Salts In Aqueous Media Research Articles

Stabilization of tetrameric metavanadate ion by tris(1,10-phenanthroline)cobalt(III): synthesis, spectroscopic, and X-ray structural study of [Co(phen)3]3(V4O12)2Cl · 27H2O

A new complex salt of composition [Co(phen)3]3(V4O12)2Cl ⋅ 27H2O (phen = 1,10-phenanthroline and [V4O12]4− = tetrameric metavanadate, dodecaoxotetravanadate ion) was synthesized by the reaction of appropriate salts in aqueous medium. The complex salt has been characterized by elemental analyses, thermogravimetric analysis, cyclic voltammetry, FT-IR, and UV-Vis spectroscopies, solubility product and conductance measurements. Single crystal X-ray structure determination revealed ionic structure consisting of three complex cations, [Co(phen)3]3+, two [V4O12]4− anions, one chloride and 27 lattice water molecules. Detailed structural and spectroscopic analyses of [Co(phen)3]3(V4O12)2Cl ⋅ 27H2O showed that the large anion is stabilized by large cationic metal complex as there is preferred shape compatibility that leads to a large number of lattice-stabilizing non-covalent interactions.

Kinetic aspects of flocculation of bentonite clay in the presence of anionic and cationic acrylamide copolymers

The flocculation kinetics in aqueous-salt medium in the presence of anionic and cationic high-molecular-weight random acrylamide copolymers was studied in the hindered sedimentation mode, with a suspension of bentonite clay as example. The influence exerted on the flocculation parameters by the concentration and order of addition of ionic acrylamide copolymers taken in various combinations was analyzed.

Host−Guest Complexation: A Convenient Route for the Electroreduction of Diazonium Salts in Aqueous Media and the Formation of Composite Materials

Electrochemical grafting of a water-insoluble diazonium salt in aqueous media onto an electrode surface was achieved by host-guest complexation. 1-(2-Bisthienyl)-4-aminobenzene (BTAB) was solubilized in a water/beta-cyclodextrin solution (beta-CD). The corresponding diazonium salt was generated in situ then electroreduced. This process leads to the attachment of bithiophene or short oligothiophene groups to the electrode surface. The modified surfaces were analyzed by cyclic voltammetry (CV), scanning electrochemical microscopy (SECM), X-ray photoelectron spectroscopy (XPS), infrared reflection absorption spectroscopy (IRRAS), and atomic force microscopy (AFM). The electrochemical investigations show that the water-based modified surface is similar to one generated in acetonitrile without beta-CD. Thus, the attached organic layer behaves like an electrochemical switch (above some threshold potential, a soluble external probe is oxidized, but the oxidized form cannot be reduced). The modified surfaces consist of grafted bisthienylbenzene (BTB) and cyclodextrins that can be removed from the surface. This procedure may be considered as a new means of creating a surface made of submicrometric holes in an organic semiconducting layer.

Computational modeling and molecular imprinting for the development of acrylic polymers with high affinity for bile salts

This work has focused on the rational development of polymers capable of acting as traps of bile salts. Computational modeling was combined with molecular imprinting technology to obtain networks with high affinity for cholate salts in aqueous medium. The screening of a virtual library of 18 monomers, which are commonly used for imprinted networks, identified N-(3-aminopropyl)-methacrylate hydrochloride (APMA·HCl), N,N-diethylamino ethyl methacrylate (DEAEM) and ethyleneglycol methacrylate phosphate (EGMP) as suitable functional monomers with medium-to-high affinity for cholic acid. The polymers were prepared with a fix cholic acid:functional monomer mole ratio of 1:4, but with various cross-linking densities. Compared to polymers prepared without functional monomer, both imprinted and non-imprinted microparticles showed a high capability to remove sodium cholate from aqueous medium. High affinity APMA-based particles even resembled the performance of commercially available cholesterol-lowering granules. The imprinting effect was evident in most of the networks prepared, showing that computational modeling and molecular imprinting can act synergistically to improve the performance of certain polymers. Nevertheless, both the imprinted and non-imprinted networks prepared with the best monomer (APMA·HCl) identified by the modeling demonstrated such high affinity for the template that the imprinting effect was less important. The fitting of adsorption isotherms to the Freundlich model indicated that, in general, imprinting increases the population of high affinity binding sites, except when the affinity of the functional monomer for the target molecule is already very high. The cross-linking density was confirmed as a key parameter that determines the accessibility of the binding points to sodium cholate. Materials prepared with 9% mol APMA and 91% mol cross-linker showed enough affinity to achieve binding levels of up to 0.4 mmol g −1 (i.e., 170 mg g −1) under flow (1 mL min −1) of 0.2 mM sodium cholate solution.

Synthesis of nanostructured Ag–Cu alloy ultra-fine particles

We report Ag–Cu solid solution formation by chemical reduction of silver and copper salts in aqueous medium. Depending on the proportion of silver and copper salts taken, varied degrees of solid solubility in the Ag–Cu system are observed. In most systems, we have got hexagonal Ag(rich)-2H phase in addition to Ag-rich face centered cubic one. It seems that the formation of Cu-rich phase is facilitated by the presence of Ag(rich)-2H phase.

Synthesis of zirconyl polyolates and their conversion to nanosized zirconia

Three new methods for the synthesis of zirconyl polyolates by the sol-gel process from zirconyl salts in aqueous media are developed. The polyolates produced are suitable precursors for zirconia nanopowders.

Flocculation of the titanium dioxide suspension (anatase) with compositions from anionic and cationic acrylamide copolymers

We have studied the kinetics of flocculation in metered introduction into an aqueous-salt medium of compositions from acrylamide anionic and cationic copolymers in the mode of hindered precipitation on a model disperse system—a suspension of titanium dioxide of the anatase form. We have noted a strong relationship between the flocculating indicators and the intensity of selective contact between oppositely charged fragments of macromolecules of ionogenic polyacrylamide flocculants and as a result of it, from the mode of introduction into the disperse system of polymer components: simultaneously or sequentially.

Second sphere coordination in fluoroanion binding: Synthesis, spectroscopic and X-ray structural study of [Co(phen) 2CO 3](Pfbz)·6H 2O

To explore the anion receptor potential of [Co(phen) 2(CO) 3] + for the pentafluorobenzoate ion, [Co(phen) 2(CO) 3](Pfbz)·6H 2O (where phen = 1,10-phenanthroline and Pfbz = pentafluorobenzoate) was synthesized by reacting appropriate salts in aqueous medium. A detailed packing analysis has been undertaken to delineate the role of second sphere C–H⋯F interactions amid other heteroatom interactions. The complex salt has been characterized by elemental analyses, spectroscopic studies (IR, UV/Vis, multinuclear NMR) and solubility product measurement. The complex salt crystallizes in the monoclinic crystal system with space group P2 1/ n having the cell dimensions a = 13.377(3) Å, b = 17.204(3) Å, c = 15.408(3) Å, β = 108.11(3)°, V = 3370.1(12) Å 3 and Z = 4. Single crystal X-ray structure determination revealed ionic structure consisting of complex cation, [Co(phen) 2(CO) 3] +, Pfbz anion and six lattice water molecules. In the crystal lattice, discrete ions [Co(phen) 2CO 3] + are forming rectangular voids in which the Pfbz anions are entrapped. Crystal lattice is stabilized by electrostatic forces of attraction and hydrogen bonding interactions, i.e. O–H⋯O, C–H⋯O, and C–H⋯F, involving second sphere coordination besides π⋯π interactions.

Semi-quantitative Approaches to the Coordination Ability of o-Bisguanidinobenzenes with Metal Salts

In order to uncover the potential functionality of o-bisguanidinobenzenes the ability of l,2-bis(l,3-diethylethyleneguanidino)benzene to form complexes with eighteen kinds of metal salts in aqueous media was examined. Complex formation ability was judged by spectral analysis, including elemental analysis, of products obtained as water-insoluble precipitates, as water-soluble and chloroform-extractable materials, or as water-soluble and chloroform-unextractable materials. Positive coordination was observed with many metal salts used. Tight water-insoluble and crystalline complexes were formed in the cases of cobalt(II), zinc(II), and cadmium(II) salts, in the first two cases among which products were analyzable by X-ray crystallography. In addition, treatment of the complex with aqueous alkali re-produced the original bisguanidinobenzene quantitatively, indicating the promising use as a recyclable ligand.

An Efficient Preparation of Bis(indole)methanes Catalyzed by Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate Salts in Aqueous Medium

An efficient and direct preparation of bis(indole)methanes from indole and the corresponding carbonyl compound in water catalyzed by metal salts of tetrakis[3,5-bis(trifluoromethyl)phenyl]borate has been developed.

Separation of Cr(VI) from Cr(III) in CaCl2 aqueous salt medium using hydrocarbon (as toluene, n-hexane, n-heptane or n-octane) mixed solvents of ter-butanol

A simple and selective solvent extraction system was developed using mixed solvent of ter-butanol(ter-BuOH), namely toluene/ter-BuOH, n-hexane/ter-BuOH, n-heptane/ter-BuOH and n-octane/ter-BuOH to separate Cr(VI) from Cr(III). Toluene/ter-BuOH mixed system excelled the others. Chromium(VI) was extracted in the presence of Cr(III) into the mixed solvents at the mole fraction of ter-BuOH (χt-but) in the range of 0.1 and 0.5 (9.0–47.1% in volume) after addition of CaCl2 (5 M). The extraction was repeated twice for quantitative extraction of Cr(VI). Chromium(III) was not extracted in the above range. The distribution ratio of ter-BuOH and the concentrations of water and CaCl2 in the organic phase were determined and their influences on the extraction of Cr(VI) were assessed. When χt-but=0, neither Cr(VI) nor Cr(III) was extracted. The chemical species in the aqueous phase was confirmed to be the CrO3Cl− species. When [salts]aq or [acid]aq=0, the separation of Cr(VI) from Cr(III) was not achieved. This study revealed that Cr(VI) was extracted as a solvated ion-pair complex of [ter-BuOH2+·CrO3Cl−]. The optimum conditions for the separation of Cr(VI) from Cr(III) are [CaCl2]aq=5 M, [HCl]aq=0.1 M and χt-but=0.3 (27.6% in volume). Further, the extracted Cr(VI) was stripped by the addition of a 2 M NaOH aqueous solution. The present method was applied to the separation and determination of Cr(VI) and Cr(III) in two industrial effluent samples. The relative standard deviations (n=14) of Cr(VI) and Cr(III) were 4.45 and 2.86% for Company A, and 5.99 and 3.31% for Company B.

Synthesis of high-purity α- and β-PbO and possible applications to synthesis and processing of other lead oxide materials

Litharge, the red tetragonal form of lead oxide α-PbO and massicot, the yellow orthorhombic form β-PbO, are synthesized from lead(II) salts in aqueous media at elevated temperatures. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the size, morphology, and crystallographic structural forms of the products. The role of impurities in the experimental synthesis of the materials and microstructural variations in the final products are described. The implications of these observations regarding the synthesis of different conducting lead oxides and other related materials are discussed.

Micellization of bile salts in aqueous medium: A fluorescence study

Owing to the physiological importance of the micellization process of bile salts, the critical micelle concentration (CMC) becomes a fundamental parameter in the evaluation of their biological activities. The present study suggests fluorescence probing, using 1,6-diphenylhexatriene (DPH), as a simple, convenient, sensitive and economic method for monitoring the micellization process of bile salts in aqueous medium. Three independent parameters: fluorescence intensity, anisotropy and lifetime of DPH have been employed successfully for determining the CMC of two bile salts, sodium deoxycholate (NaDC) and sodium cholate (NaC), in aqueous medium. The CMC values reported by all the above three parameters of DPH are found to be same and it is 16 mM for NaC and 6 mM for NaDC at 25 °C in unbuffered solution. The effect of temperature and ionic strength on the micellization process has also been investigated employing DPH as a fluorescent probe. Increasing temperature leads to the formation of fluffier micelles with less rigid interior for both NaC and NaDC. The micelle core of NaC is less perturbed by the presence of NaCl whereas in case of NaDC, the aggregates provide DPH a more nonpolar and rigid environment in presence of NaCl than that in absence of salt.

Azo‐coupling Decarboxylation Reaction of α‐Carboxy Ketene Dithioacetals in Water–a New Route to 1,2‐Diaza‐1,3‐butadienes

AbstractUnder basic conditions, a series of 4,4‐dialkylthio‐1,2‐diaza‐1,3‐butadienes were synthesized in good to excellent yields via a novel azo‐coupling decarboxylation reaction by reacting α‐carboxyl ketene dithioacetals with aryldiazonium salts in aqueous medium.

Rational Design, Synthesis, and Application of a New Receptor for the Molecular Recognition of Tricarboxylate Salts in Aqueous Media

A rational design of a tripodal receptor for the molecular recognition of tricarboxylate salts in aqueous media, based on squaramide, has been performed using high-level DFT calculations (RI-BP86/SVP level of theory) in solution using the COSMO treatment, including some preliminary ab initio calculations at the higher RI-MP2/TZVP level of theory, comparing the ability of squaramide to bind carboxylate salts with two widely used guanidinium salts. The tripodal receptor has been synthesized using a new methodology that has been recently reported by some of us, and its capability of recognizing several mono-, di-, and tricarboxylate salts has been studied experimentally by means of microcalorimetry experiments in a very high competitive media, H(2)O:EtOH 1:3. These experiments give enthalpic and entropic data, which are unfortunately scarce in the literature of molecular recognition of anions. Finally, a fluorimetric ensemble of the receptor with fluorescein has been found to be useful for the fluorimetric determination of zinc citrate in a commercial toothpaste using competition assays.

Molecular recognition of pyramidal oxoanions using cationic cobaltammine: Synthesis, characterisation, X-ray structure determination and packing of [ trans-Co(en) 2Cl 2]ClO 3 and [ trans-Co(en) 2Cl 2]BrO 3

In an effort to explore [ trans-Co(en) 2Cl 2] + as anion binding agent for weakly coordinating and pyramidal in shape halate ions, green coloured single crystals of [ trans-Co(en) 2Cl 2]ClO 3 I and [ trans-Co(en) 2Cl 2]BrO 3 II have been obtained by slowly mixing the separately dissolved trans-dichlorobis(ethylenediamine)cobalt(III) chloride with appropriate metal halate salts in aqueous medium. The newly synthesised complex salts were characterised on the basis of elemental analysis and spectroscopic techniques (IR, UV/visible, 1H and 13C NMR). Single crystal X-ray structure determinations revealed their isomorphous nature. Both the compounds I and II crystallize in the triclinic space group P-1 with a=6.327 (1) Å, b=7.501(1) Å, c=13.788(1) Å, α=87.79 (1)°, β=80.56 (1)°, γ=71.38 (1)°, V=611.65(9) Å 3, Z=2, R=0.0233 and a=6.338(1) Å, b=7.557(1) Å, c=14.089(1) Å, α=88.18(1)°, β=79.10(1)°, γ=70.83(1)°, V=625.56(14) Å 3, Z=2, R=0.0269, respectively. Supramolecular hydrogen bonding networks between ionic groups: oxygen atoms of halates and NH groups of coordinated ethylenediamine molecules, i.e. N +–H⋯O − interactions involving second sphere coordination besides electrostatic forces of attraction have been observed. This suggests that [ trans-Co(en) 2Cl 2] + is a promising anion binding agent(receptor) for the weakly coordinating halate ions. The solubility product measurements indicate that the affinity of cationic cobaltammine [ trans-Co(en) 2Cl 2] + is greater for chlorate ion than bromate ion.

A Rapid Synthesis of Iron Phosphate Nanoparticles via Surface-Mediated Spontaneous Reaction for the Growth of High-Yield, Single-Walled Carbon Nanotubes

The direct formation of iron phosphate nanoparticles on hydroxyl-terminated SiO(2)/Si substrates with a narrow size distribution (average diameter = 2.2 nm) is achieved by a simple room temperature spontaneous reaction of ferric chloride and phosphoric acid. Single-walled carbon nanotubes (SWNTs) are grown in high yield from the synthesized iron phosphate nanoparticles by the thermal chemical vapor deposition (CVD) method, as confirmed by atomic force microscopy (AFM) and Raman spectroscopy. Furthermore, three-terminal, p-type, nanotube network field effect transistor (FET) devices are successfully fabricated using the synthesized SWNTs via the photolithography technique. The reduced solubility of Fe(III) ions when they form iron phosphate salts in aqueous media is the main driving force for the nanoparticle formation. Systematic control experiments reveal that the surface property, concentration, and pH of the reaction solution play equally important roles in the formation of nanoparticles.

The interaction between poly(N‐isopropylacrylamide) and salts in aqueous media: The “salting‐out” phenomenon as studied by attenuated total reflection/fourier transform infrared spectroscopy

AbstractThe effect of two strong salting‐out salts (Na2SO4 and K2SO4) on the temperature‐induced phase‐separation process in aqueous solutions of poly(N‐isopropylacrylamide) (PNIPA) was examined by attenuated total reflectance/Fourier transform infrared spectroscopy, differential scanning calorimetry, and viscosity measurements. On the basis of these measurements, a detailed scenario of the phase‐separation process was deduced. The phase‐separation scenario of solutions containing PNIPA and water was altered in the presence of sulfate ions. Here, the sulfate ions induced partial intrachain collapse, manifested by a relatively compact structure well below the lower critical solution temperature. This led to a more gradual, smooth phase transition, with temperature‐resolved intrachain collapse and interchain aggregation and a lesser extent of hysteresis. Although at the macrolevel one may not be able to differentiate among various scenarios altering the solvent into a poor solvent, the aforementioned microlevel measurements provided a way to expose the difference between raising the temperature and adding cosolutes. Follow‐up studies on the effect of salting‐in salts will be presented. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 33–46, 2004

Binding of Copper(II), Cobalt(II), and Nickel(II) Cations with Humic Acids and Their Sodium Salts in Aqueous Media

Binding of Cu(II), Co(II) and Ni(II) cations to humic acids and their sodium salts was studied in aqueous media at pH 3-6 by spectrophotometry and potentiometric titration technique.

Magnetic property studies of manganese-phosphate complexes.

Phosphoric acid forms two distinct coordination compounds with manganese salts in aqueous media, a two-dimensional layered structure, [Mn(HPO4).(H2O)3], 1, under ambient conditions, and a three-dimensional synthetic mineral, [Mn5(mu-OH2)2(HPO4)2(PO4)2(H2O)2], 2, under hydrothermal procedures, at 120 degrees C. In compound 1, the oxygen atom of the doubly deprotonated phosphoric acid interconnects the metal centers to form a layered structure. The neutral hydrophilic layers of 1 are separated by 5.5 A and may potentially intercalate hydrophilic organic guest molecules. The metal centers in 2 are octahedral and bridged by PO4(3-), HPO4(2-), and OH2 groups to form a complex three-dimensional network. XPS analysis on 1 and 2 confirms that manganese exists in the +2 oxidation state. Compound 2 is a poor ion exchanger, but some improvement is observed on partial dehydration. The magnetic properties of both 1 and 2 were studied in detail to examine the amplitude of the magnetic interactions through phosphate ligand bridges. While 1 reveals dominant antiferromagnetic interactions between the spin carriers, a complete investigation of the magnetic properties of 2 revealed its true nature to be a glassy magnet.