Synthesis, structure, and properties of a binuclear Fe(III) complex with N-(1-propanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine

Mannich reaction of 2-Amino propanol, 2-tert-butyl-4-methylphenol, and formaldehyde in the ratio of 1:2:2 provides a new compound, N-(1-propanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine (H₃L), which has been characterized by X-ray crystallography and elemental analysis. In the presence of Et₃N, the reaction of H₃L and FeCl₃·6H₂O gives a dinuclear Fe(III) complex [Fe₂L₂] 1, which has been characterized by X-ray crystallography, magnetic measurement, and cyclic voltammetry. The value of μ_eff at room temperature (5.97 μ_B) is much less than the expected spin-only value (8.37 μ_B) of two high spin (hs) Fe³⁺ (S = 5/2) ions [μ = g[∑ZS(S + 1)]^1/2], indicating there are strong coupling interactions between Fe³⁺ ions. The magnetic behavior of 1 denotes the occurrence of intramolecular antiferromagnetic interactions (J = −13.35 cm⁻¹ ). CV of 1 reveals two reversible waves at 0.433 and 1.227 V versus AgCl/Ag, which can be ascribed to the successive redox coupling of Fe^IIFe^II/Fe^IIIFe^II and Fe^IIIFe^II/Fe^IIIFe^III, respectively.     

Preparation of Fe2O3-exfoliated graphite composite and its electrochemical properties investigated in alkaline solution

In the present work, a simple method of preparation of FeCl₄⁻- graphite intercalation compounds from HCl/FeCl₃ solution with the aid of chemical oxidant is presented. Based on X-ray diffraction measurements it was concluded, that stages 8, 6, and 5 FeCl₄⁻-graphite intercalation compounds were obtained. The compounds thus obtained were thermally treated to obtain Fe₂O₃-exfoliated graphite composites. The dispersion of Fe₂O₃ in the exfoliated graphite flakes was examined with the aid of the energy dispersive X-ray analysis combined with a scanning electron microscopy. Electrochemical behavior of electrodes was investigated in 6 M KOH solution. Electrochemical investigations proved the formation of FeOOH on the surface of exfoliated graphite during the anodic process. Besides, electrochemical investigations showed that the lower limit potential strongly affects the redox behavior of the Fe₂O₃-EG electrode.     

The Peltier heat and the standard electrode potential of ferro-ferricyanide couple at 298.15 K determined by electrochemical–calorimetry

An experiment was done on electrochemical–calorimetry to identify the Peltier heats of the ferro-ferricyanide reversible electrode reaction over the concentration range of 0.075–0.3 mol dm⁻³ at 298.15 K. A new approach has been developed to obtain the standard potential of this electrode, which was identified as (+0.3580 ± 0.0030) volt at 298.15 K and compared with previously reported values. An equation derived from the approach is also applied to several standard couples, such as Fe(CN)₆⁻³/Fe(CN)₆⁻⁴, H⁺/H₂, Cu²⁺/Cu, Cl⁻/Hg₂Cl₂,Hg, Fe³⁺/Fe²⁺, and Cl⁻/Cl₂ to determine their respective reaction heats with satisfying results.     

A Trinuclear Iron(III) Compound with an Unusual T-Shaped [Fe<Subscript>3</Subscript>(<Emphasis Type="Italic">μ</Emphasis><Subscript>3</Subscript>-O)]<Superscript>7+</Superscript> Core

Treatment of FeCl₃ with 1 equiv of 3-(pyrid-2-yl)-5-(tertbutyl)-1H-pyrazole (L) in basic methanol affords crystalline [Fe₃Cl₅(μ ₃-O)(μ-OMe)₂L₂(MeOH)] in moderate yield. The compound has an unusual isosceles triangular [Fe₃(μ ₃-O)(μ-OMe)₂]⁵⁺ core with one unbridged edge. Two of the iron(III) centres in the compound are approximately octahedral, while the third has a five-coordinate geometry. Magnetic susceptibility measurements show antiferromagnetic coupling between the iron centres, leading to a S = 3/2 magnetic ground state and S = 5/2 excited state that are almost accidentally degenerate according to simulation. An analogous reaction using Fe[ClO₄]₃ as starting material instead affords the low-spin iron(II) complex [FeL₃][ClO₄]₂.     

Ion-Exchange Processes M(II) → Fe(III) and Fe(III) → M(II) in Metal Hexacyanoferrate(II) Gelatin-Immobilized Matrices (M = Mn,Co, Ni,Cu, Zn,Cd)

Ion-exchange reactions M²⁺ Fe³⁺ and Fe³⁺ M²⁺ (M = Mn, Co, Ni, Cu, Zn, Cd) were studied in metal(II) hexacyanoferrate(II) gelatin-immobilized matrices M₂[Fe(CN)₆] in contact with aqueous FeCl₃ solutions and Fe₄[Fe(CN)₆]₃ in contact with aqueous MCl₂ solutions. It was shown that in both cases, M²⁺ was replaced by Fe³⁺ and Fe³⁺ was replaced by M²⁺ to some extent, but no complete replacement was observed in the M₂[Fe(CN)₆]–FeCl₃ or Fe₄[Fe(CN)₆]₃–MCl₂ systems under study. No electrophilic substitution Fe³⁺ Mn²⁺ was found to occur in any noticeable degree during the contact of Fe₄[Fe(CN)₆]₃ with aqueous MnCl₂ solutions even when this contact occurred for 1 h and longer.     

The Coordination Chemistry of Iron with the 1,4‐Bis(2‐pyridyl‐methyl)piperazine Ligand

The behaviour of Fe^II and Fe^III ions in combination with the potential ligand 1,4‐bis(2‐pyridyl‐methyl)piperazine (BPMP) under anhydrous conditions has been investigated. BPMP has been reacted with FeCl₂, FeCl₃ and [Fe(OTf)₂(MeCN)₂]. This led to the isolation of four new complexes, which were fully characterized and structurally investigated by single crystal X‐ray diffraction. It turned out that in the presence of chloride co‐ligands Fe^III favours the tetradentate coordination mode of BPMP with the piperazine unit in a boat configuration, like for instance in [BPMP(Cl)Fe(μ‐O)FeCl₃] or [BPMP‐FeCl₂][FeCl₄], ( 1 ). However, the employment of FeCl₂ leads to the formation of a coordination polymer [BPMP‐FeCl₂]_n, ( 2 ), containing the piperazine ring in a chair configuration binding to two iron centres each. 2 can only be dissolved in very polar solvents like dmf which is capable of breaking up the polymeric structure under formation of [Cl₂(dmf)Fe(μ‐BPMP‐1κ²N,N:2κ²N,N))Fe(dmf)Cl₂]·2 dmf, ( 3 ). In contrast, using [Fe(OTf)₂(MeCN)₂] instead of FeCl₂ as the starting material leads to a mononuclear Fe^II complex with BPMP bound in the desirable tetradentate fashion: [BPMP‐Fe(OTf)₂], ( 4 ). Unlike other complexes with tetradentate N/py ligands the two residual ligands in 4 are bound almost trans to each other with the potential to adopt a cis orientation under oxidising conditions, and it will be interesting to exploit its catalytic properties in future.     

Ferrocene/ferrocenium ion as a catalyst for the photodecomposition of chloroform

Irradiation (λ > 320 nm) of ferrocene in chloroform causes decomposition of chloroform and the accumulation of HCl, CCl₃OOH, and C₂Cl₆. This appears to occur initially through a cycle in which (a) ferrocene is oxidized to ferrocenium and tetrachloroferrate ions, (b) FeCl₄ ⁻ undergoes photodissociation, and (c) ferrocenium reoxidizes the chloroferrate(II) species. On extended photolysis, the concentrations of CCl₃OOH and FeCl₄ ⁻ build up and a competing cycle in which FeCl₄ ⁻ is restored through oxidation of the chloroferrate(II) species by CCl₃OOH accelerates the decomposition rate.     

Ultraviolet spectroscopic study of ferric equilibria at high chloride concentrations

The equilibria among the species Fe³⁺, FeCl²⁺, FeCl₂ ⁺, FeOH²⁺ and Fe(OH)₂ ⁺ have been examined by ultraviolet absorption spectroscopy. Our results indicate that previous workers have generally overestimated the stability constant of FeCl²⁺ and that the association of Fe³⁺ and Cl^– is predominantly inner sphere. The formation constant of FeOH²⁺ obtained in 0.68 m NaCl is in good agreement with our earlier results obtained in 0.68 m NaClO₄. Our results indicate that formation of FeOHCl⁺ is much less significant than has been previously reported. Molar absorptivities for the species Fe³⁺, FeCl²⁺, FeCl₂ ⁺ and FeOH²⁺ are reported for wavelengths between 220 and 400 nanometers.     

Replacement of Fe atoms by Ru in a carbidocarbonyl cluster [Fe<Subscript>6</Subscript>C(CO)<Subscript>16</Subscript>]<Superscript>2−</Superscript>. Structures of reaction products

The reaction of the carbidocarbonyl cluster [Fe₆C(CO)₁₆]²⁻ with ruthenium(IV) hydroxochloride Ru(OH)Cl₃ was studied. At 90–100 °C, the reaction gave products of replacement of Fe atoms by Ru in the [Fe₆C(CO)₁₆]²⁻ cluster along with degradation products. Treatment of the replacement products with FeCl₃ afforded the [Fe_2.96Ru_3.04C(CO)₁₇] compound (1), which was characterized by X-ray diffraction analysis. The crystals of cluster 1 are composed of two types of octahedral molecules (1a and 1b) in a ratio of 2 : 1. Molecules 1a are in general positions, and molecules 1b are located on twofold axes. In both molecules, the Fe and Ru atoms are disordered over four of six positions. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1761–1766, August, 2005.     

Studies on thermochemical properties of ionic liquids based on transition metal

A brown and transparent ionic liquid (IL), [C₄mim][FeCl₄], was prepared by mixing anhydrous FeCl₃ with 1-butyl-3-methylimidazolium chloride ([C₄mim][Cl]), with molar ratio 1/1 under stirring in a glove box filled with dry argon. The molar enthalpies of solution, Δ_s H _m, of [C₄mim][FeCl₄], in water with various molalities were determined by a solution-reaction isoperibol calorimeter at 298.15 K. Considering the hydrolyzation of anion [FeCl₄]⁻ in dissolution process of the IL, a new method of determining the standard molar enthalpy of solution, Δ_s H _m⁰, was put forward on the bases of Pitzer solution theory of mixed electrolytes. The values of Δ_s H _m⁰ and the sum of Pitzer parameters: and were obtained, respectively. In terms of thermodynamic cycle and the lattice energy of IL calculated by Glasser’s lattice energy theory of ILs, the dissociation enthalpy of anion [FeCl₄]⁻, ΔH _dis≈5650 kJ mol⁻¹, for the reaction: [FeCl₄]⁻(g)→Fe³⁺(g)+4Cl⁻(g), was estimated. It is shown that large hydration enthalpies of ions have been compensated by large the dissociation enthalpy of [FeCl₄]⁻ anion, Δ_d H _m, in dissolution process of the IL.     

Fe-exchanged fluorotetrasilicic mica as an active and reusable catalyst for Michael reaction

Fe³⁺-exchanged fluorotetrasilicic mica acts as a highly effective and reusable catalyst for the solventless Michael reaction of β-ketoesters with vinyl ketones under mild condition. The immobilized catalyst shows higher activity than homogeneous Fe³⁺ catalysts, FeCl₃·6H₂O and Fe(NO₃)₃·9H₂O.     

Kinetics and mechanism of oxidation of ferrocyanide by N-bromosuccinimide in aqueous acidic solution

The kinetics of oxidation of ferrocyanide by N-bromosuccinimide (NBS) has been studied spectrophotometrically in aqueous acidic medium over temperature range 20–35 °C, pH = 2.8–4.3, and ionic strength = 0.10–0.50 mol dm⁻³ over a range of [Fe²⁺] and [NBS]. The reaction exhibited first order dependence on both reactants and increased with increasing pH, [NBS], and [Fe²⁺]. The rate of oxidation obeys the rate law: d[Fe³⁺]/dt = [Fe(CN)₆]^4–[HNBS⁺]/(k ₂ + k ₃/[H⁺]). An outer-sphere mechanism has been proposed for the oxidation pathway of both protonated and deprotonated ferrocyanide species. Addition of both succinimide and mercuric acetate to the reaction mixture has no effect on the reaction rate under the experimental conditions. Mercuric acetate was added to the reaction mixture to act as scavenger for any bromide formed to ensure that the oxidation is entirely due to NBS oxidation.     

In situ synthesis of plate-like Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles in porous cellulose films with obvious magnetic anisotropy

Nanocomposite cellulose films with obvious magnetic anisotropy have been prepared by in situ synthesis of plate-like Fe₂O₃ nanoparticles in the cellulose matrix. The influence of the concentrations of FeCl₂ and FeCl₃ solutions on the morphology and particle size of the synthesized Fe₂O₃ nanoparticles as well as on the properties of the composite films has been investigated. The Fe₂O₃ nanoparticles synthesized in the cellulose matrix was γ-Fe₂O₃, and its morphology was plate-like with size about 48 nm and thickness about 9 nm, which was totally different from those reported works. The concentration of FeCl₂ and FeCl₃ solution has little influence on the particle size and morphology of the Fe₂O₃ nanoparticles, while the content of Fe₂O₃ nanoparticles increased with the increase of the concentration of the precursor solution, indicating that porous structured cellulose matrix could modulate the growth of inorganic nanoparticles. The unique morphology of the Fe₂O₃ nanoparticles endowed the composite films with obvious magnetic anisotropy, which would expand the applications of the cellulose based nanomaterials.     

Proton Medium Effect Based on the Ferrocinium Assumption in 80 Mass-% Propylene Carbonate + 20 Mass-% <Emphasis Type="Italic">p</Emphasis>-Xylene Medium

Conventional electrochemical studies on the ferrocinium–ferrocene (Fc⁺–Fc) redox system in 80 mass-% propylene carbonate (PC) + 20 mass-% p-xylene (PX) medium are reported, leading to a calculation of the proton medium effect. The dissociation constant of ferrocinium picrate in this medium was determined by conductivity measurements. The value of E_{Fe⁺ /Fe}^oE_{\mathrm{Fe^{+} /Fe}}^{\mathrm{o}} against the Hg/HgCl₂(s) reference electrode in 80 mass-% PC + 20 mass-% PX was determined potentiometrically in conjunction with conductivity data, and found to be 0.133±0.001 V versus the SHE at 25 °C. The E_{Fe⁺ /Fe}^oE_{\mathrm{Fe^{+} /Fe}}^{\mathrm{o}} value has also been calculated using cyclic voltammetric data obtained in 80 mass-% PC + 20 mass-% PX at a micro platinum working electrode against the Ag/AgCl (nonaq.) reference electrode, and found to be comparable with the value obtained by potentiometry. The proton medium effect for transfer from water to the present mixed solvent medium was calculated using the value of E_Fe⁺/Fe^oE_{\mathrm{Fe^{+}/Fe}}^{\mathrm{o}} versus SHE at 25 °C and found to be 4.5. Based on values of proton medium effect reported in the literature, it is inferred that the present mixed solvent medium is slightly more basic than pure PC.     

Transition metal coordination polymers with polycarboxylic acid as bridging ligands: Synthesis and structure characterization of [Fe(μ4-bta)0.5(phen)(OH)]<Subscript>n</Subscript>

A new 2D (two-dimensional) coordination polymer, [Fe(μ4-bta)o.5(phen)(OH)]_n (1), has been hydrothermally synthesized with FeCl₃ 6H₂, Na₄bta (h₄bta = 1,2,4,5-benzentetracarboxylic acid), 1,10-phen (1,10-phenanthroline) and H₂O as raw materials. The crystals of the compound belong to monoclinic P2₁/n space group, a = 1.0129(2) nm, b = 0.9265(2) nm, c = 1.5696(3) nm, β=91.37(3)°V=1.4721(5) nm³,Z=3, final R₁=0.0292, wR ₂=0.0798 for 2572 [/>2σ(/)] observed reflections. The result of structure determination shows that in the compound each bta ligand is connected with four Fe³, forming a new μ4-coordination mode. Four deprotonated carboxylic groups of bta link to Fe³ ions alternatively through monodentate and bidentate coordination fashion, constructing 2D layer network. The measurement of variable temperature magnetic susceptibility indicates that there exist antiferromagnetic interactions between Fe³ ions in the compound. The TGA spectrum displays relatively fine thermal stability of the compound. In addition, IR and UV-Vis spectra of compound 1 have also been measured.     

Study on the valence fluctuation and the magnetism of an iron mixed-valence complex, (n-C4H9)4N[FeIIFeIII(mto)3](mto = C2O3S)

In the case of iron mixed-valence complexes whose spin states are situated in the spin-crossover region, conjugated phenomena coupled with spin and charge are expected. In general, the Fe site coordinated by six S atoms is in the low-spin state, while the Fe site coordinated by six O atoms is in the high-spin state. From this viewpoint, we have synthesized and investigated physical properties for an monothiooxalato-bridged (mto = C₂O₃S) iron mixed-valence complex, (n-C₄H₉)₄N[Fe^IIFe^III(mto)₃], consisting of Fe^IIIO₃S₃ and Fe^IIO₆ octahedra, which behaves as a ferrimagnet with its magnetic transition temperature of T_N = 38 K and Weiss temperature of θ = ?93 K. From the analysis of ⁵⁷Fe Mössbauer spectra of ⁵⁷Fe enriched complexes, (n-C₄H₉)₄N[⁵⁷Fe^IIFe^III(mto)₃] and (n-C₄H₉)₄N[Fe^II57Fe^III(mto)₃], the charge transfer between Fe^II and Fe^III exists in the paramagnetic phase. Considering the time window of ⁵⁷Fe Mössbauer spectroscopy, the time scale of the valence fluctuation is at least slower than 10^?7 s. In order to confirm the valence fluctuation between Fe^II and Fe^III, we investigated the dielectric constant and found an anomalous enhancement attributed to the Fe valence fluctuation between 170 and 250 K.     

Synthesis and characterization of Fe2O3/SiO2 nanocomposites

Fe₂O₃/SiO₂ nanocomposites based on fumed silica A-300 (S_BET = 337 m²/g) with iron oxide deposits at different content were synthesized using Fe(III) acetylacetonate (Fe(acac)₃) dissolved in isopropyl alcohol or carbon tetrachloride for impregnation of the nanosilica powder at different amounts of Fe(acac)₃ then oxidized in air at 400–900 °C. Samples with Fe(acac)₃ adsorbed onto nanosilica and samples with Fe₂O₃/SiO₂ including 6–17 wt% of Fe₂O₃ were investigated using XRD, XPS, TG/DTA, TPD MS, FTIR, AFM, nitrogen adsorption, Mössbauer spectroscopy, and quantum chemistry methods. The structural characteristics and phase composition of Fe₂O₃ deposits depend on reaction conditions, solvent type, content of grafted iron oxide, and post-reaction treatments. The iron oxide deposits on A-300 (impregnated by the Fe(acac)₃ solution in isopropanol) treated at 500–600 °C include several phases characterized by different nanoparticle size distributions; however, in the case of impregnation of A-300 by the Fe(acac)₃ solution in carbon tetrachloride only α-Fe₂O₃ phase is formed in addition to amorphous Fe₂O₃. The Fe₂O₃/SiO₂ materials remain loose (similar to the A-300 matrix) at the bulk density of 0.12–0.15 g/cm³ and S_BET = 265–310 m²/g.     

Characterization of nano-iron oxyhydroxides and their application in UO<Subscript>2</Subscript><Superscript>2+</Superscript> removal from aqueous solutions

The nano-iron oxyhydroxides (α- and γ-FeOOH) were synthesized by using three ferrous and ferric salts (FeSO₄, FeCl₂, Fe(NO₃)₃) as iron precursors under alkaline conditions. Morphologies of nano-iron oxyhydroxides were characterized by employing X-ray powder diffraction (XRD) and specific surface area (SSA) analysis respectively. The occurrence of needle-like shape of nano-goethite and rod-like shape of nano-lepidocrocite were attributed to hydrolysis of Fe³⁺ cations and/or oxidization of Fe²⁺ at alkaline conditions in terms of XRD analysis. The N₂-BET SSA and BJH (Barrett–Joyner–Halenda) pore size analysis showed that internal SSA of nano-lepidocrocite is higher than that of nano-goethite, although they have similar N₂-BET SSAs. The distribution of average pore size of nano-iron oxyhydroxides are higher than that of predominant pore size due to formation of the heterogeneous nanoparticles under the experimental conditions. These nanoparticles possess the high sorption capacity and the strong affinity for contaminants. Application of nano-iron oxyhydroxides in environmental engineering plays an important role to remove a variety of contaminants, such as heavy-metal ions and organic pollutants.     

无机阴离子、异丙醇及TiO_2对Fe~(3+)诱导全氟辛酸光化学降解影响的研究

254nm紫外光辐照下,溶解性Fe3+的存在有效促进了全氟辛酸(PFOA)的光化学降解.Fe3+浓度为30μmol·L-1时,Fe2(SO4)3,FeCl3和Fe(NO3)3三种溶解性铁盐对PFOA的降解和脱氟没有显著的差别.过量的SO24-与Fe3+具有较强的形成配合物的能力,由软件Visual MINTEQ2.52计算得出,Fe3+与过量的SO42-形成Fe(SO4)+和Fe(SO4)-2两种形态的配合物,其分配比的总和占16.32%,从而减少了PFOA与铁离子形成配合物的机会,进而抑制了其有效的光化学降解;过量的Cl-与Fe3+形成一配位的FeCl2+,其生成量仅占所有铁物种形态总和的0.12%,对PFOA的降解没有明显的影响,理论计算与实验结果相一致.羟基自由基捕获剂-异丙醇的加入未抑制PFOA的降解,二氧化钛的存在亦未促进其降解,进一步表明Fe3+诱导PFOA的光化学降解不是羟基自由基直接作用的结果.     

Generation of Iron Atoms in the Gas Phase by Microwave‐Induced Plasma Afterglows

A fast‐flow reactor technique is described by which Fe atoms can be produced in the gas phase in the afterglow of microwave‐induced plasmas in hydrogen/argon and hydrogen/helium mixtures. When the iron salt FeCl₃(s) was brought into the gas phase by thermal sublimation at temperatures between 360 and 405 K, it was partly converted to Fe atoms by reaction of the gaseous compounds Fe_xCl_3x(g) with hydrogen atoms. The Fe atoms were detected by atomic absorption spectroscopy (AAS). It was shown that sublimation of the salt is the rate‐determining step of the overall plasma‐afterglow atomisation process. Experimental conditions for the generation of Fe atoms suited to kinetic studies start at a temperature of 303 K. In the downstream region the concentration of Fe atoms decays due to diffusion to the reactor wall. Binary diffusion coefficients D_Fe/Ar and D_Fe/He of 231.5±6.6 and 370.0±15.5 cm² s^?1 Torr at 303 K, respectively, were determined.