Formation Of Chelate Complexes Research Articles

Study of Anticorrosive Action of Alkylphosphonic Acid Solutions in Monoethanolamine Based on the Formation of Chelate Complexes With Iron Ions

Study of Anticorrosive Action of Alkylphosphonic Acid Solutions in Monoethanolamine Based on the Formation of Chelate Complexes With Iron Ions

The Interaction of Anthracycline Based Quinone-Chelators with Model Lipid Membranes: 1H NMR and MD Study.

Anthracycline antibiotics, e.g., doxorubicin, daunomycin, and other anthraquinones, are an important family of antitumor agents widely used in chemotherapy, which is currently the principal method for treating many malignancies. Thus, development of improved antitumor drugs with enhanced efficacy remains a high priority. Interaction of anthraquinone-based anticancer drugs with cell membranes attracts significant attention due to its importance in the eventual overcoming of multidrug resistance (MDR). The use of drugs able to accumulate in the cell membrane is one of the possible ways of overcoming MDR. In the present work, the aspects of interaction of anthraquinone 2-phenyl-4-(butylamino)naphtho[2,3-h]quinoline-7,12-dione) (Q1) with a model membrane were studied by means of NMR and molecular dynamics simulations. A fundamental shortcoming of anthracycline antibiotics is their high cardiotoxicity caused by reactive oxygen species (ROS). The important feature of Q1 is its ability to chelate transition metal ions responsible for ROS generation in vivo. In the present study, we have shown that Q1 and its chelating complexes penetrated into the lipid membrane and were located in the hydrophobic part of the bilayer near the bilayer surface. The chelate complex formation of Q1 with metal ions increased its penetration ability. In addition, it was found that the interaction of Q1 with lipid molecules could influence lipid mobility in the bilayer. The obtained results have an impact on the understanding of molecular mechanisms of Q1 biological activity.

Formation and Stability Analysis of La (III), Er (III) Ho (III) Lomatiol Chelate Complexes

The studies are carried out pH-metrically in which an interaction of trivalent metal cations La (III), Er (III) and Ho (III) under the specific conditions of thermodynamics were done, where the complex formation was achieved within ionic strength consistency and making an infinite dilution where a single mole of trivalent metal, was made to react with 02 moles of lomatiol. The formation constant in stepwise values showed no measurable difference at room temperature, but the complex formation may decline above >400C, as complex stability decreases at high temperature values. The chelate complex formation had been observed as a spontaneous process in solution with the obtained value of ΔG as a negative in all lomatiol metal systems. The observed positive value of change in entropy in all experimental study systems and minus values of free energy also justifies the spontaneity of the reaction. The stepwise formation rate constants (k1> k2> k3) showed a continuous fall in trivalent metal-lomatiol systems assigning the system formation as a normal complex formation.

Curcumin-Based β-Diketo Ligands for Ga3+: Thermodynamic Investigation of Potential Metal-Based Drugs

Curcumin is known for its therapeutic properties; among these, antioxidant, anti-inflammatory and anti-cancer ones stand out. Besides, curcumin metal complexes have shown widespread application in medicine and can be exploited as lead structures for developing metal-based drugs. Unfortunately, curcumin is poorly bioavailable, mainly due to its instability in physiological conditions; this weakness is tightly connected to the presence of the β-diketo moiety undergoing tautomeric equilibrium. Stability and metal-chelating ability can be tuned by modulating the electronic effects and steric hindrance close to the β-diketo moiety; in addition, formation of a metal complex shifts the tautomeric equilibrium towards the β-keto–enol form and increases stability in biological media. Among the metals used in clinical therapy, gallium nitrate has shown to have significant antitumor activity against non-Hodgkin lymphoma and bladder cancer, thus indicating that gallium-based drugs have potential for further development as antineoplastic agents with improved therapeutic activity. Curcuminoids have demonstrated high affinity for gallium(III), allowing the formation of stable positively charged M:L 1:2 β-diketonate complexes that benefit from the therapeutic activity of both the metal and the ligand. Seven new curcumin derivatives were synthesized and completely characterized. The new derivatives retain the solvent-dependent keto–enol tautomerism, with the prevalence of the diketo form in aqueous solution. Enhanced stability in simulated physiological conditions was observed in comparison to the lead compound curcumin. The presence of Ga3+ anticipates the dissociation of the enolic proton, allowing chelate complex formation, and simultaneously it shifts the tautomeric equilibrium towards the keto–enol form. A complete 1H/13C NMR and UV–Vis study was performed to define the metal-to-ligand stoichiometry ratio and the overall stability constants. In addition, we demonstrated that some of the derivatives have increased antiproliferative activity on colon cancer cells compared to curcumin and antioxidant properties. On the whole, the synthesized curcumin-based molecules may act as new gallium(III) chelators with improved stability with respect to curcumin and could open interesting perspectives for the development of novel therapeutic agents for cancer.

Micelle-associated endomorphin-1 has ability to bind copper in the oxidation state either Cu(II) or Cu(I)

Reduction of Cu(II) to Cu(I) in an oxidizing extracellular environment is a potential risk factor for neurodegenerative diseases, because the re-oxidation of Cu(I) to Cu(II) can be coupled to generation of reactive oxygen species. However, little is known about how the brain is protected from the copper-induced oxidative stress. In the present study, interactions of the endogenous opioid peptide endomorphin-1 (EM1, Tyr-Pro-Trp-Phe-NH2) with ionic copper were investigated. EM1 cannot bind copper with ordinary metal coordination chemistry, since the chelate complex formation of EM1 with the metal ion is inhibited by the proline residue in the second position. In the presence of SDS micelles, however, a significant quenching of fluorescence of the tryptophan side chain of EM1 was observed on addition of copper ion, either Cu(II) or Cu(I). The spectral changes of the UV absorption of the tryptophan, which are diagnostic of cation–π interaction, were also brought about by addition of copper to EM1 only in the presence of micelles. The copper-induced spectral changes of both fluorescence and UV absorption disappeared upon the substitution of Tyr1 with alanine. The obtained results indicated that EM1 binds the copper ion through the π-electrons of aromatic side chains of Tyr1 and Trp3, which are in close contact each other in the micelle-associated form. The copper-catalyzed oxidation/reduction reaction process converting dopamine to neuromelanin, which involves potentially neurotoxic intermediates, is inhibited by EM1. Owing to the ability to bind both Cu(II) and Cu(I), EM1 may have the potential to suppress the copper-mediated oxidative stress in the brain. The present results suggest an antioxidative effect of EM1, distinct from its known analgesic effect.

Non-clinical studies indicating lack of interactions between iron/calcium ions and linzagolix, an orally available GnRH antagonist

Linzagolix is an orally available gonadotropin-releasing hormone antagonist used to treat sex-hormone-dependent diseases in women. This study aimed to investigate drug-drug interactions between linzagolix and iron/calcium ions in the intended clinical setting by conducting pharmacokinetic studies in vitro and in rats. Insoluble precipitate formation with metal ions was evaluated by measuring linzagolix concentrations in four types of bio-relevant dissolution media (fasted/fed state simulated gastric fluid and fasted/fed state simulated gastric fluid version 2), and chelate complex formation with metal ions was evaluated by release of linzagolix from a cellulose membrane sac. In these in vitro studies, linzagolix showed no potential for insoluble precipitate formation under fasted/fed conditions and no chelate complex formation in the presence of metal ions. In rats, the plasma concentration-time profiles of linzagolix and iron ion were similar regardless of whether they were administered with or without ferrous sulfate and linzagolix choline at clinically relevant doses. Thus, linzagolix and iron ion had no effect on each other’s absorption in vivo. In conclusion, linzagolix is unlikely to cause clinically relevant drug-drug interactions by chelating metal ions according to the results of in vitro and in vivo studies.

Photocatalytic properties of nanosized zinc ferrite and zinc chromite

A simple one-step synthesis of developed surface zinc ferrite is proposed (S BET = 453.1 m2 g−1). The formation of zinc ferrite, zinc chromite (S BET = 53.6 m2 g−1), and mixed zinc ferrite-chromite (S BET = 37.4 m2 g−1) structures is studied. The resulting materials are analysed using x-ray phase and x-ray fluorescence analysis, IR spectrometry, electron microscopy, TGA and BET method. Single-phase sample formation mechanism is proposed, which includes transition element cation chelate complex formation stage in the presence of citric acid and subsequent thermal decomposition of the complexes formed. The synthesised materials exhibited photocatalytic activity in the decomposition of an organic dye under the action of hydrogen peroxide. The highest catalytic activity is demonstrated by zinc ferrite in acidic medium; the calculated reaction rate constant is 0.010 min−1 for ZnFe2O4, 0.008 min−1 for ZnFeCrO4, 0.007 min−1 for ZnCr2O4. The results can be applied to obtain materials suitable for wastewater treatment processes at industrial enterprises where organic dyes are used in production cycles.

A Novel Glass Fiber Coated with Sol-Gel Poly-Diphenylsiloxane Sorbent for the On-Line Determination of Toxic Metals Using Flow Injection Column Preconcentration Platform Coupled with Flame Atomic Absorption Spectrometry.

A novel simple and sensitive, time-based flow injection solid phase extraction system was developed for the automated determination of metals at low concentration. The potential of the proposed scheme, coupled with flame atomic absorption spectrometry (FAAS), was demonstrated for trace lead and chromium(VI) determination in environmental water samples. The method, which was based on a new sorptive extraction system, consisted of a microcolumn packed with glass fiber coated with sol–gel poly (diphenylsiloxane) (sol–gel PDPS), which is presented here for the first time. The analytical procedure involves the on-line chelate complex formation of target species with ammonium pyrrolidine dithiocarbamate (APDC), retention onto the hydrophobic sol–gel sorbent coated surface of glass fibers, and finally elution with methyl isobutyl ketone prior to atomization. All main chemical and hydrodynamic factors, which affect the complex formation, retention, and elution of the metal, were optimized thoroughly. Furthermore, the tolerance to potential interfering ions appearing in environmental samples was also explored. Enhancement factors of 215 and 70, detection limits (3 s) of 1.1 μg·L−1 and 1.2 μg·L−1, and relative standard deviations (RSD) of 3.0% (at 20.0 μg·L−1) and 3.2% (at 20.0 μg·L−1) were obtained for lead and chromium(VI), respec tively, for 120 s preconcentration time. The trueness of the developed method was estimated by analyzing certified reference materials and spiked environmental water samples.

Exploring the Complexation of Counterion in Novel Family of Polyelectrolytes with Unexpected Solubility Behaviour

In the present paper we study the effect of complexation in linear negatively charged polyelectrolytes with different alkali ions. With combination of IR-spectroscopy, X-ray diffraction and nanocalorimetry, we attempted to explain unusual solubility, crystallinity and thermal stability of these polymers. The increase of thermal stability and insolubility in water in series of semi-crystalline polysalts as K+ ≤ H+ <Na+ was explained by effectiveness of formation of chelating complex. Insoluble in water sodium salt shows the highest thermal stability of crystal phase up to . In contrast, well soluble in water amorphous lithium salt does not self-organize in chelating complex and is presented in ionic form.

Nutrient Supply to Seawater from Steelmaking Slag: The Coupled Effect of Gluconic Acid Usage and Slag Carbonation

Vanishing of seaweeds in coastal areas has become a serious environmental problem. Part of the reason is nutrient deficiency in seawater, especially iron. Steelmaking slag is probably one of the best nutrient suppliers in terms of cost and quantity. Utilizing steelmaking slag to fertilize coastal seaweeds may simultaneously address the two challenges of seaweed restoration and byproduct treatment. However, direct usage of slag from a basic oxygen furnace is not practical because of negative effects such as a sharp pH increase and magnesium loss. To address the disadvantages, this work investigated the leaching behavior of a practical steelmaking slag in an artificial seawater and clarified the coupled effect of gluconic acid usage and slag carbonation on aiding the nutrient supply. Slag carbonation prevents a drastic pH increase and Mg loss, while gluconic acid induces formation of stable chelated complexes. The combination of slag carbonation and gluconic acid usage results in significant improvements in the nutrient supply. By leaching the slag, the maximum concentration of Fe in seawater increases to 0.29 mg L−1, 193 times larger than the value in the initial seawater (1.5 μg L−1).

Cloud point extraction of Cefixime drug by direct (UV- Vis) spectrophotometer and indirect(Flame Atomic Absorption) technique

A new method for the determination of the Cefixime drug in some Pharmaceuticals using ultra violet-visible (UV- Vis) and indirect Flame Atomic Absorption Spectrophotometry (FAAS) by Cloud point Extraction by using Triton X-114 as surfactant, the method based to form chelating complex CEF – Pd (II) at 456nm, variables parameters were studied such as the concentration of metal ion, effect of pH, Triton X-114 amount, equilibration temperature and incubation time. The best pH for the formation of chelating complex was (9). The best temperature on cloud-point extraction was 55 0C at 20 min. then complex extracted with ethanol. The mole-ratio method has been used to determine the structure of chelate CEF – Pd (II) and found to be 1:1 L:M (Ligand : Metal). Beer’s Law was obeyed in the range 2.5-30 and 2.5-32.5μg/mL for UVVis and FAAS respectively. Limit of Detection and Limit of Quantitation LOD and LOQ values for these methods were (0.456592, 0.33374) μg/mL (1.521976, 1.112471) μg/mL respectively.the method was validated and successfully applied to drug formulations like Cefix capsules marketed in Iraq. The results of analysis have been validated statistically and by recovery studies and were found satisfactory

CHITIN- AND CHITOSAN BIOSORBENTS FROM CITRIC A CID MYCELIAL INDUSTRIAL WASTE

The goal of this study is to examine sorption capacity of chitin-glucan (ChGC) and chitosan-glucan (CsGC) biopolymer complexes extracted from the fungus Aspergillus niger mycelium. According to the findings chitosanglucan complex sorbs lead and copper ions (130–140 mg/g) better than chitin-glucan complex (50–80 ex mg/g). Langmuir theoretical model with R2= 0,996 determination coefficient well describe sorption isotherms. It is shown the chelate complex formation compound character based on ion and coordination bonds by chitin and chitosan biopolymers is more complex. According to test results the production of chitin and chitosan containing biopolymers from citric acid production mycelium by-products has a good future. The above biopolymers have a functional use. Besides of that they sorbs heavy metals and radionuclide ions.

Donor-Acceptor Properties of a Single-Molecule Altered by On-Surface Complex Formation.

Electron donor-acceptor molecules are of outstanding interest in molecular electronics and organic solar cells for their intramolecular charge transfer controlled via electrical or optical excitation. The preservation of their electronic character in the ground state upon adsorption on a surface is cardinal for their implementation in such single-molecule devices. Here, we investigate by atomic force microscopy and scanning tunneling microscopy a prototypical system consisting of a π-conjugated tetrathiafulvalene-fused dipyridophenazine molecule adsorbed on thin NaCl films on Cu(111). Depending on the adsorption site, the molecule is found either in a nearly undisturbed free state or in a bound state. In the latter case, the molecule adopts a specific adsorption site, leading to the formation of a chelate complex with a single Na+ alkali cation pulled out from the insulating film. Although expected to be electronically decoupled, the charge distribution of the complex is drastically modified, leading to the loss of the intrinsic donor-acceptor character. The chelate complex formation is reversible with respect to lateral manipulations, enabling tunable donor-acceptor molecular switches activated by on-surface coordination.

Spectrophotometric Study of the Complex Formation of Anionic Chelates of Cobalt(II) with Monotetrazolium Cations

The complex formation and extraction of anionic chelates of Co(II)–4-(2-thiazolylazo)resorcinol (TAR) with cations of monotetrazolium salts (TS) — (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and 3-(2-naphthyl)-2,5-diphenyl-2H-tetrazolium chloride (TV) — in the liquid–liquid extraction system Co(II)–TAR–TS–H2O–CHCl3 were studied by spectrophotometric methods. The optimum conditions for the extraction of Co(II) were found. The molar ratio of the components and the form of the anionic chelates of Сo(II) in the extracted compounds were determined by independent methods. The association process in the aqueous phase and the extraction process were investigated and quantitatively characterized. The following key constants were calculated: association constant, distribution constant, extraction constant, and recovery factor. The validity of the Beer’s law was checked, and some analytical characteristics were calculated. Based on the obtained results and the lower price of the monotetrazolium salt MTT compared with that of TV, the ion-associated complex of Co(II)–TAR–MTT can be implemented for determination of cobalt(II) traces in alloys and biological, medical, and pharmaceutical samples.

Determination of Cefalexin by Direct (UV- Vis) Spectrophotometer and Indirect(Flame Atomic Absorption) Technique

A new method for the determination of the drug cefalexin in some Pharmaceuticals using (UV-Vis) and indirect Flame Atomic Absorption Spectrophotometer (FAAS) , Fe III should forms a chelating complex with cefalexin (CEX –Fe III) at pH (1-8) and the best pH for the formation of (CEX –Fe III) chelating complex was (2) .The complex extracted with Methanol and Dimethy-Sulphoxide .The mole-ratio method has been used to determine the structure of chelate (CEX - Fe III) and found to be 2:1 LM ( Ligand : Metal.) .
 Keywords : Cefalexin , chelating complex.

Highly selective light-up Al3+ sensing by a coumarin based Schiff base probe: Subsequent phosphate sensing DNA binding and live cell imaging

Abstract A coumarin based simple fluorescent “turn-on” probe, 4-Hydroxy-3-[(2-hydroxy-5-methoxybenzylidene)-amino]-chromen-2-one (HMC), to detect metal ion based on the chelation enhanced fluorescence (CHEF), was synthesized by condensing 3-amino-4-hydroxycoumarin and 2-hydroxy-5-methoxybenzaldehyde. It was found to be highly selective and sensitive sensor for Al3+ in 90% aqueous methanol (MeOH: 0.01 M HEPES Buffer; 9:1; v/v) at pH 7.4 in fluorescence spectroscopy. Fluorescence intensity enhancement along with 10 nm blue shift was observed only in the presence of Al3+. The HMC binds Al3+ in 1:1 stoichiometry with a binding constant, Ka = (9.9 ± 0.04) × 103 M−1 and the detection limit was calculated to be as low as 1.62 μM. The binding mode of interaction with Al3+ and the chelate complex formation was supported with the help of a 1H NMR spectroscopy titration, ESI–MS and also by theoretical studies. Moreover, the HMC·Al3+ ensemble subsequently detected the biologically important phosphate ions and nucleotides via fluorescence quenching. The live cell imaging study indicated that HMC is highly efficient in the detection of exogenous Al3+ in living cell.

Mn(II) Scavenging Electrolyte Additive and Functional Binder

Introduction Mn(II) dissolution from lithium manganese oxide (LiMn2O4) positive electrode and Mn plating on graphite negative electrode are the well-known failure mode in lithium-ion chemistry [1]. The Mn plating degrades the electrochemical performances of graphite electrodes in two ways. One is the self-discharge of graphite, which is accompanied by Mn plating. The other is the degradation of solid electrolyte interphase (SEI), which leads to forthcoming electrolyte decomposition and film deposition. As a result, cell polarization becomes severe due to an increment in film resistance, which eventually leads to a cell failure [2]. To overcome the issues raised by Mn plating on graphite electrodes, several countermeasures have been made. For examples, the scavengers for hydrofluoric acid (HF), which attacks the positive electrodes to leach out Mn ions, have been used as the electrolyte additive. Also Mn(II) scavengers have been developed [3,4]. In this study, 1,4,8,11-tetraazacyclotetradenate (cyclam) and 1,4,7,10-tetraazacyclododecane (cyclen) is tested as a Mn(II) scavenger. Those tetradentate azamacrocyclic compounds are applied as an electrolyte additve or attached on the chains of polyvinylalcohol (PVA) binder. The Mn plating on graphite electrodes seems to be suppressed due to a strong compex formation with Mn(II) ions. Namely, the Mn plating is thermodynamically unfavored due to the complex formation since the reduction potential of Mn(II) moves to the more negative direction than that for the solvent-solvated Mn(II) ions. Moreover, the Mn plating is kinetically hindered due to higher overpotential that is caused by a strong chelate complex formation. Experimental A beaker-type three-electrode cells were fabricated with a graphite electrode (DAG 87 : Super P : PVdF binder = 85:5:10 in wt. ratio), a Li counter electrode and a Li reference electrode. 10 mM of Mn(ClO4)2 was dissolved into an electrolyte solution (1.0 M LiPF6 in EC/DEC, 1/1 = v/v) to simulate the Mn(II)-dissolved electrolyte. To examine the additive effect, 1.0 wt. % of cyclam was added into the Mn(II)-containing electrolyte solution. The cyclen-attached PVA was synthesized by mixing 8 wt. % PVA/water solution and 50 mg of cyclen that carries a carboxylic acid functional group. After casting the mixed solution on Cu foil, esterification was performed at 150 0C for 12 h under vaccum. To examine the Mn(II) scavenging action, the cyclen-attached PVA/Cu foil was immersed in the Mn(II)-containing electrolyte solution for 48 h. Finally, the Mn(II) ions entrapped in the cyclen-attached PVA were leached out by using the mixture of nitric, hydrofluoric and hydrochloric acid. Mn(II) concentration was analyzed by using inductively-coupled plasma atomic emission spectroscopy (ICP-AES). Results and discussion The differential capacity (dQ/dV) plots obtained in the first lithiation period show that the reduction current responsible for Mn plating, which appears in the wide potential range (0.0 ~ 0.8 V vs. Li/Li+) in the Mn(II)-containing electrolyte, disappears when cyclam is added (Fig. 1a). Clearly, cyclam plays the Mn(II) scavenging role. The Mn(II) concentration entrapped in the cyclen-attached PVA is compared with that entrapped in the pure PVA. The comparison shown Fig. 1b ascertains the strong compex formation betweeen Mn(II) ions and cyclen being attached in PVA. The cyclen-attached PVA can be used as a binder for graphite electrode fabrication, which has Mn(II) scavanging function.

Study on the Complex Formation of Anionic Chelates of Co(II)–4-(2-Thiazolylazo)resorcinol with Ditetrazolium Cations

Study on the Complex Formation of Anionic Chelates of Co(II)–4-(2-Thiazolylazo)resorcinol with Ditetrazolium Cations

In silico and in vivo studies of molecular structures and mechanisms of AtPCS1 protein involved in binding arsenite and/or cadmium in plant cells

This paper reports a continuation of our previous research on the phytochelatin synthase1 (PCS1) gene involved in binding and sequestration of heavy metals or metalloids in plant cells. Construction of a 3D structure of the Arabidopsis thaliana PCS1 protein and prediction of gene function by employing iterative implementation of the threading assembly refinement (I-TASSER) revealed that PC ligands (3GC-gamma-glutamylcysteine) and Gln50, Pro53, Ala54, Tyr55, Cys56, Ile102, Gly161, His162, Phe163, Asp204 and Arg211 residues are essential for formation of chelating complex with cadmium (Cd²⁺) or arsenite (AsIII). This finding suggests that the PCS1 protein might be involved in the production of the enzyme phytochelatin synthase, which might in turn bind, localize, store or sequester heavy metals in plant cells. For validation of the in silico results, we included a T-DNA tagged mutant of Arabidopsis thaliana, SAIL_650_C12, (mutation in AtPCS1 gene) in our investigation. Furthermore, using reverse transcriptase PCR we confirmed that the mutant does not express the AtPCS1 gene. Mutant plants of SAIL_650_C12 were exposed to various amounts of cadmium (Cd²⁺) and arsenite (AsIII) and the accumulation of these toxic metals in the plant cells was quantified spectrophotometrically. The levels of Cd²⁺ and AsIII accumulation in the mutant were approximately 2.8 and 1.6 times higher, respectively, than that observed in the wild-type controlled plants. We confirmed that the results obtained in in silico analyses complement those obtained in in vivo experiments.

Mechanochemical solubilization of silicon dioxide with polyphenol compounds of plant origin

Mechanochemical interaction of an amorphous silicon dioxide with catechins of plant origin was used for silicon dioxide solubilization at neutral pH. Mechanism of polyphenol interaction with silicon dioxide was suggested based on investigation of kinetics of solubilization of ‘silicon dioxide-catechol’ model system that included an interaction of hydroxyl groups on the surface of silica with polyphenols, formation of surface complexes, and solubilization of these complexes. Mechanochemical treatment of catechol—natural catechin of plant origin—with amorphous silicon dioxide resulted in an increase of the solubilization rate due to chelate complex formation.