Home About us Contact
|
Home About us Contact | ||
|
|
||
Complexation Reaction (complexation + reaction)
Selected AbstractsDensity Functional Study of the Complexation Reaction of Sn(CH3)3X (X = F, Cl, Br and I) with Halide AnionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2003Frank De Proft Abstract The Lewis acid-base reaction between Sn(CH3)3X and Y, (with X, Y = F, Cl, Br and I) has been studied using quantum chemical calculations. Complexation energies were calculated at the Density Functional Theory (DFT) level and rationalized on the basis of a local application of the hard and soft acids and bases principle. It was observed that smaller differences in the local softness of the interacting sites in the Lewis acid and base correspond to stronger interactions. Moreover, the calculated sequences in complexation energies can be reproduced using equations containing chemical concepts introduced within the framework of conceptual density functional theory and rooted in the hard and soft acids and bases principle and referring only to the reactants. A method of treating the electronegativity and softness of the halide anions is presented based on a Taylor expansion of the electronegativity of the neutral halogens and the softness-polarizability proportionality. Experimental evidence for the calculated sequences was gathered from measured 117Sn chemical shifts and 1J (13C- 119/117Sn) coupling constant changes upon complexation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Tellurated Schiff Bases Formed from {2-[(4-Methoxyphenyl)telluro]ethyl}amine and Bis(2-aminoethyl) Telluride with o -Hydroxyacetophenone: Synthesis and Complexation Reactions with HgII, PdII and RuII , Crystal Structures of the Ligands, [Ru(p -cymene)Cl{H2NCH2CH2TeC6H4 -4-OCH3}]Cl·H2O and [RuCl{4-MeOC6H4TeCH2CH2NHCH(CH3)C6H4 -2-O,}]EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2004Raghavendra Kumar P. Abstract {2-[(4-Methoxyphenyl)telluro]ethyl}amine and bis(2-aminoethyl) telluride on treatment with o -hydroxyacetophenone gave the Schiff bases 4-MeOC6H4TeCH2CH2N=C(CH3)C6H4 -2-OH (L1) and 2-HOC6H4(CH3)C=NCH2CH2TeCH2CH2N=C(CH3)C6H4 -2-OH (L3), respectively. The reduction of L1 and L3 with NaBH4 resulted in 4-MeOC6H4TeCH2CH2NHCH(CH3)C6H4 -2-OH (L2) and 2-HOC6H4(CH3)CHNHCH2CH2TeCH2CH2NHCH(CH3)C6H4 -2-OH (L4), respectively, which have 1 or 2 chiral centers. The 1H and 13C NMR spectra of L1 to L4 were found to be characteristic. Treatment of L1 with [Ru(p -cymene)Cl2]2 resulted in [Ru(p -cymene)(4-MeOC6H4TeCH2CH2NH2)Cl]Cl·H2O (1) whereas in the reaction of L2 with [Ru(p -cymene)Cl2]2, the p -cymene ligand is lost resulting in [RuCl(L2 -H)] (4). The reactions of L1, L3 and L4 with HgBr2 resulted in complexes of the type [HgBr2·(L)2] while Na2PdCl4 reacted with L1 to give [PdCl(L1 -H)]. The solid-state structures of L1, L3, 1 and 4 were determined by single-crystal X-ray diffraction studies. The very swift formation of the tellurated amine from a tellurated Schiff base (L1) by hydrolysis has been observed for the first time and has resulted in 1. The Ru,N and Ru,Te bond lengths in 1 are 2.142(3) and 2.6371 (4) Å, respectively. The replacement of the p -cymene ligand with a hybrid organotellurium ligand (L2 -H), resulting in 4, is also a first example of its kind. The Ru center in 4 has a square-planar geometry, with the Ru,N, Ru,Te, Ru,O and Ru,Cl bond lengths being 2.041(6), 2.4983(8), 2.058(5) and 2.308(2) Å, respectively. In the crystals of 4 there are secondary intermolecular Te···Cl interactions and intermolecular N,H···O hydrogen bonds. This is the first example in which coordinated Te in a complex is engaged in two intermolecular secondary interactions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Study of the Complexation, Adsorption and Electrode Reaction Mechanisms of Chromium(VI) and (III) with DTPA Under Adsorptive Stripping Voltammetric ConditionsELECTROANALYSIS, Issue 19 2003Sylvia Sander Abstract The complexation of Cr(III) and Cr(VI) with diethylenetriaminepentaacetic acid (DTPA), the redox behavior of these complexes and their adsorption on the mercury electrode surface were investigated by a combination of electrochemical techniques and UV/vis spectroscopy. A homogenous two-step reaction was observed when mixing Cr(III), present as hexaquo complex, with DTPA. The first reaction product, the electroactive 1,:,1 complex, turns into an electroinactive form in the second step. The results indicate that the second reaction product is presumably a 1,:,2 Cr(III)/DTPA complex. The electroreduction of the DTPA-Cr(III) complex to Cr(II) was found to be diffusion rather than adsorption controlled. The Cr(III) ion, generated in-situ from Cr(VI) at the mercury electrode at about ,50,mV (vs. Ag|AgCl) (3,mol,L,1 KCl), was found to form instantly an electroactive and adsorbable complex with DTPA. By means of electrocapillary measurements its surface activity was shown to be 30 times higher than that of the complex built by homogenous reaction of DTPA with the hydrated Cr(III). Both components, DTPA and the in-situ built complex Cr(III) ion were found to adsorb on the mercury electrode. The effect of nitrate, used as catalytic oxidant in the voltammetric determination method, on the complexation reaction and on the adsorption processes was found to be negligible. The proposed complex structures and an overall reaction scheme are shown. [source] A TRLFS Study on the Complexation of CmIII and EuIII with 2,6-Bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine in Water/Methanol MixtureEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2010Sascha Trumm Abstract The complexation of CmIII and EuIII with 2,6-bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine (nPr-BTP) in water/methanol solution is studied. 1:3 complexes [M(nPr-BTP)3]3+ form from the solvated metal ions upon addition of ligand. The conditional stability constants are log,K = 14.4 and log,K = 11.9. For both metal ions the complexation reaction is both enthalpy and entropy driven. ,H is 10.1 kJ/mol more negative than ,H, whereas the entropy difference is small. The difference in ,G between the formation of the CmIII and EuIII complexes is in good agreement with nPr-BTP's selectivity in liquid-liquid extraction. [source] Arbutin determination in medicinal plants and creamsINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 2 2009W. Thongchai Synopsis A simple flow injection (FI) manifold with spectrophotometric detection was fabricated and tested for arbutin determination. It is based on the measurement of a red-coloured product at 514 nm formed by the complexation reaction between arbutin and 4-aminoantipyrine (4-AP) in the presence of hexacyanoferrate (III) in an alkaline medium. On injecting 300 ,L standard solutions at various concentrations of arbutin into the FI system under optimum conditions, a linear calibration graph over the range of 1.0,30.0 ,g mL,1 arbutin was established. It is expressed by the regression equation y = 0.2188 ± 0.0036x + 0.1019 ± 0.0366 (r2 = 0.9990, n = 5). The detection limit (3,) and the limit of quantitation (10,) were 0.04 ,g mL,1 and 0.13 ,g mL,1, respectively. The RSD of intraday and interday precisions were found to be 1.2,1.4% and 1.7,2.7%, respectively. The method was successfully applied in the determination of arbutin in four selected fruits and three commercial whitening cream extracts with the mean recoveries of the added arbutin over the range of 96.2,99.0%. No interference effects from some common excipients used in commercial whitening creams were observed. The method is simple, rapid, selective, accurate, reproducible and relatively inexpensive. Résumé Un collecteur simple pour injection en flux (FI) avec détection spectrométrique a été fabriqué et testé pour le dosage de l'arbutine. Son principe repose sur la mesure à 514 nm du produit rouge formé par la réaction de complexation entre l'arbutine et le 4-aminoantipyrine (4-AP) en présence d'hexacyanoferrate (III) en milieu alcalin. On procède à une injection de 300 ,L des solutions standards à diverses concentrations d'arbutine dans le système FI aux conditions optimales, puis on réalise un graphe de calibration linéaire dans l'intervalle de 1,0 à 30,0 ,g mL,1 d'arbutine. Le graphe correspond à l'équation de régression y = 0.2188 ± 0.0036x + 0.1019 ± 0.0366 (r2 = 0.9990, n = 5). La limite de détection (3,) et la limite de quantification (10,) sont respectivement de 0.04 ,g mL,1 et 0.13 ,g mL,1. La RSD des précisions intra et inter jours sont respectivement de 1.2,1.4% et 1.7,2.7%. La méthode a été appliquée avec succès à la mesure de l'arbutine dans 4 fruits sélectionnés et 3 extraits de crèmes de blanchiment commercialisées avec une recouvrance moyenne de l'arbutine ajoutée de 96.2 à 99%. Aucune interférence avec les excipients communément utilisés dans les crèmes de blanchiment commerciales n'a été observée. La méthode est simple, rapide, sélective, précise, reproductible et relativement bon marché. [source] Preparation of a technetium-99m SPECT agent for imaging the sigma-2 receptor status of solid tumorsJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 13 2001Robert H. Mach Abstract The synthesis and in vitro binding of a novel 99mTc-labeled radiotracer for imaging the sigma-2 (,2) receptor status of breast tumors is described. Structural characterization and in vitro binding studies were conducted using the corresponding rhenium surrogate, Re-2. X-ray crystallographic studies revealed that the complexation reaction gave exclusively the syn isomer. In vitro binding studies indicated that this complex has a high affinity for ,2 (Ki=13.7 nM) versus ,1 receptors (Ki=1125 nM). These data indicate that [99mTc]2 may be a promising agent for imaging the ,2 receptor status of tumors in vivo with the functional imaging technique, single photon emission computed tomography (SPECT). Copyright © 2001 John Wiley & Sons, Ltd. [source] Influence of response factors on determining equilibrium association constants of non-covalent complexes by electrospray ionization mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2003Valérie Gabelica Abstract A method for determining the equilibrium association constant of a complexation reaction A + B , AB by electrospray ionization mass spectrometry is described. The method consists in measuring the relative intensities of the peaks corresponding to A and to AB in equimolar A,B solutions at different concentrations C0. The results are fitted by a non-linear least-squares procedure, with the two variable parameters being the equilibrium association constant Ka and a factor R, defined by I(AB)/I(A) = R × [AB]/[A]. The factor R is the ratio between the response factors of AB and A, and corrects for the relative electrospray responses of the complex and the free substrate A, mass discrimination of instrumental origin and/or moderate in-source dissociation. The method is illustrated with the following two systems: complexes between a double-stranded 12-base pair oligonucleotide and minor groove binders, and cyclodextrin complexes with ,,,-dicarboxylic acids. For the oligonucleotide complexes, it is found that the response of the complex is not dramatically different to the response of the free oligonucleotide duplex, as the double helix conformation is disturbed by the drug only to a minor extent. In the case of cyclodextrin complexes, these complexes were found to have a much higher response than free cyclodextrin. This may be due to the fact that cyclodextrin is neutral in solution, whereas the complex is charged, but it can also stem from the fact that a significant proportion of the complex is in a non-inclusion geometry. The present method requires the exact determination of the concentrations of the reactants and is applicable to 1 : 1 complexes. Copyright © 2003 John Wiley & Sons, Ltd. [source] Partition of thermodynamic energies of drug,DNA complexationBIOPOLYMERS, Issue 9 2009V. V. Kostjukov Abstract We report a computation methodology, which leads to the ability to partition the Gibb's free energy for the complexation reaction of aromatic drug molecules with DNA. Using this approach, it is now possible to calculate the absolute values of the energy contributions of various physical factors to the DNA binding process, whose summation gives a value that is reasonably close to the experimentally measured Gibb's free energy of binding. Application of the methodology to binding of various aromatic drugs with DNA provides an answer to the question "What forces are the main contributors to the stabilization of aromatic ligand,DNA complexes?" © 2009 Wiley Periodicals, Inc. Biopolymers 91: 773,790, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Protein,Inorganic Array Construction: Design and Synthesis of the Building BlocksCHEMISTRY - A EUROPEAN JOURNAL, Issue 7 2010Niculina Abstract Herein we describe the design and synthesis of the first series of di-functional ligands for the directed construction of inorganic-protein frameworks. The synthesized ligands are composed of a metal-ion binding moiety (terpyridine-based) conjugated to an epoxysuccinyl peptide, known to covalently bind active cysteine proteases through the active-site cysteine. We explore and optimize two different conjugation chemistries between the di-functionalized metal-ion ligand and the epoxysuccinyl-containing peptide moiety: peptide-bond formation (with limited success) and CuI -catalysed click chemistry (with good results). Further, the complexation of the synthesized ligands with FeII and NiII ions is investigated: the di-functional ligands are confirmed to behave similarly to the parent terpyridine. As designed, the peptidic moiety does not interfere with the complexation reaction, in spite of the presence of two triazole rings that result from the click reaction. ES-MS together with NMR and UV/Vis studies establish the structure, the stoichiometry of the complexation reactions, as well as the conditions under which chemically sensitive peptide-containing polypyridine ligands can undergo the self-assembly process. These results establish the versatility of our approach and open the way to the synthesis of di-functional ligands containing more elaborated polypyridine ligands as well as affinity labels for different enzyme families. As such, this paper is the first step towards the construction of robust supramolecular species that cover a size-regime and organization level previously unexplored. Im Folgenden beschreiben wir das gezielte Design und die Synthese di-funktionaler Liganden zum erstmaligen Aufbau supramolekularer Metall-Protein-Hybridarchitekturen. Die synthetisierten Liganden enthalten eine Metallionen-Bindungsstelle (auf Terpyridin-Basis), die mit einem Epoxysuccinyl-Peptid konjugiert wurde. Diese Peptide binden bekannterweise an die aktiven Cysteine im katalytischen Zentrum von Cystein-Proteasen. Wir untersuchen und optimieren zwei verschiedene Arten chemischer Konjugations-Systeme zwischen den di-funktionalen Metallionen-Liganden und dem Epoxysuccinyl-enthaltenden Peptidrest: Bildung einer Peptid-Bindung (mit geringem Erfolg) und CuI -katalysierte click Chemie (mit signifikantem Erfolg). Wie beabsichtigt, erfolgt die Komplexierung von FeII - und NiII -Ionen an den synthetisierten Liganden hochselektiv am Terpyridylrest und nicht an den Triazol-Ringen des Peptidrests, die aus der click Reaktion resultieren. Struktur, Stöchiometrie der Komplexbildung und Bedingungen für den Selbstorganisationsprozess der empfindlichen poly-Pyridyl-Peptid-Liganden wurden durch ESI-MS-, NMR- und UV-VIS-Untersuchungen dokumentiert. Diese Ergebnisse demonstrieren die Vielseitigkeit unseres neuartigen Ansatzes zur Synthese maßgeschneiderter di-funktionaler Liganden mit poly-Pyridyl-Resten und Affinity Label für unterschiedliche Enzymfamilien. Die Arbeit repräsentiert somit den ersten Schritt in der Entwicklung einer stabilen, supramolekularen Architektur in bisher unerreichter Größenordnung und Organisationsgrad. [source] A model describing the interactions between anaerobic microbiology and geochemistry in a soil amended with glucose and nitrateEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2004F. Dassonville Summary Under anaerobic conditions, microbes closely interact with geochemical reactions and can have an impact on the soil, the deep vadose zone, the underlying aquifer and the atmosphere. We have designed a model combining anaerobic microbial activities with geochemical reactions in the soil, and assessed it in batch experiments. The model describes the dynamics of six functional microbial communities, their decomposition after death, and the catabolism of carbohydrates through denitrification, dissimilatory NH4+ production, Fe(III) reduction, fermentation, acetogenesis, and SO42, reduction. It was combined with a model that thermodynamically describes acid,base, reduction,oxidation and complexation reactions in solution, and kinetic precipitation and dissolution. Batch incubations were done on a Calcic Cambisol, either without amendment, or after supplying (i) glucose or (ii) glucose and NO3,. Gases, mineral cations and anions, glucose, fatty acids and alcohols were measured during incubation. Net production of CO2 was similar for both glucose treatments, about 40 times larger than in the control. For the glucose treatments, the main microbial activities were fermentation, acetogenic transformation of ethanol, and oxidation of H2. When the soil was enriched with NO3,, no H2 was produced, and microbial activities were rapidly inhibited by NO2,. The model shows these trends as well as geochemical characteristics including pH and reduction,oxidation potential. [source] Protein,Inorganic Array Construction: Design and Synthesis of the Building BlocksCHEMISTRY - A EUROPEAN JOURNAL, Issue 7 2010Niculina Abstract Herein we describe the design and synthesis of the first series of di-functional ligands for the directed construction of inorganic-protein frameworks. The synthesized ligands are composed of a metal-ion binding moiety (terpyridine-based) conjugated to an epoxysuccinyl peptide, known to covalently bind active cysteine proteases through the active-site cysteine. We explore and optimize two different conjugation chemistries between the di-functionalized metal-ion ligand and the epoxysuccinyl-containing peptide moiety: peptide-bond formation (with limited success) and CuI -catalysed click chemistry (with good results). Further, the complexation of the synthesized ligands with FeII and NiII ions is investigated: the di-functional ligands are confirmed to behave similarly to the parent terpyridine. As designed, the peptidic moiety does not interfere with the complexation reaction, in spite of the presence of two triazole rings that result from the click reaction. ES-MS together with NMR and UV/Vis studies establish the structure, the stoichiometry of the complexation reactions, as well as the conditions under which chemically sensitive peptide-containing polypyridine ligands can undergo the self-assembly process. These results establish the versatility of our approach and open the way to the synthesis of di-functional ligands containing more elaborated polypyridine ligands as well as affinity labels for different enzyme families. As such, this paper is the first step towards the construction of robust supramolecular species that cover a size-regime and organization level previously unexplored. Im Folgenden beschreiben wir das gezielte Design und die Synthese di-funktionaler Liganden zum erstmaligen Aufbau supramolekularer Metall-Protein-Hybridarchitekturen. Die synthetisierten Liganden enthalten eine Metallionen-Bindungsstelle (auf Terpyridin-Basis), die mit einem Epoxysuccinyl-Peptid konjugiert wurde. Diese Peptide binden bekannterweise an die aktiven Cysteine im katalytischen Zentrum von Cystein-Proteasen. Wir untersuchen und optimieren zwei verschiedene Arten chemischer Konjugations-Systeme zwischen den di-funktionalen Metallionen-Liganden und dem Epoxysuccinyl-enthaltenden Peptidrest: Bildung einer Peptid-Bindung (mit geringem Erfolg) und CuI -katalysierte click Chemie (mit signifikantem Erfolg). Wie beabsichtigt, erfolgt die Komplexierung von FeII - und NiII -Ionen an den synthetisierten Liganden hochselektiv am Terpyridylrest und nicht an den Triazol-Ringen des Peptidrests, die aus der click Reaktion resultieren. Struktur, Stöchiometrie der Komplexbildung und Bedingungen für den Selbstorganisationsprozess der empfindlichen poly-Pyridyl-Peptid-Liganden wurden durch ESI-MS-, NMR- und UV-VIS-Untersuchungen dokumentiert. Diese Ergebnisse demonstrieren die Vielseitigkeit unseres neuartigen Ansatzes zur Synthese maßgeschneiderter di-funktionaler Liganden mit poly-Pyridyl-Resten und Affinity Label für unterschiedliche Enzymfamilien. Die Arbeit repräsentiert somit den ersten Schritt in der Entwicklung einer stabilen, supramolekularen Architektur in bisher unerreichter Größenordnung und Organisationsgrad. [source] Cross-Reactive Sensor Arrays for the Detection of Peptides in Aqueous Solution by Fluorescence SpectroscopyCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2010Sébastien Rochat Abstract A simple but powerful method for the sensing of peptides in aqueous solution has been developed. The transition-metal complexes [PdCl2(en)], [{RhCl2Cp*}2], and [{RuCl2(p -cymene)}2] were combined with six different fluorescent dyes to build a cross-reactive sensor array. The fluorescence response of the individual sensor units was based on competitive complexation reactions between the peptide analytes and the fluorescent dyes. The collective response of the sensor array in a time-resolved fashion was used as an input for multivariate analyses. A sensor array comprised of only six metal,dye combinations was able to differentiate ten different dipeptides in buffered aqueous solution at a concentration of 50,,M. Furthermore, the cross-reactive sensor could be used to obtain information about the identity and the quantity of the pharmacologically interesting dipeptides carnosine and homocarnosine in a complex biological matrix, such as deproteinized human blood serum. The sensor array was also able to sense longer peptides, which was demonstrated by differentiating mixtures of the nonapeptide bradykinin and the decapeptide kallidin. [source] | ||||||||||