Fluorometric sensing of alkali metal and alkaline earth metal cations by novel photosensitive monoazacryptand derivatives in aqueous micellar solutions

Novel monoazacryptand-type fluorescent chemosensors, (derived from an 18-crown-6) and (derived from a 15-crown-5) both with a pyrene ring as their photoresponsive moiety, were synthesized. Their fluorescence properties for alkali metal and alkaline earth metal cations in water were then examined. The detection of metal cations was accomplished by a change in the fluorescence intensity of the host compounds, based on a photoinduced electron transfer (PET) mechanism. In aqueous solution, showed little fluorescence upon the addition of Ba2+ because of the very weak complexation with Ba2+, but the presence of micelles of polyoxyethylene(10) isooctylphenyl ether (Triton X-100) enabled to show highly sensitive and selective Ba2+ detection among alkali metal and alkaline earth metal cations. With respect to the selective fluorescent detection of important metal cations (Na+, K+, Mg2+, Ca2+) relevant to living organisms, was found to detect K+ with high selectivity in aqueous micellar solutions of polyoxyethylene(20) sorbitan monostearate (Tween-60). The selectivity for metal cations was mainly dependent on the goodness of fit of the host cavity and the metal cation size. In the presence of anionic surfactants, detected alkaline earth metal cations more effectively than alkali metal cations.     

Tetraphenylborate salts of alkali and alkaline earth metal complex cations

An introductory review summarises complex formation between poly(alkyleneoxy) adducts and inorganic salts. This is followed by preparative and IR and NMR spectroscopic features of the tetraphenylborates of complexes of polyethylene glycols, nonylphenoxy(polyethyleneoxy)ethanols and polypropylene glycols with sodium, magnesium, calcium, strontium and barium ions. Generally, an alkylene oxide:cation ratio of 8.5:1 is indicated for the complexes with sodium, and 12:1 (∼10.5:1 for the polyethylene glycols)_for the complexes with the alkaline earth metals.     

Determination of ammonium cations and alkali and alkaline earth metal cations in jellyfish by capillary zone electrophoresis.

We developed a capillary zone electrophoresis method with indirect UV detection for determination of ammonium cations and alkali and alkaline earth metal cations in jellyfish. As the background electrolyte, a mixture of N-methylbenzylamine, citrate, and 18-crown-6 was used for the complete separation of all analyte cations. The limits of detection were 0.13 - 0.34 mg l(-1) at a signal-to-noise ratio of three. The values of the relative standard deviation of peak area were 3.2 - 4.9%. The proposed method successfully determined the above analyte cations in jellyfish for approximately 4 min.     

Modification of sulfonated polyphenylquinoxaline by alkali and alkaline earth metal cations

Salts of sulfonated polyphenylquinoxaline (SPPQ) containing alkaline earth metal ions—Mg²⁺, Ca²⁺, and Ba²⁺—were synthesized. The paper considers their solubilities, the properties of solutions, and thermal stability in comparison with analogous characteristics of SPPQ salts with alkali metals. The introduction of alkaline earth metal cations into SPPQ affords soluble polymeric salts having high thermal stability. Solutions of SPPQ salts in N-methylpyrrolidone (N-MP) containing Mg²⁺, Ca²⁺, and Ba²⁺ ions do not exhibit polyelectrolyte properties, unlike solutions of SPPQ salts in which the counterions are Li⁺, Na⁺, and K⁺. Solutions of SPPQ and its salts in N-MP can be converted to water-soluble form by dialysis. This opens up new prospects for using the polymeric salts.     

Tryptophan fluorescence quenching by alkaline earth metal cations in deionized bacteriorhodopsin

Tryptophan quenching by the addition of alkaline earth metal cations to deionized bacteriorhodopsin suspensions was determined. The results show that the addition of cation primarily quenches fluorescence from surface tryptophan residues. The quenched intensity exhibits a 1/R dependence, where R is the ionic radius of the corresponding metal ion. This observation results from a stronger energy transfer coupling between the tryptophan and the retinal. The membrane curvature may be involved as a result of cations motion and correlated conformational changes.     

Spectrophotometric study of the complexation reactions between alkaline earth cations and murexide in some non-aqueous solutions

The complexation reactions between alkaline earth cations and murexide in methanol, dimethylformamide and dimethylsulphoxide solutions have been studied spectrophotometrically at 25°C. The formation constants of the resulting 1 : 1 complexes were determined. In all solvents used, the stabilities of the murexide complexes vary in the order Ca²⁺ > Sr²⁺ > Ba²⁺ > Mg²⁺. There is an inverse relationship between the stabilities of the complexes and the Gutmann donicity of the solvents.     

Potentiometric titration of metal ions in ethanol

The potentiometric titrations of Zn2+, Cu2+ and 12 Ln3+ metal ions were obtained in ethanol to determine the titration constants (defined as the at which the [-OEt]/[Mx+]t ratios are 0.5, 1.5, and 2.5) and in two cases (La3+ and Zn2+) a complete speciation diagram. Several simple monobasic acids and aminium ions were also titrated to test the validity of experimental titration measurements and to establish new constants in this medium that will be useful for the preparation of buffers and standard solutions. The dependence of the titration constants on the concentration and type of metal ion and specific counterion effects is discussed. In selected cases, the titration profiles were analyzed using a commercially available fitting program to obtain information about the species present in solution, including La3+ for which a dimer model is proposed. The fitting provides the microscopic values for deprotonation of one to four metal-bound ethanol molecules. Kinetics for the La3+-catalyzed ethanolysis of paraoxon as a function of are presented and analyzed in terms of La3+ speciation as determined by the analysis of potentiometric titration curves. The stability constants for the formation of Zn2+ and Cu2+ complexes with 1,5,9-triazacyclododecane as determined by potentiometric titration are presented.     

Transfer coefficients of cations and anions upon glow discharge-induced nonequilibrium vaporization of solutions of alkaline earth metal salts

Firing of atmospheric-pressure, electrolytic-cathode glow discharge leads to an effect that is similar to well-known cathode sputtering. This process can be called nonequilibrium vaporization of the solution. Unlike quasi-equilibrium vaporization, the nonequilibrium process entails the transfer of nonvolatile components of the solution to the gas phase. Previously, studying glow discharge with calcium and barium chloride solutions as the cathode, we have shown that the transfer of cations and anions via the nonequilibrium vaporization of the nonvolatile solutes is not necessarily stoichiometric [1].     

Chiral aminoacid containing acyclic ligands - II. Complexation of alkaline earth cations

The abilities of the title ligands for alkali and alkaline earth cations are estimated by ¹H and ¹³C NMR and by picrate extraction from water to methylene chloride. These ligands are shown to be excellent complexing agents for alkaline earth cations. Complexation occurs preferably at the ether and amide carbonyl groups. The stoichiometry of complexation is evaluated by ¹H NMR.     

Synthetic noncyclic ionophores with multiple carboxylate groups for alkaline earth metal cations

A series of synthetic ionophores containing two carboxylic acid groups were synthesized as carriers for alkaline earth metal cations. Among them, the lipophilic derivative having a trimenthylene bridge and multiple quinaldate moieties selectively transported barium ion from the basic aqueous phase to the acidic aqueous phase through the bulk dichloromethane liquid membrane. The cation selectivity was explained by considering the fit of the cation diameter with the pseudocyclic cavity.     

Hydrophobic interactions between polymethacrylic acid and sodium laureth sulfate in aqueous solutions

The role of hydrophobic interaction in the development of associative processes is demonstrated, based on the concentration dependences of the viscosity and pH of binary solutions of polymethacrylic acid as an anionic polyelectrolyte and sodium laureth sulfate as an anionic surfactant. It is found that the inflection point on the dependence of the difference between the pH values of binary solutions of polymethacrylic acid and sodium laureth sulfate on the polyelectrolyte concentration is a criterion for determining the predominant contribution from hydrophobic interaction, as is the inflection point on the dependence of pH of individual solutions of polymethacrylic acid on the polyelectrolyte concentration.     

Interaction between fluorenyl alkaline earth salts and ethylene oxide

The ineraction of fluorenyl alkaline earth salts with ethylene oxide in THF was studied. Based on spectral data, a mechanism of the reaction between difluorenylbarium and ethylene oxide was proposed. The kinetics were followed. It was found that the solvent-separated ion pairs were more reactive than the contact ion pairs in the epoxy ring opening. Only low molecular products were obtained in the ethylene oxide polymerization with the fluorenyl salts used.     

Transport of alkali and alkaline earth cations by a crown ether-alkylphosphoric acid system

Abstract

Competitive transport of alkali and alkaline earth cations has been carried out by using a mixed carrier system composed of dibenzo-14-crown-4 and bis(2-ethylhexyl)phosphoric acid. In the absence of crown ether, bis(2-ethylhexyl)phosphoric acid transported alkaline earth cations with high selectivity. The combination of dibenzo-14-crown-4 and bis(2-ethylhexyl)phosphoric acid showed a synergistic enhancement in lithium transport, and the enhancement effect was not apparent in transport of other cations. On the other hand, the mixed carrier systems consisting of dibenzo-14-crown-4 and dodecylbenzenesulfonic acid, and of dibenzo-14-crown-4 and 1-bromohexadecanoic acid exhibited the enhancement effects both in lithium transport and in sodium transport. The formation of the synergistic complex was analyzed by using fast atom bombardment mass spectrometry.     

Potentiometric and coulometric titration of 2-thiobarbituric acid

A new method for the determination of 2-thiobarbituric acid, using its reaction with iodine in an alkaline medium is presented. In the volumetric titration with potentiometric end-point detection, the determinability range is 10-400 micromol (1.4-58 mg). In coulometric titration using the biamperometric end-point detection, 0.1-20 micromol (1.4 x 10(-2)-2.9 mg) of 2-thiobarbituric acid was successfully determined.     

FTIR study of ion solvation and ion-pair formation in alkaline and alkaline earth metal salt solutions in acetonitrile

The IR spectra of alkaline and alkaline earth metal perchlorate and of lithium bromide solutions in acetonitrile, obtained with the help of FTIR measurements in the region of the C-N stretching mode of the solvent, reveal bands produced by acetonitrile molecules in the solvation shells and bands of ClO ₄ ^– ions in contact and solvent separated ion pairs. The shift and the attenuation of the C-N stretching band of acetonitrile at 2254 cm^–1 is used for the calculation of cation solvation numbers for Li⁺(4), Na⁺(4), Mg²⁺(6), Ca²⁺(6), and Ba²⁺(6). No solvation is assumed for the contact ion pairs of LiClO₄, LiBr, NaClO₄, Mg(ClO₄)₂, Ca(ClO₄)₂, and Ba(ClO₄)₂. The association constants of the symmetrical electrolytes are compared to those obtained from other methods.     

Potentiometric study of the mixed-metal complex formation of tetracarboxylate-18-crown-6 with aluminum and alkali and alkaline earth cations

We give evidence for the formation of mixed-metal complexes of tetracarboxylate-18-crown-6 in the form of Al³⁺-macrocycle-M^Z+, with M^Z+ being an alkali or an alkaline earth cation. These binuclear systems are characterized by potentiometric p[H] titrations and the equilibrium constants for all major complexes formed are described. The results are presented in the form of distribution diagrams revealing the concentrations of individual complex species as a function of p[H]. The stability of the resulting mixed-metal complexes with Al³⁺ and alkali and alkaline earth cations vary in the order Na⁺>K⁺>Cs⁺ and Ca²⁺>Sr²⁺>Ba²⁺. The complex behavior can be rationalized in terms of electrostatic interactions and direct coordination of the cations by the carboxylate groups from the crown ether periphery.