemInform Abstract: Organic,Inorganic Hybrids Constructed by Anderson-Type Polyoxoanions and Copper Coordination Complexes.

CHEMINFORM, Issue 13 2009
Rui-Ge Cao
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Hydrothermal Synthesis of Vanadium Oxyfluoride Chains Incorporating Covalently Bound Copper Coordination Complexes.

CHEMINFORM, Issue 51 2008
Thushitha Mahenthirarajah
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Coordination complexes of functionalized pyrazines with metal ions: reagents for the controlled release of flavourant molecules at elevated temperatures

FLAVOUR AND FRAGRANCE JOURNAL, Issue 2 2006
Colin Baillie
Abstract The potential for stabilization of volatile flavourant molecules such as functionalized pyrazines by coordination to metal ions, and the application of the resultant coordination complexes as controlled release agents at elevated temperatures were explored. New complexes containing the flavourant molecules 2,3,5-trimethylpyrazine (TMP), 2-ethyl-3-methylpyrazine (EMP) and 2-acetylpyrazine (ACP) with copper(II) and copper(I) salts were prepared and structurally characterized. Representative examples of known copper(II) and calcium(II) complexes containing pyrazine carboxylic acids were also prepared. The complexes were examined by thermal analysis techniques and demonstrated, by a combination of thermogravimetric (TGA) and pyrolysis GC,MS analyses, to act as convenient reagents for the release of the parent pyrazine at elevated temperatures. Thus, pyrolysis GC,MS revealed that the complex [Cu3Cl3(EMP)2]n cleanly releases EMP in 96.5% selectivity at 200 °C. Of particular significance is that the calcium complex [Ca(3-aminopyrazine-2-carboxylate)2·H2O], under ramped pyrolysis conditions, was shown to undergo decarboxylation prior to the release of 2-aminopyrazine (AMP), as essentially the only volatile component, in the temperature range 600,800 °C. This finding provides a precedent for the application of complexes of pyrazinecarboxylate salts with metal ions (of which an almost infinite number of combinations is potentially available) as controlled release agents of the parent pyrazine molecule at elevated temperatures, suitable for exploitation by the foodstuffs, flavour and fragrance industries. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Micro-Hydration of the MgNO3+ Cation in the Gas Phase

CHEMPHYSCHEM, Issue 11 2007
Barbara Jagoda-Cwiklik Dr.
Abstract Coordination complexes of the magnesium nitrate cation with water [MgNO3(H2O)n]+ up to n=7 are investigated by experiment and theory. The fragmentation patterns of [MgNO3(H2O)n]+ clusters generated via electrospray ionization indicate a considerable change in stability between n=3 and 4. Further, ion,molecule reactions of mass-selected [MgNO3(H2O)n]+ cations with D2O reveal the occurrence of consecutive replacement of water ligands by heavy water, and in this respect the complexes with n=4 and 5 are somewhat more reactive than their smaller homologs with n=1,3 as well as the larger clusters with n=6 and 7. For the latter two ions, the theory suggests the existence of isomers, such as complexes with monodentate nitrato ligands as well as solvent-separated ion pairs with a common solvation shell. The reactions observed and the ion thermochemistry are discussed in the context of ab initio calculations, which also reveal the structures of the various hydrated cation complexes. [source]

Transition Metal-Assisted Hydrolysis of Pyrazole-Appended Organooxotin Carboxylates Accompanied by Ligand Transfer

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2007
Vadapalli Chandrasekhar
Abstract The reaction of the potentially multi-site coordination ligands [{nBu2SnO2CL}2O]2 (1), [{nBu2SnO2CL,}2O]2 (2), [nBuSn(O)O2CL]6 (3), and [nBuSn(O)O2CL,]6 (4), (L = (Pz)2CH-); L, = (3,5-Me2Pz)2CH-; Pz = pyrazolyl) with hydrated metal salts leads to the hydrolysis of the organotin carboxylates accompanied by the formation of insoluble organotinoxide/hydroxides and metal complexes. The in situ generated LCOO and L,COO ligands bind to the metal ions. The complexes [Cu(LCOO)2(NO3)2(nBu2Sn((H2O)2)]n[Cu(LCOO)2] (5), [Mg(L,COO)2] (6), [Cu(LCOO)2] (7), and [{(Cu(L,COO)2(Cu(MeOH))3}{ClO4}2]n (8) were isolated and structurally characterized. The solid-state structure of 5 reveals that two discrete molecules are present in the same asymmetric unit; a heterobimetallic coordination polymer, [Cu(LCOO)2(NO3)2(nBu2Sn((H2O)2)]n and a discrete coordination complex, [Cu(LCOO)2]. The cationic portion of the heterobimetallic compound contains alternate six-coordinate SnIV and CuII centers bridged by the carboxylate oxygen atoms of the LCOO ligand.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Boron,Nitrogen Adducts of 1,3,5-Triaza-7-phosphaadamantane (PTA): Synthesis, Reactivity, and Molecular Structure

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2006
Brian J. Frost
Abstract Addition of BH3 to 1,3,5-triaza-7-phosphaadamantane (PTA) leads to the formation of the first coordination complex of PTA in which a nitrogen and not the phosphorus of PTA is involved in the bonding. Multinuclear NMR spectroscopy, X-ray crystallography, and computational chemistry are utilized in the characterization of the products. Crystal structures of PTA,BH3 (1) and O=PTA,BH3 (2) adducts are described. In addition a coordination polymer, [CpRu(PTA)2Cl(Ph3B3O3)]n (3), resulting from Lewis acid,base adduct formation between the PTA ligands of CpRu(PTA)2Cl and the product of the cyclocondensation of phenylboronic acid is described. The polymeric compound 3 was also characterized by X-ray crystallography. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

Facile fabrication of novel Eu-containing copolymer and luminescent properties

POLYMER ENGINEERING & SCIENCE, Issue 7 2009
Ziqun Huang
A new Eu-containing copolymer was successfully fabricated through two steps. First, the Eu-containing monomer was synthesized from 4-Vinylbenzoic acid and europium ion (Eu3+) complex, which rare-earth ions connect with the ligand by covalent bands. Next, the copolymer was obtained by free-radical copolymerization of Eu-containing monomer with methyl methacrylate using 2, 2,-azobis(isobutyronitrile) (AIBN) as initiator at low temperature. Infrared spectroscopy, gel permeation chromatography and scanning electron microscopy were applied to characterize the structure of the polymer. UV-visible absorption/photoluminescence spectra and fluorescence spectra were taken to valuate the photophysical properties of the obtained Eu-containing copolymer. The experimental result shows that the strong luminescence of europium ions substantiates optimum energy match and effective intramolecular energy transfer between the triplet state energy of coordination complex and the emissive energy level of the rare-earth ions. A study of the dependence of emission intensities of the Eu-containing nanoparticles on the Eu content showed that the emission intensities increased nearly linearly with increasing Eu content. In addition, no significant emission concentration quenching phenomenon was observed at the Eu content of 0,4.61 mol%. The hybrid material systems can be expected to have potential applications in light conversion materials. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source]

Enantioselective Recognition of Aspartic Acids by Chiral Ligand Exchange Potentiometry

ELECTROANALYSIS, Issue 11 2004
Yanxiu Zhou
Abstract Enantioselective resolution is realized by combining potentiometry with ligand exchange (CE) in a new method called chiral ligand exchange potentiometry (CLEP). A chiral selector, N -carbobenzoxy- L -aspartic acid (N-CBZ-L-Asp), preferentially recognizes D -aspartic acid (D-Asp) and undergoes ligand exchange with the enantiomeric labile coordination complexes of [Cu(II)(D-Asp)2] or [Cu(II)(L-Asp)2] to form a diastereoisomeric complex [(D-Asp)Cu(II)(N-CBZ-L-Asp)] (a) or [(L-Asp)Cu(II)(N-CBZ-L-Asp)] (b). Considerable stereoselectivity occurs in the formation of these diastereoisomeric complexes, and their net charges were ,2 (a) and 0 (b), respectively, resulting in different Nernst factor (electrode slope), thus enabling chiral D-Asp to be distinguished by potentiometry without any pre- or postseparation processes. [source]

Copper Complexes with Neutral N4 Tripodal Ligands: Influence of the Number of Nitrogen Donors on Their Structures, Properties, and Reactivity,

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 26 2009
Kiyoshi Fujisawa
Abstract Copper coordination complexes of the neutral tetradentate nitrogen-containing ligands tris(3,5-dimethylpyrazol-1-ylmethyl)amine (L0N4) and tris(3,5-diisopropylpyrazol-1-ylmethyl)amine (L1N4), namely the copper(II) chlorido complexes [CuII(L0N4)Cl2] (1) and [CuII(L1N4)Cl2] (2), the copper(II) nitrato complexes [CuII(L0N4)(NO3)](NO3) (3) and [CuII(L1N4)(NO3)](NO3) (4), and the copper(II) sulfato complexes [CuII(L0N4)(SO4)] (5) and [CuII(L1N4)(SO4)] (6), and the copper(I) complexes [CuI(L0N4)](PF6) (7) and [CuI(L0N4)(PPh3)](ClO4) (8), have been systematically synthesized in order to investigate the influence of the number of nitrogen donors on their structures, properties, and reactivity. All copper(II) complexes were fully characterized by X-ray crystallography and by IR/far-IR, UV/Vis absorption, and ESR spectroscopy. Although the structure of 7 was not determined by X-ray crystallography, this complex and the structurally characterized copper(I) triphenylphosphane complex 8 were fully characterized by IR/far-IR and NMR spectroscopy. A comparison of the copper(II) complexes with two tris(pyrazol-1-ylmethyl)amine ligands with different bulkiness of the pyrazolyl rings has allowed us to evaluate the second coordination sphere effects of the ligands. Moreover, the structures and physicochemical properties of these complexes are compared with those of related complexes containing the neutral tridentate tris(pyrazolyl)methane ligand and the neutral bidentate bis(pyrazolyl)methane ligand. Finally, the relative stability of the copper(I) complexes is discussed. The influence of the number of nitrogen donors in copper complexes is observed from these systematic results.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Synthesis and Luminescent Properties of Novel Europium(III) Heterocyclic ,-Diketone Complexes with Lewis Bases: Structural Analysis Using the Sparkle/AM1 Model

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2005
Rani Pavithran
Abstract Tris(,-diketonato)europium(III) complexes of general formula [Eu(TPI)3·L], with chelating ligands such as 3-phenyl-4-(4-toluoyl)-5-isoxazolone (HTPI) and adduct-forming reagents [L = H2O, tri- n -octylphosphane oxide (TOPO), triphenylphosphane oxide (TPhPO), 1,10-phenanthroline], have been synthesized and characterized by elemental analysis and FT-IR, 1H NMR, and photoluminescence spectroscopy. The coordination geometries of the complexes were calculated using the Sparkle/AM1 (Sparkle model for the calculation of lanthanide complexes within the Austin model 1) model. The ligand,Eu3+ energy-transfer rates were calculated using a model of intramolecular energy transfer in lanthanide coordination complexes reported in the literature. The room-temperature PL spectra of the europium(III) complexes are composed of the typical Eu3+ red emission, assigned to transitions between the first excited state (5D0) and the multiplet (7F0,4). The results clearly show that the substitution of water molecules by TOPO leads to greatly enhanced quantum yields (i.e., 1.3,% vs. 49.5,%) and longer 5D0 lifetimes (220 vs. 980 ,s). This can be ascribed to a more efficient ligand-to-metal energy transfer and a less efficient nonradiative 5D0 relaxation process. The theoretical quantum yields are in good agreement with the experimental quantum yields, which highlights that the present theoretical approach can be a powerful tool for the a priori design of highly luminescent lanthanide complexes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

The SmtB/ArsR family of metalloregulatory transcriptional repressors: structural insights into prokaryotic metal resistance

FEMS MICROBIOLOGY REVIEWS, Issue 2-3 2003
Laura S. Busenlehner
Abstract The SmtB/ArsR family of prokaryotic metalloregulatory transcriptional repressors represses the expression of operons linked to stress-inducing concentrations of di- and multivalent heavy metal ions. Derepression results from direct binding of metal ions by these homodimeric ,metal sensor' proteins. An evolutionary analysis, coupled with comparative structural and spectroscopic studies of six SmtB/ArsR family members, suggests a unifying ,theme and variations' model, in which individual members have evolved distinct metal selectivity profiles by alteration of one or both of two structurally distinct metal coordination sites. These two metal sites are designated ,3N (or ,3) and ,5 (or ,5C), named for the location of the metal binding ligands within the known or predicted secondary structure of individual family members. The ,3N/,3 sensors, represented by Staphylococcus aureus pI258 CadC, Listeria monocytogenes CadC and Escherichia coli ArsR, form cysteine thiolate-rich coordination complexes (S3 or S4) with thiophilic heavy metal pollutants including Cd(II), Pb(II), Bi(III) and As(III) via inter-subunit coordination by ligands derived from the ,3 helix and the N-terminal ,arm' (CadCs) or from the ,3 helix only (ArsRs). The ,5/,5C sensors Synechococcus SmtB, Synechocystis ZiaR, S. aureus CzrA, and Mycobacterium tuberculosis NmtR form metal complexes with biologically required metal ions Zn(II), Co(II) and Ni(II) characterized by four or more coordination bonds to a mixture of histidine and carboxylate ligands derived from the C-terminal ,5 helices on opposite subunits. Direct binding of metal ions to either the ,3N or ,5 sites leads to strong, negative allosteric regulation of repressor operator/promoter binding affinity, consistent with a simple model for derepression. We hypothesize that distinct allosteric pathways for metal sensing have co-evolved with metal specificities of distinct ,3N and ,5 coordination complexes. [source]

Coordination complexes of functionalized pyrazines with metal ions: reagents for the controlled release of flavourant molecules at elevated temperatures

Recovering Ga(III) from coordination complexes using pyridine 2,6-dicarboxylic acid chelation ion chromatography

BIOMEDICAL CHROMATOGRAPHY, Issue 9 2010
K. Staff
Abstract Ion exchange chelation chromatography is an effective means to extract metals from coordination complexes and biological samples; however there is a lack of data to verify the nature of metal complexes that can be successfully analysed using such a procedure. The aim of this study was to assess the capability of pyridine 2,6-dicarboxylic acid (PDCA) to extract and quantify Ga(III) from a range of environments using standard liquid chromatography apparatus. The PDCA chelation method generated a single Ga(III) peak with a retention time of 2.55 ± 0.02 min, a precision of <2% and a limit of detection of 110 ,M. Ga(III) hydroxide complexes (highest stability constant 15.66) were used to successfully cross-validate the chelation method with inductively coupled plasma mass spectrometry. The PDCA assay extracted 96.9 ± 1.2% of the spiked Ga(III) from porcine mucus and 100.7 ± 2.7% from a citrate complex (stability constant 10.02), but only ca 50% from an EDTA complex (stability constant 22.01). These data suggest that PDCA chelation can be considered a suitable alternative to inductively coupled plasma mass spectrometry for Ga(III) quantification from all but the most strongly bound coordinated complexes i.e. a stability constant of <15. Copyright © 2010 John Wiley & Sons, Ltd. [source]

A Facile Method for Reversibly Linking a Recombinant Protein to DNA

CHEMBIOCHEM, Issue 9 2009
Russell P. Goodman Dr.
Abstract A simple modification allows DNA to be linked to recombinant proteins. DNA functionalized with three nitrilotriacetic acid groups forms coordination complexes with nickel ions and the His6 -tag of the recombinant protein (here, GFP). This noncovalent linkage is reversible, site-specific and has a high (nanomolar) affinity. We present a facile method for linking recombinant proteins to DNA. It is based on the nickel-mediated interaction between a hexahistidine tag (His6 -tag) and DNA functionalized with three nitrilotriacetic acid (NTA) groups. The resulting DNA,protein linkage is site-specific. It can be broken quickly and controllably by the addition of a chelating agent that binds nickel. We have used this new linker to bind proteins to a variety of DNA motifs commonly used in the fabrication of nanostructures by DNA self-assembly. [source]

Formation of 1,D and 3,D Coordination Polymers in the Solid State Induced by Mechanochemical and Annealing Treatments: Bis(3-cyano-pentane-2,4-dionato) Metal Complexes

CHEMISTRY - A EUROPEAN JOURNAL, Issue 34 2008
Jun Yoshida
Abstract Bis(3-cyano-pentane-2,4-dionato) (CNacac) metal complex, [M(CNacac)2], which acts as both a metal-ion-like and a ligand-like building unit, forms supramolecular structures by self-assembly. Co-grinding of the metal acetates of MnII, CoII, NiII, CuII and ZnII with CNacacH formed a CNacac complex in all cases: mononuclear complex was formed in the cases of MnII, CuII and ZnII, whereas polymeric ones were formed in the cases of FeII, CoII and NiII. Subsequent annealing converted the mononuclear complexes of MnII, CuII and ZnII to their corresponding polymers as a result of dehydration of the mononuclear complexes. The resultant MnII, FeII, CoII, NiII and ZnII polymeric complexes had a common 3,D structure with high thermal stability. In the case of CuII, a 1,D polymer was obtained. The MnII, CuII and ZnII polymeric complexes returned to their original mononuclear complexes on exposure to water vapour but they reverted to the polymeric complexes by re-annealing. Co-grinding of metal chlorides with CNacacH and annealing of the mononuclear CNacac complexes prepared from solution reactions were also examined for comparison. [Mn(CNacac)2(H2O)2], [M(CNacac)2(H2O)] (M=CuII and ZnII) and [M(CNacac)2], (M=MnII, FeII and ZnII) are new compounds, which clearly indicated the power of the combined mechanochemical/annealing method for the synthesis of varied metal coordination complexes. [source]

Ruthenium(II) Complexes for Two-Photon Absorption-Based Optical Power Limiting

CHEMPHYSCHEM, Issue 11 2008
Camille Girardot Dr.
Long-lived excitation: Novel bifluorene-substituted 1,10-phenanthroline-based RuII coordination complexes are presented (see picture). They fulfil several requirements for optimized optical power limiting in the visible-NIR, as they are stable, soluble and transparent at low laser fluences. The two-photon absorption of these complexes are strongly related to those of the ligand. [source]