Metal Complexes with Macrocyclic Ligands,IV. Synthesis,Properties and Kinetics of Complexation with Three N-methyl Substituted 1,4,8,11-tetraazacyclotetradecanes

The synthesis, properties and complexation of 1-methyl-1,4,8,11-tetraazacyclotetradecane (1-MeCyclam-14), 1,5-dimethyl-1,5,8,12-tetraazacyclotetradecane (2-MeCyclam-14) and 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (4-MeCyclam-14) are described. While the Ni²⁺ and Cu²⁺ complexes of 1-MeCyclam-14 and 2-MeCyclam-14 exhibit square planar geometries, 4-MeCyclam-14 forms Ni²⁺ and Cu²⁺ complexes, whose absorption spectra are best explained by assuming pentaco-ordination of the metal ions. The complexation rate of the three N-methyl substituted macrocycles with Cu²⁺ and Ni²⁺ is slower than can be accounted for by water exchange and little affected by introducing methyl groups at the nitrogens. Both results are in contrast to what is known for open chain amine ligands. A mechanism for the complexation is proposed, which also explains why the products of the reaction of 4-MeCyclam-14 with Cu²⁺ and Ni²⁺ are pentaco-ordinated.     

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⁺.     

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。     

Kinetics of the exchange between MnO or Mn3O4 and some divalent cations in aqueous solution

The kinetics of the exchange between MnO or Mn₃O₄ and Co²⁺, Cu²⁺, Ni²⁺, or Zn²⁺ ions in solution, was determined by measuring the γ-activity of⁵⁶Mn acquired by the solution after shaking with the neutron irradiated solid. The results indicated a fast exchange followed by a slower apparently diffusion-controlled exchange. The exchange capacity increased in the series: Co²⁺<Ni²⁺<Cu²⁺=Zn²⁺ for MnO and Ni²⁺<Co²⁺<Zn²⁺<Cu²⁺ for Mn₃O₄. The trends could not be satisfactorily explained by the ionic radii or crystal field stabilisation-energies. In the case of MnO, the results were discussed in terms of the estimated standard enthalpy change of the exchange reaction.     

Synthesis and study of properties of the polyhexamethyleneguanidine complexes with the ions Cu2+, Zn2+, and Ni2+

The reaction products of polyhexamethyleneguanidine hydrochloride with the Cu²⁺, Zn²⁺, and Ni²⁺ ions, which are the polyligand coordination compounds formed by polyguanidine and hydroxyl ligands, were studied using IR, UV, and ESR spectroscopy. The influence of the nature of the chelating agent on the structure of the complexes formed was revealed. Antibacterial properties of the synthesized complexes were assessed.     

Metal complexes with macrocyclic ligands. XVI. Spectrophotometric and thermodynamic studies of solvents and unidentate ligands interaction with the pentacoordinate Co2+-, Ni2+- and Cu2+-complexes of 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane

The interaction of solvents and of unidentate ligands such as N, SCN^?, OCN^? and OH^? with the Co²⁺-, Ni²⁺ and Cu²⁺-complexes of 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (TMC) have been studied by Spectrophotometric and calorimetric techniques. The spectra in different solvents (Table 2) show that the Ni²⁺- and probably also the Cu²⁺-complex with TMC exist as square planar or pentacoordinate species or as a mixture of both, depending on the donor properties of the solvent. The [Co(TMC)]²⁺-complex is pentacoordinate in all the solvents studied. Ternary complexes [M(TMC)X]ⁿ⁺ are also formed by the unidentate ligands X = N, OCN^?, OH^?, F^? and NH₃ and their stability constants have been determined. Interesting is the high selectivity of [Ni(TMC)]²⁺ towards the addition of a further donor (Table 3). Only small ligands such as those listed above form stable adducts, whereas the larger ones such as imidazole or pyridine do not. This is a consequence of the special structure of the complex and of the trans-I-(RSRS)- conformation of the ligand in these complexes. Since the four methyl groups are all on the side of the macrocycle to which the additional unidentate ligand binds, steric interaction between the four methyl groups and the larger ligands prevents the formation of the adducts. The calorimetric measurements show that the stability of the complexes [M(TMC)X]ⁿ⁺ is due to both an enthalpic and entropic contribution which differ in their magnitude (Table 4). This indicates that several antagonistic factors are important in determining the overall stability.     

Electron capture dissociation and collision-induced dissociation of metal ion (Ag+, Cu2+, Zn2+, Fe2+, and Fe3+) complexes of polyamidoamine (PAMAM) dendrimers

The electron capture dissociation (ECD) and collision-induced dissociation (CID) of complexes of polyamidoamine (PAMAM) dendrimers with metal ions Ag⁺, Cu²⁺, Zn²⁺, Fe²⁺, and Fe³⁺ were determined by Fourier transform ion cyclotron resonance mass spectrometry. Complexes were of the form [PD + M + mH]⁵⁺ where PD = generation two PAMAM dendrimer with amidoethanol surface groups, M = metal ion, m = 2−4. Complementary information regarding the site and coordination chemistry of the metal ions can be obtained from the two techniques. The results suggest that complexes of Fe³⁺ and Cu²⁺ are coordinated via both core tertiary amines, whereas coordination of Ag⁺ involves a single core tertiary amine. The Zn²⁺ and Fe²⁺ complexes do not appear to involve coordination by the dendrimer core.     

Novel nanostructured dendrimer based on 1,3-bis(4,6-dichloro-1,3,5-triazine-2-yl)urea as an excellent adsorbent for Pb2+, Ni2+, Co2+ and Zn2+ metal ions

Human health is seriously harmed by the consumption of poor-quality water. Due to high toxicity and water solubility, heavy metals are present in wastewater discharged from numerous industries. In the environmental realm, metal-containing water must be treated before being released. A dendrimer is a superior adsorbent for the removal of heavy metal ions due to its nanostructure and hydrophilic end group. In this work, a novel triazine-based hydroxy-terminated dendrimer up to generation three is designed employing a carbamide core. The dendrimer's structure was explored using FT-IR and ¹H NMR studies. Full generation dendrimers UG1.0, UG2.0, and UG3.0 were utilized as an adsorbent for Pb²⁺, Ni²⁺, Co²⁺ and Zn²⁺ metal ion removal from water in a series of tests. The ability of dendrimers to uptake Pb²⁺, Ni²⁺, Co²⁺ and Zn²⁺ metal ions was investigated under various pH, time interval and dendrimer generation parameters. The presence of metal in the dendrimer was confirmed by FT-IR studies of dendrimer-metal complexes. The overall results show that Pb²⁺, Ni²⁺, Co²⁺ and Zn²⁺ metal ions uptake increases with the generation, time, and pH.     

Interaction Structure and Affinity of Zwitterionic Amino Acids with Important Metal Cations (Cd2+, Cu2+, Fe3+, Hg2+, Mn2+, Ni2+ and Zn2+) in Aqueous Solution: A Theoretical Study

Heavy metals are non-biodegradable and carcinogenic pollutants with great bio-accumulation potential. Their ubiquitous occurrence in water and soils has caused serious environmental concerns. Effective strategies that can eliminate the heavy metal pollution are urgently needed. Here the adsorption potential of seven heavy metal cations (Cd²⁺, Cu²⁺, Fe³⁺, Hg²⁺, Mn²⁺, Ni²⁺ and Zn²⁺) with 20 amino acids was systematically investigated with Density Functional Theory method. The binding energies calculated at B3LYP-D3/def2TZVP level showed that the contribution order of amino acid side chains to the binding affinity was carboxyl > benzene ring > hydroxyl > sulfhydryl > amino group. The affinity order was inversely proportional to the radius and charge transfer of heavy metal cations, approximately following the order of: Ni²⁺ > Fe³⁺ > Cu²⁺ > Hg²⁺ > Zn²⁺ > Cd²⁺ > Mn²⁺. Compared to the gas-phase in other researches, the water environment has a significant influence on structures and binding energies of the heavy metal and amino acid binary complexes. Collectively, the present results will provide a basis for the design of a chelating agent (e.g., adding carboxyl or a benzene ring) to effectively remove heavy metals from the environment.     

Complexation and thermodynamic studies of oxathiadibenzocrown ethers with Cu2+, Pb2+, Zn2+ and Cd2+ ions

A thermodynamic study of the complexation of Cu²⁺, Pb²⁺, Zn²⁺ and Cd²⁺ ions with 1 and 2 in acetonitrile has been carried out. The study was conducted in the temperature range 283–308 K using a conductometric technique. The observed molar conductivity, Λ, was found to decrease significantly for mole ratios [L]_t/[M]_t less than unity in all cases. A model involving 1:1 stoichiometry has been used to analyze the conductivity data. The stability constant, K, for each 1:1 complex was determined from the conductivity data by using a nonlinear least-squares curve fitting procedure. The results show that compound 1 has no peak selectivity for any of the metal cations, while compound 2 selectively associates with Cu²⁺ and Pb²⁺. Complexes of 1 have the following stability order Pb²⁺ > Cu²⁺ > Zn²⁺ > Cd²⁺  and Pb²⁺ > Cu²⁺ for the complexes of 2. The ?H° and ?S° values for the complexation process were obtained from the slope and intercept of the Van’t Hoff plots respectively. All ?G° values were negative and were determined from the Gibbs–Helmholtz equation and the significance of these values is discussed.     

Simultaneous Analysis of Co2+, Cu2+ Mn2+, Ni2+ and Zn2+ in The Ultraviolet Region Using 4-(Pyridil-2-AZO) Resorcinol and Multivariate Calibration

ABSTRACT

A multicomponent spectrophotometric methodology for the simultaneous determination of Co²⁺, Cu²⁺, Mn²⁺, Ni²⁺ and Zn²⁺ in aqueous solution is reported, using (4-(pyridil-2-azo) resorcinol), a diode array spectrophotometer and multivariate calibration by partial least-squares and principal component regerssions. Spectra are recorded in the UV region. The 225 – 320 nm range is selected as optimal, through a criterion based on tederivatives of the differences between individual spectra, which compares favorably with a genetic algorithm. The methodology is applied to the simultaneous determination of the five than 1.5 mgL^?1. The best result are obtanied at pH 9.0, with average absolute errors of prediction lower than 0.09 mgL^?1     

Study of some metallic silicates as ion-exchangers

The extraction of ammine complexes of Cu²⁺, Cd²⁺, Ni²⁺, Co²⁺ and Zn²⁺ by synthesised manganese, nickel and zinc silicates has been studied at different pH and ionic concentrations in the external solution. It has been found that the uptake of the metal ion Co²⁺, Cu²⁺ and Zn²⁺ increases with increase in pH of the external solution, attains a maximum and then decreases. However, the uptake for Cd²⁺ and Ni²⁺ increases continuously. The q_A values of all the silicates increases with the increase in the concentration of the exchanging ion and its order for the investigated metal ions is Ni²⁺ < Co²⁺ < Cd²⁺ < Zn²⁺ < Cu²⁺.     

Potentiometric and thermodynamic studies of 2-mercapto-5-(2-hydroxynaphthylideamino)-1,3,4-thiadiazole and its metal complexes

Summary Proton-ligand dissociation constant of 2-mercapto-5-(2-hydroxynaphthylideamino)-1,3,4-thiadiazole (MHT) and the stepwise stability constants of its metal complexes were determined potentiometrically in 40 mass/mass% ethanol-water mixture containing 0.1 M KCl. The stabilities of the complexes follow the order: Cu²⁺>Ni²⁺>Co²⁺>Mn²⁺. The dissociation constant (pK^H) of MHT and the stability constants (logK) of its metal complexes were determined at different temperatures and the corresponding thermodynamic parameters were calculated and discussed. The proton dissociation process is non-spontaneous, endothermic and entropically unfavoured. The formation of the metal complexes was found to be spontaneous, endothermic and entropically favoured.     

Spectrophotometric study of complexation of dibenzopyridino-18-crown-6 with some transition and post-transition metal ions in DMSO solution using murexide as a metallochromic ligand

The complexation reaction of dibenzopyridino-18-crown-6 (DBPY 18C6) with Co²⁺, Cu²⁺, Zn²⁺, Pb²⁺, Cd²⁺, Hg²⁺, and Ag⁺ have been studied in DMSO at 25°C by the spectrophotometric method. Murexide was used as a competitive colored ligand. The stoichiometry of metal ion-murexide and metal ions with DBPY18C6 complexes were estimated by mole ratio and continuous variation methods and emphasized by the KINFIT program. The stoichiometry of all the complexes was found to be 1: 1 (metal ion/ligand). The order of stability constants for the obtained metal ion-murexide complexes (1: 1) varies in the order Cu²⁺ > Cd²⁺ > Co²⁺ ∼ Pb²⁺ > Zn²⁺ > Ag⁺ > Hg²⁺. This trend shows that the transition metal ions clearly obey the Irving-Williams role. For the post-transition metal ions, the ionic radius and soft-hard behavior was the major affects in varying of this order. The dibenzopyridino-18-crown-6 complexes with the used metal ions vary as Ag⁺ > Pb²⁺ > Cu²⁺ > Cd²⁺ > Hg²⁺ > Zn²⁺ > Co²⁺. The article is published in the original.     

Coordination properties of dehydroacetic acid – binary and ternary complexes

Complex formation equilibria of dehydroacetic acid with Cu²⁺, Ni²⁺, Co²⁺, Zn²⁺ and Mn²⁺ and the ternary complexes involving Cu²⁺, dehydroacetic acid and some amino acids containing different functional groups are investigated. Stoichiometry and stability constants for the complexes are estimated at 25°C and 0.1 M ionic strength in 25% dioxane-water mixtures. The concentration distribution diagrams of the complexes were evaluated. The effect of temperature and organic solvent on the acid dissociation constant of dehydroacetic acid and the formation constant of Cu²⁺ complex was studied and thermodynamic parameters calculated.     

Spectroscopic Characterization of <Emphasis Type="Italic">N,N-bis</Emphasis>(2-{[(2,2-Dimethyl-1,3-Dioxolan-4-yl)Methyl]Amino}Ethyl) N′,N′-Dihydroxyethanediimidamide and Its Complexes

A new dioxime ligand, N,N-bis(2-{[(2,2-dimethyl-1,3-dioxolan-4-yl)methyl]amino} ethyl)N′,N′-dihydroxyethanediimidamide (H₂L), and its mononuclear complexes with Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Cd²⁺ are synthesized. H₂L forms transition metal complexes [Co(LH)₂(H₂O)₂] and [M(LH)₂] (M = Ni²⁺, Cu²⁺) with a metal : ligand ratio of 1 : 2. Complexes [M(H₂L)(Cl)₂] (Zn²⁺, Cd²⁺) have a metal : ligand ratio of 1 : 1. The mononuclear Co²⁺, Ni²⁺, and Cu²⁺ complexes indicate that the metal ions coordinate ligand through its two N atoms, as the most of dioximes. In the Co²⁺ complex, two water molecules and in the Zn²⁺ and Cd²⁺ complexes two chloride ions are also coordinated to the metal ion. The structures of these compounds are identified by elemental analyses, IR, ¹H and ¹³C NMR, electronic spectra, magnetic susceptibility measurements, conductivity, and thermogravimetric analysis.__________From Koordinatsionnaya Khimiya, Vol. 31, No. 7, 2005, pp. 540–544.Original English Text Copyright © 2005 by Canpolat, Kaya.The text was submitted by the authors in English.     

Vibrational and scanning electron microscopy study of the mordenite modified by Mn, Co, Ni, Cu, Zn and Cd

The mordenite samples loaded with divalent nitrates of Mn, Co, Ni, Cu, Zn and Cd were investigated using FTIR and scanning electron microscopy (SEM) methods. It was found from FTIR spectra that in 3000-4000 cm⁻¹ region of mordenite samples with similar water concentration ions, Mn²⁺, Co²⁺, Cu²⁺, and Zn²⁺ tend to break hydrogen bonds formed between water molecules and zeolite framework, whereas Ni²⁺ and Cd²⁺ accommodate to hydrogen bonds. From SEM results it was concluded, that ions Mn²⁺, Co²⁺, Zn²⁺ form innersphere complexes with oxygens from Brönsted acid sites, whereas Ni²⁺ and Cd²⁺ associate with Brönsted acid sites without exchange of protons.     

Extraction studies of metal complexes with some macrocyclic tetraaza ligands and xanthene dyes : Spectrophotometric determination of Cadmium(II) with Tetramethyltetraazacyclotetradecane and Erythrosin A

The liquid-liquid extraction of ion-pair complexes of zinc(II), copper(II) and cadmium(II) is described. The macrocyclic ligands 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (4Me-cyclam-14) and rac-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (Tet b) are used with xanthene dyes as the counter ions. The apparent extraction constants (D′_c) are reported. The sequences of extraction efficiency of both ligands are related to the structure of the complexes. The apparent molar absorptivity of the Cd(4Me-cyclam-14)—erythrosin A ion-associate is 1.1 × 10⁵ l mol^? cm^?1. The calibration graph is linear over the range 0—10^?5 M, which allows even 0.05 μg ml^?1 cadmium to be determined in a 0.5 M sodium hydroxide medium. No interference was observed from Ni²⁺, Pb²⁺, Zn²⁺, Mg²⁺, Sn⁴⁺, Ga³⁺, Al³⁺ and Fe³⁺. Interferences were Cu²⁺, Hg²⁺, Ag⁺ and large anions.     

Stabilities and Near UV. Charge transfer spectra of binuclear and heterobinuclear complexes of N,N′-bis-[2-(2-pyridylmethyl-amino)-ethyl]-oxamide with transition-metal ions

The formation of complexes of N,N′-bis-[2-(2-pyridylmethyl-amino)-ethyl]-oxamide (PAOH₂) with Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ has been studied potentiometrically and spectrophotometrically. Besides mononnclear species, PAOH₂ forms the binuclear or heterobinuclear complexes Cu₂(PAOH₂)⁴⁺, Cu₂PAO²⁺, Zn₂PAO²⁺, CuNiPAO²⁺, and probably CuZnPAO²⁺ Some of these five compounds show an UV. absorption band near 350 nm reminiscent of that to dimeric copper acetate. The results suggest that charge transfer from the oxamidato group to Cu²⁺ is responsible for the near UV. absorption.     

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.