Adduct Formation Constants Research Articles

SYNERGISTIC EXTRACTION OF SILVER FROM NITRIC ACID MEDIUM WITH DITHIZONE IN THE PRESENCE OF A SECONDARY AMINE- AMBERLITE LA-2 USING 110mAg-RADIOISOTOPE

Synergistic extraction of silver has been investigated in the presence of two different kinds of extractants, one of which is a chelating ligand, dithizone and the other is a long-chain secondary amine amberlite LA-2 at pH 3.0 using a radiotracer technique. The apparent formation constant, overall equilibrium constant and adduct formation constants were calculated from distribution coefficients. Interestingly, it was observed that the adduct formation constant is too high when the ligand concentration is increased by keeping the amine concentration fixed at 0.044 M compared to that obtained when the ligand concentration is kept fixed at 8.74×10-4 M.

Halide-Adducts of OsO4. Structure and Reactivity in Alcohol-Oxidation

Abstract Interaction of osmium tetroxide (OsO4) with a series of halide ions (X− = I−, Br−, Cl−, and F−) is examined. Stable 1:1 adducts, [OsO4(X)]− (1X), are formed in the case of Br−, Cl−, and F−, whereas redox reaction takes place with I− to give [OsVIIO4]− and I•. The adduct formation constant (KfX) increases as the basicity of the halide ion increases (Br− < Cl− < F−). Upon the adduct formation, the symmetric (ν(Os=O)sym) and asymmetric (ν(Os=O)asym) Os=O stretching vibration energies are lowered as compared with those of OsO4. The X-ray crystallographic analyses of the halide adducts indicate that the structural distortion of the osmium center from tetrahedron to trigonal bipyramid becomes larger as the KfX value becomes larger. 1F shows much higher reactivity compared with 1Br and 1Cl in the oxidation of benzyl alcohol to benzaldehyde, even though 1F has a lower reduction potential compared to 1Br and 1Cl. Mechanistic details of the alcohol oxidation reaction are evaluated by kinetic studies including Hammett analysis and kinetic deuterium isotope effect as well as by DFT calculations.

Enantiomeric NMR signal separation mechanism and prediction of separation behavior for a praseodymium (III) complex with (S,S)-ethylenediamine-N,N-disuccinate.

Because choice of chiral nuclear magnetic resonance (NMR) shift reagents and concentration conditions have been made empirically by trials and errors for chiral NMR analyses, the prediction of NMR signal separation behavior is an urgent issue. In this study, the separation of enantiomeric and enantiotopic 1 H and 13 C NMR signals for α-amino acids and tartaric acid was performed by using the praseodymium(III) complex with (S,S)-ethylenediamine-N,N'-disuccinate ((S,S)-EDDS). All the present D-amino acids exhibited larger downfield shift of their α-protons and α-carbons compared with those for the corresponding L-amino acids in common. This regularity is applicable to absolute configurational assignment and determination of optical purity of amino acids. The chemical shifts of β-protons of d- and l-alanine fully bound with the Pr(III) ((S,S)-EDDS) complex (δb s) and the adduct formation constants of both enantiomers (Ks) were obtained by dependences of the observed downfield shifts of the β-protons on the total concentrations of the respective enantiomers in the presence of a constant concentration of the Pr(III) complex. The difference in the K values was found to be predominant determining factor for the enantiomeric signal separation. The chemical shifts of both enantiomers (δs) and the enantiomeric signal separations (Δδs) under given conditions could be calculated from the δb and K values. Furthermore, prediction of the signal separation behavior was enabled by using the calculated δ values and the signal broadening obtained by dependences of the half-height widths of the observed signals on the bound/free substrate concentration ratios for the respective enantiomers.

Spectrophotometric Study on Adduct Formation Constants of Nickel(II) Chelates of Di(O-Tolylcarbazone) and Di(O-Tolylthiocarbazone) with Nitrogen Bases Using Job's Method of Continuous Variation Method

Spectrophotometric Study on Adduct Formation Constants of Nickel(II) Chelates of Di(O-Tolylcarbazone) and Di(O-Tolylthiocarbazone) with Nitrogen Bases Using Job's Method of Continuous Variation Method

Enantiomeric NMR signal separation behavior and mechanism of samarium(III) and neodymium(III) complexes with (S,S)-ethylenediamine-N,N'-disuccinate.

Enantiomeric 1 H and 13 C NMR signal separation behaviors of various α-amino acids and DL-tartarate were investigated by using the samarium(III) and neodymium(III) complexes with (S,S)-ethylenediamine-N,N'-disuccinate as chiral shift reagents. A relatively smaller concentration ratio of the lanthanide(III) complex to substrates was suitable for the neodymium(III) complex compared with the samarium(III) one, striking a balance between relatively greater signal separation and broadening. To clarify the difference in the signal separation behavior, the chemical shifts of β-protons for fully bound D- and L-alanine (δb (D) and δb (L)) and their adduct formation constants (Ks) were obtained for both metal complexes. Preference for D-alanine was similarly observed for both complexes, while it was revealed that the difference between the δb (D) and δb (L) values is the significant factor to determine the enantiomeric signal separation. The neodymium(III) and samarium(III) complexes can be used complementarily for higher and smaller concentration ranges of substrates, respectively, because the neodymium(III) complex gives the larger difference between the δb (D) and δb (L) values with greater signal broadening compared to the samarium(III) complex.

Aminoalkanoic Acids as Alternatives to Mercaptoalkanoic Acids for the Linker-Assisted Attachment of Quantum Dots to TiO2.

Linear aminoalkanoic acids (AAAs) and mercaptoalkanoic acids (MAAs) were characterized as bifunctional ligands to tether CdSe QDs to nanocrystalline TiO2 thin films and to mediate excited-state electron transfer (ET) from the QDs to TiO2 nanoparticles. The adsorption of 12-aminododecanoic acid (ADA) and 12-mercaptododecanoic acid (ADA) to TiO2 followed the Langmuir adsorption isotherm. Surface adduct formation constants (Kad) were ∼10(4) M(-1); saturation amounts of the ligands per projected surface area of TiO2 (Γ0) were ∼10(-7) mol cm(-2). Both Kad and Γ0 differed by 20% or less for the two linkers. CdSe QDs adhered to ADA- and MDA-functionalized TiO2 films; data were well modeled by the Langmuir adsorption isotherm and Langmuir kinetics. For ADA- and MDA-mediated assembly values of Kad were (1.8 ± 0.4) × 10(6) and (2.4 ± 0.4) × 10(6) M(-1), values of Γ0 were (1.6 ± 0.3) × 10(-9) and (1.2 ± 0.1) × 10(-9) mol cm(-2), and rate constants were (14 ± 5) and (60 ± 20) M(-1) s(-1), respectively. Thus, the thermodynamics and kinetics of linker-assisted assembly were slightly more favorable for MDA than for ADA. Steady-state and time-resolved emission spectroscopy revealed that electrons were transferred from both band-edge and surface states of CdSe QDs to TiO2 with rate constants (ket) of ∼10(7) s(-1). ET was approximately twice as fast through thiol-bearing linker 4-mercaptobutyric acid (MBA) as through amine-bearing linker 4-aminobutyric acid (ABA). Photoexcited QDs transferred holes to adsorbed MBA. In contrast, ABA did not scavenge photogenerated holes from CdSe QDs, which maximized the separation of charges following ET. Additionally, ABA shifted electron-trapping surface states to higher energies, minimizing the loss of potential energy of electrons prior to ET. These trade-offs involving the kinetics and thermodynamics of linker-assisted assembly; the driving force, rate constant, and efficiency of ET; and the extent of photoinduced charge separation can inform the selection bifunctional ligands to tether QDs to surfaces.

Influence of Dispersion Forces and Ordering on the Compositions of Mixed Monolayers of Alkanoic Acids on Nanocrystalline TiO2 Films

Lateral dispersion forces induce the ordering of n-alkanoic acids on nanocrystalline TiO2 films and cause the compositions of mixed monolayers to change. The equilibrium formation of single-component monolayers of n-alkanoic acids and 6-bromohexanoic acid (Br6A) on TiO2 was well-modeled by the Langmuir adsorption isotherm. Surface adduct formation constants were 10(3)-10(4) M(-1), and saturation amounts of adsorbates per projected surface area of TiO2 were on the order of 10(-7) mol cm(-2). The adsorption of n-heneicosanoic acid (21A) followed Langmuir kinetics, whereas the net rates of adsorption of shorter n-alkanoic acids and Br6A were slower than predicted by simple Langmuir kinetics, suggesting that desorption was non-negligible. At high surface coverages, n-alkanoic acids with 14 or more methylene groups formed ordered, crystalline monolayers, as evidenced by shifts of asymmetric and symmetric CH2 stretching bands in IR spectra. The extent of ordering was similar to that of self-assembled monolayers of alkanethiols on gold. The formation of ordered monolayers was well-modeled by an idealized mechanism, in which adsorption and desorption followed Langmuir kinetics and ordering was first-order with respect to the fractional surface coverage of adsorbates. Dispersion forces and ordering affected the compositions of mixed monolayers of 21A and Br6A on TiO2 films that remained in contact with mixed coadsorption solutions. When the fractional surface coverage of 21A was sufficiently high to induce ordering, it displaced Br6A from TiO2. We propose that these compositional changes were driven by the stabilization of 21A via cohesive lateral dispersion forces. Our results reveal that mixed monolayers on nanocrystalline TiO2 films are dynamic and that noncovalent intermolecular interactions can profoundly influence their compositions and properties.

Adduct Formation Constants in the Synergistic Solvent Extraction of Several Lanthanoids with Two Chelating Extractants: β-Diketone and Bidentate Nitrogen Bases

The synergistic solvent extraction of La(III), Nd(III), Eu(III), Ho(III), and Lu(III) with a chelating extractant 4-benzoyl-3-phenyl-5-isoxazolone (HPBI) or 2-thenoyltrifluoroacetone (HTTA) and neutral bidentate heterocyclic amines, such as 1,10-phenanthroline (phen) or 2,2′-bipyridine (bipy), in CHCl3 was investigated. Synergism was found to be due to formation of the ternary complex, Ln(PBI)3·S or Ln(TTA)3·S, in the organic phase, where S denotes a neutral ligand. On the basis of the experimental data, the values of the equilibrium constants were calculated. The parameters of the extraction process were determined. The influence of the synergistic agent on the extraction process is discussed. The synergistic and separation factors were determined.

Steric Crowding Effect of 1,3-Diketonates on the Structures and the Solution Behaviors of Nickel(II) Mixed-Ligand Complexes

Abstract Seven nickel(II) mixed-ligand complexes were synthesized: Ni(dike)(diam)X, where dike is a 1,3-diketonate such as 3,5-heptanedionate (dedk) or 2,6-dimethyl-3,5-heptanedionate (dmhd), diam is an N-alkylated ethylenediamine such as N,N,N′,N′-tetramethylethylenediamine (tmen) or 1,2-dipiperidinoethane (dipe), and X is BPh4− or NO3−. The crystal structures were analyzed: each nitrate complex has a six-coordinated octahedral structure with a bidentate-coordinated nitrate, and each tetraphenylborate complex has a four-coordinated square-planar structure. The ligand field strength of [Ni(dike)(diam)]BPh4 in the solid state increases in the order: [Ni(dmhd)(dipe)]BPh4 < [Ni(dedk)(dipe)]BPh4 < [Ni(dmhd)(tmen)]BPh4 = [Ni(dedk)(tmen)]BPh4. In solution, the change of the color depending on the donor/acceptor ability of the solvent, i.e., solvatochromism was observed. When dimethyl sulfoxide was added to a solution of [Ni(dike)(diam)]BPh4 in inert 1,2-dichloroethane, the adduct formation constants are in the order: [Ni(dmhd)(dipe)]BPh4 < [Ni(dedk)(dipe)]BPh4 << [Ni(dmhd)(tmen)]BPh4 = [Ni(dedk)(tmen)]BPh4, reflecting the difference in steric hindrance of the ligands rather than the difference in ligand field strength. The steric crowding effect of 1,3-diketonates was observed in the solid state and solution when bulky dipe is used as diamine.

Adduct Formation of Dichloridodioxidomolybdenum(VI) and Methyltrioxidorhenium(VII) with a Series of Bidentate Nitrogen Donor Ligands

AbstractThe stability of a variety of bidentate N‐base adducts of MoO2Cl2 and (CH3)ReO3 (MTO) was investigated in thf and CH2Cl2 as solvents. The formation constants were determined from the spectrophotometric data based on 1:1 adduct formation. The adduct formation constants for [MoO2Cl2L2] (L2 = bidentate nitrogen ligand) are 104–106 times higher than those for [(CH3)ReO3L2] with the same ligands under the same conditions. The adduct stability of both systems is very sensitive to the electronic nature of the ligands and increases with their donor ability. Hammett correlations of the formation constants against σ give relatively large negative values for the reaction constants (ρRe = –5.9, ρMo = –6.6). The stability is also governed by steric and strain factors. Thus, sterically hindered 6,6′‐disubstituted‐2,2′‐bipyridines do not form adducts with MTO, and only 6,6′‐dimethyl‐ and 6,6′‐diphenyl‐2,2′‐bipyridines form adducts with MoO2Cl2. However, these adducts are much less stable than other methyl derivatives of 2,2′‐bipridine adducts. The steric strain between the two methyl groups in 3,3‐dimethyl‐2,2′‐bipyridine influences the bipyridine planarity upon complexation and reduces the adduct stability. The thermodynamic parameters (enthalpy and entropy) were determined from temperature‐dependence studies. The adduct stability is mainly due to the strongly exothermic binding of the nitrogen‐bidentate ligand. The entropy change is small and has little effect on adduct stability.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Singlet oxygen chemistry in water. 2. Photoexcited sensitizer quenching by O2 at the water-porous glass interface.

Insight into the O2 quenching mechanism of a photosensitizer (static or dynamic) would be useful for the design of heterogeneous systems to control the mode of generation of 1O2 in water. Here, we describe the use of a photosensitizer, meso-tetra(N-methyl-4-pyridyl)porphine (1), which was adsorbed onto porous Vycor glass (PVG). A maximum loading of 1.1 x 10(-6) mol 1 per g PVG was achieved. Less than 1% of the PVG surface was covered with photosensitizer 1, and the penetration of 1 reaches a depth of 0.32 mm along all faces of the glass. Time-resolved measurements showed that the lifetime of triplet 1*-ads was 57 microseconds in water. Triplet O2 quenched the transient absorption of triplet 1*-ads; for samples containing 0.9 x 10(-6)-0.9 x 10(-8) mol 1 adsorbed per g PVG, the Stern-Volmer constant, K(D), ranged from 23,700 to 32,100 M(-1). The adduct formation constant, Ks, ranged from 1310 to 510 M(-1). The amplitude of the absorption at 470 nm decreased slightly (by about 0.1) with increased O2 concentrations. Thus, the quenching behavior of triplet 1*-ads by O2 was proposed to be strongly dependent on dynamic quenching. Only approximately 10% of the quenching was attributed to the static quenching mechanism. The quenching of triplet 1*-ads was similar to that observed for photosensitizers in homogeneous solution which are often quenched dynamically by O2.

Temporal Evolution of the Composition of Mixed Monolayers on TiO2 Surfaces: Evidence for a Dimerization-Induced Chelate Effect

Mixed monolayers of octanoic acid (OA) and 16-mercaptohexadecanoic acid (MHDA) were adsorbed to nanocrystalline TiO(2) films from mixed solutions in tetrahydrofuran. For a range of solution compositions, the mole fraction of MHDA within the mixed monolayers (chi (MHDA,surf)) exceeded that of the coadsorption solution. In addition, chi (MHDA,surf) increased with time, while the sum of the surface coverages of MHDA and OA remained constant. To account for these effects, we propose a mechanism involving disulfide formation between the terminal thiol groups of surface-adsorbed MHDA molecules. Disulfide formation leads to an increase in the surface adduct formation constant ( K(ad)) of dimeric MHDA, causing the gradual displacement of OA from the surface. The mechanism is supported by spectroscopic evidence and desorption kinetics. These are the first examples of mixed monolayers that undergo time-dependent compositional changes as a result of covalent bond formation between surfactants. Our findings illustrate that dimerization and other intermolecular interactions between surfactants may dramatically influence the composition and terminal functionalization of a wide range of mixed monolayer systems.

Synergistic Extraction and Solution Structures of Ternary Complexes of Lanthanoids with 2-Thenoyltrifluoroacetone and Linear Poly(oxyethylene) in 1,2-Dichloroethane

Abstract Synergistic extraction of thenoyltrifluoroacetone (tta) complexes of 14 trivalent lanthanoids (Ln3+) into 1,2-dichloroethane with linear poly(oxyethylene) compounds (POE) was investigated at 25.0 °C, where the linear POE [HO–(CH2CH2O–)nR] are monodispersed DEOn (R=C12H25; n=4, 6, and 8) and polydispersed TX-100 (R = octylphenyl; nave=9.6). Equilibrium studies showed a 1:1 adduct complex with POE compound, Ln(tta)3·(POE), formed in the organic phase. The adduct formation constant, βadd, increased as the ionic radius of lanthanoid increased for any kind of POE. The very high stability of the 18-crown-6 adducts is explained by the incorporation of Ln3+ ion into the cavity of the crown ether. Adduct formation constants of the POE having short ethylene oxide (EO) chain, such as DEO4 and 12-crown-4, were fairly small; thus, it was estimated that those coordinate to the metal ion as a bidentate or tridentate ligand. Relatively large values of βadd of long chain POE (n≥6) indicate the indirect outer-sphere interaction of the uncoordinated residual EO units with the metal ion. Adduct formation with linear POEs significantly reduced the difference in extraction constants among the lanthanoid ions. Therefore, this synergistic extraction system is advantageous for the separation of lanthanoid ions as a group from other metal ions.

Spectrophotometric Study of Nitrogen Base Adducts of Nickel(II)‐4‐methyl‐8–quinolinate

Adduct formation constants have been determined by spectrophotometric study of a few typical bases with nickel(II) chelate of 4‐methyl‐8‐quinolinol in chloroform. Bathochromic and hypsochromic shifts were observed in the visible range due to the adduct formation. Monobasic bases like pyridine, methyl substituted anilines and such other bases exhibit 1: 2 stoichiometry giving hexa – coordinated adductds . The dibasic bases such as 1,10‐phenanthroline and 2,9‐ neocuproine exhibit 1 : 1 stoichiometry giving hexacoordinated adducts . The experimental results are discussed in terms of the basicity and steric effects of the various bases.

Adsorption of CdSe Nanoparticles to Thiolated TiO2 Surfaces: Influence of Intralayer Disulfide Formation on CdSe Surface Coverage

Mixed monolayers of hexadecanoic acid (HDA) and 16-mercaptohexadecanoic acid (MHDA) were adsorbed to nanocrystalline TiO2 films, and CdSe nanoparticles were attached to the mixed monolayer functionalized surfaces. IR absorption spectroscopy was used to characterize the equilibrium binding of HDA and MHDA to TiO2. Surface adduct formation constants (Kad) of (4+/-2)x10(3) M(-1) and (6+/-4)x10(3) M(-1) were measured for HDA and MHDA, respectively. CdSe nanoparticles were adsorbed to the terminal thiol groups of MHDA. The surface coverage of CdSe was greater on mixed monolayers, consisting of approximately 12% MHDA and 88% HDA, than on pure MHDA monolayers. A mechanism is proposed wherein intralayer disulfide formation between MHDA thiol groups causes decreased reactivity toward CdSe nanoparticles. Disulfide formation is less significant at low fractional surface coverages of MHDA. The mechanism is supported by an increase of CdSe adsorption upon chemical reduction of surface disulfides to thiols. Our findings highlight the effect of intermolecular interactions on the affinity of nanoparticles for monolayer-functionalized surfaces.

Anionic ring‐opening polymerization of small phosphorus heterocycles and their borane adducts: An ab initio investigation

AbstractThe kinetics and thermodynamics of anionic ring‐opening reactions of phosphiranes, phosphetanes, and phospholanes and their borane adducts have been studied by high‐level ab initio procedures. For the free heterocycles, model propagation reactions involving nucleophilic attack by Me2P− at the ring α‐carbon were found to be feasible for the three‐ and four‐membered rings, but not for the five‐membered ring. For the borane adducts, nucleophilic attack by Me2(BH3)P− was only facile for the three‐membered ring, despite an increased thermodynamic tendency toward ring opening for the borane adducts of both the three‐ and four‐membered rings. The formation constants of the borane adducts of methylphosphirane and methylphosphetane were K = 2.6 × 1013 L mol−1 and K = 1.2 × 1020 L mol−1, respectively. A Marcus analysis of the ring‐opening reactions of methylphosphirane, methylphosphetane, and their borane adducts showed that the release of ring strain and an “additional factor'' contribute to rate enhancement compared with their strain‐free analogues. The additional factor was larger for the three‐membered rings than for the four‐membered rings and was larger in the free heterocycles than in their borane adducts. The additional factor is complex in origin and appears to reflect an increase in the separation between the bonding and antibonding orbitals of the breaking bond on going from the three‐membered rings to the four‐membered rings, and on going from the free heterocycles to the borane adducts. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:118–128, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20323

Photocatalytic Patterning of Monolayers for the Site-Selective Deposition of Quantum Dots onto TiO2Surfaces

A novel photochemical mechanism is reported for the site-selective deposition of quantum dots onto nanocrystalline TiO2 films. The patterning mechanism involves the combination of surfactant-mediated self-assembly and monolayer photolithography. In the self-assembly process, CdS and CdSe quantum dots were attached to TiO2 surfaces through bifunctional mercaptoalkanoic acid (MAA) linkers. MAAs were adsorbed to the TiO2 surface as the deprotonated carboxylates, primarily through monodentate coordination to Ti4+ sites. CdSe quantum dots were bound to the terminal thiol groups of surface-adsorbed MAAs, with a surface adduct formation constant, Kad, of (2.1 +/- 0.7) x 104 M-1. The color and optical density of the quantum dot-functionalized TiO2 films were tunable. Monolayer photopatterning involved the TiO2-catalyzed oxidative degradation of surface-adsorbed mercaptohexadecanoic acid (MHDA). A mechanism is proposed wherein MHDA degradation occurs through both oxidative decarboxylation and the formation of interchain disulfides. These MHDA photodegradation processes regulate the extent to which CdSe quantum dots adsorb onto the TiO2 surface. Illumination through a photomask yielded optically patterned, quantum dot-functionalized TiO2 films that were characterized by scanning electron microscopy and energy-dispersive X-ray analysis.

Controlling Reduction Potentials of Semiconductor-Supported Molecular Catalysts for Environmental Remediation of Organohalide Pollutants

The spectroscopic and redox properties of iron(lll) protoporphyrin chloride (hemin) and cobalt(lll) meso-tetra-(4-carboxyphenyl) porphyrin chloride (CoTCP) were quantified in fluid solution and when anchored to mesoporous nanocrystalline TiO2 thin films. Surface binding was well-described by the Langmuir adsorption isotherm model from which adduct formation constants of 10(5) M(-1) and limiting surface coverages of 10(-8) mol/cm2 were abstracted. In acetonitrile and dimethyl sulfoxide electrolytes, TiO2 binding was found to induce a substantial negative shift in the M(III/II) formal reduction potentials. In DMSO electrolyte, the Co(III/II) and Fe(III/II) potentials were -559 and -727 mV versus ferrocenium/ferrocene (Fc+/Fc) and shifted to -782 and -1063 mV, respectively, after surface binding. The Bronsted acidity of the TiO2 surface was found to correlate with the measured reduction potentials. For TiO2 pretreated with aqueous solutions from pH 4-9, the Co(III/II) potential showed a -66 mV/pH unit change, while the Fe(llI/II) potential of hemin changed by -40 mV/pH from pH 1 to 14. Spectroelectrochemical data gave isosbestic, reversible spectral changes in the visible region assigned to M(III/II) redox chemistry with lambda(iso) = 410, 460, 530, 545, 568, and 593 nm for CoTCP/TiO2 and lambda(iso) = 408, 441, 500, 576, and 643 nm for hemin/TiO2. In aqueous solution, the CoTCP reduction potentials were also found to be pH dependent upon surface binding, with CoTCP = -583 mV and CoTCP/TiO2 = -685 mV versus Fc+/Fc at pH 6. For CoTCP/TiO2, the aqueous pH dependence of the potentials was -52 mV/pH. The rate constant for heme/TiO2 reduction of CCl4 increased from 3.9 +/- 0.7 x 10(-4) to 2.0 +/- 0.1 x 10(-3) s(-1) when the pH was raised from 4 to 8.

Synergistic extraction of cobalt (II) by beta hydroxy naphthaldoxime and neutral donors.

Liquid - liquid extraction of Cobalt (II) from aqueous hydrochloric acid medium by the use of oxime derivative of beta-hydroxy naphthaldehyde in o-xylene medium is being reported. The ligand was synthesized and characterized in our laboratory. The typical pH range of extraction of Co (II) by the ligand - donor combination was seen to be between 8 - 9. The effect of different donors like dimethyl sulphoxide (DMSO), trioctyl phosphine oxide (TOPO) and bis(2-ethylhexyl) phosphonate and the effect of various diluents on the extraction of Co(II) by the present method were studied in detail. The binary adduct formation constant (log kex) in the organic phase was found to be 3.182. The overall equilibrium constant (log K) for the ternary species [Co(A)(DMSO)(Cl)], [Co(A)(TOPO)(Cl)] and [Co(A)(phosphonate)(Cl)] were estimated to be 6.42, 6.22 and 6.25 respectively. The trend in equilibrium constants were in accordance with their basic character, i.e., (DMSO > or = TOPO approximately/= phosphonate). The results were extrapolated in the determination of Cobalt in pharmaceutical drugs and cobalt bearing ore samples.

Synergistic effect of neutral donors on the extraction of zirconium(IV) by salicylaldoxime in dichloromethane

Liquid–liquid extraction of zirconium(IV) was investigated from dilute hydrochloric acid medium by salicyaldoxime (HA) in dichloromethane. The metal was spiked with 95 Zr and analyzed by its radioactivity. The effects of different donors, like trioctyl phosphine oxide (TOPO), triphenyl phosphine oxide (TPPO), tributyl phosphine oxide (TBPO), tributyl phosphate (TBP), trioctyl amine (TOA) and Amberlite LA-2 were studied. The adduct formation constants for both binary species (metal–ligand) and ternary species (metal–ligand–donor) were also calculated form the distribution data.