Application of artificial neural network to simultaneous potentiometric determination of silver(I), mercury(II) and copper(II) ions by an unmodified carbon paste electrode

The response characteristics and selectivity coefficients of an unmodified carbon paste electrode (CPEs) towards Ag⁺, Cu²⁺ and Hg²⁺ were evaluated. The electrode was used as an indicator electrode for the simultaneous determination of the three metal ions in their mixtures via potentiometric titration with a standard thiocyanate solution. A three-layered feed-forward artificial neural network (ANN) trained by back-propagation learning algorithm was used to model the complex non-linear relationship between the concentration of silver, copper and mercury in their different mixtures and the potential of solution at different volumes of the added titrant. The network architecture and parameters were optimized to give low prediction errors. The optimized networks were able to precisely predict the concentrations of the three cations in synthetic mixtures.     

Quantum Chemical Calculations on the Structure and Adsorption Properties of NO and N2O on Ag+ and Cu+ Ion-Exchanged Zeolites

Ab initio cluster quantum chemical calculations at the Hartree–Fock (HF/Lanl2dz) and correlated second-order Moller–Plesset perturbation theory (MP2/Lanl2dz) levels were performed for NO and N₂O interactions with Ag⁺ and Cu⁺ ion-exchanged zeolites. The interaction energies were estimated in a conventional way and also corrected for basis set superposition errors. It was shown that the highly dispersed Ag⁺ counterions establish twofold coordination to the lattice oxygens on the zeolite surface, similar to the case of Cu⁺ ions. However, both NO and N₂O bind relatively strongly to the Cu active sites of Cu⁺ ion-exchanged zeolites than those of the Ag⁺ site of the Ag⁺ ion-exchanged zeolites. Based on the results of these calculations, the two different forms of adsorption for these molecules on the catalyst surface, the nature of their binding and characteristics of the adsorption properties have been discussed. Finally, some comparisons with the results obtained by a variety of density functional theory calculations on target systems have been presented.     

Thermochemistry of interactions of Na+ with benzo-15-crown-5 ether in acetonitrile-water mixtures at 298.15 K

Enthalpies of dissolution of benzo-15-crown-5 ether (B15C5) in mixtures of acetonitrile with water and in solutions of NaI and NaBPh₄ (I=0.05 mol dm^–3) in these mixtures were measured at 298.15 K. From the obtained results and appropriate literature data, the thermodynamic functions of B15C5/Na⁺ complex formation in acetonitrile-water mixtures were determined. The enthalpies of transfer of the complex B15C5/Na⁺ from pure acetonitrile to the examined mixtures were calculated and are discussed.     

Proton NMR probing of stoichiometry and thermodynamic data for the complexation of Na and Li ions with 15-Crown-5 in acetonitrile-nitrobenzene mixtures

Proton NMR was used to study the complexation reaction of Li⁺ and Na⁺ ions with 15-Crown-5 (15C5) in a number of binary acetonitrile (AN)-nitrobenzene (NB) mixtures at different temperatures. In all cases, the exchange between free and complexed 15C5 was fast on the NMR timescale and only a single population average ¹H signal was observed. The formation constants of the resulting 1:1 complexes in different solvent mixtures were determined by computer fitting of the chemical shift mole ratio data. There is an inverse relationship between the complex stability and the amount of AN in the solvent mixtures. The enthalpy and entropy values for the complexation reaction were evaluated from the temperature dependence of the formation constants. In all the solvent mixtures studied, the resulting complex is enthalpy stabilized but entropy destabilized. Finally, the experimental results were compared with theoretical ones that were obtained from molecular modeling methods. Based on our results, it is most probable that Li⁺-15C5 in solvent stays in a rather nesting complex form with greater LogK_f values, but Na⁺-15C5 forms a complete perching complex form with lower LogK_f values.     

Solvation of ions. Part XXIX. Ionic conductances in acetonitrile-water and pyridine-water mixtures

The limiting conductance of various salts of Na⁺, Ag⁺, Cu⁺, Cu²⁺ and Ph₄As⁺ in acetonitrile-water (AN-H₂O) and pyridine-water (Py–H₂O) mixtures are reported. Single ion values are calculated for AN-H₂O mixtures using the TATB assumption [_o(Ph ₄ As ⁺) = _o(Ph ₄ B ^–)]. The trends observed for the limiting Walden products (_o) of the electrolytes and individual ions are discussed in terms of specific ion-solvent interactions and the structural effects of the solvent mixtures.Deceased, August 30, 1982.     

Photoactive chemosensors 4: a Cu protein cavity mimicking fluorescent chemosensor for selective Cu recognition

Fluorescent chemosensor 3 can sense Cu²⁺ ions (1-8 μM) even in the presence of elevated levels of Ni²⁺, Cd²⁺, Zn²⁺, Hg²⁺, Ag⁺ and Pb²⁺ (5000 μM). 3 can also analyze for Ag⁺ ions (50-500 μM) in the presence of Ni²⁺, Cd²⁺, Zn²⁺, Hg²⁺ and Pb²⁺ (5000 μM) but Cu²⁺ strongly interferes.     

Study on the synthesis of novel fluorescent macrocyclic sensors and their sensitive properties for Cu2+ and Fe3+ in aqueous solution

In this work, we synthesised and characterised three novel fluorescence macrocyclic sensors containing optically active dansyl groups. The studies for the interaction of the synthesised compounds with various mental ions (Li⁺, Na⁺, K⁺, Ag⁺, Mg²⁺, Ca²⁺, Ba²⁺, Pb²⁺, Zn²⁺, Co²⁺, Cd²⁺, Hg²⁺, Ni²⁺, Cu²⁺, Mn²⁺, Cr³⁺, Al³⁺, Fe³⁺) were performed by fluorescence titration, Job’s plot, ESI-MS and DFT calculations. The results showed that the sensors 1a–1c displayed selective recognition for Cu²⁺ and Fe³⁺ ions and formed stoichiometry 1:1 complex through PET mechanism in DMSO/H₂O solution (1:1, v/v, pH 7.4 of HEPES). The binding constant (K) and detection limit were calculated.     

Functionalized calix[4]arene as an ionophore: Synthesis,crystal structures and complexation study with Na and K ions

Calix[4]arenes with substituents at three of the four OH groups of the lower rim have been synthesized to investigate their properties as ionophores for Na⁺ and K⁺ metal ions. Crystal structures of these trisubstituted compounds revealed that the calixarene moiety has adopted a partial cone conformation, however the precise shape of the molecule, and intra- and intermolecular interactions, are significantly different due to variations of the substituents. Compound L² encapsulated an acetonitrile molecule in the cavity of the calix moiety, held by C–H?π interactions. In the case of L³, the 2-(2-chloroethoxy)-ethanol substituent is involved in strong intramolecular C–H?π interactions with the centroid of the phenyl rings of the calix, bringing the 2-(2-chloroethoxy)-ethanol moiety inward the calix cone, which prevented the entry of any solvent molecule into the cavity. The complexation properties of L²–L⁴ with Na⁺ and K⁺ ions have been investigated in chloroform–methanol mixture by ¹H NMR and an attempt has been made to isolate these complexes in the solid state. Complexation studies reveal that only L³ forms a complex selectively with K⁺, involving 2-(2-chloroethoxy)-ethanol as a coordinating moiety. The association constant (1.4 × 10⁵ M⁻¹) of the complex has also been determined.     

A novel BINOL-based cyclophane via click chemistry: synthesis and its applications for sensing silver ions

A novel BINOL-based cyclophane 1 incorporating two triazole moieties was synthesized via click chemistry and characterized. Among the metal ions screened, only Ag⁺ was found to have the ability to quench the fluorescence of 1 in methanol solution. The 1:1 binding mode of 1-Ag⁺ was confirmed. The competitive experiment showed that compound 1 can be used as a specific fluorescent sensor for Ag⁺ over a wide range of competing cations.     

Flow-injection chemiluminescence simultaneous determination of cobalt(II) and copper(II) using partial least squares calibration

A flow-injection chemiluminescence (CL) system is proposed for simultaneous determination of Co²⁺ and Cu²⁺ using partial least squares (PLS) calibration. This method is based on the fact that both Co²⁺ and Cu²⁺ catalyse the CL reaction of luminol-H₂O₂, and that their kinetic characteristics of Co²⁺ and Cu²⁺ are significantly different in the luminol-H₂O₂ system. The CL intensity was measured and recorder at different reaction times of luminol-H₂O₂Co²⁺Cu²⁺, and the obtained data were processed by the chemometric approach of partial least squares. The experimental calibration set was composed of 16 sample solutions using an orthogonal calibration design for two component mixtures. The proposed method offers the potential advantages of high sensitivity, simplicity and rapidity for Co²⁺ and Cu²⁺ determination, and was successfully applied to the simultaneous determination of both analytes in real water sample. The present paper demonstrated that the simultaneous determination of two metal ions without any prior separation has been possible using flow-injection CL system.     

Azo 8-hydroxyquinoline benzoate as selective chromogenic chemosensor for Hg and Cu

Azo 8-hydroxyquinoline benzoate (2) was synthesized and studied to detect metal ions. Distinct color change was found for compound 2 in the presence of transition metal ions Hg²⁺ or Cu²⁺ in CH₃CN, respectively, which makes it possible for distinguishing Hg²⁺ and Cu²⁺ from other metal ions by the ‘naked eye’.     

A new fluorescent sensor bearing three dansyl fluorophores for highly sensitive and selective detection of mercury(II) ions

A novel fluorometric sensor bearing three dansyl moieties based on tris[2-(2-aminoethylthio)ethyl]amine was prepared by a simple approach using a conventional two-step synthesis. The sensor exhibits highly Hg²⁺-selective ON-OFF fluorescence quenching behavior in aqueous acetonitrile solutions and is shown to discriminate various competing metal ions, particularly Cu²⁺, Ag⁺, and Pb²⁺ as well as Ca²⁺, Cd²⁺, Co²⁺, Fe³⁺, Mn²⁺, Na⁺, Ni²⁺, and Zn²⁺, with a detection limit of 1.15 × 10⁻⁷ M or 23 ppb.     

Synthesis of crownophanes possessing three pyridine rings

Novel crownophanes with three pyridine moieties (pyridinocrownophanes 4 and 5) were prepared by means of intramolecular [2+2] photocycloaddition of vinylpyridine derivatives. In the liquid-liquid extraction of heavy metal cations, 4 and 5 exhibited high efficiency toward Ag⁺. Comparing the high extractability and complexing stability constant for Ag⁺ to those of the corresponding pyridinocrownophanes 2 and 3 and observing the ¹H NMR spectra in the presence of Ag⁺, the ethereal oxygen atoms and the three nitrogen atoms were found efficiently and cooperatively to act as ligating sites.     

Hg- and Cu-selective fluoroionophoric behaviors of a dioxocyclam derivative bearing anthrylacetamide moieties

New dioxocyclam derivatives bearing two anthracene fluorophores were prepared, and their fluoroionophoric properties toward transition metal ions were investigated. Chemosensor 2 having anthrylacetamide moieties exhibited pronounced Hg²⁺- and Cu²⁺-selective fluoroionophoric properties in aqueous acetonitrile solution over other representative transition metal ions, as well as alkali and alkaline earth metal ions. Chemosensor 2 also exhibited Hg²⁺ and Cu²⁺ selectivity under competitive conditions in the presence of physiologically and environmentally important metal ions. The detection limits for the sensing of Hg²⁺ and Cu²⁺ ions were 7.8 × 10⁻⁶ and 1.5 × 10⁻⁶ M, respectively, in aqueous 95% acetonitrile solution.     

Synthesis and evaluation of multitopic bisbenzothiazolyl calix[4]arenes for ionic toxicants

Abstract

Two new benzothiazolyl calix[4]arene-based multitopic molecular receptors L-1 and L-2 have been synthesised and evaluated for recognition of ionic toxicants. The receptors selectively interact with copper, silver and fluoride ion toxicants as assessed through UV-visible, NMR and colorimetric techniques. The stability of L-1:Cu⁺² and L-2:Cu⁺² complexes was found to be higher than that of complexes formed with Ag⁺ and F^– complexes in the presence of trifluoroacetic acid. Superiority of L-1 over L-2 for analysis of identified toxicants has been determined by measurement of binding constants.     

Recombination of KrD and XeD ions with electrons

Recombination rate coefficients of protonated and deuterated ions KrH⁺, KrD⁺, XeH⁺ and XeD⁺ were measured using Flowing Afterglow with Langmuir Probe (FALP). Helium at 1600 Pa and at temperature 250 K was used as a buffer gas in the experiments. Kr, Xe, H₂ and D₂ were introduced to a flow tube to form the desired ions. Because of small differences in proton affinities of Kr, D₂ and H₂ mixtures of ions, KrD⁺/D₃⁺ and KrH⁺/H₃⁺ are formed in the afterglow plasma, influencing the plasma decay. To obtain a recombination rate coefficient for a particular ion, the dependencies on partial pressures of gases used in the ion formation were measured. The obtained rate coefficients, α_KrD+(250 K) = (0.9 ± 0.3) × 10⁻⁸ cm³ s⁻¹ and α_XeD+(250 K) = (8 ± 2) × 10⁻⁸ cm³ s⁻¹ are compared with α_KrH+(250 K) = (2.0 ± 0.6) × 10⁻⁸ cm³ s⁻¹ and α_XeH+(250 K) = (8 ± 2) × 10⁻⁸ cm³ s⁻¹.     

Reduction of Cu2+ to Cu+ in Xerogels Prepared from (3-Aminopropyl)Trimethoxysilane

Silica gels doped with Cu²⁺ ions were prepared from the (3-aminopropyl) trimethoxysilane (APTMOS)/tetraethoxysilane (TEOS) systems. Sols showed a broad absorption peak at 640 nm, suggesting 3–5 coordination of the aminopropyl groups to Cu²⁺. For gels prepared from APTMOS and dried at room temperature, the 640 nm peak decreased and a red-shifted absorption appeared below 400 nm within a few months. The luminescence spectra of the xerogels showed emission bands at 430–470 and 510 nm. The former and latter bands are ascribed to Cu⁺ monomer and dimer emissions, respectively. These results indicate that Cu²⁺ ions are reduced to Cu⁺. When xerogels were prepared from APTMOS/TEOS = 1 (vol/vol), the color of xerogels was blue with an absorption peak at around 670 nm, indicating no reduction of Cu²⁺ ions.     

New Cu+2 Complexes with N-Sulfonamide Ligands: Potential Antitumor,Antibacterial, and Antioxidant Agents

Nowadays, the discovery of a new non-toxic metal complex with biological activity represents a very active area of research. Two Cu⁺² complexes, [Cu(L1)₂(H₂O)₃] (C1) (HL1= N-(5-(4-methylphenyl)-[1,3,4]–thiadiazole–2-yl)-naphtalenesulfonamide) and [Cu(L2)₂(py)₂(H₂O)] (C2) (HL2= N-(5-ethyl-[1,3,4]–thiadiazole–2-yl)-naphtalenesulfonamide), with two new ligands were synthesized. The X-ray crystal structures of the complexes were determined. In both complexes, Cu⁺² is five-coordinated, forming a CuN₂O₃ and CuN₄O chromophore, respectively. The ligands act as monodentate, coordinating the metal ion through a single N_thiadiazole atom; for the C2 complex, the molecules from the reaction medium (pyridine and water) are also involved in the coordination of Cu⁺². The complexes have a distorted square pyramidal square-planar geometry. The compounds were characterized by FT-IR, electronic EPR spectroscopy, and magnetic methods. The nuclease activity studies confirm the complexes’ capacity to cleave the DNA molecule. Using a xanthine-xanthine oxydase system, the SOD mimetic activity of the complexes was demonstrated. Cytotoxicity studies were carried out on two tumor cell lines (HeLa, WM35) and on a normal cell line (HFL1) using the MTT method, with cisplatin used as a positive control. The antibacterial activity of the complexes was investigated against two Gram-positive and two Gram-negative bacteria, and compared with Amoxicillin and Norfloxacin using the disk diffusion method. Both complexes showed in vitro biological activity but the C2 complex was more active. A lack of in vivo toxicity was demonstrated for the C2 complex by performing hepatic, renal, and hematological studies on Swiss mice.     

Conductance Study of the Thermodynamics of Complexation of K+, Rb+, Cs+ and Tl+ Ions with Dibenzo-24-crown-8 in Binary Acetonitrile–Nitromethane Mixtures

The complexation reactions between dibenzo-24-crown-8 (DB24C8) and K⁺, Rb⁺, Cs⁺ and Tl⁺ ions were studied conductometrically in different acetonitrile–nitromethane mixtures at various temperatures. The formation constants of the resulting 1:1 complexes were calculated from the computer fitting of the molar conductance–mole ratio data at different temperatures. At 25 °C and in all solvent mixtures used, the stability of the resulting complexes varied in the order Tl⁺ > K⁺ > Rb⁺ > Cs⁺. The enthalpy and entropy changes of the complexation reactions were evaluated from the temperature dependence of formation constants. It was found that the stability of the resulting complexes increased with increasing nitromethane in the solvent mixture. The TΔS° vs. ΔH° plot of all thermodynamic data obtained shows a fairly good linear correlation indicating the existence of enthalpy–entropy compensation in the complexation reactions.     

Design and synthesis of a new coumarin-based ‘turn-on’ fluorescent probe selective for Cu

The novel coumarin-based ‘turn-on’ fluorescent probe (E)-3-(2,5-dimethoxybenzylideneamino)-7-hydroxy-2H-chromen-2-one (MGM) was designed, synthesized, and characterized. This compound shows high selectivity for Cu⁺², combined with a large fluorescence enhancement upon binding to Cu²⁺. Benesi-Hildebrand and Job plots demonstrate that the stoichiometry of the Cu²⁺ complex formed is 2:1. Preliminary studies employing epifluorescence microscopy demonstrated that Cu⁺² could be imaged in human neuroblastoma SH-SY5Y cells treated with MGM.