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Journal ArticleDOI

Solution and solid study of Zn(II) and Cd(II) complexes with N-(6-amino-3,4-dihydro-3-methyl-5-nitroso-4-oxo-pyrimidin-2-yl)glycine as ligand. Crystal structures of [ZnL2(H2O)4]·6H2O and {[Cd(μ-L)Cl(H2O)2]·H2O}n

15 Jun 2000-Inorganica Chimica Acta (Elsevier)-Vol. 304, Iss: 1, pp 137-143
TL;DR: In this article, a 1:1 and 1:4 metal/ligand ratio was obtained for N -pyrimidine aminoacids with Zn(II) and Cd(II), respectively.
About: This article is published in Inorganica Chimica Acta.The article was published on 2000-06-15. It has received 16 citations till now. The article focuses on the topics: Carboxylate & Ligand.
Citations
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Journal ArticleDOI
TL;DR: Compound 3 exhibits remarkable interactions between two noncoordinated nitrate anions and the two faces of the electron-deficient heteroaromatic ring, corroborating earlier theoretical investigations in this area.
Abstract: The reaction of Zn(NO3)2·6H2O or Cu(NO3)2·3H2O with the star-shaped ligand 2,4,6-tris(di-2-picolylamino)[1,3,5]triazine (dipicatriz) in acetonitrile results in the formation of the mono- or trinuclear coordination compounds [Zn(dipicatriz)(NO3)2] (1), [Zn3(dipicatriz)(NO3)6](CH3CN)3 (2), and [Cu3(dipicatriz)(NO3)2(H2O)6](NO3)4 (3), depending on the metal-to-ligand ratios used during the crystallization process. Their crystal structures exhibit unique supramolecular interactions. Compounds 1 and 2 show anion−π interactions between coordinated nitrate ions and the s-triazine ring. Compound 3 exhibits remarkable interactions between two noncoordinated nitrate anions and the two faces of the electron-deficient heteroaromatic ring, corroborating earlier theoretical investigations in this area. New theoretical investigations have been carried out on nitrate−π interactions, taking into account the particular position of the anion toward the aromatic ring observed in the crystal structures.

90 citations

Journal ArticleDOI
TL;DR: Zinc complexes of a new symmetric dinucleating ligand, N,N'-Bis[2-carboxybenzomethyl]-N,N'Bis [carboxymethyl]-1,3-diaminopropan-2-ol (H5ccdp) with mixed donating groups, have been studied in the solid state as well as in solution.
Abstract: Zinc complexes of a new symmetric dinucleating ligand, N,N′-Bis[2-carboxybenzomethyl]-N,N′-Bis[carboxymethyl]-1,3-diaminopropan-2-ol (H5ccdp) with mixed donating groups, have been studied in the solid state as well as in solution. In methanol, the reaction of stoichiometric and substoichiometric amounts of Zn(ClO4)2·6H2O and the ligand H5ccdp, in the presence of K2CO3 or Et3N, afforded a mononuclear zinc complex, [Zn(H2O)6][Zn(H2ccdp)(H2O)2]2·12H2O (1). The solid state structure of 1 contains two units of the zinc-ligand anion, [Zn(H2ccdp)(H2O)2]−, and one [Zn(H2O)6]2+ counter cation. The Zn(II) center of the anion is in a distorted octahedral geometry. However, in methanol, the reaction of ZnSO4·7H2O and the ligand H5ccdp in the presence of NaOH afforded a unique μ6-sulfato hexanuclear zinc complex, Na6[Zn6(ccdp)3(μ6-SO4)](OH)·10.5H2O (2). The structure of 2 contains a [ZnII6(μ6-SO4)] core unit which is held together by three heptadentate bridging ligands, ccdp5−. Three of the Zn(II) centers are in highly distorted square pyramidal geometry, the other three Zn(II) centers are in a distorted octahedral geometry.

43 citations

Journal ArticleDOI
TL;DR: In this article, the performance of HL anchored to activated carbon (AC) was evaluated as a molecular receptor for Zn2+ and Cd2+ metal ions in aqueous solution.
Abstract: The compound N-(4-amino-1-methyl-5-nitroso-6-oxo-1,6-di-hydropyrimidin-2-yl)-N'-[bis(2-aminoethyl)]ethylenedi-amine (HL) was synthesised and structurally characterised by analytical methods and 1H, 13C and 15N NMR spectroscopy. The protonation of HL and its coordinating ability towards Zn2+ and Cd2+ ions in water solution were also studied by potentiometric methods and UV/Visible and 1H-13C NMR spectroscopy. The molecular structures of [H3L]2+[CdI4]2–·2H2O and [(Cl3Zn)(μ-Cl){Zn(μ2-HL)}]2·2.5H2O were solved by single-crystal X-ray diffraction methods. On the basis of these data, the performance of HL anchored to activated carbon (AC) was evaluated as a molecular receptor for Zn2+ and Cd2+ metal ions in aqueous solution. This was done by a comparative study of the adsorption capacity of the adsorbents AC alone and HL anchored on the AC (AC-HL) for these metal ions and by a structural study of the AC-HL, AC-HL-Zn2+ and AC-HL-Cd2+ solid phases by XPS and IR spectroscopy. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

31 citations

Journal ArticleDOI
TL;DR: In this article, the influence of the supporting electrolyte and the solvent of crystallisation on the nature of cadmium complexes of 2,6-bis(1-salicyloylhydrazonoethyl)pyridine (H4daps), obtained by an electrochemical procedure, has been investigated.
Abstract: The influence of the supporting electrolyte and the solvent of crystallisation on the nature of cadmium complexes of 2,6-bis(1-salicyloylhydrazonoethyl)pyridine (H4daps), obtained by an electrochemical procedure, has been investigated. [Cd(H2daps)(H2O)2] (1), [Cd(H2daps)(H2O){(CH3)2CHOH}] (2), [Cd(H3daps)Cl]·CH3CN·0.25H2O (3), [Cd(H3daps)Cl(CH3OH)]·2H2O·CH3OH (4), and [Cd(H2daps)Cl(H2O)]N(CH3)4 (5), have all been isolated and crystallographically characterised. X-ray diffraction studies show that the cadmium atom in 3 is in an unusual pentagonal pyramidal [CdN3O2Cl] geometry, while in the other compounds the cadmium atom is in a bipyramidal pentagonal environment. The organic ligand acts as a pentadentate dianionic ligand in 1, 2, and 5, and as a pentadentate monoanionic ligand in 3 and 4.

29 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of N-alkylation on the selectivity of the ligands towards metal ions is analyzed. And the results are discussed in terms of the different basicities, steric requirements and solvation both of ligands and of the complexes formed.
Abstract: AgI, CdII and CoII complex formation with the primary and tertiary tetraamines 1,4,7,10-tetraazadecane (trien) and 1,1,4,7,10,10-hexamethyltriethylenetetraamine (hmtrien) has been studied at 298 K in the aprotic solvent dimethyl sulfoxide (DMSO) and in an ionic medium set to 0.1 mol·dm−3 with Et4NClO4 under anaerobic conditions. UV/Vis spectrophotometric and calorimetric measurements have been carried out to obtain the thermodynamic parameters for the systems investigated. Mononuclear 1:1 complexes are formed for all systems. In addition, trien also forms the ML2 mononuclear complex and a polynuclear M2L3 species with M = Cd2+ and Co2+. All the complexes are enthalpy stabilized, whereas the entropy changes counteract the complex formation. The results are discussed in terms of the different basicities, steric requirements and solvation both of the ligands and of the complexes formed. The influence of N-alkylation on the selectivity of the ligands towards metal ions is analysed. In the case of the CoII complexes, their ability to take up dioxygen has also been studied by voltammetric and UV/Vis measurements and gasometric absorption. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

20 citations

References
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Journal ArticleDOI
01 Jan 1952-Analyst
TL;DR: In this article, the potential -volume curve obtained during potentiometric titrations shows only a small potential change at the end-point, and it has been customary to plot a deltaE/deltaV-volume curve and to take the peak of this curve as the equivalent point.
Abstract: When the potential - volume curve obtained during potentiometric titrations shows only a small potential change at the end-point, it has been customary to plot a deltaE/deltaV - volume curve and to take the peak of this curve as the equivalent point. In 1950, the author proposed a method of transforming these curves by a numerical manipulation into straight lines intersecting at the equivalence point. In this article another way of transforming titration curves into straight lines has now been developed. A simple theoretical treatment shows that the method can be applied to titrations involving acids and bases, ionic precipitations, formation of complexes, and oxidation - reduction reactions. To facilitate the use of the method a table has been compiled giving quantities to be calculated and plotted against volume of titrant added. These quantities can be evaluated by simple slide rule calculations and, since straight line relationships hold, end-points can be obtained by simple extrapolation. The practice of the method is applicable to potentiometers calibrated either in millivolts or in pH units, even when titrations other than acid - alkali reactions are in use.

2,757 citations

Book
01 Jan 1992
TL;DR: In this article, the authors present a complete metal complex data base with linear stability constants and species concentrations of complex systems, including a mixed-ligand binuclear dioxygen system nonaqueous solvents complex multicomponent systems equilibrium with solid phases equilibrium involving hydrolytic species species distributions of hydroxo and fluoro complexes of AI(III).
Abstract: Part 1 Introduction: stability constants - early work recent developments historical evolution of computational methods purpose of this book. Part 2 Equilibrium constants, protonation constants, formation constants: concentration constants and activity constants conventions employment for expressing equilibrium constants equilibrium constants and stability constants for EDTA species distribution curves. Part 3 Experimental methods for measuring equilibrium constants: methods available potentiometric pH measurements displacement methods pH and p[H]measurement of metal complex equilibria: materials, the reaction mixture calibration of the potentiometric apparatus the experimental runs computation of stability constants.Part 4 Common errors and their elimination or minimization: measurements errors calibration and electrode care reagents equilibrium measurements calculations selection of the model. Part 5 Examples of stability constant determination: iminodiacetic acid (IDA) procedure for IDA C-BISTREN procedure for C-BISTREN. Part 6 Macroscopic and microscopic constants: some definitions and concepts ionization of tyrosine microscopic protonation equilibria of DOPA general comments and conclusions. Determination of stability constants and species concentrations of complex systems: a mixed-ligand binuclear dioxygen system non-aqueous solvents complex multicomponent systems equilibrium with solid phases equilibrium involving hydrolytic species species distributions of hydroxo and fluoro complexes of AI(III). Part 7 Critical stability constants and their selection: general criteria examples of critical data selection need for additional critical constants. Part 8 Development of a complete metal complex data base: introduction linear stability. constant correlations estimation of estability constants not measured experimentally metal speciation in sea water with and without added ligands.

962 citations

Journal ArticleDOI
TL;DR: The acid base properties of the pyrimidine derivative 4,6-dimethyl-2-thiopyrimidine (HL) have been determined by potentiometric measurements at 25 °C and 0.1 M KCl ionic strength as discussed by the authors.

43 citations

Journal ArticleDOI
TL;DR: In this article, a potentiometric method for determining the ionization product of water in a constant ionic medium is presented, and the method is shown to be effective for water ionization.
Abstract: Presents a potentiometric method for determining the ionization product of water in a constant ionic medium.

41 citations

Journal ArticleDOI
TL;DR: In this article, a mixture of ZnCl2 with 2 equivalents of 5-aminoorotic acid (5-amino-2,6dioxo-1,2,3,6-tetrahydropyrimidine-4-carboxylic acid, H4L) was obtained by using NaOH in refluxing water.
Abstract: Treatment of ZnCl2 with 2 equivalents of 5-aminoorotic acid (5-amino-2,6-dioxo-1,2,3,6-tetrahydropyrimidine-4-carboxylic acid, H4L) and 2 equivalents of NaOH in water–methanol yielded a mixture of crystals and powder of complexes [{Zn(H2L)(H2O)2}n] 1 and [Zn(H3L)2(H2O)4] 2, respectively. A good yield (ca. 70%) of pure 2 can be obtained by the reaction of Zn(O2CMe)2·2H2O and 2 equivalents of H4L in refluxing water. The crystal structure of 1 consists of neutral octahedral [Zn(H2L)(H2O)2] units which form polymer chains along the b axis; H2L2– behaves as a bis(bidentate) bridging ligand co-ordinating to two zinc atoms via the amino nitrogen, the oxygen of the neutral carboxamide group, the deprotonated carboxamide nitrogen and one of the carboxylate oxygens and forming two five-membered chelate rings. The 1H NMR spectra of 1 in (CD3)2SO at 290 and 310 K suggest that its solid-state structure is not retained in solution. Slow crystallization of 1 or 2 from dmso solutions yielded crystals of the monomeric octahedral complex [Zn(H3L)2(dmso)2(H2O)2] 3 the structure of which was solved by single-crystal X-ray crystallography. The monoanion H3L– utilizes only one carboxylate oxygen for metal binding in the centrosymmetric complex 3. The difference in anionic charge and co-ordination mode between H2L2– and H3L– leads to different hydrogen-bonded supramolecular structures for 1 and 3. The IR and 1H NMR spectra of the prepared complexes are discussed.

37 citations

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