Phenothiazine-pyridyl chalcone: an easily accessible colorimetric and fluorimetric ‘on-off’ dual sensing probe for Cu

Phenothiazine-pyridyl chalcone, a new internal charge transfer (ICT) probe, has been designed that allows naked eye detection and a reversible, ratiometric ‘on-off’ sensing capability for biologically and environmentally significant Cu²⁺ in CH₃OH-H₂O (4:1 v/v) under buffered conditions. The association constants determined using spectrophotometric and the fluorimetric techniques follow the order Cu²⁺ > Ni²⁺ > Co²⁺ > Zn²⁺ > Cd²⁺ > Mg²⁺ ≈ Ba²⁺ ≈ Ca²⁺ ≈ K⁺≈ Na⁺ ≈ Li⁺.     

A new intramolecular charge transfer receptor as a selective ratiometric ‘off-on’ sensor for Zn

A new intramolecular charge transfer (ICT) probe 3 is found to display a highly selective photophysical response in the presence of Zn²⁺, among various biologically significant metal ions examined. The absorption band of 3 is red shifted by 84 nm and the fluorescence intensity increases 13-fold in the presence of Zn²⁺. The binding interaction follows the order Zn²⁺ > Cd²⁺ > Mg²⁺ > Ba²⁺ > Ca²⁺ > K⁺ ≅ Na⁺ ≅ Li⁺ and the stability constant for 3 + Zn²⁺ is over an order of magnitude higher compared to biologically competing Ca²⁺ and Mg²⁺.     

A simple internal charge transfer probe offering dual optical detection of Co (II) via color and fluorescence modulations

A newly designed internal charge transfer chemosensor, DIPZON exhibits Co²⁺ selective optical responses, which include 112 nm red shift in absorption and a dramatic 37-fold enhancement in the fluorescence output in the buffer CH₃OH/H₂O (1:1 v/v) system. By contrast, the optical responses were not as sensitive with several other biologically relevant metal ions examined with the binding interactions following the sequence Co²⁺ > Cu²⁺ > Zn²⁺ > Cd²⁺ >> Ba²⁺ ≈ Ca²⁺ ≈ Mg²⁺ ≈ K⁺ ≈ Na⁺ ≈ Li⁺.     

COMPETITIVE NMR STUDY OF THE COMPLEXATION OF SOME ALKALINE EARTH AND TRANSITION METAL IONS WITH 12-CROWN-4, 15-CROWN-5 AND BENZO-15-CROWN-5 IN ACETONITRILE SOLUTION USING THE LITHIUM-7 NUCLEUS AS A PROBE

Abstract

⁷Lithium NMR measurements were used to determine the stoichiometry and stability of Li⁺ complexes with 12-crown-4, 15-crown-5 and benzo-15-crown-5 in acetonitrile solution. A competitive ⁷Li NMR technique was also employed to probe the complexation of Mg²⁺, Ca²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Cd²⁺ ions with the same crown ethers. In all cases, the stability of the resulting 1:1 complexes was found to decrease in the order 15-crown-5 > benzo-15-crown-5 > 12-crown-4. Ca²⁺ and Cd²⁺ ions formed the most stable complexes in the series.     

A circular dichroism sensor for Ni and Co based on l-cysteine capped cadmium sulfide quantum dots

A new circular dichroism sensor for detecting Ni²⁺ and Co²⁺ was proposed for the first time using chiral chelating quantum dots. The detection principle was based on changing of circular dichroism signals of the chiral quantum dots when forming a chiral complex with Ni²⁺ or Co²⁺. l-Cysteine capped cadmium sulfide quantum dots (l-Cyst-CdS QDs) were proposed as a chiral probe. The CD spectrum of l-Cyst-CdS QDs was significantly changed in the presence of Ni²⁺ and Co²⁺. On the other hand, other studied cations did not alter the original CD spectrum. Moreover, when increasing the concentration of Ni²⁺ or Co²⁺, the intensity of the CD spectrum linearly increased as a function of concentration and could be useful for the quantitative analysis. The proposed CD sensor showed linear working concentration ranges of 10–60 μM and 4–80 μM with low detection limits of 7.33 μМ and 1.13 μM for the detection of Ni²⁺ and Co²⁺, respectively. Parameters possibly affected the detection sensitivity such as solution pH and incubation time were studied and optimized. The proposed sensor was applied to detect Ni²⁺ and Co²⁺ in real water samples, and the results agreed well with the analysis using the standard ICP-OES.     

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.     

Fluorescent chemosensor based-on naphthol-quinoline for selective detection of aluminum ions

In this study, an assay to quantify the presence of aluminum ions with a receptor containing naphthol and quinoline moieties was developed using a turn-on fluorescence enhancement approach. Upon treatment with aluminum ions, the fluorescence of the receptor was enhanced at 510 nm due to the formation of a complex between the ligand and aluminum ions at room temperature. As the concentration of Al³⁺ was increased, the fluorescence gradually increased. Other metal ions, such as K⁺, Ag⁺, Ca²⁺, Mg²⁺, Zn²⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Cd²⁺, Cr³⁺, Fe³⁺, In³⁺, had no significant effect on the fluorescence.     

Factorial design for optimization of experimental variables in preconcentration of copper by a chromotropic acid loaded Q-Sepharose adsorbent

An agarose-based anion exchanger (Q-Sepharose) was loaded with chromotropic acid (CTA) and used for column preconcentration and determination of copper by flame AAS. Preliminary experiments indicated that a sample pH of 5.7-6.5 is best suited for accumulation of copper and a 2.5 ml portion of a 0.02 mol l⁻¹ HCl solution can efficiently desorb the analyte from the column. An incomplete factorial design was used for optimization of five different variables that affect recovery of copper. The results indicated that ionic strength, pH and sample volume variables are the most important effects, respectively. Hence, these variables and their possible interactions were studied more carefully. In optimized conditions, the column could tolerate up to 0.18 mol l⁻¹ sodium nitrate in the matrix. A 5 ml portion of a 0.02 mol l⁻¹ CTA was sufficient for loading of a 0.5 ml column prior to preconcentration of copper from a 150 ml sample solution. Matrix ions of Ca²⁺, Mg²⁺, Na⁺ and K⁺ and potentially interfering ions of Pb²⁺, Ni²⁺, Cd²⁺, Co²⁺, Zn²⁺ and Mn²⁺ with relatively high concentrations did not have any significant effect on the recovery of the analyte. A preconcentration factor of 60 and a detection limit of 1.0 μg l⁻¹ was obtained for the determination of copper by the flame AAS method. A precision better than 2.5%, expressed as R.S.D., was also achieved. Application of the method to tap water and two different river water samples resulted in values well confirmed by direct determinations with ET-AAS.     

1,8-萘酰亚胺为发色团的Zn2+荧光探针的合成及性能研究

合成了以1,8-萘酰亚胺为发色团,以联吡啶为离子受体的Zn²⁺荧光探针,并进行了表征及离子识别性能的研究。研究表明该化合物对Zn²⁺具有良好的识别性能,同时相对于Ca²⁺, Cd²⁺, Co²⁺, Cu²⁺, Hg²⁺, Fe³⁺, Mn²⁺, Ni²⁺, Pb²⁺等金属离子具有良好的选择性。     

Schiff碱配合物的研究——Ⅸ.表面Schiff碱配合物对H2O2分解的催化作用

制备了两种表面Schiff碱及其Cu²⁺、Co²⁺、Ni²⁺、Zn²⁺配合物,考察了它们对H₂O₂分解的催化性能,其活性顺序为:Co²⁺>Cu²⁺>Ni²⁺>Zn²⁺,且与金属离子氧化还原电位有关。溶液的pH值增加有利于催化反应,有机配体的加入则对反应有所抑制。     

Complexation of 3-hydroxy-2,2′-iminodisuccinic acid (HIDS) with Mg2+, Ca2+, Mn2+, Fe3+, Fe2+, Co2+, Ni2+, Cu2+, and Zn2+ ions in aqueous solution

In a search for environmental-friendly metal chelating ligands for industrial applications, the protonation and complex formation equilibria of 3-hydroxy-2,2′-iminodisuccinic acid with Mg²⁺, Ca²⁺, Mn²⁺, Fe³⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ ions in aqueous 0.1 mol L^?1 NaCl solution were studied at 25°C by potentiometric titration. The model for complexation and the stability constants of the different complexes were determined for each metal ion using the computer program SUPERQUAD. In all cases, complex formation was dominated by stable ML ^{n ?4} complexes.     

Complexation Studies of a Calix[4](aza)crown and Crystal Structure of its Magnesium Complex

A systematic study of extraction properties and complexation behaviour of the calix[4](aza)crown 1 towards alkaline earth (Mg²⁺, Ca²⁺,Sr²⁺, Ba²⁺) and transition metal (Co²⁺, Ni²⁺, Cu²⁺,Zn²⁺) cations is presented. The binding behaviour of 1 was also investigated by ¹H-NMR and the crystal structure of the 1:1 complex with Mg²⁺ isdescribed.     

Effect of Solvent on Competitive Bulk Membrane Transport of Transition and Post Transition Metal Cations Using Decyl-18-crown-6

A series of competitive metal ion transport experiments have been performed. Each involved transport from an aqueous source phase across an organic membrane phase into an aqueous receiving phase. The source phase contained equimolar concentrations of cobalt(II), nickel(II), cupper(II), zinc(II), cadmium(II), silver(I) and lead(II) metal cations. The membrane phase incorporated ionophore, decyl-18-crown-6. The membrane solvents include: chloroform, dichloromethane, 1,2-dichloroethane, nitrobenzene and chloroform–nitrobenzene binary solvents. A good transport efficiency and selectivity of Pb²⁺ transport from aqueous solutions are observed in this investigation. The selectivity order for competitive bulk liquid membrane transport of the studied transition and post transition metal cations through chloroform is: Pb²⁺>Co²⁺>Ni²⁺>Ag⁺>Cd²⁺, but in the case of dichloromethane, 1,2-dichloroethane and nitrobenzene as liquid membranes, the selectivity sequences were found to be: Pb²⁺>Co²⁺>Cd²⁺>Cu²⁺>Ag⁺>Ni²⁺>Zn²⁺, Pb²⁺>Co²⁺>Ag⁺>Ni²⁺>Zn²⁺ and Pb²⁺>Co²⁺>Ni²⁺>Zn²⁺>Cd²⁺>Ag⁺, respectively. The transport rate of the metal cations in chloroform–nitrobenzene binary solvents is sensitive to the solvent composition. The transport processes were studied in absence and presence of the stearic acid and the results show that the sequence of selectivities and ion transport rates change in the presence of stearic acid.     

Spectrophotometric and conductometric studies of the thermodynamics complexation of Zn2+, Ni2+, Co2+, Pb2+ and Cu2+ ions with 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane ligand in acetonitrile solution

The complexation reaction between 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane ligand (Kryptofix5) and Zn²⁺, Ni²⁺, Co²⁺, Pb²⁺ and Cu²⁺ ions were studied conductometrically in acetonitrile solution. The formation constants of the resulting 1:1 complexes were calculated from the computer fitting of the molar conductance and absorbance measurements in various mole ratios. The enthalpy and entropy changes of the complexation reactions were derived from titration conductometry in acetonitrile at various temperatures. At 25 °C, the stability of the resulting complexes varied in the order Pb²⁺ > Zn²⁺ > Cu²⁺> Co²⁺> Ni²⁺.     

A diamide-diamine based Cu chromogenic sensor for highly selective visual and spectrophotometric detection

A diamide-diamine based sensor 3 possessing anthracene-9,10-dione as a chromogenic moiety has been synthesized and demonstrates a highly selective colour change from red to blue with Cu²⁺ for visual detection of Cu²⁺ (5-50 μM). Other metal ions, viz. Fe²⁺, Cr³⁺, Co²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Ag⁺, Pb²⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ cations do not lead to any change in colour and their presence does not interfere with the visual and quantitative analysis of Cu²⁺. The selective deprotonation of an aryl amine NH by Cu²⁺ is responsible for a bathochromic shift and significant colour changes. Significantly, the stability of the 3·Cu²⁺ complex between pH 7 and 12 allows Cu²⁺ estimation under neutral and basic conditions.     

Selective removal of heavy metal ions using sol-gel immobilized and SPE-coated thiacrown ethers

Sorbent materials based on three thiacrown ethers, 1,4,7,10-tetrathiacyclododecane (12S4), 1,4,7,10,13-pentathiacyclopentadecane (15S5) and 1,4,7,10.13,16-hexathiacyclooctadecane (18S6) were prepared either by immobilizing the ligands into sol-gel (SG) matrix or coating on commercial solid phase extraction (SPE) column. SG sorbents were characterized by FT-IR, energy dispersive X-ray microanalysis (EDX) and thermogravimetric analysis/derivative thermogravimetric analysis (TGA/DTG). A marked thermal stability of the ligands when immobilized in sol-gel matrix was noted. The competitive sorption characteristics of a mixture of eleven metal ions (Mg²⁺, Zn²⁺, Cd²⁺, Co²⁺, Mn²⁺, Ca²⁺, Cu²⁺, Ni²⁺, Ag⁺, V⁴⁺, Hg²⁺) using: (i) batch method with ligands trapped in SG matrices, and (ii) off-line SPE column containing coated ligands were studied using ICP-MS. The extraction of metals were optimized for key parameters such as pH, contact time/flow rate, particle size (for SG sorbents) and ligand concentration. Under the optimized conditions, all the immobilized thiacrown ethers exhibited highest selectivity toward Ag⁺, with lesser responses to Hg²⁺ while the extraction of other metal ions were negligible. Among the SG sorbents, 18S6-SG offer the highest capacity and the best selectivity over Hg²⁺. However, for practical applications such as for selective isolation and preconcentration of Ag⁺, the SPE type especially based on 18S6 is preferred as analysis time and recoveries are favorable. The sorbents can be repeatedly used three times as there was no significant deterioration in the metal uptake (%E > 90%) or interference from other metal ions. The optimized procedures were successfully applied for the separation and preconcentration of traces Ag⁺ in different water samples.     

Rapid capillary zone electrophoresis method for the determination of metal cations in beverages

A rapid and reliable capillary zone electrophoresis method for the determination of inorganic cations was developed. The complete separation of K⁺, Ba²⁺, Ca²⁺, Na⁺, Mg²⁺, Mn²⁺, Ni²⁺, Cd²⁺, Li⁺ and Cu²⁺ can be achieved in 4 min with a simple electrolyte composed by 10 mM imidazole as the carrier buffer and background absorbance provider and acetic acid as the complexing agent (pH 3.60). Injection was performed hydrostatically by elevating the sample at 10 cm for 30 s. The running voltage was +25 kV at room temperature. Indirect UV-absorption detection was achieved at 185 nm. The detection limit was in the range between 0.06 mg/l (Mg²⁺) and 0.57 mg/l (K⁺) and the quantification limits ranged from 0.10 mg/l (Ni²⁺) to 0.80 mg/l (Cu²⁺). The calibration graphs were linear in the concentration range from the quantification limit till at least 1 g/l in K⁺, 10 mg/l in Ba²⁺, Ca²⁺, Mg²⁺, Mn²⁺, Ni²⁺ and Cd²⁺, 40 mg/l in Na⁺ and 12 mg/l in Li⁺ and Cu²⁺. The repeatability, intraday and interday analysis were ≤1.55% and ≤3.64% for migration time and ≤3.38% and ≤3.63% for peak area. The method developed has been applied to several beverage samples with only a simple dilution and filtration treatment of the sample. The proposed method is simple, fast, cheap and it is achieved with common products in either laboratory. For these reasons, it is a very useful method for routine analysis.     

Cation exchange behaviour of mercury (II) on Dowex 50W-X8

Summary Quantitative studies are reported on the behaviour of mercury at milligram level, using cation exchange resin Dowex 50W-X8. Various eluants such as nitric acid, hydrochloric acid, sulphuric acid, ammonium acetate, sodium nitrate solutions, sodium nitrate-nitric acid mixtures, ammonium acetate-acetic acid mixture are used for column operation. The elution constants are evaluated. Mercury(II) is separated from different cations, i.e., Ca²⁺, Ba²⁺, Sr²⁺, Mg²⁺, Fe³⁺, Al³⁺, Co²⁺, Ni²⁺, Zn²⁺, Cu²⁺ by selective elution.

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Zusammenfassung Das Verhalten von mg-Mengen Quecksilber am Kationenaustauscher Dowex 50W-X8 wird quantitativ untersucht. Dabei werden folgende Eluierungsmittel benutzt: Salpetersäure, Salzsäure, Schwefelsäure, Lösungen von Ammoniumacetat und Natriumnitrat sowie die Gemische Salpetersäure-Natriumnitrat und Essigsäure-Ammoniumacetat. Die Elutionskonstanten werden berechnet. Durch selektive Eluierung kann Quecksilber von mehreren Kationen (Ca²⁺, Ba²⁺, Sr²⁺, Mg²⁺, Fe³⁺, Al³⁺, Co²⁺, Ni²⁺, Zn²⁺, Cu²⁺) getrennt werden.

     

Fluorescence quenching studies on the interaction of a novel deepened cavitand towards some transition metal ions

A novel ‘three-level’ deepened cavitand featuring a significantly sizable portal has been synthesized and its interaction with some transition metal ions has been investigated in THF/H₂O binary solvent using fluorescence quenching technique. The results suggest that among the used transition metal ions including Ag⁺, Cd²⁺, Cu²⁺, Fe³⁺, Cr³⁺, Hg²⁺, La³⁺, Mn²⁺, Ni²⁺, Zn²⁺ and Co²⁺, only Fe³⁺ and Cu²⁺ show good quenching ability. In order to interpret the quenching mechanism, the Stern–Volmer kinetics, and the presence of both the dynamic and static quenching have been discussed. It was found that the simultaneous presence of the sphere-of-action static quenching and dynamic quenching model agrees very well with the experimental results. The limits of detection for Fe³⁺ and Cu²⁺ were found to be 2.1 × 10⁻⁶ mol L⁻¹ (3σ) and 3.6 × 10⁻⁶ mol L⁻¹ (3σ), respectively. Cations with potential interference, such as K⁺, Na⁺, Mg²⁺, Ca²⁺, Co²⁺, La³⁺ and Mn²⁺ do not have significant effects on the determinations of Fe³⁺ and Cu²⁺. This cavitand can be potentially applied as optical sensor for the detection of Fe³⁺ and Cu²⁺.     

Fluorescence sensing of Cu within a pseudo 18-crown-6 cavity

We report herein a pseudo-crown based fluorescent receptor (1) for the selective detection of Cu²⁺ cation. Receptor 1 can detect Cu²⁺ even in 5 μM level in acetonitrile-water (9:1 v/v). Compound 1 is very effective for the detection of Cu²⁺ amongst the series of metal ions studied (Li⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺, Ba²⁺, Pb²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺ and Mn²⁺).