Complex Formation Of Metal Ions Research Articles

Effects of Heterogeneous Mixing of Imidazolium-Based Ionic Liquids with Alcohols on Complex Formation of Ni(II) Ion.

Understanding the complex formation of metal ions in room-temperature ionic liquids (ILs) is essential for the application of ILs in solvent extraction. Nevertheless, the research on metal complex formation in ILs lags behind other applications. The complex formation equilibria may be influenced by specific interactions among the metal ion, ligand molecule, and IL cation and anion. In the present investigation, the complex formation of Ni2+ with ethanol (EtOH) and methanol (MeOH) molecules in ILs, 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([CNmim][TFSA], where N represents the alkyl chain lengths of 2 and 8) was discussed in terms of the microscopic interactions among alcohol molecules, [CNmim]+ and [TFSA]-, and the mesoscopic mixing states of alcohols in [CNmim][TFSA], with N = 2-12. The microscopic interaction of alcohol molecules with the imidazolium ring H atoms in the ILs was evaluated by using ATR-IR and 1H and 13C NMR spectroscopies. The self-hydrogen bonding of alcohol molecules was clarified from the O-H stretching vibration of alcohol molecules. MeOH molecules can be more strongly hydrogen-bonded with themselves than EtOH molecules due to the less steric hindrance and the weaker dispersion force of MeOH with the IL cation's alkyl chain. In fact, small-angle neutron scattering (SANS) experiments revealed the more heterogeneous mixing of MeOH with the ILs by the self-hydrogen bonding among MeOH molecules than EtOH. The longer the IL cation's alkyl chain, the more the MeOH clusters significantly form. In contrast, the formation of EtOH clusters becomes weaker with elongating the alkyl chain. Ultraviolet (UV)-visible spectroscopic measurements on Ni2+-[CNmim][TFSA]-alcohol solutions with N = 2 and 8 revealed that di-, tetra-, and hexa-alcohol-Ni2+ complexes are formed in both the ILs. With N = 2, the stabilities of Ni2+-EtOH and Ni2+-MeOH complexes are comparable in the IL. However, with N = 8, the complexes are more stable in the EtOH solutions than in the MeOH solutions. This is because the less heterogeneous mixing of EtOH molecules with the IL results in the larger enthalpic contribution in the complex formation, as shown by the thermodynamic parameters estimated by the van't Hoff plots on the stability constants at several temperatures.

Chelation and Metal-Ion Complex Formation of Chitosan Treated Cotton


 
 
 Chitin dan chitosan adalah bahan “chelate” yang sangat kuat untuk ion transisi logam terutama tembaga, nikel dan merkuri, dan sifat-sifat ini yang akan intensif di bahas. Pada studi ini kain kapas (cotton) dikerjakan dengan larutan chitosan-asam polikarboksilat untuk memperoleh kain kapas-chitosan yang mengandung gugus group karboksilat (-COOH) dan gugus amina (-NH2) fungsional. Penggunaan asam polykarboksilat (asam sitrat dan maleik) pada pelarutan chitosan menghasilkan group karboksil 0,5 meqs/g pada kain yang dicelup dengan larutan chitosan asam karboksilat. Kemudian kain kapas yang telah mengandung gugus karboksilat dan gugus amina ini dicelupkan pada larutan garam logam (garam tembaga dan seng). Terbukti bahwa larutan garam tembaga (copper) memberikan warna biru pada kain, hal ini mengindikasikan telah terjadi reaksi kompleks atau “Chelate”. Implikasi dari hasil ini maka diperkirakan kandungan group karboksil dan amina ini akan mempengaruhi pada pencelupan kain, namun hal ini tidak diuji.
 Kata kunci : Chitosan, Kain Kapas, Chelate, Asam asetat, Asam citrate, Asam maleik, Tembaga sulphate, Tembaga acetate.
 Abstract
 Chitin and chitosan are powerfull chelating agents for transition metal ions, particularly copper, nickel and mercury, and these properties have been extensively reviewed. In this study, cotton fabric has been treated with chitosan- polycarboxylic acid solution to form chitosan treated cotton fabric containing carboxyl (-COOH) and amine (-NH2) functional groups. The use of polycarboxylic acids (citric and maleic acids) to dissolve chitosan has given carboxyl groups 0.5 meqs/g into chitosan treated cotton fabrics. Instead, the complexing of the treated cotton samples with copper and zinc salts was examined. The copper salt solutions gave blue fabrics confirming easily that complexing or chelation had occurred. There are implications for dyeing cotton making use of these groups but this was not investigated.
 Keyword : Chitosan, Cotton fabric, Chelation, Acetic acid, Citric acid, Maleic acid, Copper (II) sulphate, Copper (II) acetate.
 
 

Facile Phase-Selectable Chemical Synthesis of Tin Selenide Nanosheets toward Nanostructured Materials for Energy-Related Applications

Here, we present a facile, phase-selectable, size-controllable chemical method for the synthesis of Sn-Se nanosheets (NSs). The resultant NSs were characterized using XRD, SEM, TEM, STEM, and EDS. Phase control was achieved by changing the input molar ratio of Sn:Se. At ratios of 1:1 and 1:2, pure-phase, rectangular SnSe NSs; at ratios of 1:6 and 1:10, pure-phase, hexagonal SnSe2 NSs; and at a ratio of 1:4, a mix of the two NSs were produced. The produced NSs were large (a few hundred nm in diameter) and thin (10–20 nm), although there was no significant increase in the optical band gap calculated from UV–vis–NIR spectroscopy, indicating an absence of quantum confinement effects. Size control of both phases was achieved by changing the amount of the ligand, trioctylphosphine oxide (TOPO). Increasing the amount of TOPO decreased the size of the SnSe NSs and increased the size of the SnSe2 NSs. Finally, the formation mechanism was investigated and it was found that the formation of metal-ion complexes, namely, Sn-TOPO and Se-oleylamine, played an important role in the phase selectivity and size distribution of the NSs by changing the effective ratio of Sn:Se and slowing the nucleation of the NSs.

Thermodynamic Study of the formation of transition metal ion complexes carrying medicinal drug in mixed solvent media

Thermodynamic Study of the formation of transition metal ion complexes carrying medicinal drug in mixed solvent media

Recent developments in supramolecular complexes of azabenzenes containing one to four N atoms: synthetic strategies, structures, and magnetic properties.

For the last couple of decades, azabenzene-based ligands have drawn much attention from inorganic chemists due to their ability to coordinate with different metal ions to form supramolecular clusters. These azabenzenes are weak σ donors and strong π acceptors and electron-deficient. Metallogrid complexes and non-grid oligomers are well-defined supramolecular clusters, formed by appropriate chelating ligands, and can show interesting optical, magnetic, and electronic properties. Self-assembly of [n × n] metallogrid complexes is dominated by the entropic factor while the formation of oligonuclear metal ion complexes is dominated by other effects like CFSE, electrostatic factors, ligand conformational characters, etc. Herein, the present article gives an overview of six-membered heterocyclic azine-based ligands and their potential for different metal ions to form polynuclear complexes. Moreover, their temperature-dependent magnetic properties and SCO phenomena are well described and tabulated.

Iron(III) and Zinc(II) Metal Alkaloid Complexes: Synthesis, Characterization and Biological Activities

Alkaloids possess various pharmacological actions and hence are considered as active biological moieties. Metal ions are essential for the normal functioning of the human body and any deficiency may cause diseases. In biomedical sciences, alkaloid metal ion complex formation has become a significant research area. In this study, three alkaloid ligands (L1, L2 and L3) underwent metal complex formation to produce iron(III) and zinc(II) metal complexes. Later, the biological activities of these alkaloid ligands and their iron(III) and zinc(II) metal complexes were investigated. These ligands and their metal complexes were characterized using ultraviolet-visible spectroscopy (UV-Vis), fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS). Pharmacological tests including antibacterial, antifungal, antioxidant and antitumor assays were performed. All compounds showed antibacterial and antifungal activity, but the metal complexes showed better activities than the original ligands, especially the zinc(II) complexes of all ligands. All compounds showed more significant antifungal activity against Candida albicans than Candida glabrata. Free ligands illustrated better antioxidant behaviour and antitumour activity compared to the metal complexes. Thus, both ligands and their metal complexes, being active agents, should be explored further particularly with reference to their mechanism of action

Potentiometric Investigation on Complex Formation and Stabilities of Some Divalent Metal Ions with l-Cysteine and Glycine as Ligands in Aqueous Solutions

Potentiometric Investigation on Complex Formation and Stabilities of Some Divalent Metal Ions with l-Cysteine and Glycine as Ligands in Aqueous Solutions

Research progress on the response of tea catechins to drought stress.

Drought stress (DS) is the most important abiotic stress affecting yield and quality of tea worldwide. DS causes oxidative stress to cells due to the accumulation of reactive oxygen species (ROS). As non-enzymatic antioxidants, tea catechins can scavenge excess ROS in response to DS. Further, catechin accumulation contributes to the formation of oxidative polymerization products (e.g. theaflavins and thearubigins) that improve the quality of black tea. However, there are no systematic reports on the response of tea catechins to DS. First, we reviewed the available literature on the response of tea plants to DS. Second, we summarized the current knowledge of ROS production in tea leaves under DS and typical antioxidant response mechanisms. Third, we conducted a detailed review of the changes in catechin levels in tea under different drought conditions. We found that the total amounts of catechin and o-quinone increased under DS conditions. We propose that the possible mechanisms underlying tea catechin accumulation under DS conditions include (i) autotrophic formation of o-quinone, (ii) polymerization of proanthocyanidins that directly scavenge excess ROS, and (iii) formation of metal ion complexes and by influencing the antioxidant systems that indirectly eliminate excess ROS. Finally, we discuss ways of potentially improving black tea quality using drought before picking in the summer/fall dry season. In summary, we mainly discuss the antioxidant mechanisms of tea catechins under DS and the possibility of using drought to improve black tea quality. Our review provides a theoretical basis for the production of high-quality black tea under DS conditions. © 2021 Society of Chemical Industry.

A compact fluorescence/circular dichroism dual-modality probe for detection, differentiation, and detoxification of multiple heavy metal ions via bond-cleavage cascade reactions

Selective detection of multiple analytes in a compact design with dual-modality and theranostic features presents great challenges. Herein, we wish to report a coumarin-thiazolidine masked d-penicillamine based dual-modality fluorescent probe COU-DPA-1 for selective detection, differentiation, and detoxification of multiple heavy metal ions (Ag+, Hg2+, Cu2+). The probe shows divergent fluorescence (FL) /circular dichroism (CD) responses via divergent bond-cleavage cascade reactions (metal ion promoted C-S cleavage and hydrolysis at two distinctive cleavage sites): FL “turn-off” and CD “turn-on” for Ag+ (no hydrolysis), FL “turn-on” and CD “turn-off” for Hg2+ (imine hydrolysis), and FL “self-threshold ratiometric” and CD “turn-off” for excess Cu2+ (lactone and imine hydrolysis), providing the first example of a fluorescence/CD dual-modality probe for multiple species with complimentary responses. Moreover, the bond-cleavage cascade reactions also lead to the formation of d-penicillamine heavy metal ion complexes for potential detoxification treatments.

Metal Ion-Dependent Interfacial Organization and Dynamics of Metal-Phosphonate Monolayers.

Self-assembled monolayers have been studied extensively due to their relative ease of synthesis and the broad range of applications for this class of materials. Monolayer-support interactions can range in strength from physisorption through covalent bond formation, with consequent variability in the robustness and fluidity of the monolayer. Monolayer-support bonding by metal ion complexation is especially attractive because of the ability to adjust the strength of interaction through metal ion identity. For such systems, both the exchange kinetics and thermodynamics of metal ion-complex formation contribute to the observed properties of the monolayer. We have synthesized metal-phosphate/phosphonate monolayers using Zr4+ and In3+ and have evaluated the metal ion dependence of monolayer dynamics for free and bound chromophores. Our findings reveal significant metal ion-dependent variations in monolayer dynamics and organization.

Fidelity of Al2(SO4)3 for the Discharge of Pectin during the Pretreatment of Apocynum Venetum

ABSTRACT During the extraction of fibers from the bast of A. venetum, there is an issue of the existence of undesirable macromolecules, for example, pectins. Separation of these compounds is mostly done by pretreatment with H2SO4 and then by NaOH boiling in the traditional method (Fiber-C). The use of Sulfuric acid for pretreatment may cause harm to both fibers and the environment. In order to overcome these limitations, attempts were made to find a new pretreatment (Fiber-N) method. The hypothetical premise of the new pretreatment strategy dependent on the use of Al2(SO4)3 is presented. Four model solutions were investigated using a method of measuring zeta potential. Furthermore, fibers obtained by pretreatment methods along with the raw fibers of A. venetum had been characterized by Electron spin resonance spectroscopy (ESR), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR), and water retention value (WRV). Results showed that pure salts of Al2(SO4)3 presented improved binding properties with the pectin and causes better swelling and eventually helps to remove pectin than other pretreatment processes. Ultimately, Donnan equilibrium, metal ion complex formation, and Gouy–Chapman–Stern (GCS) model were used to theoretically elucidate the discharging mechanism of pectin macromolecules from A. venetum in the presence of Al3+ ions during pretreatment.

Investigation of Acidic and Coordination Properties of Octabromo-Substituted Porphyrins in the System of 1,8-Diazabicyclo[5,4,0]unde-7-ene-Acetonitrile

Acidity and metal ion coordination are described for three porphyrin derivatives, different in their macrocycle conformation and electronic substitution effects due to bromine substitution in pyrrole rings and trifluorometyl or phenyl groups in meso-positions. Combination of these facts allows modulating both steric and electronic effects on the macrocycle π-conjugated system. The role of electronic substitution effects in the macrocycle deprotonation and metal ion complex formation is found dominating with comparable resonance and inductive contributions, whereas non-planar conformation of reactive species contributes to the reaction rates to a lesser extent. The interaction of two single-electron (a1ueg) and (a2ueg) configurations is studied as a function of non-planar distortions of the molecular structure for the three tetrapyrrole compounds. The additive influence of disturbing factors on the configuration interaction of single-electron (a1ueg) and (a2ueg) configurations in the tetrapyrrole macrocycle is demonstrated.

Facile and Robust Solvothermal Synthesis of Nanocrystalline CuInS₂ Thin Films.

This work demonstrates that the solvothermal synthesis of nanocrystalline CuInS2 thin films using the amino acid l-cysteine as sulfur source is facile and robust against variation of reaction time and temperature. Synthesis was carried out in a reaction time range of 3–48 h (at 150 °C) and a reaction temperature range of 100–190 °C (for 18 h). It was found that at least a time of 6 h and a temperature of 140 °C is needed to produce pure nanocrystalline CuInS2 thin films as proven by X-ray and electron diffraction, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Using UV-vis spectroscopy, a good absorption behavior as well as direct band gaps between 1.46 and 1.55 eV have been determined for all grown films. Only for a reaction time of 3 h and temperatures below 140 °C CuInS2 is not formed. This is attributed to the formation of metal ion complexes with l-cysteine and the overall slow assembly of CuInS2. This study reveals that the reaction parameters can be chosen relatively free; the reaction is completely nontoxic and precursors and solvents are rather cheap, which makes this synthesis route interesting for industrial up scaling.

Application of simple, fast and eco-friendly ultrasound-assisted-cloud point extraction for pre-concentration of zinc, nickel and cobalt from foods and vegetables prior to their flame atomic absorption spectrometric determinations

ABSTRACTIn this study, a simple, fast and eco-friendly ultrasound-assisted-cloud point extraction method for extraction and pre-concentration of zinc, nickel and cobalt from vegetables and foods prior to their determination by flame atomic absorption spectrometry (FAAS) was proposed. Ultrasound energy was used to shorten extraction time and reduce steps needed or to improve selectivity. The method is based on complex formation of metal ions with carmine in presence of cationic surfactant at pH 5.0, and then extraction of their hydrophobic complexes into the micellar phase of Igepal CO-630 as extractant. After optimisation, calibration curves for Zn, Co and Ni were linear in the range of 2–120, 2–220 and 2–180 μg kg−1, respectively. Limits of detection, which is described as ratio of 3×standard deviation of 12 replicate measurements of blank analysis to slope of calibration curves, were 0.5, 0.6 and 0.6 μg kg−1 for Zn, Ni and Co, respectively. Relative standard deviations (RSDs%, n: 5) for 25 μg kg−1 of each analyte were less than 3.1%. The recovery rate was higher than 94% with a lower RSD than 3.1% for five replicate measurements of 25 μg kg−1 of each analyte. The accuracy was verified using two different standard reference materials (SRM 1570a-Trace elements in spinach leaves and SRM 1548a-Typical diet), and the results were in good agreement with the certified values. The method was applied to the determinations of Zn, Ni and Co in vegetables and foods by FAAS.

Redox and Photophysical Behaviour of Complexes of NpO2+ Ions with Carbomyl methyl phosphine oxide in 1-Hexyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide Ionic Liquid

Room temperature ionic liquids (RTIL) have attracted considerable attention due to their many remarkable properties useful for technological applications not only involving formation of metal ion complexes but also as electrolyte. For understanding the role of ionic liquid in such applications requires the experimental and theoretical studies on the metal ion complexes. Therefore, an electrochemical, theoretical and luminescence studies have been carried out in the present work to correlate redox behavior, complexation, and photophysical characteristics NpO2+ complexes with carbomyl methyl phosphine oxide (CMPO) ligand in ionic liquid, which is important for the actinide partitioning. The electrochemical behavior of NpO2+extracted by CMPO in 1-Hexyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (HmimNTf2) (IL) was studied at glassy carbon (GC) electrode. The redox reaction of NpO2+ to NpO22+and vice versa in HmimNTf2 is quasi-reversible and controlled by diffusion as well as charge transfer kinetics. The cyclic voltammograms obtained in ionic liquid were much broader with reduced cathodic and anodic peak current densities (jpc and jpa) as compared to the one obtained with aqueous solution. The transport properties and kinetics of Np(V) were deduced from electrochemical calculations. The complexation behaviour of CMPO with Np(V) in aqueous solution as well as in HmimNTf2 was studied using density function theory (DFT). Based on these calculations NpO2+forms [Np(CMPO)2(NO3)2]1− type of complex in aqueous solution whereas [Np(CMPO)2(NO3)2]1−.(IL)2complex in IL. Oxidation state of neptunium was further confirmed using Time resolved fluorescence spectroscopy (TRFS) and UV–vis absorption spectroscopy. Moreover TRFS data depicted the stabilization of Np as NpO2+ in both aqueous as well as in RTIL phases. The emission spectroscopic measurement also pin pointed the fact that emission peaks of Np-CMPO complex in RTIL is blue shifted with respect to aqueous solution, which is attributed to the change in equatorial bonding/coordination of the NpO2+in the basal plane. From Photoluminescence (PL) spectroscopy and its kinetics; it was also observed that emission intensity and average lifetime are more in case of Np-CMPO complex in RTIL as compared to aqueous phase because of presence of relatively higher concentration OH group in aqueous phase which are known to be fluorescence quencher. This is a rare study where electrochemical measurements established the redox behavior, DFT calculations confirms the complexation behavior and TRFS brings out the interesting optical features of NpO2+in aqueous and ionic liquid media.

Thermal Behavior of d-Ribose Adsorbed on Silica: Effect of Inorganic Salt Coadsorption and Significance for Prebiotic Chemistry.

Understanding ribose reactivity is a crucial step in the "RNA world" scenario because this molecule is a component of all extant nucleotides that make up RNA. In solution, ribose is unstable and susceptible to thermal destruction. We examined how ribose behaves upon thermal activation when adsorbed on silica, either alone or with the coadsorption of inorganic salts (MgCl2 , CaCl2 , SrCl2 , CuCl2 , FeCl2 , FeCl3 , ZnCl2 ). A combination of 13 C NMR, in situ IR, and TGA analyses revealed a variety of phenomena. When adsorbed alone, ribose remains stable up to 150 °C, at which point ring opening is observed, together with minor oxidation to a lactone. All the metal salts studied showed specific interactions with ribose after dehydration, resulting in the formation of polydentate metal ion complexes. Anomeric equilibria were affected, generally favoring ribofuranoses. Zn2+ stabilized ribose up to higher temperatures than bare silica (180 to 200 °C). Most other cations had an adverse effect on ribose stability, with ring opening already upon drying at 70 °C. In addition, alkaline earth cations catalyzed the dehydration of ribose to furfural and, to variable degrees, its further decarbonylation to furan. Transition-metal ions with open d-shells took part in redox reactions with ribose, either as reagents or as catalysts. These results allow the likelihood of prebiotic chemistry scenarios to be evaluated, and may also be of interest for the valorization of biomass-derived carbohydrates by heterogeneous catalysis.

Formation and spectral properties of metal ion complexes of tripeptides

The aim of this study was to develop complexes that could be used to eleviate the inflammation associated with arthritis by facilitating the dermal absorption of copper. To this end, copper(II) complexes of two tripeptides sarcosyl-l-histidyl-l-lysine (L1) and sarcosyl-l-lysyl-l-histidine (L2) were studied using potentiometric and spectroscopic (UV–vis, ESR, 1H NMR) techniques as well as molecular mechanics (MM) calculations. Since Zn(II) and Ni(II) are in vivo competitors of Cu(II), equilibrium constants of H+, Cu(II), Ni(II) and Zn(II) with the peptides were measured in aqueous solution at 25±0.01°C and an ionic strength of 0.15M (NaCl) using glass electrode potentiometry. In the pH range 2.00–11.00, four species; MLH, ML, MLH−1, and MLH−2 were observed. 1H NMR identified the binding sites to be the imidazole nitrogen, the amide nitrogen and the terminal amino group. The ε-amino group of lysine did not coordinate to the Cu(II). The ML2H−2 species involved coordination of two deprotonated amide groups to give a neutral complex. UV/vis and EPR spectroscopy confirmed the mode of coordination, which was different in L1 and L2. Molecular mechanics calculations were used to support the structures postulated from potentiometric and spectroscopic data. Speciation calculations of Cu(II) using a computer model of blood plasma indicated that Sar-Lys-His (L2) was the best at mobilising copper in silico.

El problema de los 9 frascos: un clásico de laboratorio para alumnos de química básica, simulado en computadora

The 9 bottle problem is a classical lab job in high school and college chemistry.In solving this chemical “crossword” puzzle, students will be forced to integrate the knowledge acquired on a great variety of items such as solubility and colors of common inorganic precipitates, the possible evolution of gases, acid-base properties of salts, formation of metal-ion complexes, acid-base reactions, and oxidation-reduction reactions, including the influence of pH on them.A free copy of the program and the teacher guide, in Spanish, are available from the authors upon request.

Extraction of Zinc, Copper, and Lead Ions with a Zeolite Loaded by a Multidentate Schiff Base Ligand Followed by Flame Atomic Absorption Spectrometric Analysis

A multi-element preconcentration–separation technique for metal ions is established. The procedure is based on complex formation of metal ions with Bis(2-hydroxy-1-naphtaldimine)-N-diethylentriamine (BHNDT) on nanoporous Analcime as sorbent followed by their determination using flame atomic absorption spectrometry. The effects of analytical parameters like pH, flow rates, eluent types, and sorption capacity on the recoveries of metal ions are investigated. In order to predict the extraction ability of BHNDT for different metallic ions, DFT method is used to compute the binding energies of the cations to the title Schiff base compound. The calculated binding energies are in good agreement with the observed extraction power of the Shiff-base ligand.

ESI-MSを用いたケイ酸と金属イオンの反応機構の解明

ESI-MSを用いたケイ酸と金属イオンの反応機構の解明