Cathodic electrochemiluminescence of metal ions in acid fluoride solutions

The conditions for exciting the cathodic electrochemiluminescence (ECL) of mercury-like ions and manganese in dilute HF solutions at aluminum and magnesium electrodes are described. ECL spectra are measured. It is shown that Mn(II) can be determined with a detection limit of 10^?7 M.     

Complexing of alginic acid with metal ions

Summary The gelation or precipitation of alginate with a number of divalent metal ions occurs through cross-linkage, forming complexes which involve carboxyl groups of one macromolecule and pairs of hydroxyl groups of another. For most of the ions the pair of hydroxyl groups involved has to be vicinal and thus belong to one uronic acid residue. Only Cu²⁺ and Cd²⁺ seem to include single hydroxyl groups also. The extent to which these complexes are formed or, in other words, their stability depends greatly on the metal ion. Decreasing stability of complexes with different ions appears to be in the following order: Ba²⁺, Cd²⁺, Cu²⁺, Sr²⁺, Ni²⁺, Ca²⁺, Zn²⁺, Co²⁺, and Mn²⁺.Another group of metals including tri- and tetravalent ions but also divalent ions with either very low or very high atomic weights form precipitates but apparently do not cross-link in any way.

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Zusammenfassung Die Gelierung oder AusfÄllung von Alginat durch eine Anzahl von zweiwertigen Metallionen geschieht durch Vernetzung, indem Komplexe gebildet werden, die Karboxylgruppeneiner Makromolekel und Hydroxylgruppenpaare einer anderen Makromolekel enthalten. Für die meisten Ionen mu\ das Hydroxylgruppenpaarvizinal sein, d. h. beide Hydroxylgruppen müssen dem gleichen UronsÄurerest angehören. Nur Cu²⁺ und Cd²⁺ können anscheinend auch einzelne Hydroxylgruppen mit einbegreifen. Der Bildungsgrad dieser Komplexe oder, mit anderen Worten, ihre StabilitÄt hÄngt sehr stark vom Metallion ab. Abnehmende StabilitÄt von Komplexen mit verschiedenen Ionen scheint in folgender Reihenfolge vorzuliegen: Ba²⁺, Cd²⁺, Cu²⁺, Sr²⁺, Ni²⁺, Ca²⁺, Zn²⁺, Co²⁺ und Mn²⁺.Eine andere Gruppe von Metallen, die hauptsÄchlich drei- und vierwertige Ionen mit entweder sehr niedrigen oder sehr hohen Atomgewichten umfa\t, bildet zwar NiederschlÄge, vernetzt jedoch anscheinend in keiner Weise.

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Presented before Division of Carbohydrate Chemistry 147^th. Nat. Meeting of Amer. Chem. Soc., Philadelphia, Penna/U.S.A. April 1964.     

A colorimetric chemosensor for both fluoride and transition metal ions based on dipyrrolyl derivative

The synthesis, characterization and ion binding studies of 2,3-di(1H-2-pyrrolyl)pyrido[2,3-b]pyrazine (1) have been described. 1, which has been targeted with a view to sensing both F- and transition metal ions, exhibits binding-induced color changes from yellowish green to red/brown observable by the naked eye. The binding site for the metal ion in the system has been unambiguously established by single-crystal X-ray diffraction study of a Ni(II) complex of 1. While the estimated value of the binding constant of 1 with F- is 4.9 x 10(3) M(-1), the binding constants for the cations are found to be two orders higher in magnitude in acetonitrile. Even though 1 possesses two separate binding sites for F- and metal ions, it is shown that the presence of the cation influences the binding of the anion and vice versa. The binding constant values of an ion in the presence of oppositely charged species are measured to be significantly lower.     

Interaction of metal ions with polypyrrole on polyacrylic acid matrix

The oxidative matrix polymerization of pyrrole (Py) by Fe(III), Cu(II), Ni(II), Co(II), and Zn(II) in the presence of polyacrylic acid (PAA) was studied and water‐soluble products along with insoluble products were obtained. The metal (Me) content of the insoluble part was determined by using atomic absorption spectroscopy (AAS). The effects of the oxidation potential of Me ions and ligands on the aggregation of polypyrrole (PPy) on the matrix polymer were measured by ultraviolet (UV)‐visible spectra. These findings also were checked by cyclic voltammetry (CV) measurements on PAA–Cu and PAA–PPy–Cu interactions. The conductometric titration results of PAA–PPy–Me ternary solutions were explained in the light of the interaction of Me ions with Py to polymerize on the PAA matrix resulting in some free carboxyl groups with a possibility of having Me–polymer complexes and a ternary complex (PAA–Me–PPy). The insoluble products were characterized by Fourier transform infrared (FTIR), elemental analysis, scanning electron microscopy (SEM), and four point probe conductivity measurements. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1115–1123, 1999     

Radiation synthesis of chitosan beads grafted with acrylic acid for metal ions sorption

Radiation-induced grafting of acrylic acid onto chitosan beads was performed in solution at a dose rate of 20.6 Gy/min of cobalt-60 gamma rays. The effect of absorbed dose on grafting yield was investigated. The characterization of the grafted material was performed by FTIR spectroscopy and the swelling measurements at different pHs. The grafting yield increased with the increase in dose, it reached 80% at 40 kGy irradiation dose.The removal of Pb and Cd ions from aqueous solutions was investigated with both ungrafted and grafted chitosan beads. The sorption behavior of the sorbents was examined through pH, kinetics and equilibrium measurements. Grafted chitosan beads presented higher sorption capacity for both metal ions than unmodified chitosan beads.     

Complexes of divalent metal ions with cinchomeronic and dinicotinic acid thermal properties

The thermal properties of the complexes of cinchomeronic and dinicotinic acid with several divalent metal ions were determined by thermogravimetry (TG) and differential thermal analysis (DTA).For the thermal stability of the anhydrous compounds a sequence may be observed for the metal ions with cinchomeronic (3,4-H₂PC) and dinicotinic acid (3,5-H₂PC):

The thermal stability of the pyridine carboxylic acid for each metal of the series is: dinicotinic > cinchomeronicThe activation energy values for each thermal reaction were also calculated, using the Coats and Redfern algorism, by the Univac 1108 computer, by a program properly implemented for the statistical analysis of the data to obtain the reaction order and the activation parameters with the relative confidence limits.     

Complexes of the selected transition metal ions with 4-methoxycinnamic acid

In this study, 4-methoxycinnamates of Mn(II), Co(II), Ni(II), Cu(II), Cd(II), Nd(III) and Gd(III) were synthesised. From the infrared (IR) spectra analysis of complexes, sodium salt and according to the spectroscopic criteria the carboxylate groups seem to be bidentate chelating. The complexes of 4-methoxycinnamates lose the water molecules in one or two steps. The final products of their decomposition are oxides of the respective metals. The enthalpy values of dehydration process were determined. The FTIR spectra of the gas phase products indicate that the decomposition of the complexes is connected mainly with the release of molecules of water (H₂O), carbon dioxide (CO₂), carbon monoxide (CO), methane (CH₄) and other hydrocarbons. The analysed compounds follow the Curie?CWeiss law. The magnetic moment values experimentally determined change as follows: from 5.90??? _B to 6.27??? _B for Mn(II) complex, from 4.57??? _B to 4.99??? _B for Co(II) complex, from 3.68??? _B to 3.30??? _B for Ni(II) complex, from 1.87 ?? _B to 1.96 ?? _B for Cu(II) complex, from 3.06??? _B to 3.51??? _B for Nd(III) complex, and from 6.91??? _B to 6.90??? _B for Gd(III) complex.     

Thermodynamic interactions of the alkaline earth metal ions with citric acid

By using the isothermal titration calorimetry (ITC) technique, thermodynamic parameters have been determined for reactions of the Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺ ions with the citrate anion. The measurements were run in the Cacodylate, Pipes and Mes buffer solutions of a pH of 6, at 298.15 K, as well as in the Tricine, Tapso, and Tris–HCl buffer solutions of a pH of 8. Further, based on the results of potentiometric titration, the conditional stability constants were determined for the citrate complexes at both pH values. The effect of the reaction environment and the metal ion identity on the interaction energy with the citrate ligand and the stability of the resulting compounds have been discussed.     

Thermal properties of some complexes of quinolinic acid with divalent metal ions

Studies of the complexes of pyridinecarboxylic acids with divalent metal ions as a function of the position of the carboxyl groups were extended. The thermal properties of the complexes of quinoline acid (pyridine-2,3-dicarboxylic acid) with several divalent metal ions were determined by thermogravimetry (TG) and differential thermal analysis (DTA). A correlation between these compounds and others obtained by reaction between the studied metal ions with similar acids (lutidinic acid (pyridine-2,4-dicarboxylic acid) and isocinchomeronic acid (pyridine-2,5-di-carboxylic acid) is discussed in terms of the position of the carboxyl group far from the aza group. The thermal stability of the metal complexes is in the order Mn(II) > Fe(II) > Zn(II) ? Co(II) > Ni(II) > Cu(II).     

Calixarene complexes with metal ions

Selected complexes of metal ions are presented showing their syntheses and possible applications, an attention was paid to their usefulness in chemosensors design and in the environmental protection.     

Anion-exchange separation of metal ions in dimethyl sulphoxide-methanol-hydrochloric acid

The effect of dimethyl sulphoxide on the anion-exchange behaviour of many metals m a methanolic system with hydrochloric acid was explored. Distribution coefficients for 26 elements were determined in a mixed solvent system of dimethyl sulphoxide-methanol-0.6M hydrochloric acid, in which the proportions of dimethyl sulphoxide and methanoi were varied. Lead(II) and silver(I) complexes are soluble in this system. Interesting effects were noted for gold(III), iron(III), molybdenum(VI) and uranium(VI). As a measure of the usefulness of the systems studied, 27 anion-exchange separations of two- to four-component mixtures of metal ions were carried out, each with quantitative results.     

Adsorption of heavy metal ions by immobilized phytic acid

Applied Biochemistry and Biotechnology - Phytic acid (myoinositol hexaphosphate) or its calcium salt, phytate, is an important plant constituent. It accounts for up to 85% of total phosphorus in...     

Graphite fluoride intercalation compounds for manufacturing composites with metal nanoparticles

The feasibility of using graphite fluoride intercalation compounds (GFICs) containing metal compounds for manufacturing metal nanoparticles in a graphite or graphite fluoride matrix is shown using the hydrogen reduction of a dicarbon fluoride matrix intercalated with a chloroform solution of palladium acetylacetonate Pd(AA)₂. The composite manufactured with a GFIC containing about 10.5 wt % Pd(AA)₂ at 80°C is Pd-fluorographite; at 450°C, Pd-graphite is manufactured. The palladium particle size in the composites is about 20–30 nm; the palladium concentration is about 5 and 9 wt %, respectively.     

Fluorination of fluoro-cyclobutene with high-valency metal fluoride

Fluorinations of 1,4,4-trifluorocyclobutene and 3,3,4,4-tetrafluorocyclobutene using high-valency metal fluorides such as CoF₃, MnF₃, AgF₂, CeF₄ and KCoF₄, and elemental fluorine were examined. In these reactions with CoF₃ and MnF₃, vic-difluorination proceeded mainly. While, 1,4,4-trifluorocyclobutene yielded 3,3,4,4-tetrafluorocyclobutene, and 3,3,4,4-tetrafluorocyclobutene yielded 1,3,3,4,4-pentafluorocyclobutene mainly in the case of AgF₂. The further fluorinated products were increased under severer conditions. Also, the plausible reaction mechanism was suggested.     

Organoboron compounds as Lewis acid receptors of fluoride ions in polymeric membranes

Newly synthesized organoboron compounds – 4-octyloxyphenylboronic acid (OPBA) and pinacol ester of 2,4,6-trifluorophenylboronic acid (PE-PBA) – were applied as Lewis acid receptors of fluoride anions. Despite enhanced selectivity, the polymer membrane electrodes containing the lipophilic receptor OPBA exhibited non-Nernstian slopes of the responses toward fluoride ions in acidic conditions. Such behavior was explained by the lability of the B–O bond in the boronic acids, and the OH⁻/F⁻ exchange at higher fluoride content in the sample solution. In consequence, the stoichiometry of the OPBA–fluoride complexes in the membrane could vary during the calibration, changing the equilibrium concentration of the primary anion in membrane and providing super-Nernstian responses. The proposed mechanism was supported by ¹⁹F NMR studies, which indicated that the fluoride complexation proceeds more effectively in acidic solution leading mainly to PhBF₃⁻ species. Finally, the performances of the membranes based on the phenylboronic acid pinacol ester, with a more stable B–O bond, were tested. As it was expected, Nernstian fluoride responses were recorded for such membranes with worsened fluoride selectivity.     

A spectroscopic investigation of complexes of divalent metal ions with maleic acid copolymers

The absorption spectra of complexes of copper(II), nickel(II), and barium(II) with three partially neutralized maleic acid copolymers in aqueous solution have been investigated in the range 195–720 nm. Copper ions are always very strongly bound, giving electron transfer complexes. Relevant spectral features are found to depend on the number of methyl groups in the polymer backbone, and in particular, for each given polymer, on the amount of available ligand negative charge per divalent counterion. The spectra of the complexes of nickel(II) and barium(II) suggest that they interact with the polycarboxylates much more weakly than copper(II).     

Phosphoric acid activated carbon as borderline and soft metal ions scavenger

Three activated carbons have been prepared, two from oil-palm shell and one from coconut shell, by the phosphoric acid activation process. Adsorption isotherms of copper(II) were determined to evaluate and compare the performance of experimental carbons. The obtained data are fitted very well to Langmuir and Freundlich adsorption models. All prepared activated carbons show 4–7-fold high adsorption capacity (q_max 19.5–23/18.6–21?mg?g^?1) than that of the commercial ones (q_max 5.6/2.9?mg?g^?1) under the conducted experimental conditions. The mechanism of adsorption was evaluated from the competitive adsorption of copper(II) and calcium(II) in a binary solution depending on their behaviour as Lewis acid and assessed as inner-sphere complexation. The competitive adsorption of copper(II) with other borderline and soft metal ions was evaluated by the best scavenger using a solution of ternary solute of copper(II), nickel(II) and lead(II). The adsorption selectivity order is determined as follows: Pb?>?Cu???Ni.     

Interaction of different metal ions with carboxylic acid group: a quantitative study

The binding strength of the carboxylic acid group (-COOH) with different divalent metal ions displays considerable variation in arachidic acid (AA) thin films. It is considered that in AA thin films the metal ions straddle the hydrophilic regions of the stacked bilayers of AA molecules via formation of carboxylates. In this study first the uptake of different divalent cations in films of AA is estimated by atomic absorption spectroscopy (AAS). Through the amount of cation uptake, it is found that the strength of binding of different cations varies as Ca2+>Co2+>Pb2+>Cd2+. Variation in the binding strength of different ions is also manifested in experiments where AA thin films are exposed to metal ion mixtures. The higher binding strength of AA with certain metal ions when exposed individually, as well as the preference over the other metal ions when exposed to mixtures, reveal some interesting deviation from the expected behavior based on considerations of ionic radii. For example, Pb2+ is always found to bind to AA much more strongly than Cd2+ even though the latter has smaller ionic radius, indicating that other factors also play an important role in governing the binding strength trends apart from the effects of ionic radii. Then, to get a more meaningful knowledge regarding the binding capability, first-principles calculations based on density functional theory have been applied to study the interaction of different cations with the simplest carboxylic acid, acetic acid, that can result in formation of metal diacetates. Their electronic and molecular structures, cohesive energies, and stiffness of the local potential energy well at the cation (M) site are determined and attempts are made to understand the diversity in geometry and the properties of binding of different metal ions with -COOH group. We find that the calculated M-O bond energies depend sensitively on the chemistry of M atom and follow the experimentally observed trends quite accurately. The trends in M-O bond energies and hence the total M-acetate binding energy trends can actually be related to their molecular structures that fall into different categories: Ca and Cd have tetrahedral coordination; Fe, Ni, and Co exhibit planar 4-fold coordination; and Pb is off-centered from the planar structure (forming pyramidal structure) due to its stereochemically active lone pair of electrons.     

A new fluorescent PET chemosensor for fluoride ions

A new anthracene derivative bearing two phenylurea group at the 1,8-position of anthracene shows a selective fluorescence quenching effect with fluoride ion via a PET mechanism.