Showing papers on "Aquation published in 2007"

Structure-activity relationships for NAMI-A-type complexes (HL)[trans-RuCl4L(S-dmso)ruthenate(III)] (L = imidazole, indazole, 1,2,4-triazole, 4-amino-1,2,4-triazole, and 1-methyl-1,2,4-triazole): aquation, redox properties, protein binding, and antiproliferative activity.

Abstract: Imidazolium [trans-tetrachloro(1H-imidazole)(S-dimethylsulfoxide)ruthenate(III)] (NAMI-A) and indazolium [trans-tetrachlorobis(1H-indazole)ruthenate(III)] (KP1019) are the most promising ruthenium complexes for anticancer chemotherapy. In this study, the azole ligand of NAMI-A was systematically varied (from imidazole of NAMI-A to indazole, 1,2,4-triazole, 4-amino-1,2,4-triazole, and 1-methyl-1,2,4-triazole), and the respective complexes were evaluated with regard to the rate of aquation and protein binding, redox potentials, and cytotoxicity by means of capillary zone electrophoresis, electrospray ionization mass spectrometry, cyclic voltammetry, and colorimetric microculture assays. Stability studies demonstrated low stability of the complexes at pH 7.4 and 37 degrees C and a high reactivity toward proteins (binding rate constants in the ranges of 0.02-0.34 and 0.01-0.26 min-1 for albumin and transferrin, respectively). The redox potentials (between 0.25 and 0.35 V) were found to be biologically accessible for activation of the complexes in the tumor, and the indazole-containing compound shows the highest antiproliferative activity in vitro.

Osmium(II) and Ruthenium(II) Arene Maltolato Complexes: Rapid Hydrolysis and Nucleobase Binding

Abstract: Density functional calculations show that aquation of [Os(eta(6)-arene)(XY)Cl](n+) complexes is more facile for complexes in which XY=an anionic O,O-chelated ligand compared to a neutral N,N-chelated ligand, and the mechanism more dissociative in character The O,O-chelated XY=maltolato (mal) [M(eta(6)-p-cym)(mal)Cl] complexes, in which p-cvm=p-cymene, M=Os-II (1) and Run (2) were synthesised and the X-ray crystal structures of I and 2-2H(2)O determined Their hydrolysis rates were rapid (too fast to follow by NMR spectroscopy) The aqua adduct of the Os-II complex 1 was 16 pK(a) units more acidic than that of the Ru-II complex 2 Dynamic NMR studies suggested that O,O-chelate ring opening occurs on a millisecond timescale in coordinating proton-donor solvents, and loss of chelated mal in aqueous solution led to the formation of the hydroxo-bridged dimers [(eta(6)-p-cyrn)M(mu-OH)(3)M(eta(6)-p-cym)](+) ne proportion of this dimer in solutions of the Os-II complex 1 increased with dilution and it predominated at micromolar concentrations, even in the presence of 01 M NaCl (conditions close to those used for cytotoxicity testing) Although 9-ethylguanine (9-EtG) binds rapidly to Os-II in 1 and more strongly (log K=44) than to Ru-II in 2 (log K=39), the Os-II adduct [Os(eta(6)-p-cym)(mal)-(9EtG)](+) was unstable with respect to formation of the hydroxo-bridged dimer at micromolar concentrations Such insights into the aqueous solution chemistry of metal-arene complexes under biologically relevant conditions will aid the rational design of organometallic anticancer agents

Dual triggering of DNA binding and fluorescence via photoactivation of a dinuclear ruthenium(II) arene complex

Abstract: The dinuclear RuII arene complexes [{(η6-arene)RuCl}2(μ-2,3-dpp)](PF6)2, arene = indan (1), benzene (2), p-cymene (3), or hexamethylbenzene (4) and 2,3-dpp = 2,3-bis(2-pyridyl)pyrazine, have been synthesized and characterized. Upon irradiation with UVA light, complexes 1 and 2 readily underwent arene loss, while complexes 3 and 4 did not. The photochemistry of 1 was studied in detail. In the X-ray structure of [{(η6-indan)RuCl}2(μ-2,3-dpp)](PF6)2 (1), 2,3-dpp bridges two RuII centers 6.8529(6) A apart. In water, aquation of 1 in the dark occurs with replacement of chloride with biexponential kinetics and decay constants of 100 ± 1 min-1 and 580 ± 11 min-1. This aquation was suppressed by 0.1 M NaCl. UV or visible irradiation of 1 in aqueous or methanolic solution led to arene loss. The fluorescence of the unbound arene is ∼40 times greater than when it is complexed. Irradiation of 1 also had a significant effect on its interactions with DNA. The DNA binding of 1 is increased after irradiation. The non-irr...

The study of induced aquation of Rh(III) sulfate complexes

Abstract: The processes of aquation of Rh(III) complexes in the presence of BaCl2 and Ba(ClO4)2 were studied by the 103RH and 17O NMR methods. In the first case, the final products were found to be the monomeric aqua chloride complexes, while in the second case, aqua hydroxo complexes were formed. The chloride ions present in the system significantly increase the process rate.

Kinetics and mechanism of tris-quinolinatochromium(III) aquation in HClO4 media

Abstract: The chromium(III)-quinolinato complexes, [Cr(quinH)3]0, [Cr(quinH)2(H2O)2]+ and [Cr(quinH)(H2O)4]2+ (where quinH = N,O-bonded quinolinic acid anion), were obtained and characterized in solution. The tris-quinolinato complex undergoes acid-catalyzed aquation to give the diaqua-product, whereas subsequent ligand liberation processes are exceptionally slow. Kinetics of the aquation were studied spectrophotometrically over the 0.1–1.0 M HClO4 range, at I = 1.0 M. The first aquation stage, the chelate-ring opening at the Cr-N bond, is much faster than the second one. The following rate laws were established: kobs = k1 + k−1/Q1[H+] and kobs = k2Q2[H+]/(1 + Q2[H+]), where k1 and k2 are the rate constants for the chelate-ring opening and the ligand liberation, respectively, k−1 is the rate constant of the chelate-ring closure, Q1 and Q2 are the protonation constants of the pyridine nitrogen and 3-carboxylate group in the one-end bonded intermediate, respectively. Kinetic parameters have been determined and the mechanism has been discussed.

Conserved water molecular dynamics of the different X-ray structures of rusticyanin: an unique aquation potentiality of the ligand bonded Cu++ center.

Abstract: The invariant water molecular interaction involving in the Rusticyanin of Thiobacillus ferrooxidans is thought to be important for its molecular complexation with other proteins at differential acidophilic situation. The comparative analysis of the different x-ray, energy minimized, and auto solvated structures of Rusticyanin revealed the presence of five specific invariant bound water molecules (among the approximately 150 water molecules per monomer) in the crystals. The five W 205, W 206, W 112, W 214, and W 221 water molecules (in Rusticyanin PDB code: 1RCY) were seem to be invariant in all the seven structures (PDB codes: 1RCY, 1A3Z, 1A8Z, 1E3O, 1GY1, 1GY2, 2CAL). Among the five conserved water molecules the W 221 (of 1 RCY or the equivalent water molecules in the other oxidized form of Rusticyanin structures) had endowed an interesting coordination potentiality to Cu(+2) ion during the energy minimization. The W 221 was observed to approach toward the tetrahedrally bonded Cu(+2) ion through the opposite (or trans) route of metal-bonded Met 148. This direct water molecular coordination affected the tetrahedral geometry of Cu(+2) to trigonal bipyramidal. Presumably this structural dynamics at the Cu(+2) center could involve in the electron transport process during protein-protein complexation.

Cobalt(III) complexes of tripod amines. Kinetics of aquation of dichloro[ N -(2-aminoethyl)- N , N - bis - (3-aminopropyl)amine]cobalt(III) ion

Abstract: A new series of six-coordinate cobalt(III) complexes containing tripod tetradentate-N donors (N4), [Co(abap)Cl2]ClO4 · H2O, [Co(abap)(H2O)Cl]Cl(ClO4) and [Co(N4)X2]ClO4 (N4 = abap, X = N3, NO2; N4 = TPA, X = Cl, NO2) where abap = N-(2-aminoethyl)-N,N-bis(3-aminopropyl)amine and TPA = tris(2-pyridylmethyl)amine were synthesized and characterized by elemental analyses, UV–Vis, and IR. The kinetics of the primary aquation of the complex ion [Co(abap)Cl2]+ to [Co(abap)(H2O)Cl]2+ was followed spectrophotometrically in 50/50 (v/v) CH3CN/aqueous HClO4 (16–37°C and I = 0.50 M NaClO4). Rate constants (k 1) evaluated under pseudo first-order conditions, were found to be independent of the [H3O+] over the range of 0.10–0.50 M HClO4 and of the initial complex concentration. At 25°C, the k 1 value was found to be 1.65 × 10−3 s−1 indicating that this process is, unexpectedly, slightly slower than the corresponding reaction in [Co(tren)Cl2]+ (k 1 = 2.96 × 10−3 s−1). The activation parameters were calculated ( = 61.9 ± ...

Method for continuous preparing 1,2,-propylene glycol

Abstract: This invention relates to a preparation of 1,2- propylene glycol, the main steps are: In the condition that catalyst 1 is existent, first epoxypropane and carbon dioxide are carred out esterification to produce propylene carbonate ester, then propylene carbonate ester processes lytic response to produce target matter in the condition that catalyst 2 is existent and temperature is 30- 180DEG C. This invention overcomes the flaw of low reactive selectivity that exists in present technology of direct pressurizing aquation of epoxypropane.

Influence of solvent structure on the aquation of trans-[Ru(3-MePy)4Cl2] complex in mixed aqueous solvents

Abstract: The kinetics of the solvolytic aquation of trans-[Ru (3-Me Py)4Cl2] was studied spectrophotometrically in water – isopropanol in the range (30–90% v/v), and water acetonitrile in the range (10–70% v/v), and in the temperature range 50–65 °C. Plots of log k versus the reciprocal of the relative permittivity and Grunwald–Winstien gave non-linear plots. This non-linearity is derived from a large differential effect of solvent structure between the initial and transition states. The plot of log k versus water concentration was also non linear; evidence for the presence of a S N 1 mechanism. However, extrema in the variation of enthalpy ΔH* and entropy ΔS* of activation correlate well with the extrema in physical properties of the mixtures which are related to changes in solvent structure. Linear plots of ΔH* versus ΔS* were obtained and the iso- kinetic temperature indicates that the reaction is entropy controlled.

First aminoacetone chelate: [Co(tren){NH2CH2C(O)CH3}]3+—a substrate binding and activation model for zinc(II)-dependent 5-aminolaevulinic acid dehydratase

Abstract: The complex p-[Co(tren){NH(2)CH(2)C(O)CH(3)}](ClO(4))(3).H(2)O was produced stereoselectively from [Co(tren)(O(3)SCF(3))(2)]O(3)SCF(3) () and 2-(aminomethyl)-2-methyl-1,3-dioxolane. The structure of was determined by X-ray crystallography. The complex is the first aminoacetone chelate to be reported and the first structurally characterized example of a non-conjugated ketone moiety coordinated to cobalt(iii). The robust complex was stable to aquation in strong acid and behaved as an acid with pK(a) = 4.99(1) indicative of a strong activation of the aminoacetone ligand towards deprotonation. The complex constitutes a structural model for a proposed substrate binding mode relevant for substrate activation of the zinc(ii)-dependent enzyme 5-aminolaevulinic acid dehydratase.

Effect of Triton‐X‐100 Solvent in the Micellar Catalysis of the Aquation of Tris(2‐nitroso‐1‐naphtholate) Ferrate (II)

Abstract: The effect of triton‐X‐100 micelles on the aquation of Fe(C10H6N2O)3 2+ has been investigated with triton‐X‐100 as solvent. In liquid triton‐X‐100, over a range of [H2O] T (0.0–3 M), significant rate enhancement factors of 50–150 are observe. Acid inhibits the rate of aquation at fixed [H2O] T . A mechanism based on effective solvent participation in a chemical environment similar to that in reversed micelles is proposed in liquid triton‐X‐100 with dispersed water pockets. This mechanism predicts direct H2O substitution into the coordination sphere of Fe(C10H6N2O)3 2+ in the highly polar water pockets or cavities where the Fe (II) complex molecules are solubilized. Changes in the tumbling rate, structure, and activity of water are suggested to account for the observed changes in the rate of aquation as a function OH [H2O] T . All k ψ–[H2O] T profiles are structured and exhibit maxima with k ψ(max) shifted to progressively higher [H2O] T as the fixed concentration [H+] T is increased.

Emulsion polymerization initiated by alkylcobalt–tridentate Schiff base complexes in relation to kinetics and mechanism of their decomposition

Abstract: Former studies of decomposition of the title alkylcobalt(III)–tridentate Schiff base complexes (RCo) in acidic media have been extended to neutral and alkaline aqueous solutions including micellar ones. In combination, results of both the works indicate a common reaction mechanism, with homolysis of the Co–C bond preceded by substitution of extra ligand(s) with water molecules. Both protons and hydroxyl ions catalyze the latter aquation step after the conventional pattern of acid–base catalysis. Effect of surfactants on the reaction rate has been explained by electrostatic and hydrophilic/hydrophobic interactions between the cationic complexes and other components of micelles formed.