Facile and Reversible Formation of Iron(III)–Oxo–Cerium(IV) Adducts from Nonheme Oxoiron(IV) Complexes and Cerium(III)

Ceric ammonium nitrate (CAN) or Ce^IV(NH₄)₂(NO₃)₆ is often used in artificial water oxidation and generally considered to be an outer-sphere oxidant. Herein we report the spectroscopic and crystallographic characterization of [(N4Py)Fe^III-O-Ce^IV(OH₂)(NO₃)₄]⁺ ( 3 ), a complex obtained from the reaction of [(N4Py)Fe^II(NCMe)]²⁺ with 2 equiv CAN or [(N4Py)Fe^IV=O]²⁺ ( 2 ) with Ce^III(NO₃)₃ in MeCN. Surprisingly, the formation of 3 is reversible, the position of the equilibrium being dependent on the MeCN/water ratio of the solvent. These results suggest that the Fe^IV and Ce^IV centers have comparable reduction potentials. Moreover, the equilibrium entails a change in iron spin state, from S=1 Fe^IV in 2 to S=5/2 in 3 , which is found to be facile despite the formal spin-forbidden nature of this process. This observation suggests that Fe^IV=O complexes may avail of reaction pathways involving multiple spin states having little or no barrier.     

Homogeneous Solid‐State Titanium Phosphate Potentiometric Sensor and its Application; Sorption of Iron (III) by Modified Chitosan in Two Modes of Operations

Abstract

A solid state iron (III) potentiometric sensor based on a pure tablet of titanium phosphate (TP) ion exchanger as sensitive membrane is elaborated. A homogeneous sensor prepared by this exchanger displays a useful analytical response with a super Nernestian cationic response (slope 22.5±1 mV/decade), excellent reproducibility and applicability over a wide range of iron (III) concentration (1×10^?6 ?1× 10^?2 mol l^?1). It also offers the advantages of fast response time (<1 min.), low cost, and simple construction. The proposed potentiometric sensor was successfully used in direct potentiometry as a low cost monitoring in sorption of iron (III) using modified chitosan in two modes of operations. Langmuir and Freundlich constants have been determined. In continuous flow system, the influences of varying parameters such as bed depth and solution flow rate have been studied. In a new approach (low cost monitoring/low cost treatment), the feasibility of the proposed potentiometric sensor in monitoring and the modified chitosan as sorbent in treatment of iron (III) from liquid waste streams were addressed.     

Oxidized Hemithioindigo Photoswitches—Influence of Oxidation State on (Photo)physical and Photochemical Properties

The photophysical and photochemical properties of sulfoxide and sulfone derivatives of hemithioindigo photoswitches are scrutinized and compared to the unoxidized parent chromophores. Oxidation results in significantly blue-shifted absorptions and mostly reduction of photochromism while thermal stabilities of individual isomers remain largely unaltered. Effective photoswitching takes place at shorter wavelengths compared to parent hemithioindigos and high isomeric yields can be obtained reversibly in the respective photostationary states. Reversible solid-state photoswitching is observed for a twisted sulfone derivative accompanied by visible color changes. These results establish oxidized hemithioindigo photoswitches as promising and versatile tools for robust light-control of molecular behavior for a wide range of applications.     

Immediate Formation/Precipitation of Icosahedrally Structured Iron–Molybdenum Mixed Oxides from Solutions Upon Mixing Simple Iron(III) and Molybdate Salts

The present investigation refers to nanostructured mixed metal oxides—more specifically to iron–molybdenum oxides most simply obtained by addition of iron(III) chloride to an aqueous solution of sodium molybdate acidified with acetic acid. The immediately obtained yellow non-crystalline solid consists of highly symmetrical icosahedral {Mo₇₂Fe₃₀} motifs which is proven by IR, Raman, ⁵⁷Fe Mössbauer and XP spectra. This remarkable result is obtained in spite of the immediate precipitation of the mentioned compound and even from an inhomogeneous mixture of the educts. This again proves the high formation tendency of spherical clusters. The procedure offers in principle the option to encapsulate species present in solution.     

The Effect of Concentration Parameters on Complexation in the Iron(0)–Iron(II)–Glycine–Water System

The processes of formation of iron(II) complexes in aqueous glycine solutions in the pH range of 1.0–8.0 at 298 K and ionic strength of 1 mol/L (NaClO₄) are studied using Clark and Nikolskii’s oxidation potential method. The type and number of coordinated ligands, the nuclearity, and the total composition of the resulting complexes are determined. The following complex species are formed in the investigated system: [Fe(OH)(H₂O)₅]⁺, [FeHL(H₂O)₅]²⁺, [Fe(HL)(OH)(H₂O)₄]⁺, [Fe(OH)₂(H₂O)₄]⁰, [Fe₂(HL)₂(OH)₂(H₂O)₈]²⁺, and [Fe(HL)₂(H₂O)₄]²⁺. Their formation constants are calculated by the successive iterations method using Yusupov’s theoretical and experimental oxidation function. The model parameters of the resulting coordination compounds are determined.     

Selective Activation of Ar–Cl and Ar–C Bonds with Iron(II) Complexes

The electrophilic iron–carbene chelate complexes 1 and 2 react with alkoxides RO⁻ to give the neutral chelate complex 3 and the carbene complex 4 , respectively. Depending on the nature of the chelating ortho substituent, selective activation of the Ar–Cl or Ar–C bond occurs; these processes are promoted by the chelation.     

Solid–Gas Phase Synthesis of Coordination Networks by Using Redox-Active Ligands and Elucidation of Their Oxidation Reaction

Formation of coordination networks is a complex process affected by a multitude of factors. Many synthetic strategies have been developed that attempt to control these factors and direct the structure of the final product. Coordination bond formation and structural assembly processes, however, typically take place either in the solution or solid states. In comparison, gas-phase network synthesis remains largely unexplored. Herein, two new two-dimensional coordination networks are obtained from the solid–gas phase reaction between ZnX₂ (X=I, Br) and the redox-active 2,5,8-tri(4-pyridyl)1,3-diazaphenalene (HTPDAP) ligand. Their structures were solved by ab initio powder X-ray diffraction analysis and feature a novel Zn halide trimeric cluster. This strategy is contrasted with a conventional solvothermal synthesis, which led to a one-dimensional coordination polymer instead. The intrinsic electroactive properties of these materials were probed by solid-state cyclic voltammetry measurements, which revealed the presence of HTPDAP and halide-based processes. Chemical oxidation of the two-dimensional networks by using NOPF₆ agent, unexpectedly, led to the formation of a nitrated analog of HTPDAP, the PF₆⁻ salt of diprotonated 4,6,7,9-tetranitro-2,5,8-tris(4-pyridyl)diazaphenalene cation (denoted N-TPDAP), which was isolated and characterized. These results provide deeper insights into the oxidation process of HTPDAP-containing networks and uncover unique redox-induced chemical transformations.     

Spectroscopy and Speciation Studies on the Interactions of Aluminum (III) with Ciprofloxacin and β-Nicotinamide Adenine Dinucleotide Phosphate in Aqueous Solutions

In this study, both experimental and theoretical approaches, including absorption spectra, fluorescence emission spectra, ¹H- and ³¹P-NMR, electrospray ionization mass spectrometry (ESI-MS), pH-potentiometry and theoretical approaches using the BEST & SPE computer programs were applied to study the competitive complexation between ciprofloxacin (CIP) and b-nicotinamide adenine dinucleotide phosphate (NADP) with aluminum (III) in aqueous solutions. Rank annihilation factor analysis (RAFA) was used to analyze the absorption and fluorescence emission spectra of the ligands, the binary complexes and the ternary complexes. It is found, at the mM total concentration level and pH = 7.0, the bidentate mononuclear species [Al(CIP)]²⁺ and [Al(NADP)] predominate in the aqueous solutions of the Al(III)-CIP and Al(III)-NADP systems, and the two complexes have similar conditional stability constants. However, the pH-potentiometry results show at the mM total concentration level and pH = 7.0, the ternary species [Al(CIP)(HNADP)] predominates in the ternary complex system. Comparing predicted NMR spectra with the experimental NMR results, it can be concluded that for the ternary complex, CIP binds to aluminum ion between the 3-carboxylic and 4-carbonyl groups, while the binding site of oxidized coenzyme II is through the oxygen of phosphate, which is linked to adenosine ribose, instead of pyrophosphate. The results also suggested CIP has the potential to be a probe molecular for the detection of NADP and the Al(III)-NADP complexes under physiological condition.     

The Influence of Di-(2-Ethylhexyl)Phosphoric Acid on the Properties of Microemulsion in the Sodium Di-(2-Ethylhexyl)Phosphate–Di-(2-ethylhexyl)Phosphoric Acid–Decane–Water System

It has been shown that the presence of small amounts of di-(2-ethylhexyl)phosphoric acid (below 6 mol % in the mixture of surfactants) in a sodium di-(2-ethylhexyl)phosphate–di-(2-ethylhexyl)phosphoric acid–decane–water system widens the region of microemulsion existence with respect water and decreases the slope of the dependence of hydrodynamic droplet diameter of on water-to-sodium di-(2-ethylhexyl) phosphate molar ratio. At di-(2-ethylhexyl)phosphoric acid concentrations in its mixture with sodium di-(2-ethylhexyl)phosphate higher than 6 mol %, the fraction of water bound with ions in microemulsion droplets decreases, the region of microemulsion existence narrows, specific conductance decreases, and the slope of the dependence of the hydrodynamic droplet diameter of on the water-to-sodium di-(2-ethylhexyl) phosphate molar ration increases.     

Synthesis and Antitumor Activity of Novel 2-(Thymin-1 ′ -ylmethoxy)ethyl Alkyl Sulfides and Their Oxidation Products

A series of novel 2-(thymin-1′-ylmethoxy)ethyl alkyl sulfides have been synthesized in three steps from thymine. They have been oxidized into sulfoxide and sulfone derivatives by means of NaIO ₄ and H ₂ O ₂ 30%/diethyl azodicarboxylate (DEAD), respectively, in high yields. All products were characterized by ¹ H NMR and IR spectra and elemental analyses. The preliminary bioassay indicates that the compound 6g exhibited potential antitumor activity.     

The Role of Iron–Carbon Galvanic Contact in the Formation of Dispersed Iron Hydr(oxides) in Water and Electrolyte Solutions

The comparative analysis of phase formation on the iron surface in aqueous medium in the presence and absence of iron–carbon (coke) galvanic contact was carried out. The role of galvanic contact in phase formation processes was determined. It was shown that, in the presence of galvanic contact almost complete oxidation of iron ions on the surface of an iron half-element and a rather efficient stationary formation of dispersed phases serving as sorbents of heavy metals from solutions take place. The effect of anionic composition of solution on the parameters of phase formation was studied. It was established that maximal amount of iron–oxygen-containing phases is formed in zinc chloride solution. The presence of sulfate and nitrate ions in solution decreased significantly the rate of phase formation in iron–carbon galvanic contact.     

Preparation and Characterization of Uranium–Iron Triple-Bonded UFe(CO)3− and OUFe(CO)3− Complexes

We report the preparation of UFe(CO)₃⁻ and OUFe(CO)₃⁻ complexes using a laser-vaporization supersonic ion source in the gas phase. These compounds were mass-selected and characterized by infrared photodissociation spectroscopy and state-of-the-art quantum chemical studies. There are unprecedented triple bonds between U 6d/5f and Fe 3d orbitals, featuring one covalent σ bond and two Fe-to-U dative π bonds in both complexes. The uranium and iron elements are found to exist in unique formal U(I or III) and Fe(−II) oxidation states, respectively. These findings suggest that there may exist a whole family of stable df–d multiple-bonded f-element-transition-metal compounds that have not been fully recognized to date.     

Synthesis of Iron,Cobalt, Nickel,and Copper Hexacyanoferrates Nanoparticles Stabilized with Sodium Hexametaphosphate,and Their Use for Modification of Langmuir—Blodgett Films

Russian Journal of General Chemistry - Langmuir-Blodgett films were obtained on the basis of octadecylamine monolayers containing nanoparticles of various metals hexacyanoferrates. Nanoparticles...     

Adsorptive Voltammetric Measurement of Trace Level of Iron(III) with 4–(2–Pyridylazo) Resorcin

Abstract

The polarographic behavior of the complex of iron–4– (2–pyridylazo) resorcin(PAR) was studied. In HAc– NaAc– EDTA buffer solution, the complex can be adsorped on a hanging mercury drop electrode giving a sensitive adsorptive complex reduction peak with a peak potential at -0.36V(vs. SCE). Optimum experimental conditions were found by the use of 0.08mol/L HAc, 0.06mol/L NaAc, 5.0 × 10^?3mol/L EDTA and 1.0 × 10^?5mol/L PAR. With preconcentration for 60s, the derivative peak height of the complex compound is linearly proportional to the concentration for Fe in the range from 1.0 × 10^?9mol/L to 1.0 × 10^?7mol/L. For a 2–min pre–concentration time, the detection limit found was 2.0 × 10^?10mol/L. This method has high sensitivity and selectivity. It has been applied to the determination of trace iron in food and water samples without any pre–separation step.     

Sorption–Desorption Photometric Determination of Trace Iron in Sodium, Potassium, and Ammonium Thiocyanates Using Polyurethane Foams

A reagent-free sorption photometric method for determining trace iron(III) in alkali-metal and ammonium thiocyanates was developed. The method consists in the adsorption of iron(III) thiocyanate complexes on polyurethane foams at pH 2–3 followed by the desorption of complexes with acetone and a measurement of the absorbance of solutions. The analytical range for iron was 0.5–20 g in a 0.2–2.5-g portion of salt. The determination limit and relative standard deviation were 2 × 10^–5% and 20–30%, respectively (n= 3; P= 0.95). The specific feature of the determination is that an additional photometric reagent is not introduced in the solution of the salt to be analyzed, because thiocyanate, that is, the matrix component of the test sample, acts as such a reagent.     

Enantiospecific Synthesis of (–)-Cuspareine and (–)-Galipinine

An enantiospecific route to the synthesis of tetrahydroquinoline alkaloids (–)-cuspareine and (–)-galipinine is reported. Coupling of an iodide derivative of D-serine with aromatic dithianes and Pd-catalyzed intramolecular C–N coupling are the key steps in the synthesis.     

Selective Preparation of Phosphorus Mononitride (P≡N) from Phosphinoazide and Reversible Oxidation to Phosphinonitrene

The interstellar candidate phosphorus mononitride PN, a metastable species, was generated through high-vacuum flash pyrolysis of (o-phenyldioxyl)phosphinoazide in cryogenic matrices. Although the PN stretching band was not directly detected because of its low infrared intensity and possible overlaps with other strong bands, o-benzoquinone, carbon monoxide, and cyclopentadienone as additional fragmentation products were clearly identified. Moreover, an elusive o-benzoquinone-PN complex formed when (o-phenyldioxyl)phosphinoazide was exposed to UV irradiation at λ=254 nm. Its recombination to (o-phenyldioxyl)-λ⁵-phosphinonitrile was observed upon irradiation with the light at λ=523 nm, which demonstrates for the first time the reactivity of PN towards an organic molecule. Energy profile computations at the B3LYP/def2-TZVP density functional theory level reveal a concerted mechanism. To provide further evidence, UV/Vis spectra of the precursor and the irradiation products were recorded and agree well with time-dependent DFT computations.