Adduct Formation Constants Research Articles

Radical reactions of C 60Ph 5Cl: EPR study and DFT calculations

UV-irradiation of a toluene solution of C 60Ph 5Cl leads to the formation of the stable C 60Ph 5 cyclopentadienyl-type fullerenyl radical. Under UV-irradiation of a toluene solution of C 60Ph 5Cl containing Hg[P(O)(OPr i ) 2] 2 (Pr i =CH(CH 3) 2), three isomers of the adducts of phosphoryl radicals with C 60Ph 5Cl are formed. Density functional (DFT) approach with the B3LYP functional was used for estimating of the enthalpies of the formation and hyperfine coupling constants for all possible adducts of phosphoryl radicals with C 60Ph 5Cl. Biradical particles C 60Ph 5[P(O)(OPr i ) 2]– C 60Ph 5[P(O)(OPr i ) 2] with a distance between unpaired electrons of about 10.5 Å, are also obtained.

Selective Functionalization of Two-Component Magnetic Nanowires

Gold, nickel, and two-segment nickel−gold nanowires have been synthesized by electrodeposition into alumina templates. The nanowires have ∼350-nm diameters and were typically 12−22 μm in length. The nanowires were removed from the templates and were functionalized with organic molecules. Adsorption isotherms were constructed for the binding of 8,13-bis(1-hydroxyethyl)-3,7,12,17-tetramethyl-21H,23H-porphine-2,18-dipropionic acid to nickel nanowires in ethanol solution at 298 K. Adduct formation constants of 9 ± 5 × 106 M-1 and limiting surface coverages of 8 × 10-10 mol/cm2 were abstracted from the isotherms. Surface functionalization conditions were identified where thiols bind selectively to gold and carboxylic acids bind to nickel. Nanowires with free amino or thiol functional groups were reacted with activated dyes to yield amide, thiourea, and thioether covalent linkages that were quantified by fluorescence microscopy. These reactions with two-segment nickel−gold nanowires produced materials that emit...

Synergistic extraction and separation of mixture of lanthanum and neodymium by hollow fiber supported liquid membrane

Separation of lanthanum and neodymium by supported liquid membrane has been studied. Synergistic extraction and recovery of lanthanum and neodymium with thenoyltrifluoroacetone (HTTA) in benzene have been found by the addition of Trioctylamine (TOA). Results indicate that percentage of extraction is highly dependent on pH of feed solution, which the maximum value is 2.5. When TOA was added to HTTA, the percentage of extraction and recovery considerably increased due to synergism. Lanthanum can be extracted and recovered more than neodymium because of the adduct formation constant,β 1 . Theβ 1 values decreased with an increase in atomic number of lanthanide and showed a difference between lanthanum and neodymium. Percentage of extraction and recovery is enhanced when the HTTA concentration is increased, but its difference is larger when TOA concentration is increased. Finally, multi-column module of supported hollow fiber membrane was used and the percentage and difference of extraction and recovery was found to be more increased due to resident time.

Extraction of Ternary Beta‐Diketonates of Uranyl Ion Using Some Substituted Monoamides

The extraction behavior of uranyl ion from dilute nitric acid medium employing 1‐phenyl‐3‐methyl‐4‐benzoyl‐5‐pyrazolone (HPMBP)/2‐thenoyl‐ trifluoroacetone (HTTA) in toluene and their mixture with several structurally modified monoamides viz. di‐2‐ethylhexyl acetamide (D2EHAA), di‐2‐ethylhexyl propanamide (D2EHPrA), di‐2‐ethylhexyl isobutyramide (D2EHiBA), and di‐2‐ethylhexyl pivalamide (D2EHPvA) was investigated. The species of the type UO2(A)2 and UO2(A)2·B were extracted for the binary and ternary extraction systems respectively where A = PMBP/TTA and B = D2EHAA, D2EHPrA, D2EHiBA, or D2EHPvA. The extraction constants (log K ex) for the binary species UO2(A)2 were determined to be −2.32 ± 0.03 for HTTA and 0.21 ± 0.02 for HPMBP, which was an inverse function of their pK a value. The overall extraction constants (log K) for the ternary species UO2(A)2·B were determined as 4.70, 4.22, 4.00, 3.61, 2.65, 2.39, 2.32, and 1.76 for UO2(PMBP)2·D2EHAA, UO2(PMBP)2·D2EHPrA, UO2(PMBP)2·D2EHiBA, UO2(PMBP)2·D2EHPvA, UO2(TTA)2·D2EHAA, UO2 (TTA)2·D2EHPrA, UO2(TTA)2·D2EHiBA, and UO2(TTA)2·D2EHPvA, respectively. A linear correlation was observed between the basicity of the amide and the corresponding adduct's formation constants.

Steric Effect of Ortho Substituents of 1‐Phenyl‐3‐methyl‐4‐aroylpyrazol‐5‐ones on the Synergic Extraction of Scandium and Lanthanum with Tri‐n‐octylphosphine Oxide

The substituent effect of ortho‐substituted 4‐aroyl derivatives of 1‐phenyl‐3‐methylpyrazol‐5‐one (HA) on the adduct formation reaction between their scandium or lanthanum (M) chelates and a neutral ligand, tri‐n‐octylphosphine oxide (TOPO, L), in benzene was studied using a liquid–liquid distribution system. The 15 extraction constants and 30 adduct formation constants were obtained for the extraction systems of trivalent scandium and lanthanum ions using eight kinds of ortho‐substituted 4‐aroylpyrazol‐5‐ones. Obvious steric hindrance by the ortho substituents was observed in the extraction reactions, especially in adduct formation reactions. The correlation between the steric hindrance and the size of the central metal ions was discussed on the basis of equilibrium constants, ionic radii and van der Waals volumes. The stepwise formation constants of their adducts indicate that the steric hindrance mainly occurs in the first step of the adduct formation, MA3L, for lanthanum and in the second step of the adduct formation, MA3L2, for scandium. The factors that cause the steric hindrance were considered to be the bulkiness of the ortho substituents, the proximity of the neutral ligand to the metal chelate and the crowdedness of the ligands around the central metal ion.

Electronic spectral determination of the heterocyclic nitrogen base adducts of nickel(II)-di(2,6-dichlorophenyl)carbazonate

The ligand di(2,6-dichlorophenyl)carbazone (hereafter named as D2,6DClPC) and its nickel(II) complex have been synthesised and characterised by elemental analyses, magnetic moment and spectral measurements. The adduct formation constants of various heterocyclic nitrogen bases with nickel(II) chelates of D2,6DClPC have been determined in a monophase chloroform by electronic spectral study. Bathochromic and hypsochromic shifts were observed in the optical spectra in the visible range, due to adduct formation. The saturated monodentate bases such as pyrrolidine, piperidine, etc., form pentacoordinate adducts of 1:1 stoichiometry, whereas bidentate and unsaturated monodentate bases form hexacoordinated adducts with 1:1 metal–ligand stoichiometry. The experimental results are discussed in terms of steric properties, basicity and ring structures of the various heterocyclic bases.

Heterocyclic nitrogen base adducts of nickel(II)–di(2,4-dibromophenyl)carbazonate

The title complex was prepared and characterized by elemental and spectral analyses. The formation constants of various heterocyclic nitrogen base adducts with the NiII–di(2,4-dibromophenyl)carbazonate have been determined in a monophase by spectrophotometry at 25 ± 0.1 °C. The monodenatate and bidentate bases form penta- and hexa-coordinated adducts respectively with 1:1 stoichiometry for the metal chelate-base, whereas the unsaturated monodentate bases form hexa-coordinated adducts with 1:2 stoichiometry. The behaviour of saturated heterocyclic bases such as pyrrolidine, piperidine, hexamethyleneimine and morpholine towards the metal chelate has been studied, and the results are discussed in terms of steric hindrance, basicity and ring structure.

Water Molecules in Organic Solvents Involved in the Synergistic Extraction of Europium(III) with β -Diketones and Lewis Bases

Abstract To explain the difference in the magnitude of synergistic extraction among organic solvents, the water solubility in hexane, carbon tetrachloride, benzene, and chloroform was measured, and then the residual hydration number of europium(III) in the β-diketonato chelate and in their adducts with 1,10-phenanthroline as well as the adduct formation constants were determined. Using the data, the formation constants of the adduct according to a novel definition, in which the water concentration in the organic phase is treated as one variable, were determined. The constants are approximately constant irrespective of the organic solvents, although those according to the conventional definition are different among the solvents. It has been concluded that one of the most important factors controlling the magnitude of synergistic effects is the presence of water, such as the water content dissolved in organic solvents, and the hydration and dehydration of the relevant species, because water molecules compete with a Lewis base in complexation to the metal(III) chelates in the organic solvents.

Synergistic effect of tris(4-isopropyltropolonato)cobalt(III) on the extraction of lanthanoid(III) with 2-thenoyltrifluoroacetone.

Synergistic enhancement of the extraction of lanthanoid(III) (Ln) with 2-thenoyltrifluoroacetone (Htta) in benzene has been found by the addition of tris(4-isopropyltropolonato)cobalt(III) (Co(ipt)3). The synergistic effect of Co(ipt)3 was ascribed to the formation of a 1:1 adduct of Ln(tta)3 with Co(ipt)3, i.e., a binuclear complex, in the organic phase. The adduct formation constant (beta s,1) determined by the extraction equilibrium analysis was reasonably consistent with that determined by spectrophotometry. The beta s,1 values decreased with increase in the atomic number of Ln and showed a large difference between light and heavy Ln. Spectroscopic studies were performed to explain the difference in the beta s,1 values. Electronic absorption spectra showed that the change in the structure of Co(ipt)3 complexed with the light Ln chelate is larger than that with the heavy Ln. The IR spectra showed the displacement of the coordinated water molecules of the light Ln chelates with Co(ipt)3. On the other hand, the adduct formation of heavy Ln was caused by the hydrogen bonding between Co(ipt)3 and the coordinated water of the Ln chelate.

Equilibrium studies on complexation in water and solvent extraction of zinc(II) and cadmium(II) with benzo-18-crown-6

The formation constants ( K ML) in water of 1:1 complexes of benzo-18-crown-6 (B18C6) and 18-crown-6 (18C6) with Zn 2+ and Cd 2+, the sizes of which are much smaller than the ligand cavities, were determined at 25°C by conductometry. Compared with Cd 2+, the crown ethers form more stable complexes with Zn 2+ although the size of Zn 2+ is less suited for the cavities. B18C6 forms a more stable complex with each metal ion than 18C6. Moreover, the extraction equilibria of these metal ions (M 2+) with B18C6 (L) for the benzene/water system in the presence of picric acid (HA) were investigated at 25°C. The association between L and HA in benzene was examined for evaluating the intrinsic extraction equilibria of M 2+ with B18C6. The extracted species were found to be MLA 2 and ML 2A 2, and the overall extraction constants ( K ex,1 and K ex,2, respectively) were obtained. The values of K ex,1 for these metal ions are almost the same, but the K ex,2 is larger for Zn 2+ than for Cd 2+. The extraction selectivity was interpreted quantitatively by the constituent equilibrium constants, i.e. K ML, the ion-pair extraction constant of ML 2+ with A −, and the adduct formation constant of MLA 2 with L in benzene.

Influence of charge on adduct formation of [M(phen)3]z+ (M = Ru2+, Co3+, Si4+) with 1,10-phenanthroline in aqueous solution

Adduct formation of the inert complexes Ru(phen)32+, Co(phen)33+ and Si(phen)34+ with 1,10-phenanthroline (phen) has been studied by potentiometry and calorimetry in aqueous solution containing 0.1 mol dm−3 NaCl as an ionic medium at 298 K. Formation of a 1:1 adduct, in which planar 1,10-phenanthroline molecules are stacked, has been found for all the inert complexes and their formation constants, enthalpies and entropies were obtained. Adduct formation constants are hardly influenced by the ionic charges of the metal center. The enthalpy values are all negative, indicating that a specific π–π interaction operates between stacked 1,10-phenanthroline molecules. The corresponding entropy values are positive for Ru(phen)32+ and Co(phen)33+, while it is negative for Si(phen)34+. The positive entropies indicate that reduction of hydrophobic hydration upon stacking also plays a key role in the adduct formation. Both enthalpy and entropy values significantly decrease with increasing charge, and they strongly compensate to give similar formation constants. This implies that hydrophobic hydration around aromatic rings within the inert complexes is reduced to a greater extent with increasing charge, Ru(phen)32+<Co(phen)33+<Si(phen)34+. 1,10-Phenanthroline forms protonated H(phen)+ and H(phen)2+ species in an acidic solution, and 1,10-phenanthroline molecules are stacked in the latter. The enthalpy and entropy of formation of H(phen)2+ are significantly negative, also indicating that π–π interaction play an essential role in the formation of H(phen)2+. On the other hand, both the enthalpy and entropy of solution of 1,10-phenanthroline remain unchanged in solution containing NaCl over the range 0.05–1 mol dm−3, suggesting that hydrophobic hydration shells are restricted at the vicinity of 1,10-phenanthroline.

Effect of the Chain Length of Carboxylic Acids and Alcohols on the Extraction of Copper(II) with the Acids Using Alcohols as Solvents

Abstract The solvent extraction of copper(II) with aliphatic carboxylic acids (CH3(CH2)nCOOH : n = 2—7) in alcohols (CH3(CH2)nOH : n = 4—7) was carried out at 25 °C and an aqueous ionic strength of 0.1 mol dm-3 (NaClO4). Each extraction equilibrium for these systems was determined in detail by a slope analysis and a curve-fitting method. In all of the extraction systems, except for butanoic acid ones, copper(II) carboxylates were found to be extracted as monomeric and dimeric species: CuA2, Cu2A4, and Cu2A4(HA)2. The dimerization and the adduct formation constants of copper(II) carboxylates in the organic phase were estimated. The dimerization and the adduct formation constants in the organic phase were found to be dependent on the chain length of the acids and alcohols, although the extraction constant of CuA2 were found to be independent of their chain length.

Extraction of zirconium(IV) from hydrochloric acid solutions by tri-octylamine and neutral donors

Solvent extraction of Zr(IV) from aqueous HCl solutions by mixtures of TOA and different organophosphorous bases in carbontetrachloride solvent have been found to be always higher than that by any single extractant. Synergism has been observed in the range of 2.4–9.6M HCl. Although the species extracted with neutral donor alone seems to be ZrCl4·TOPO etc, with a mixture of extractants, however, the extracted species appears to be Q2ZrCl6·TOPO where Q is R3NH. The extraction has also been found to increase with increase in the concentration of amines and neutral donors. Enhancement of extraction has been explained by the formation of a complex adduct in organic phase. Synergistic coefficients and apparent formation constants of the complex adducts have also been calculated.

Recovery of lactic acid from aqueous model solutions and fermentation broths

The aim of the investigations was to recover lactic acid from fermentation broths in the presence of citric acid and acetic acid. For this purpose the reactive extraction of lactic acid was investigated from model media and fermentation broths with various carrier/modifier/solvent combinations. Experiments were performed using a secondary amine (Hoe F 2562), a tertiary amine (Hostarex A 327) as well as a phosphine oxide as carriers and butylacetate and kerosene as solvents. The effects of the type and concentration of the carrier and modifier and the temperature on the equilibrium distribution were evaluated. Relationships for the equilibrium distribution were developed and the calculated data were compared with the measured data. In the case of non-polar kerosene solvent, good agreement was found between the calculated and measured values. With the polar solvent, butylacetate, the physical extraction also had to be taken into account. By means of the developed relationships the adduct formation constants were determined for the extraction systems investigated. In order to investigate the selectivity of the carriers, tests were also performed to separate lactic acid from acetic and citric acid in model media and in fermentation broths. The separation of the acids is only possible in a multistage process. In situ extraction of lactic acid was not possible because of the toxicity of the carriers and modifiers.

Synergistic extraction of cobalt(II) by tri-octylamine and neutral donors

This work reports a study on the synergistic extraction of cobalt(II), spiked with60Co from hydrochloric acid solutions by mixtures of trioctylamine (TOA) and neutral organophosphorous donors into carbon tetrachloride. Synergistic coefficients and adduct formation constants have been evaluated from distribution measurements and correlated with the basic character of donors.

SYNERGISTIC EXTRACTION EQUILIBRIUM OF LANTHANOIDS(III) WITH 2-THENOYLTRIFLUOROACETONE AND NITROGEN-CONTAINING BIDENTATE LIGANDS, ETHYLENEDIAMCME DERIVATIVES

ABSTRACT The synergistic extraction of lanthanoids(III), Ln(III), i e., La, Sm, Tb, Tm and Lu, using 2-thenoyltrifluoroacetone (Htta) and nitrogen-containing neutral bidentate ligands (S), i.e., three ethylenedi-amine derivatives, such as N,N'-dimethylethylenediamine (dmen), N,N'-diethylethylenediamine (deen) and cis-l,2-cyclohexanediamine (chda), was studied in the benzene and aqueous system. The synergistic enhancement in these extraction systems was mainly attributed to the formation of an adduct, Ln(tta)3S, in the benzene phase. The variation of the adduct formation constants (βs,l) was discussed with the basicity of ligands and structure hindrance around the metal ion.

Photoluminescence quenching of quantum‐confined cadmium sulfide clusters by norbornadiene derivatives

AbstractInfluence of norbornadiene and its derivatives on the photoluminescence (PL) of quantum‐confined cadmium sulfide clusters (Q‐CdS) prepared in reverse micelles wm investigated. It was found that norbornadiene‐2,3‐dicarboxylic acid (3) and its monopotassium salt (4) quenched PL intensity by 77% and 62%, respectively, whereas its dipotassium salt (a), norbornadiene (1) and norbornadiene‐2,3‐dimethylcarboxylate (2) had no effect on PL intensity. The formation constants for adducts formed between defect sites at the surface of Q‐CdS clusters and 3 or 4 were also determined. PL quenching effect was attributed to the presence of ionizable proton which is considered to be able to trap photogenerated electrons and remove them from possible decay process. Measurements of the PL decay by single photon counting technique also supported these steady‐state observations.

Polymerization and Adduct Formation of Some Lanthanide(III) Decanoates in the Extraction of Lanthanides(III) with Decanoic Acid Using 1-Octanol and Benzene as a Solvent.

The solvent extraction of lanthanum(III), cerium(III), neodymium(III), samarium(III), gadolinium(III), dysprosium(III), erbium(III) and ytterbium(III) with decanoic acid in 1-octanol and benzene was carried out at 25°C and at an aqueous ionic strength of 0.1 mol dm-3 (NaNO3). In extraction systems using 1-octanol as a solvent, all of the lanthanides were found to be extracted as two kinds of monomeric decanoates; in those using benzene, the monomeric, dimeric and tetrameric lanthanide(III) decanoates were proven to be responsible for the extraction, except for gadolinium(III), whose extracted species were the monomeric and dimeric species. The dimerization, tetramerization and adduct formation constants of lanthanide(III) decanoates in the organic phase were estimated. A so-called “gadolinium break” was observed for the polymerization constants of lanthanide(III) decanoates.

Modulation of Cadmium Selenide Photoluminescence Intensity by Adsorption of Silapentanes and Chlorinated Silanes

The band gap photoluminescence (PL) intensity of n-CdSe single crystals is reversibly enhanced by adsorption of seven of the nine silapentane isomers, SiC4H12, from the gas phase onto the (0001) surface of this substrate; only tetramethylsilane and tert-butylsilane elicit no PL response. The adsorbate-induced increase in PL intensity is consistent with the species acting as Lewis bases toward the surface. Quantitatively, the PL changes can be fit by a dead-layer model, allowing estimation of the adduct-induced reduction in depletion width as ranging from ∼100 to 500 Å. Adduct formation constants, estimated from fits of the concentration-dependent PL changes to the Langmuir adsorption isotherm model, range from ∼10 to 103 atm-1 and are ∼102 atm-1 for most of the isomers. Two chlorinated silanes, H2SiCl2 and HSiCl3, yielded reversible PL quenching after an initial conditioning period, although the magnitude of the quenching was not in accord with the dead-layer model. Possible surface binding modes are discussed for these silanes, as are implications for their on-line detection as precursor molecules for growth of semiconductors by chemical vapor deposition (CVD).

Synergic extraction of uranium(VI) by combination of tri-iso-octylamine and neutral donors

Synergistic effect of neutral donors like tri-butyl phosphate (TBP), triphenyl phosphine oxide (TPPO), trioctyl phosphine oxide (TOPO), and dimethyl sulphoxide (DMSO) on the extraction of uranium(VI) by tri-isooctyl amine into CCl4 is reported. Synergistic coefficients and adduct formation constants are calculated from distribution data and correlated with relative donor abilities of added bases.