Home About us Contact
|
Home About us Contact | ||
|
|
||
Complex Formation Constants (complex + formation_constant)
Selected AbstractsLower Rim Substituted p-tert -Butyl-Calix[4]arene.ELECTROANALYSIS, Issue 17-18 2009Abstract Tetrasubstituted p-tert- butylcalix[4]arene-thioamides (1,5) were applied as ionophores in ion-selective membrane electrodes (ISE) and were tested towards Pb-selectivity. The selectivity coefficients of the electrodes were determined. The tertiary calix[4]thioamides (1, 2) show remarkable selectivity for Pb(II) cations when compared with respectable calix[4]amides. The electrode membranes with those ligands are stable, the Pb-characteristics are close to nernstian within a wide linear range (,log c=6,1). Compounds 3,5, the secondary calix[4]thioamides form less stable electrode membranes. Complex formation constants of the ligands 1, 2, 3 and 5 with Pb(II) and some most interfering ions were determined. [source] Water-Soluble Sal2en- and Reduced Sal2en-Type Ligands: Study of Their CuII and NiII Complexes in the Solid State and in SolutionEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2006Isabel Correia Abstract The CuII and NiII complexes of the Schiff base pyr2en [N,N, -ethylenebis(pyridoxyliminato)] and reduced Schiff bases Rpyr2en [N,N, -ethylenebis(pyridoxylaminato)] and R(SO3,sal)2en (SO3,sal = salicylaldehyde-5-sulfonate) were prepared and characterized by elemental analysis, IR, UV/Vis, and EPR spectroscopy. The structure of Ni(pyr2en)·3H2O was determined by single-crystal X-ray diffraction. The pyr2en2, ligand is coordinated through two phenolate-O and imine-N atoms, in a distorted square-planar geometry. The complexation of CuII and NiII with Rpyr2en in aqueous solution is studied by pH-potentiometry, UV/Vis spectroscopy, as well as by EPR spectroscopy for the CuII system, and 1H NMR spectroscopy for the NiII system. Complex formation constants were determined and binding modes proposed. While for the CuII system all complexes present a 1:1 stoichiometry with different protonation states, for the NiII system the 2:1 (L/M) complexes become important in the basic pH range at a higher ligand excess. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] X-ray Crystal Structure and Characterization in Aqueous Solution of{N,N,-Ethylenebis(pyridoxylaminato)}zinc(II)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2006Isabel Correia Abstract The complexation of ZnII with H2Rpyr2en [H2Rpyr2en = N,N,-ethylenebis(pyridoxylaminato)] in aqueous solution has been studied by pH potentiometry and 1H NMR spectroscopy. Complex formation constants are determined and binding modes proposed. Complex formation starts at around pH 4, and several species with a 1:1 ligand-to-metal ratio with different protonation states form up to pH 12. Only above pH 10 does a hydrolytic species [ZnLH,1], become important. The crystal and molecular structures of [ZnCl(H2Rpyr2en)]+Cl,·1.5H2O (1) have been determined by X-ray diffraction. The coordination of the H2Rpyr2en ligand involves the two phenolate-O and two amine-N atoms in a distorted square-pyramidal geometry. The two pyridine-N atoms are protonated, and a Cl, atom completes the coordination sphere. Upon coordination, both N-amine atoms of H2Rpyr2en become stereogenic centres, and in both molecules of the unit cell of 1 one of the N-amine donors has an (R)-configuration, and the other an (S)-configuration. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Development of a Novel Automatic Potentiometric System for Determination of Selenium and Its Application in Pharmaceutical Formulations and Anodic SlimeELECTROANALYSIS, Issue 9 2008Ayman Abstract Poly(vinyl chloride) polymeric membrane sensors containing Sn(IV) phthalocyanine dichloride (SnPC) and Co(II) phthalocyanine (CoPC) as novel electroactive materials dispersed in o -nitrophenyl octylether (o -NPOE) as a plasticizer are examined potentiometrically with respect to their response toward selenite (SeO32,) ions. Fast Nernstian response for SeO32, ions over the concentration ranges 7.0×10,6,1.0×10,3 and 8.0×10,6,1.0×10,3 mol L,l at pH,3.5,8.5 with lower detection limit of 5.0×10,6 and 8.0×10,6 mol L,1 and calibration slopes of ,25.4 and ,29.7,mV decade,1 are obtained with SnPC and CoPC based membrane sensors, respectively. The proposed sensors reveals by the modified separate solution method (MSSM) a good selectivity over different anions which differ significantly from the classical Hofmeister series. A segmented sandwich membrane method is used to determine complex formation constants of the ionophores in situe in the solvent polymeric sensing membranes. Membrane incorporating CoPC in a tubular flow detector is used in a two channels flow injection set up for continuous monitoring of selenite at a frequency of ca. 50 samples h,1. Direct determination of selenium in pharmaceutical formulations and anodic slime gives results in good agreement with data obtained using standard ICP method. [source] Structure Comparison of Early and Late Lanthanide(III) Homodinuclear Macrocyclic Complexes with the Polyamine Polycarboxylic Ligand H8OHECEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2004Ulrike A. Böttger Abstract The solid-state structures of two new homodinuclear chelate complexes with the late lanthanide(III) ions Yb and Lu, [Na2(Yb2OHEC)].14.5H2O (1), and [Na2(Lu2OHEC)].14.5H2O (2) (H8OHEC = 1,4,7,10,14,17,20,23-octaazacyclohexacosane- 1,4,7,10,14,17,20,23-octaacetic acid), have been determined by X-ray crystal structure analysis. Each lanthanide(III) ion is coordinated by eight donor atoms of the ligand and the geometry of the coordination polyhedron approaches a bicapped trigonal prism. These structures are compared with those of the homodinuclear chelate complexes with the same ligand and the mid to early lanthanide(III) ions Gd, Eu, La and also Y. A distinctive structural change occurs across the lanthanide series. The centrosymmetric mid to early lanthanide(III) complexes are all ninefold-coordinated in a capped square antiprismatic arrangement with a water molecule coordinated in a prismatic position. This structure is maintained in aqueous solution, together with an asymmetric minor isomer. The late lanthanide(III) OHEC complexes not only lack the inner-sphere water, but the change of coordination sphere also results in a loss of symmetry of the whole complex molecule. The observed change of coordination mode and number of the lanthanide ion may offer a geometric model for the isomerization process in eight- and ninefold-coordinated complex species that are isomers in a possible coordination equilibrium observed by NMR in aqueous solution. This model may also explain the intramolecular rearrangements necessary during water exchange in the inner coordination sphere of the complex [(Gd2OHEC)(H2O)2]2, through a slow dissociative mechanism. Protonation constants of the H8OHEC ligand and complex formation constants of this ligand with GdIII, CaII, CuII and ZnII have been determined by solution thermodynamic studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] | ||||||||||