Electrical properties and initial permeability of Cu–Mg ferrites

A series of polycrystalline spinel ferrites with composition Cu_1−xMg_xFe₂O₄ where 0.0 ≤ x ≤ 1 are prepared by the standard ceramic method. The single-phase cubic spinel structure of all the samples has been confirmed from X-ray diffraction analysis. The lattice constant increases linearly with increasing magnesium content obeying Vegard's law. The electrical properties (ɛ′, and σ) of the prepared samples are measured at different temperatures as a function of applied frequency ranging from 100 kHz up to 5 MHz. The general trend of ɛ′, and σ is decreased with increasing Mg²⁺ and increases with increasing temperature. The observed variation of dielectric properties is explained on the basis of Cu²⁺/Cu¹⁺ ionic concentration as well as the electronic hopping frequency between Fe²⁺ and Fe³⁺ ions in the present samples. The data of initial permeability is also discussed.     

Mixed benzohydroxamato-acetylacetonato metal complexes: spectral,thermal and photochemical behaviour

Summary Bis(acetylacetonato)VO^II,–Co^II,–Ni^II,–Cu^II,–Zn^II, –UO ₂ ^II and tris(acetylacetonato)Fe^III react with benzohydroxamic acid to yield the corresponding mixed ligand complexes as a result of displacement of one acetylacetone molecule. Intermolecular association may be the reason for six-coordination geometry around the metal ions. A t.g.a. study of the complexes shows, in most cases, initial loss of alcohol and water molecules associated with the complexes; subsequent decomposition steps are characterised by very sharp weight loss. The photochemical stability of the complexes has been studied. Intraligand excitation causes a decomposition in the case of Fe^III and VO^II-complexes but no detectable effect for Co^II, Ni^II, Cu^II, Zn^II, or UO ₂ ^II -complexes.     

Catalyzed Peptide Bond Formation in the Gas Phase. Role of Bivalent Cations and Water in Formation of 2-Aminoacetamide from Ammonia and Glycine and in Dimerization of Glycine

The formation of 2-aminoacetamide from ammonia and glycine and N-glycylglycine from two glycine molecules with and without Mg²⁺, Cu²⁺, and Zn²⁺ cations as catalysts have been studied as model reactions for peptide bond formation using the B3LYP functional with 6–311+G(d,p) and 6–31G(d) basis sets. The B3LYP method was also used to characterize the nine gas–phase complexes of neutral glycine, its amide (2-aminoacetamide), and N-glycylglycine with Lewis acids Mg²⁺, Cu²⁺, and Zn²⁺, respectively. Further, the gas-phase hydration of metal-coordinated complexes of glycine, 2-aminoacetamide, and N-glycylglycine was also investigated. Finally, the effect of water on the structure and reactivity of the metal coordinated complexes was determined. Enthalpies and Gibbs energies for the stationary points of each reaction have been calculated to determine the thermodynamics of the reactions investigated. A substantial decrease in reaction enthalpies and Gibbs energies was found for glycine–ammonia and glycine–glycine reactions coordinated by Mg²⁺, Cu²⁺, and Zn²⁺ ions compared to those of the uncoordinated 2-aminoacetamide bond formation. The formation of a dipeptide is a more exothermic process than the creation of simple 2-aminoacetamide from glycine. The energetic effect of the transition metal ions Cu²⁺ and Zn²⁺ is of similar strength and more pronounced than that of the Mg²⁺ cation. The basicity order of the amides investigated shows the order: NH₂CH₂CO₂H < NH₂CH₂CONH₂ < NH₂CH₂CONHCH₂CO₂H. Interaction enthalpies and Gibbs energies of metal ion–amide complexes increase as Mg²⁺2+2+. In both reactant (glycine) and reaction products (2-aminoacetamide, N-glycylglycine) dihydration caused considerable reduction (about 200–500 kJ-mol^–1) of the strength of the bifurcated metal–amide bonds. Solvent effects also reduce the reaction enthalpy and Gibbs energy of reactions under study.     

Fluctuation in occupancy of Cu2+ ions in Zn- and Cd-substituted Cu-ferrites

Mössbauer effect technique has been used for the comparative study of Cu_1?x Zn _x Fe₂O₄ and Cu_1?x Cd _x Fe₂O₄ ( _x = 0.0?1.0) ferrites. Both Zn²⁺ and Cd²⁺ cations are divalent, non-magnetic ions with different ionic radii. With the substitution of these non-magnetic cations the average internal magnetic field decreases and paramagnetic behavior is dominated at x = 0.7 in both series. It is observed that the occupancy of Cu²⁺ ions for tetrahedral site is not constant for all compositions but fluctuate between 8–15%. It is also found that Cu²⁺ ions have more preference for tetrahedral site in Cu-Zn system as compared to the Cu-Cd system. Zn²⁺ and Cd²⁺ both ions occupy tetrahedral site completely and form normal spinels for x = 1.0.     

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.     

The influence of Ni2+ lons on the distribution of Mg2+ and Cu2+ lons in spinel ferrites

Cation distribution in quenched and furnace-cooled samples of composition Ni_xM_1?xFe₂O₄ (where M is either Mg²⁺ or Cu²⁺) has been studied through magnetization measurements. It has been found that cation distribution in these mixed ferrites cannot be predicted by site preference energies. In magnesium-nickel ferrites, cation distribution is controlled by heat treatment up to x = 0.5, beyond which the effect of heat treatment diminishes. Addition of Ni²⁺ ions in copper ferrite reduces the diffusibility of Cu²⁺ ions and the distribution tends toward inverse spinel in the high-nickel region.     

Dissociation and coordinating ability of 1,2,3,4-tetrahydro-8-hydroxyquinoline in aqueous solution

The state of 1,2,3,4-tetrahydro-8-hydroxyquinoline is studied spectrophotometrically in the near-UV and visible regions at different pH in an aqueous solution in the presence and absence of Cu²⁺, Zn²⁺, and Cd²⁺ cations. The dissociation constant (pK ₁ ≈ 5.6 (293 K)) is (293 K)) is estimated from the pH-metric data. The stability of the complexes formed decreases in the series Cu²⁺ > Zn²⁺ ≥ Cd²⁺. The influence of tetrahydro atoms on the dissociation, complexation, and change in the state of 1,2,3,4-tetrahydro-8-hydroxyquinoline in an aqueous solution is discussed.     

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.     

Probing Metal Ion Complexation of Ligands with Multiple Metal Binding Sites: The Case of Spiropyrans

Among known molecular switches, spiropyrans attract considerable interest because of their reversible responsiveness to external stimuli and the deep conformational and electronic changes that characterize the switching process between the two isomeric forms [spiropyran (SP) and merocyanine (MC)]. Metal coordination is one of the most interesting aspects of spiropyrans for its potential in sensing, catalysis, and medicinal chemistry, but little is known about the details surrounding spiropyran–metal ion binding. We investigated the interplay between an N‐modified 8‐methoxy‐6‐nitrospiropyran (SP‐E), designed to provide appropriate molecular flexibility and a range of competing/collaborative metal binding sites, with Mg²⁺, Cu²⁺ and Zn²⁺, which were chosen for their similar coordination geometry preferences while differing in their hard/soft character. The formed molecular complexes were studied by means of UV/Vis, fluorescence, and NMR spectroscopies and mass spectrometry, and the crystal structure of the SP‐E–Cu complex was also obtained. The results indicate that the Mg²⁺, Zn²⁺ and Cu²⁺ complexes have identical coordination stoichiometry. Furthermore, the Mg²⁺ and Zn²⁺ complexes display fluorescence properties in solution and visible‐light responsiveness. These results provide important spectroscopic and structural information that can serve as a foundation for rational design of spiropyran‐based smart materials for metal sensing and scavenging applications.     

Bifunctional 3-Hydroxy-4-Pyridinones as Potential Selective Iron(III) Chelators: Solution Studies and Comparison with Other Metals of Biological and Environmental Relevance

The binding ability of five bifunctional 3-hydroxy-4-pyridinones towards Cu²⁺ and Fe³⁺ was studied by means of potentiometric and UV–Vis spectrophotometric measurements carried out at I = 0.15 mol L⁻¹ in NaCl_(aq), T = 298.15 K and 310.15 K. The data treatments allowed us to determine speciation schemes featured by metal-ligand species with different stoichiometry and stability, owing to the various functional groups present in the 3-hydroxy-4-pyridinones structures, which could potentially participate in the metal complexation, and in the Cu²⁺ and Fe³⁺ behaviour in aqueous solution. Furthermore, the sequestering ability and metal chelating affinity of the ligands were investigated by the determination of pL_0.5 and pM parameters at different pH conditions. Finally, a comparison between the Cu²⁺ and Fe³⁺/3-hydroxy-4-pyridinones data herein presented with those already reported in the literature on the interaction of Zn²⁺ and Al³⁺ with the same ligands showed that, from the thermodynamic point of view, the 3-hydroxy-4-pyridinones are particularly selective towards Fe³⁺ and could therefore be considered promising iron-chelating agents, also avoiding the possibility of competition, and eventually the depletion, of essential metal cations of biological and environmental relevance, such as Cu²⁺ and Zn²⁺.     

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.     

Theoretical estimate of the stability constants of metal complexes of aliphatic and heterocyclic amines in aqueous solutions

The stability constants of 1: 1 complexes of Mg²⁺, Ca²⁺, Cd²⁺, Co²⁺, Cu²⁺, Fe²⁺, Mn²⁺, Ni²⁺, and Zn²⁺ with 29 N-donor ligands (ammonia, alkylamines, aniline, pyridine, imidazole, pyrazole, benzimidazole, isoquinoline, and their alkyl-and halogen-substituted derivatives) in aqueous solutions at 298 K were calculated by integration of the ligand distribution function. The stability constants are determined by the effective charge on the electron donor atom of the ligand and by the sizes of the cation and ligand, as well as by the degree of covalence of the coordination bond.     

AxMn1-xFe2O4铁氧体(A=Zn,Ni)中阳离子的占位有序化行为研究

基于尖晶石晶体结构信息,本文采用热力学三亚晶格模型,将材料热力学计算和第一性原理计算相结合,研究了Zn_xMn_1-x Fe₂O₄和Ni_xMn_1-xFe₂O₄立方相中的Zn²⁺、Ni²⁺、Mn²⁺以及Fe³⁺在8a和16d亚晶格上的占位有序化行为。结果表明:在锰铁氧体中,室温下Mn²⁺完全占据在8a亚晶格上,Fe³⁺完全占据在16d亚晶格上,属于正尖晶石结构;随着热处理温度升高,在1 273 K达到热处理平衡时的占位构型为(Fe_0.09³⁺Mn_0.91²⁺)[Fe_1.91³⁺Mn_0.09²⁺]O₄,在热处理温度升至1 473 K时,达到热处理平衡时的占位构型为(Fe_0.11³⁺ Mn_0.89²⁺)[Fe_1.89³⁺Mn_0.11²⁺]O₄,均与实验结果符合较好。在锌铁氧体中,室温下Zn²⁺完全占据在8a亚晶格上,Fe³⁺完全占据在16d亚晶格上,属于正尖晶石结构;在热处理温度较高时,Zn²⁺和Fe³⁺发生部分置换,符合实验结果。在镍铁氧体中,半数的Fe³⁺在室温下占据在8a亚晶格上,Ni²⁺与剩下另一半的Fe³⁺共同占据在16d亚晶格上,仅在热处理温度较高的时候发生微弱变化,亦与已有的实验结果吻合。在此基础上,本文进一步通过热力学预测建立了立方相尖晶石结构的Zn_xMn_1-xFe₂O₄、Ni_xMn_1-xFe₂O₄复合体系中阳离子占位行为与热处理温度对占位的影响。     

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.     

ADDUCTS OF THEOBROMINE WITH 3d METAL PERCHLORATES

Abstract

Adducts of theobromine (tbH) with 3d metal perchlorates (Mⁿ⁺ = Cr^3-. Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn^2- I here prepared by refluxing mixtures of the Iigand and a metal salt in ethyl acetate-triethyl orthoformate. The new complexes invariably involve 2: 1 molar ratios of tbH to metal ion and are apparently monomeric with terminal tbH ligands binding riaa ring nitrogen (N9 or Nl). The Mn²⁺, Cu²⁺ and Zn^2- complexes are distorted tetrahedral, involving tuo tbH and two unidentate perchlorato ligands in the first coordination sphere of the metal ion. The remaining metal(II) complexes (Fe, Co, Ni) were obtained as monohydrates. These compounds are pentacoordinated of the [M(tbH)₂(OClO₃)₂(OH₂)] type, containing one aqua ligand in addition to the tbH and perchlorato ligands. The Cr³⁺ and Fe³⁺ complexes are low-symmetry hexacoordinated, with two tbH ligands. two unidentate and one bidentate chelating perchlorate Iigands.     

Complexes of 1-isonicotinoyl-4-benzoyl-3-thiosemicarbazide with manganese(II), iron(III), chromium(III), cobalt(II), nickel(II), copper(II) and zinc(II)

1-Isonicotinoyl-4-benzoyl-3-thiosemicarbazide (IBtsc) and its Cr^III, Mn^II, Fe^III, Co^II, Ni^II, Cu^II and Zn^II complexes have been prepared and characterized by elemental analyses, magnetic susceptibility measurements, u.v.–vis., i.r., n.m.r. and FAB mass spectral data. The room temperature e.s.r. spectra of the Cr^III, Fe^III and Cu^II complexes yield values, characteristic of octahedral, tetrahedral and square-planar complexes, respectively. The Mössbauer spectra of [Fe(IBtsc-H)Cl₂] at room temperature and at 78 K suggest the presence of high-spin Fe^III. The Ni^II, Cr^III and Cu^II complexes show semiconducting behaviour in the solid state, but the Zn^II complex is an insulator at room temperature. IBtsc and its soluble complexes have been screened against several bacteria, fungi and tumour cell lines.     

Die Löslichkeit der Übergangsphasen des Zinkferrits in Salpetersäure

Zusammenfassung Es wurde die Löslichkeit bei 20° C von durch Sinterung eines Gemisches von ZnO mit Fe₂O₃ bei 500° C bis 1100° C erhaltenen Präparaten in 2n-HNO₃ untersucht. Unter 600° gesinterte Präparate geben kein Fe³⁺ an die Lösung ab, dagegen leicht Zn²⁺. Bei Sintertemperaturen von 650 bis 950° C ist die Zinklöslichkeit noch ziemlich groß, aber fallend. Die Fe³⁺-Lösbarkeit wächst stark bei Temperaturen bis 850° C und ist noch bei 900° C erheblich. Oberhalb 950° C Sintertemperatur fällt der Fe³⁺- und der Zn²⁺-Gehalt stark ab. Röntgenographisch wurde der Ferritisierungsprozeß im Bereich von 650 bis 950° C bestätigt. Oberhalb 1000° C tritt ein vollkommen ausgebildetes Zinkferrit auf.

---

The solubility of transition phases of zinc ferrites in HNO₃

The solubility in 2n-HNO₃ of the products of baking a mixture of ZnO and Fe₂O₃ between 500° and 1100° C was investigated. From the products of baking up to 600° C, Fe³⁺ does not dissolve, while Zn²⁺ dissolves easily. In products of sintering between 650° to 950° C the solubility of Zn²⁺ is still large, yet decreasing. The content of the solution on Fe³⁺ increases very strongly for temperatures up to 850° C and is appreciable even at 900° C. Above 950°C sintering temperature, the Fe³⁺ and Zn²⁺ content of the solution drops very strongly. The formation of ferrites in the range of 650° to 950° C was confirmed by X-ray powder methods. Above 1000° C fully developed zinc ferrite is found.

---

---

Mit 3 Abbildungen     

A novel BF<Subscript>2</Subscript>–curcumin-based fluorescent chemosensor for detection of Cu<Superscript>2+</Superscript> in aqueous solution and living cells

A novel BF₂–curcumin-based chemosensor 1, namely monopicolinate of BF₂–curcumin complex, was designed, synthesized and applied for the detection of Cu²⁺ in aqueous buffer solution and living cells. Sensor 1 exhibited sensitive naked-eye color change toward Cu²⁺ from blue to pink in TBS solution and the detection limit was estimated to be 0.12 µM. The selectivity of sensor 1 for Cu²⁺ was high over competing metal ions (Ag⁺, Cu⁺, Hg²⁺, Mg²⁺, Ca²⁺, Co²⁺, Zn²⁺, Mn²⁺, Ni²⁺, Fe²⁺ and Fe³⁺). Based on the experimental results, the sensing mechanism was proposed for the Cu²⁺ triggered hydrolysis of 1 to BF₂–curcumin which has unique chromogenic and fluorogenic properties. Compared with other chemosensors with a similar mechanism, chemosensor 1 had a comparatively large Stokes shift and the emission wavelength was close to NIR. Moreover, cell imaging investigations indicated that sensor 1 has the potential to be applied for practical Cu²⁺ detection in biological systems.     

Tridentate benzimidazole ligand and its metal complexes: Synthesis,characterization, photo physical and sensor properties

A tridentate bisbenzimidazole-pyridine ligand (L-C⁵) with two pentyl side-units and its metal complexes with Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ metal ions were synthesized and characterized. The structures of the ligand (L-C⁵) and its five coordinate [Mn(L-C⁵)Cl₂] were elucidated by single crystal X-ray diffraction studies. The absorption and photoluminescence properties of the compounds were studied in solution media. The ligand is highly fluorescent, and binding of the metal ions to the ligand has caused significant changes in the emission band (shift or quenching). Moreover, the effect of aggregation on UV–Vis. absorption and emission properties was examined in MeOH-water mixtures. The ligand was found to show aggregation-induced quenching in the MeOH-water mixture. The ligand was also screened for its colorimetric and fluorometric sensing ability of several metal ions [Na⁺, K⁺, Mg²⁺, Al³⁺, Ca²⁺, Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Hg²⁺, Pb²⁺]. The ligand showed selective sensing ability towards Zn²⁺, and the limit of detection was calculated as 3.09 × 10⁻⁷ m . The ligand also showed a distinguishable color change in the presence of Fe²⁺ under daylight.     

Thermogravimetric investigations on A(H2O)6BX6 complexes and the formation of ABX6 and ABO3 structures

Thermogravimetry (TG) of A(H₂O)₆BX₆ complexes are presented, with A  Cd²⁺, Co²⁺, Cu²⁺, Fe²⁺, Mg²⁺, Mn²⁺, Ni²⁺, Pb²⁺, Zn²⁺, BSi⁴⁺, Sn⁴⁺, Ti⁴⁺, Zr⁴⁺, and XCl^?, F^?. On a selected number of complexes, differential thermal analyses (DTA) and differential scanning calorimetric measurements (DSC) have been performed. It was found possible to synthesize most complexes including Cd(H₂O)₆TiF₆ as single crystals. The hexafluoride and the titanate compounds are formed from the corresponding cadmium hexaquo—hexafluoride complex. The cadmium titanate could be made either in the ilmenite or in the perovskite structure. The decomposition programs for the preparation of NiTiO₃ and CdTiO₃ are presented.The hexaquo—hexahalide complexes, in general, show one of two decomposition types. The intermediate product in one type is the metal(II) fluoride AX₂ and in the other the mixed hexahalide compounds ABX₆. Which type of decomposition occurs depends on the anion BX^2?₆.