Catalytic concept of mineralizing effects

The subject of this work is the mechanism of phase transformations and chemical reactions of pure aluminas and kaolinite doped by Cu^{2 +}, Mn^{3 +}/Mn^{2 +} and Fe^{3 +}/Fe^{2 +} ions. Accelerated phase transformations of metastable aluminas and mullite formation of metal doped samples are explained by catalytic mechanism in terms of Jahn-Teller effect.     

Two Recent Studies Involving Pressure Tuning Spectroscopy

In this paper we present two recent studies utilizing pressure tuning spectroscopy. In the first of these we use high pressure photoluminescence to characterize the large difference in luminescence efficiency at one atmosphere between [Ru(bpy)₃]²⁺ and [Ru(bpy)₂py₂]²⁺ ions. The lower efficiency of the latter ion is due to dissipation of excitation energy by motion of the pyridines. The second study involves a combination of photo-and thermoluminescence of doped ZnS phosphors of technical importance. In the phosphor doped with CI and Cu⁺ we demonstrate that the donors are pinned to the conduction band and the acceptors to the valence band. We invoke the presence of “deep levels” to describe the behavior of the traps. In the phosphor doped with Mn⁺² plus C1- and Cu⁺ a series of traps appeared as the pressure was increased. By comparison with ZnS doped only with Mn⁺² it was possible to assign some of the traps to C1- and others to Mn⁺².     

The thermal decomposition of doped ammonium perchlorate

The thermal decomposition of ammonium perchlorate doped with Cu²⁺, Mn²⁺, Co²⁺ and Fe³⁺ (with and without H⁺) was studied using DTA and TG. Small concentrations of these ions inhibit the decomposition by eliminating the first exothermic peak. At higher concentrations, a catalyzed decomposition is observed. Either the influence of the doping ions on the mechanism of the thermal decomposition is different from that of added oxides or a modification of the electron transfer mechanism is needed.     

Zero-Field Splittings and Redox Potentials in an Isostructural Series of Dinuclear FeIITiIV,FeIIITiIV, and MnIITiIV Complexes with a Face-Sharing Bridging Motive

The ligand H₆ioan has been used to synthesize the three dinuclear complexes [(ioan)Mn^IITi^IV], [(ioan)Fe^IITi^IV], and [(ioan)Fe^IIITi^IV]⁺. The face-sharing bridging mode of the three phenolates provides short M-Ti^IV distances of ≈3.0 Å. Mössbauer spectra of [(ioan)Fe^IIITi^IV]⁺ show a magnetically split six-line spectrum at 3 K in zero magnetic field demonstrating a slow magnetic relaxation. Magnetic measurements provide a zero-field splitting of |D|=5 cm⁻¹ in [(ioan)Fe^IITi^IV]. EPR spectroscopy demonstrates sizable zero-field splittings of the S=5/2 spin systems of [(ioan)Mn^IITi^IV] (D=0.246 cm⁻¹) and [(ioan)Fe^IIITi^IV]⁺ (D<−1 cm⁻¹) that can be related to enforced covalency of the M-O^ph bonds. [(ioan)Fe^IIITi^IV]⁺ exhibits a reversible reduction at −0.26 V vs. Fc⁺/Fc demonstrating the facile accessibility of Fe^III and Fe^II. In contrast to an irreversible oxidation in [(ioan)Ni^IITi^IV] at 0.78 V vs. Fc⁺/Fc, the reversible oxidation at 0.25 V vs. Fc⁺/Fc in [(ioan)Mn^IITi^IV] indicates even the access of Mn^III. These results indicate that pentanuclear complexes [(ioan)FeM¹M²M¹Fe(ioan)]ⁿ⁺ are meaningful targets to access electron delocalization in mixed-valence systems over five ions due to the facile accessibility of both Fe^II and Fe^III in the terminal positions. This study provides important local spin-Hamiltonian and Mössbauer parameters that will be essential for the understanding of the potentially complicated electronic structure in the anticipated pentanuclear complexes.     

Electrically induced fluorescence Fe sensing behavior of nanostructured Tiron doped polypyrrole

Nanostructured polypyrrole (PPy) film doped with Tiron was electrodeposited from aqueous solution on the surface of transparent electrode and used for sensitive, selective and rapid electrically controlled fluorescence detection of Fe³⁺ in aqueous media. The fluorescence intensity of PPy-Tiron film decreases linearly in the presence of Fe³⁺ by applying negative potential over a concentration range from 5.0 × 10⁻⁸ to 1.0 × 10⁻⁶ mol L⁻¹, with a relatively fast response time of less than 30 s at pH 7.4. The detection is not affected by the coexistence of other competitive metal ions such as Al³⁺, Ce³⁺, Tl³⁺, La³⁺, Bi³⁺, Cr²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺. The proposed electro-fluorescence sensor has a potential application to the determination of Fe³⁺ in environmental and biological systems. The fluorescent thin film sensor was also used as a novel probe for Fe³⁺/Fe²⁺ speciation in aqueous solution.     

Sorption Properties of Natural Aluminosilicates (Clay,Loam, Sandy Loam,Zeolite)

Sorption of Ni^{2 +}, Cu^{2 +}, Mn^{2 +}, Fe^{3 +}, and Cr^{3 +} from model solutions with natural sorbents (clay, loam, sandy loam, zeolite) was studied. The optimal conditions of sorption were determined. The effect of pH and electrolytes on the sorption efficiency was studied.     

Micro-heterometric determination of bismuth with sodium diethyldithiocarbamate

The reaction between bismuth(III) and sodium diethyldithiocarbamate was investigated. The conditions necessary for the heterometric determination of small amounts ot bismuth in other metals were studied. Various complexing agents were used. Methods and conditions are presented for the direct determination of bismuth (~2%) in salts of the following cations: Ca⁺², Ba⁺², Mg⁺², Zn⁺², Mn⁺², Co⁺², Ni⁺², Al⁺², Cr⁺³, Fe⁺³, Cd⁺², Pb⁺², Hg⁺² and Ag⁺. A titration lasted 10–15 minutes, and the error in most cases was close to zero.     

Fluorimetric Detection of Phosphates in Water Using a Disassembly Approach: A Comparison of FeIII-, ZnII-, MnII- and MnIII-salen Complexes

Details of the reaction sequence used for the fluorimetric detection of phosphates by disassembly of transition metal Schiff base complexes were investigated for [Fe^III(salen)(H₂O)]⁺, [Zn^II(salen)], [Mn^II(salen)(H₂O)₂], and [Mn^III(salen)(H₂O)]⁺. The reactivity of these compounds towards phosphorus oxoanions of differing charge, number of donor atoms and steric hindrance was detected by UV/Vis and fluorescence spectroscopy in both aprotic organic and aqueous media. Selectivity of [Fe^III(salen)(H₂O)]⁺ towards pyrophosphate over all other tested phosphorus-containing analytes was strongly supported. [Zn^II(salen)] showed a faster reactivity but was much less selective. In contrast, [Mn^III(salen)(H₂O)]⁺ proved to be more stable than the iron complex but generally showed little reactivity towards phosphorus oxoanions. The influence of the charge of the central atom was investigated using the Mn^II analogue [Mn^II(salen)(H₂O)₂]. As expected, the reduced charge resulted in a reactivity comparable to the Zn^II complex in organic solution but lead to hydrolysis of the complex in water. Finally, the reaction products of [Fe^III(salen)(H₂O)]⁺ with phosphates were characterized by IR spectroscopy and mass spectrometry, providing further insights into the reaction mechanism of the disassembly process.     

Selective and Sensitive Two New Macroacyclic Schiff base Fluorescent Turn-Off Receptors for Fe3+, DFT Calculation and Their Antibacterial Activity

Two new Macroacyclic Schiff base chemosensors (L₁ and L₂) were synthesized by the one pot condensation reaction of 2-[3-(2-formyl phenoxy)propoxy]benzaldehyde and aminophenol in a 1:2 molar ratio and were characterized by IR, NMR spectroscopy. Both Schiff bases displayed high selectivity and sensitivity towards Fe³⁺ over other metal ions in H₂O-DMF solution (Ag⁺,Cu²⁺, Ni²⁺, Zn²⁺, Mg⁺², Mn⁺², Pb⁺², Co⁺², Hg⁺², Cr⁺³, Na⁺, Ba⁺² and Cd²⁺) due to their structure including oxygen donor atoms. The test results showed fluorescence quenching of the fluorophores when Fe³⁺ was bound to the recognition units. From test results, a high selectivity for Fe³⁺ were discovered in this type of sensors, especially, the probe based on 2-aminophenol exhibited more significant quenching in fluorescence intensity compared with 4-aminophenol-based due to its rigidity structure. In addition, the structure of ligands and their antibacterial properties was investigated.     

Quadrivalent uranium as a reducing agent in potentiometric titrations: Estimation of dichromate,permanganate, bromate and tellurate

Quadrivalent uranium can further be used for the estimation of K₂Cr₂O₇ KmnO₄ (in acid or alkali), H₂TeO₄ and KbrO₃ either alone or in conjunction with Fe⁺³, Ce⁺⁴ and V⁺⁵ The reaction proceeds rapidly in dilute acid solutions and especially when Fe⁺³ iron is used as a catalyst. Reduction of aqueous KmnO₄ gives MnO₂ which then dissolves in the acid of the reagent and undergoes reduction to Mn⁺². In acid solutions no MnO₂ separates. In alkaline medium (1.5–3N NaOH) KmnO₄ is reduced absolutely to MnO₂.     

A heterometric micro-determination of lead with sodium diethyldithiocarbamate

The reaction between lead and sodium diethyldithiocarbamate is studied hcterometrically. The influence of the milieu, conditions of acidity and of different complexing agents, was studied. 0.02–0.04 mg lead per ml of solution can be determined either alone or in the presence of large excesses of other metals. A titration is carried out at 20°C in 8–15 minutes with an error of 0.0–1.0%. The analysed solution may contain ~ 99.5% of the following cations: Ca⁺². Sr⁺², Ba⁺², Mg⁺² Zn⁺², Mn⁺², Ni⁺², Co⁺², Al⁺³, Cr⁺³, Fe⁺³, Cd⁺². Cu⁺², Sb⁺³, Hg⁺², Ag⁺.     

State of manganese ions in the structure of corundum synthesized in supercritical water fluid

The kinetics and formation mechanism of doped corundum (α-Al₂O₃) from hydrargillite (γ-Al(OH)₃) in supercritical water fluid (SCWF) in the presence of manganese ions are studied. It was ascertained that due to the reversible dehydroxylation in an aqueous medium, solid-phase transformation of hydrargillite into boehmite (γ-AlOOH) and then into corundum occurs with the formation of well-faceted corundum micro-crystals that are uniformly doped with manganese. It was found that when Mn²⁺ or MnO₄⁻ ions are introduced into the reaction medium, Mn⁵⁺, Mn⁴⁺, Mn³⁺, and Mn²⁺ ions are observed in the synthesized corundum. Meanwhile, the manganese ions form a complex defect in the corundum structure, which comprises oxygen vacancies and hydroxyl groups. The defects in corundum that emerge upon doping with manganese in SCWF are different from those in corundum doped during high-temperature synthesis.     

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。     

Configuration mixing in the s-hole states of metal ions

Configuration interaction calculation have been carried out on the s-hole states of Mn²⁺ Fe²⁺ (both high- and low-spin configurations). Co²⁺, Ca²⁺, K⁺ and Na⁺ including configurations involving virtual orbitals. The results show good agreement with the multiplet structures found in X-ray photoelectron spectra of these ions.     

A quick and precise heterometric microdetermination of traces of palladium in metals with nitron

A heterometric study was made of the reaction between palladium chloride and nitron in thiocyanate solutions in the presence of excesses of various masking agents.A method is presented for the hetorometric determination of ~0.5 mg palladium in 20 ml aqueous solution with nitron, which can be carried out within 5–10 mn. The solution to be analysed may in general contain ~99.5% of the following foreign metals as cations: Ca⁺², Ba⁺², Mg⁺², Zn⁺², Mn⁺², Co⁺², Ni⁺², Al⁺³, Fe⁺³, Cr⁺³, UO₂⁺², Cu⁺², Cd⁺², Hg⁺², Pb⁺², Tl⁺, Sb⁺³,Bi⁺³, Th⁺⁴, Ce⁺³ and ZrO⁺². The error is between 0 and 1%.     

Mechanistic Insight into the Nitric Oxide Dioxygenation Reaction of Nonheme Iron(III)–Superoxo and Manganese(IV)–Peroxo Complexes

Reactions of nonheme Fe^III–superoxo and Mn^IV–peroxo complexes bearing a common tetraamido macrocyclic ligand (TAML), namely [(TAML)Fe^III(O₂)]^2? and [(TAML)Mn^IV(O₂)]^2?, with nitric oxide (NO) afford the Fe^III–NO₃ complex [(TAML)Fe^III(NO₃)]^2? and the Mn^V–oxo complex [(TAML)Mn^V(O)]^? plus NO₂^?, respectively. Mechanistic studies, including density functional theory (DFT) calculations, reveal that M^III–peroxynitrite (M=Fe and Mn) species, generated in the reactions of [(TAML)Fe^III(O₂)]^2? and [(TAML)Mn^IV(O₂)]^2? with NO, are converted into M^IV(O) and ^.NO₂ species through O?O bond homolysis of the peroxynitrite ligand. Then, a rebound of Fe^IV(O) with ^.NO₂ affords [(TAML)Fe^III(NO₃)]^2?, whereas electron transfer from Mn^IV(O) to ^.NO₂ yields [(TAML)Mn^V(O)]^? plus NO₂^?.     

Distribution of dopant metals between PbTiO3 crystals and PbO-B2O3 flux

Single crystals of lead titanate PbTiO₃ doped with silicon, calcium, chromium, manganese, cobalt, nickel, copper, zinc, and cadmium were grown. The compositions and crystallographic parameters of the crystals were studied. The lowest distribution coefficients of dopants between PbTiO₃ crystals and flux were observed with Mn⁺² and Co⁺² and the highest, with Ca⁺². Doping with niobium leads to the formation of solid solutions with the pyrochlore structure A₂B₂O₇ and even higher distribution coefficient. A correlation was found between dopant concentrations and crystal cell parameters.     

ESR studies of non-silicate inorganic glasses through their glass transformation ranges

ESR spectra of three inorganic glasses doped with Mn²⁺ and Fe³⁺ have been studied through their glass transition temperatures (T_g). Spectral features in each case have been discussed with reference to site symmetries. The intensity of the ESR signal has been bound to decrease in the region of T_g. An attempt has been made to explain this interesting feature on the basis of a two-state model.     

Effect of Additives on the Activity of Tannase from <Emphasis Type="Italic">Aspergillus awamori</Emphasis> MTCC9299

Tannase from Aspergillus awamori MTCC 9299 was purified using ammonium sulfate precipitation followed by ion-exchange chromatography. A purification fold of 19.5 with 13.5% yield was obtained. Temperature of 30 °C and pH of 5.5 were found optimum for tannase activity. The effects of metals and organic solvents on the activity of tannase were also studied. Metal ions Mg⁺², Mn⁺², Ca⁺², Na⁺, and K ⁺ stimulated the tannase activity, while Cu⁺², Fe⁺³, and Co⁺² acted as inhibitors of the enzyme. The addition of organic solvents like acetic acid, isoamylalcohol, chloroform, isopropyl alcohol, and ethanol completely inhibited the enzyme activity. However, butanol and benzene increased the enzyme activity.     

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.