Log Ks Research Articles

Intramolecular Sandwich Complexation of Light Lanthanoid Nitrates with Bis(benzo-12-crown-4)s: Enhanced Selectivity for Eu

Spectrophotometric titrations performed in anhydrous acetonitrile at 25°C give the complex stability constants (log Ks) and the Gibbs free energy changes (-ΔG° for the stoichiometric 1 : 1 intramolecular sandwich complexation of light lanthanoid (III) nitrates (La ∼ Gd) with the polymethylene-bridged bis(benzo-12-crown-4)s 1, the corresponding dioxo derivative 2 and its dihydroxy analogue 3. The complex stability sequence as a function of reciprocal ionic radius of lanthanoids showed similar profiles in stability constants (log Ks) and maximum stabilities were obtained at Eu3+ for the complexation of light lanthanoids with the three bis(benzo-12-crown-4)s 1–3. The cation binding abilities and relative selectivities for the trivalent lanthanoid ions of these structurally related bis(benzo-12-crown-4)s 1–3 are discussed according to the derivatization of the bridging.

Complexing ability of monensin anion for alkali metal cations in binary mixtures of dipolar aprotic solvents

AbstractCyclic voltammetric studies have been carried out on monensin anion complexes with the alkali metal cations in binary mixtures of dimethylsulfoxide with acetonitrile, acetone and hexamethylphosphoric triamide. respectively. The log Ks values obtained for the complexity constants can be well described by empirical relation log Ks = αDN + β, where DN stands for the effective donor number of a given solvent mixture and α and β mark the regression coefficients. This result is in agreement with the predominant role of cation solvation. The complexes show a sharp stability maximum for the Na+ complex in all media under investigation.

Modeling Sorption of Trace Metals on Natural Sediments by Surface Complexation Model

The potential possibility of the surface complexation models to describe the sorption of trace metals on natural sediments has been suggested since the late 1980s, which should be of natural importance to predict the bioavailability of trace metals in aquatic sediments. This possibility was tested based on 11 geographically and hydrologically diverse natural aquatic sediment samples. The sorption of Cu(II), Zn(II), Pb(II), and Cd(II) on these sediments was studied by both sorption isotherm and pH−edge sorption experiments. The experimental sorption data were fit well by the surface complexation model (the double-layer model). The linear free energy relationship (LFER) between the surface complexation constants (Ks) of trace metals on the sediments and the corresponding first-hydrolysis constants (*K1) was observed, which could be expressed as log Ks = a log *K1 + b. The slope of the linear regression, a, was dependent on the sediment composition: a = 0.19TOC − 0.09Oxides + 1.31 (n = 11), where TOC (%) is...

Evaluation of the transannular interaction of 5-substituted [2.2]metacyclophanes carrying a diazonio group on their outer position

A diazonio group has been introduced into the outer (13-)position of 5-substituted [2.2]metacyclophanes (MCPs) (3). The absorption maxima of the substituted [2.2]MCP diazonium salts are bathochromically shifted from those of unsubstituted reference compounds. Stability constants (log Ks) of the complexation between the [2.2]MCP diazonium salts have been measured in order to estimate their cationic character. When log Ks for [2.2]MCP diazonium salts which carry the functional groups are plotted against Brown–Okamoto’s substituent constant (σp+) for them, a linear relationship is obtained. This result establishes that the electronic effect of the functional group is transmittable between two aromatic rings in [2.2]MCPs through a transannular interaction.

Partitioning of trace metals between the dissolved and particulate phases and particulate surface reactivity in the Lena River estuary and the Laptev Sea (Russia)

Abstract Trace metal distribution between suspended matter and dissolved phase has been determined in an organic rich aquatic system: the Lena River estuary and the adjacent Laptev Sea. The partitioning between dissolved and particulate phases of Cs Cd, Co, Cs, Mn and Zn is determined through the so-called fast distribution coefficient (FDC). Application of a surface complexation model has been attempted so as to describe the FDC's variations in the estuarine system. The relative effects of inorganic dissolved species and colloidal and particulate reactivity on FDC are discussed. The particulate reactivity is related either to the composition of the particulate component (mineral and organic) or to the bulk particulate surface properties such as the ammonium saturation index or the heat of immersion in water. For Cd, the low FDC variation with the salinity can be explained by the variation of the chloro and sulphato dissolved species, by the complexation of some colloidal organic species and by a high particulate surface reactivity. The complexation constant of the particulate phase (log Ks(Cd)) has been calculated equal to 5.2. Zn exhibits a similar range of FDC variations but the scattered relationship with salinity does not allow an identification of the determining parameters. Co and Mn exhibit similar behaviours. The high changes in their FDC (compared to Cd) have been simulated by a surface complexation model in which the effect of the major cations (Ca2+ and Mg2+) is taken into account. The complexation constant of the particulate phase (log Ks(Mn)) and log Ks(co) calculated from the model is 7.2. For Cs, the competitive sorption with K+ chiefly controls the change in FDC. Using the number of sites given by the ammonium saturation index, a mean value of the particulate complexation constant (log Ks(Cs)) has been estimated to be 5.1. Implications of the low temperature of the water in the studied area on the trace metal sorption on the particulate phase are discussed.

Antiradiation Compounds. 24. Stability of Copper(II) Complexes of Bis(methylthio) and Methylthio Amino Derivatives of 1-Methylpyridinium- and 1-Methylquinolinium-2-dithioacetic Acids in the Presence of Amino Acids, Simple Peptides, and a Protein

The radiation-protective bis(methylthio) and methylthio amino derivatives of 1-methylpyridinium- and 1-methylquinolinium-2-dithioacetic acids, a series of non-thiol sulfur-containing compounds, have been examined for their ability to complex Cu(II) ion and remain stable in the presence of α-amino acids, peptides, and a protein. Copper-binding stability constants were found that were considered sufficiently large to be capable of existence under cellular conditions, with log Ks values in the range of 13–15. Copper-binding constants for α-amino acids are comparable to those for the radioprotective ligands, but overall binding constants for simple peptides are usually 104–106 lower in magnitude. Essentially no change was found in the UV spectra of the Cu(II) complexes in the presence of α-amino acids and simple peptides, and the binding capacity to bovine serum albumin was quite low for two Cu(II) complexes of the best protective ligands, with values of 10−6–10−7 M. The possibility that these radioprotectors may act in vivo as copper complexes, possibly as superoxide dismutase mimics, is thus feasible. The magnitude of the copper-binding stability constants, the lack of copper exchange between the radioprotective ligands and amino acids or peptides, and the very low tendency of the copper complexes of the radioprotective ligands to bind to a protein indicate the potential of the complexes to contribute to the radioprotective ability of the ligands.

Thermodynamics of Lithium−Crown Ether (12-crown-4 and 1-Benzyl-1-aza-12-crown-4) Interactions in Acetonitrile and Propylene Carbonate. The Anion Effect on the Coordination Process

Titration microcalorimetry in nonaqueous media (acetonitrile and propylene carbonate) has been used for the determination of stability constants (log Ks) and enthalpies of complexation of lithium and crown ethers (12-crown-4 and 1-benzyl-1-aza-12-crown-4 at 298.15 K. To ensure that the data are referred exclusively to the complexation process, salts containing highly polarizable anions (hexafluoroasenate, tetrafluoroborate, trifluoromethanesulfonate, and perchlorate) are used as sources for lithium. From stability constants and standard enthalpies, standard Gibbs energies and standard entropies are calculated. In propylene carbonate, a correlation is found between the stability of the lithium crown complex and the increase in conductance of the complexed relative to the free cation. Eight new lithium coronand salts of 12-crown-4 and 1-benzyl-1-aza-12-crown-4 were isolated. Standard enthalpies of these salts and crown ethers in acetonitrile and propylene carbonate at 298.15 K measured calorimetrically are ...

On the Velocity Covariance and Transport Modeling in Heterogeneous Anisotropic Porous Formations: 2. Unsaturated Flow

Velocity covariances, and the resultant macrodispersion coefficient tensor, derived by Russo (this issue) for saturated flow conditions, are applied for unsaturated flow conditions, employing the assumption that for a given mean capillary pressure head, water saturation is a deterministic constant and log conductivity is a multivariate normal, stationary random space function. The applicability of the approach for modeling flow and transport in the vadose zone was evaluated by the use of the stochastic theory of Yeh et al. (1985a, b) for steady, unsaturated flow. Results of the analyses suggest that the approach may be applicable to vadose zone flow and transport, as long as the scale of heterogeneity in the direction of the mean flow is smaller than approximately one tenth of the characteristic length of unsaturated flow. For porous formation of given statistics, the magnitude of macrodispersion in unsaturated flow is larger than that in saturated flow, and increases as water saturation decreases. For a given water saturation, transport in unsaturated flow may approach asymptotic Fickian behavior more slowly than in saturated flow, when the two formation properties log Ks and α are positively cross‐correlated and when the correlation scale of α is relatively large as compared with the correlation scale of log Ks.

Synthesis, X‐ray structure, spectroscopic and cation complexation studies of macrocyclic ligands incorporating the 9,9′‐(ethane‐1,2‐diyl)bis(anthracene) photoactive subunit

AbstractTwo 9,9′‐(ethane‐1,2‐diyl)bis(anthracene) ligands, incorporating an ethano bridge, namely the bis‐anthracene coronand 1 and the bis‐anthracene cryptand 2, respectively, have been studied in parallel to compare their binding abilities, spectroscopic and photochemical properties in the presence and absence of cations as a function of their X‐ray structure. The ethano bridge imposes a twisted shape (torsion angles between the vicinal C‐H being 47° for 1 and 62° for 2a and 47° for 2b, the two conformers of compound 2), which inhibits the cation‐binding ability of 1 and attenuates that of cryptand 2 (log Ks ≈︁ 1.8 for Na+ or K+, ≈︁ 4 for Tl+ and ≈︁ 8 for Ag+); in CH3OH, both 1 and 2 emit essentially excimer‐type fluorescence at λmax 520‐535 nm, which is red‐shifted compared with that of the single crystals ( ≈︁ 465‐480 nm) where the rotation about the CH2‐CH2 bond is hindered. The presence of cations, which has no influence on the photocycloisomerization quantum yield of 1 (as expected), clearly affects that of 2. Cryptand 2 was shown to display photochromic properties.

Stochastic modeling of macrodispersion for solute transport in a heterogeneous unsaturated porous formation

A framework for the prediction of solute spread in partially saturated heterogeneous porous formation is presented by combining a general Lagrangian formulation, relating the spatial moments of the solute body to the velocity field, with the stochastic theory of Yeh et al. (1985a, b) for steady unsaturated flow, relating the statistical moments of the velocity field to properties of the heterogenous formation. The relevant formation properties are log saturated conductivity, log Ks, and the pore size distribution parameter, α, which, in turn, are viewed as independent, random spatial functions. First‐order approximations of the longitudinal and transverse components of the velocity covariance function are derived for unidirectional, vertical mean flow in partially saturated, heterogeneous porous formations of three‐dimensional structure. Neglecting pore scale dispersion, and by using basic, kinematical relationships to relate the displacement to the velocity field, the effect of mean water saturation, and of statistical parameters of porous formation properties on longitudingal and transverse components of the time‐dependent displacement covariance tensor X, is evaluated. Results of the analyses show that solute spread increases as water saturation decreases. In the case where the correlation scale of α was small, as compared with that of log Ks, however, the longitudinal component of X is essentially robust to water saturation, suggesting that in this case, vadose zone transport might be amenable to an analysis similar to that for saturated groundwater transport.

Nd(III) Hydrolysis Constants and Solubilities of Nd(III) Hydroxide.

高レベル放射性廃棄物地層処分の性能評価研究において,アクチニド元素の熱力学データは重要であるがまだ十分そろっているとはいえない。また,熱力学データを得るための溶解度実験では固相の同定が重要となる。本研究は,純粋な結晶性水酸化ネオジム[Nd(OH)3(c)]の溶解度実験を行い,実験前後で固相が変化しないことをX線回折により確認し,結晶性水酸化ネオジムの溶解度積,加水分解定数を得ること黙よびアメリシウム(III)の報告例との比較により両者の溶解挙動の類似性を検討することを目的とした。実験は炭酸塩の生成を防ぐためアルゴンガス雰囲気制御下(22℃)で行い,測定されたネオジム(III)の溶解度から溶解度積および加水分解定数を算出した。また,本研究で求められた加水分解定数とBrownらの手法による予測と比較した結果,誤差の範囲内で一致していた。さらに,ネオジム(III)の支配的水溶性化学種の異なるpH領域での変化が,アメリシウム(III)の報告例の傾向と似ていることから,両者の水酸化物の溶解挙動の類似性を確認した。

Statistical analysis of spatial variability in unsaturated flow parameters

Core scale estimates of soil parameters of the Gardner‐Russo and van Gemachten models of the hydraulic conductivity and water retention functions were obtained for 417 undisturbed soil cores taken from a wall of a trench (20 m long, 2.5 m deep), using a procedure based on inverse problem methodology. These estimates were used to evaluate the first two statistical moments of the underlying random space functions (RSFs), using the restricted maximum likelihood estimation procedure, coupled with the weighted least squares procedure, to estimate parameters of models of the covariance and the drift functions of the pertinent RSFs. The fitted models were used to evaluate the mean and covariance functions of the hydraulic conductivity and water rentention functions for given water saturations. Covariance functions of log‐saturated conductivity (log Ks) and the “shape” parameters of the Gardner‐Russo and van Genuchten models exhibited statistical anisotropy characterized by aspect ratios that vary between 3 to 4. Correlation scales of log Ks were larger than those of the “shape” parameters. Consequently, the product of the variance of log unsaturated conductivity and its correlation scale remained essentially invariant for a considerable range of water saturation. The implications of these results regarding stochastic modeling of transport in heterogeneous porous formations and possible applications of the results of this study are discussed briefly.

On solute transport in a heterogeneous porous formation under saturated and unsaturated water flows

The results of a recent study of solute transport in a hypothetical scale‐heterogeneous soil under transient unsaturated flow conditions (Russo, this issue) suggested that the time‐dependent components of the spatial covariance tensor, based on a single realization of the solute concentration in unsaturated flow, are in relatively good agreement with the components of the spatial covariance tensor, based on the ensemble‐average solute concentration derived by Dagan (1984), for solute transport under steady saturated flow. Furthermore, the asymptotic value of the longitudinal component of the dispersivity tensor λzz, estimated from the horizontally averaged solute concentration in the unsaturated flow domain, was found to be in good agreement with the asymptotic λzz derived by Dagan (1982, 1984) and Gelhar and Axness (1983) for saturated flow. These findings are explored in a general Lagrangian formulation, using small‐perturbation, first‐order approximations. The results of the analysis of the velocity field in the unsaturated flow domain of the hypothetical scale‐heterogeneous soil of Russo (this issue) suggest that there was good agreement between the result of the Lagrangian kinematic analysis and the result of the analysis of the spatial moments of the concentration distribution, in agreement with the stochastic theory of transport in saturated flow. This is explained by the finding that under unsaturated flow conditions there is an increase in the variability of the hydraulic conductivity K (and concurrently an increase in the variability of the velocity Vz), accompanied by a decrease in the correlation scale of K (and concurrently a decrease in the correlation scale of Vz) relative to the saturated conditions. The increase in the variability of the unsaturated conductivity stemmed from the variability in the water content θ and the strong nonlinear dependence of K on θ, while the accompanying decrease in its correlation scale stemmed from the negative correlation between F = log Ks and θ, which persisted for a relatively large separation distance in the longitudinal vertical direction. Consequently, the product between the conductivity variance and its correlation scale is of similar magnitude for both saturated and unsaturated flow regimes. The results suggest that in spite of the complexity of unsaturated flow, as compared with saturated flow, it might be amenable to a similar analysis.

Structure and solution stability of indium and gallium complexes of 1,4,7-triazacyclononanetriacetate and of yttrium complexes of 1,4,7,10-tetraazacyclododecanetetraacetate and related ligands: kinetically stable complexes for use in imaging and radioimmunotherapy. X-Ray molecular structure of the indium and gallium complexes of 1,4,7-triazacyclononane-1,4,7-triacetic acid

Of the four triazacycloalkanetriacetic acids screened for their ability to bind 111ln, triazacyclononanetriacetate bound indium most quickly and formed a complex whose dissociation as a function of pD was monitored by 13C NMR spectrometry using a labelled ligand (k296 1.8 × 10–1 dm3 mol–1 s–1) in the pD range 0 to –0.6. The corresponding gallium complex is even more stable with respect to acid dissociation and may be observed by 71Ga NMR spectrometry both in vitro(δGa+ 171 ppm) and in vivo. Crystal structures of the neutral gallium and of the protonated indium complexes are reported. The syntheses of a series of octadentate ligands are described and their relative efficiency to bind 90Y reported. Ligands based on tetraazacyclododecane bind 90Y most rapidly, and tetraazacyclododecanetetraacetate forms a strong complex with yttrium (log Ks 24.9, 298 K) which dissociates at low pH (< 2) as measured by HPLC and 13C NMR spectrometry.

Synergism with amides

Synergistic extraction of uranyl ion with 1-phenyl-3-methyl-4-benzoylpyrazolone-5 (HPMBP) and N,N′-dibutyl derivatives of hexanamide (DBHA), octanamide (DBOA) and decanamide (DBDA) has been studied at various fixed temperatures of 20, 30, 40 and (50±0.1)°C. Results indicate that the equilibrium constants of the organic phase addition reaction (log Ks) with these amides follow their order of basicity (Kh) viz. 4.01 (DBHA, Kh=0.09)<4.05 (DBOA, Kh=0.1)<4.09 (DBDA, Kh=0.13). These values of log Ks (≃4) are lower than those (≃5) of HTTA system with these amides, which may perhaps be attributed to the effect of steric hindrance exerted by the uranyl pyrazolone ohelate to the incoming rigid amide molecule. High negative ΔH and negative ΔS values for this system indicate the organic phase reaction to be an addition and not a substitution.

Reactivity and pH dependence of thiol conjugation to N-ethylmaleimide: detection of a conformational change in chalcone isomerase

The reactivity of simple alkyl thiolates with N-ethylmaleimide (NEM) follows the Brønsted equation, log kS- = log G + beta pK, with G = 790 M-1 min-1 and beta = 0.43. The rate constant for the reaction of the thiolate of 2-mercaptoethanol with NEM is 10(7) M-1 min-1, whereas the rate constant for the reaction of the protonated thiol is less than 0.0002 M-1 min-1. The intrinsic reactivity of the protonated thiol (SH) is over (5 X 10(10]-fold less than the thiolate (S-) and makes a negligible contribution to the reactivity of thiols toward NEM. The rate of NEM modification of chalcone isomerase was conveniently measured by following the concomitant loss in enzymatic activity. The pseudo-first-order rate constants for inactivation show a linear dependence on the concentration of NEM up to 200 mM and yield no evidence for noncovalent binding of NEM to the enzyme. Evidence is presented demonstrating that the modification of chalcone isomerase by NEM is limited to a single cysteine residue over a wide range of pH. Kinetic protection against inactivation and modification by NEM is provided by competitive inhibitors and supports the assignment of this cysteine residue to be at or near the active site of chalcone isomerase. The pH dependence of inactivation of the enzyme by NEM indicates a pK of 9.2 for the cysteine residue in chalcone isomerase. At high pH, the enzymatic thiolate is only (3 X 10(-5))-fold as reactive as a low molecular weight alkyl thiolate of the same pK, suggesting a large steric inhibition of reaction on the enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Potentiometric investigation of the stability of palladium(II) complex of pralidoxime chloride in aqueous solution

The formation of a complex between palladium(II) chloride and pralidoxime chloride (PAM-2Cl) has been studied by means of potentiometric pH measurements. The real stability constant of the complex in aqeous medium of ionic strength 0.3 M (KCl) at 25.0 degrees C was log Ks = 7.29. This value was close to that (log Ks = 7.02) obtained previously by spectrophotometric methods after appropriate correction with respect to the corresponding value of the acidic constant of PAM-2Cl (pKca = 8.05), which was also determined under the same experimental conditions.

Synthesis and binding properties of amide-functionalised polyaza macrocycles

A series of amide N-functionalised coronands has been prepared based on parent [9]-N3, [12]-N3, [12]-N2O2, and [12]-N4 polyazamacrocycles. Complexation with alkali and alkaline earth cations, particularly Li+, Na+, and Ca2+, has been monitored by using 13C NMR and IR spectroscopy, fast atom bombardment mass spectrometry, calorimetric, and potentiometric analysis in aqueous and alcoholic media. Particularly strong complexation in water has been observed for Ca2+ with 1,4,7,10-tetrakis(N,N-dimethylacetamido)-1,4,7,10-tetra-azacyclododecane, (9)(log Ks= 6.82-[H2O, 298 K]), and selective Ca2+ complexation was observed with 1,7-dioxa-4,10-bis(dimethylethanamido)-4, 10-diazacyclododecane, (7).

Anodic oxidation of mercury in the presence of monocyclic ligands in propylene carbonate

AbstractA series of 12 macrocycles containing 4, 6, or 8 N, S, and O heteroatoms (with increasing size from 14 to 24 atoms in the cycle) was studied to ascertain size and heteroatoms effects on the formation and 14 redox characteristics of their mercuric complexes. The concentration dependence of anodic currents at mercury electrodes in solutions of these ligands led to the determination of the formation constants of the complexes generated according to the folling of In propylene carbonate, the resulting mercuric complexes were stable (log Ks up to 40) mono‐ and dinuclear species. Their stability depends both on the nature of the heteroatoms and on the size of the macrocycle. For identical ligand sizes, the stability sequence N &gt; S &gt; O was established for mercuric complexes.

Relationship between green and ampt parameters based on scaling concepts and field‐measured hydraulic data

For possible use in resource management models we examined the relationship aspects of wetting front suction head τwf and near‐saturated hydraulic conductivity Ks, the parameters of the Green and Ampt infiltration equation. Analysis of nonsimilar‐media scaling and a capillary tube bundle implied the power function relationship of negative slope linearity of log τwf versus log Ks. Experimentally, τwf and Ks were obtained from field‐measured hydraulic conductivity versus suction head for five soils. For each soil, of the total variation of log τwf regressed linearly on log Ks, less than half was due to regression, although the correspondingly small correlation coefficients were highly significant statistically. Hence log τwf versus log Ks displayed more independence than dependence. Also, based on regression line intercepts, only three soils could be reasonably grouped together. Whether such an indifferent relationship is useful, as in a large ensemble of τwf and Ks over spatially variable areas, must await further evaluation.