Redox behavior of gamma-pyrilocyanines,their heteroanalogues,and flavilium dyes

Potentials of the reduction of gamma-pyrilocyanines, their heteroanalogues, and flavilium dyes on a mercury film electrode and potentials of their oxidation on a glassy-carbon electrode in nonaqueous media are obtained for the first time ever by a voltammetry method. It is shown that the oxidation and reduction potentials depend on the dye molecule structure, in particular, on the nature of the heteroatom in the heterocycle. It is established that the ClO ₄ ^? anion and complex anions InCl ₄ ^? and TlCl ₄ ^? , which enter the composition of cationic flavilium dyes, undergo neither reduction nor oxidation in the potential region studied.     

Crystal structure of hexakis-(<Emphasis Type="Italic">N</Emphasis>-methylthiourea) bismuth(III) triperchlorate

A bismuth(III) complex of N-methylthiourea (Mtu, C₂H₆N₂S) [Bi(C₂H₆N₂S)₆](ClO₄)₃ has been synthesized, and its crystal structure has been determined. The structure is built of octahedral Bi(Mtu) ₆ ³⁺ cations and ClO ₄ ^? anions. Sulfur atoms are coordinated to bismuth(III) (at axis 2) at octahedron vertices (Bi-S, 2.7670(8), 2.8142(8), and 2.8315(8) Å); angles SBiS vary from 82.26(3)° to 96.13(2)°. The presence of amino groups and oxygen atoms in the structure results in the emergence of numerous hydrogen bonds (HBs). All H atoms of amino groups are involved in HBs; one of them is bound to the sulfur atom. One of the oxygen atoms of ClO ₄ ^? anions does not participate in HBs.     

Degradation of trichloroethylene in aqueous solution by persulfate activated with Fe(III)–EDDS complex

In this study, an environmentally friendly complexing agent, S,S′-ethylenediamine-N,N′-disuccinic acid (EDDS), was applied in Fe(III)-mediated activation of persulfate (PS), and the degradation performance of trichloroethylene (TCE) was investigated. The effects of PS concentration, Fe(III)/EDDS molar ratio, and inorganic anions on TCE degradation were evaluated, and the generated reactive oxygen species responsible for TCE removal were identified. The results showed that nearly complete TCE degradation was achieved with PS of 15.0 mM and a molar ratio of Fe(III)/EDDS of 4:1. An increase in PS concentration or Fe(III)/EDDS molar ratio to a certain value resulted in enhanced TCE degradation. All of the anions (Cl^?, HCO₃ ^?, SO₄ ^2?, and NO ₃ ^? ) at tested concentrations had negative effects on TCE removal. In addition, investigations using radical probe compounds and radical scavengers revealed that sulfate radicals (SO ₄ ^·? ), hydroxyl radicals (^·OH), and superoxide radical anions (O ₂ ^·? ) were all generated in the Fe(III)–EDDS/PS system, and ^·OH was the primary radical responsible for TCE degradation. In conclusion, the Fe(III)–EDDS-activated PS process is a promising technique for TCE-contaminated groundwater remediation.     

The effect of substituents in ligands and of anionic composition on the exchange interaction in binuclear Cu(II) complexes based on 2,6-diformyl-4-methylphenol

A series of novel binuclear Cu(II) complexes based on 2,6-diformyl-4-methylphenol and containing aminoguanidine and hydrazinobenzthio(oxo)zole as variable chelatophore fragments were synthesized. In these complexes, Cl^?, Br^?, NO ₃ ^? , and ClO ₄ ^? are both the inner-and outer-sphere ions. The magnetochemical properties of the title complexes were compared and the anion nature was shown to influence the structure of the complexes and the strength of antiferromagnetic interaction.     

Theoretical study of oxoborate complexes with MO<Stack><Subscript>4</Subscript><Superscript><Emphasis Type="Italic">n</Emphasis>−</Superscript></Stack> tetraoxo anions in the inner and outer spheres of the B<Subscript>20</Subscript>O<Subscript>30</Subscript> cluster

The energies and structural and spectroscopic characteristics of endohedral (MO₄©B₂₀O ₃₀ ^n? ) and exohedral (MO₄ · B₂₀O ₃₀ ^n? ) isomers of oxoborate complexes with MO ₄ ^n? tetraoxo anions with 32 valence electrons located in the inner and outer spheres of the B₂₀O₃₀ cluster have been calculated by the density functional theory method (B3LYP). It has been demonstrated that, among the endohedral MO₄©B₂₀O ₃₀ ^n? clusters with strong multiply charged anions (VO ₄ ^3? , CrO ₄ ^2? , PO ₄ ^3? , SO ₄ ^2? , AsO ₄ ^3? , SeO ₄ ^2? , etc.), the isomer in which a “guest” tetrahedron MO₄ is located at the center of the B₂₀O₃₀ cage and bonded to it through internal oxygen bridges M-O*-B is the most favorable one. Among the exohedral analogues MO₄ · B₂₀O ₃₀ ^n? , two most favorable isomers contain the “capping” MO₄ tetrahedron bonded to the B₂₀O₃₀ cage through two and three external M-O-B bridges. For the complexes with doubly charged SO ₄ ^2? and SeO ₄ ^2? anions, the third exohedral isomer in which the sulfite or selenite group MO₃ is bidentately coordinated to the oxidized B₂₀O₂₉(OO) cage with one peroxide bridge turns out to be close in energy to the above two isomers. For the systems with high negative charge n, the exohedral isomers are much more favorable than the endohedral isomer; however, with decreasing charge, the difference in energy between them decreases to ~10–18 kcal/mol, so that the exo–endo transition between them can require moderate energy inputs. For the endohedral complexes with singly charged ClO ₄ ^? and BrO ₄ ^? anions, two isomers with close energies are preferable in which the central atoms of the guest tetrahedra are reduced to the state of singly charged ions, while the oxoborate cage is oxidized to B₂₀O₂₆(OO)₄ with four peroxide groups B-O-O-B and retains its closed (closo) structure. In the most favorable isomer of the complexes with multicharged ortho-anions BO ₄ ^5? , CO ₄ ^4? , and NO ₄ ^3? , the outersphere anion is reduced to, respectively, borate, carbonate, and nitrate bidentately coordinated to the oxidized B₂₀O₂₉(O)₂ cage with an open structure and two strongly elongated terminal B-O bonds. The results are compared with the data of previous calculations of endohedral and exohedral vanadate complexes MO₄©V₂₀O ₅₀ ^n? and MO₄ · V₂₀O ₅₀ ^n? with the same guest anions MO ₄ ^n? .     

Regularities of electrochemical behavior of polyaniline doped by electroactive anions

Electrochemical potentiodynamic and potentiostatic synthesis is used to obtain polyaniline (PANI) modified by new electroactive anions: organic dianion of the diammonium salt of 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfo acid) (ABTS) and inorganic ammonium hexachloroiridate dianion IrCl ₆ ^2? (HCI). Electrochemical behavior of the modified PANI-ABTS and PANI-HCI polymers is studied by means of the meth ods of cyclic voltammetry (CV) and charge-discharge dependences. It is shown that modified PANI-ABTS and PANI-HCI remain electroactive at much higher potential sweep rates as compared to PANI doped by HSO ₄ ^? (PANI-sulfo). Electrochemical capacity values are calculated on the basis of the data of CVs and discharge curves and coulombic efficiency of the new polymers that exceeds significantly the corresponding values for PANI-sulfo. This effect is enhanced when the ABTS and HCI additives are introduced into the supporting electrolyte in all electrochemical processes.     

ClO<Stack><Subscript>4</Subscript><Superscript>−</Superscript></Stack>/Al-MCM-41 nanoparticles as a solid acid catalyst for the synthesis of 2-amino-3-cyanopyridines

A one-pot four-component reaction of various types of aldehydes, acetophenone, malononitrile, and ammonium acetate was studied in the presence of perchlorated Al-MCM-41 (ClO ₄ ^? /Al-MCM-41) nanoparticles for the synthesis of 2-amino-3-cyanopyridines. Mesoporous Al-MCM-41 molecular sieves with the Si/Al molar ratios of 30, 40, and 50 were synthesized by the sol–gel method and ClO ₄ ^? /Al-MCM-41 with different calcination temperatures were prepared and characterized by SEM, TEM, XRD, FT-IR, potentiometric titration and, N₂ adsorption-desorption techniques. The characterization results show that ClO ₄ ^? /Al-MCM-41 with calcination temperature of 300 °C has the best catalytic activity for the synthesis of 2-amino-3-cyanopyridines. The catalyst is reusable many times with moderate loss in its activity.     

Structural Inhomogeneity in Electrolyte Solutions: The Calcium Perchlorate–Water System

A new approach has been proposed to study the structure of aqueous electrolyte solutions. NIR, Raman and attenuated total reflectance, Fourier transform infra-red (ATR FTIR) spectra have been measured for aqueous calcium perchlorate solutions in the 0.22–4.3 mol·L^?1 (0.22–7.46 mol·kg^?1) concentration range at 25 °C. By the methods of principal component analysis (PCA) and multivariate curve resolution—alternating least squares (MCR-ALS) the number, spectra and concentration profiles have been determined for spectroscopically distinguishable forms of water and ClO ₄ ^? ion in solutions. The results have been analyzed using a phenomenological model, establishing thereby: concentration ranges for structural rearrangements of the solution, the nature of structural microirregularities and different states of the ClO ₄ ^? ion in the areas of domination of the natural water structure, and of cybotactic groups of calcium perchlorate hexa and tetra hydrates.     

Influence of the nuclearity of copper(II) chloride complexes on their activity in catalytic C-Cl bond metathesis

Catalytic systems containing mainly mononuclear (CuCl ₄ ^2? ) or dinuclear (Cu₂Cl ₆ ^2? ) tributylbenzylammonium chlorocuprates are prepared by adsorption on silica surfaces of different structures (Aerosil and Silokhrom). Using ESR, XANES, and electronic spectroscopy, the CuCl ₄ ^2? ions are shown to be reduced rapidly under conditions of C-Cl bond metathesis, whereas the dinuclear chlorocuprates are relatively stable. A correlation between the number of copper ions in the chlorocuprate anion and its catalytic activity is established: the mononuclear complexes are several times more active than their dinuclear counterparts.     

Electrochemical properties of polyaniline film doped by Ce3+ cation

Electrochemical Synthesis (ES)of polyaniline (PAni) is carried out in the presence in electrolyte (1 M H₂SO₄) of cerium (III) sulfate under potentiostatic and potentiodynamic modes. It is shown that Ce³⁺ cations in electrolyte catalyze ES, i.e. accelerate both ES variants. The obtained polymers were characterized using the scanning electron microscopy (SEM) technique and also on the basis of the calculation of electrochemical characteristics. Relaxation in PAni polymers doped by the Ce³⁺ cation occurs several times faster than in proton-doped PAni. The minimum change in ΔE and E is observed in polymers doped by Ce³⁺ cations during the electrochemical cycling of PAni and PAni-Ce at high rates.     

The conformational changes of 5SrRNA from lupin seeds in presence of ClO 4 − , NO 3 − , Br−, BF 4 − , SO 4 2− , Cl−, COO− anions by adiabatic scanning calorimetry

The results of calorimetric studies of 5SrRNA solutions isolated from lupin seeds in the pressence of the ClO ₄ ^? , NO ₃ ^? , Br ₄ ^? , SO ₄ ^2? , Cl^?, COO^? (maleic and fumaric acids) anions were reported. The plots of calorimetric curves, enthalpy of conformational changes of two state transitions were presented. Using the deconvolution method proposed by Freire and Biltonen the elementary transitions were distinguished and discussed.     

Electrical conductivity and ionic association of lithium and sodium perchlorates in tetrahydrofuran

The total limiting molar electrical conductivities of ions and triads of ions and the association constants of ions with the formation of ion pairs and triads of ions were calculated from the concentration dependences of the electrical conductivity of solutions of lithium and sodium perchlorates in tetrahydrofuran at 278.15–318.15 K with the use of the method specially developed earlier. The experimental total limiting electrical conductivities were used to calculate the limiting molar electrical conductivities and attraction friction factors of separate ions (Li⁺, Na⁺, ClO ₄ ^? , Li₂ClO ₄ ⁺ , Na₂ClO ₄ ⁺ , Li(ClO₄) ₂ ^? , and Na(ClO₄) ₂ ^? ). The constants of ion association into ion pairs were used to calculate the Gibbs energy of non-Coulomb interionic interaction (ΔG*_+?), and the constants of association into triads of ions, to determine the a ₃ distance parameter between the centers of the ion and the dipole of the ion pair. Positive ΔG*_+?), values and deviations of the experimental a ₃ value from the distance parameter calculated theoretically (a ₃ ⁰ ) for the triad of ions (Δa ₃ = a ₃ ? a ₃ ⁰ ) were related to non-Coulomb repulsion in the region of overlap of the solvation shells of ions and the influence of temperature and ion charge density on this repulsion.     

Effect of the salting-out agent anion nature on the phase separation of a potassium salt–potassium bis(alkyl polyoxyethylene)phosphate–water systems

The effect the salting-out agent anion nature has on the temperature and concentration intervals of the existence of the separation area is established by analyzing the phase diagrams of pseudoternary KCl (KBr, KI, KNO₃, K₂SO₄, K₄P₂O₇)–potassium bis(alkyl polyoxyethylene)phosphate (oxyphos B)–water systems. It is concluded that the anionic salting-out capability is reduced in the order P₂O₇^4-> SO₄^2-> Cl^? > Br^?> NO₇^4-> SO₃^-> I^?. The thermodynamic parameters of phase separation used to interpret the results are calculated. The observed pattern of a change in the salting-out ability of the investigated salts relative to aqueous solutions of the surfactants is in good agreement with the lyotropic (Hofmeister) series.     

Crystal structure of 4,7,13,16,21,24-hexaoxa-1,10-diazoniabicyclo [8.8.8]hexacosane nitrate-hydrogen nitrate perchlorate semihydrate

An adduct of 2.2.2-cryptand with nitric and perchloric acids of the [H₂(Crypt-222)· 0.52H₂O]²⁺·ClO ₄ ^? ·NO ₃ ^? ·HNO₃ composition (I) is prepared and characterized by single crystal X-ray diffraction. The triclinic structure of I (space group \(P\overline 1 \), a = 10.176 Å, b = 11.272 Å, c = 12.870 Å, α = 78.61°, β = 76.62°, γ = 79.88°, Z = 2) is solved by a direct method and refined in the full-matrix anisotropic approximation to R = 0.062 for all 3642 measured independent reflections (CAD-4 automated diffractometer, λMoK _α). The structure of I contains a dication of 2.2.2-cryptand in the endo-endo conformation, two hydrogen atoms at the protonated N atoms are directed inside the cavity which also includes a water molecule with a site occupation factor of 0.52. Tetrahedral ClO ₄ ^? anion in I is disordered. In I, the H atom of the NO ₃ ^? ·HNO₃ dimer is split over two close positions with occupation factors of 0.33 and 0.67; this dimer is joined by a very strong single disordered hydrogen bond N-O-H?O = N between the molecule of nitric acid and its anion.     

Chaotropic Monovalent Anion‐Induced Rectification Inversion at Nanopipettes Modified by Polyimidazolium Brushes

A nonintuitive observation of monovalent anion‐induced ion current rectification inversion at polyimidazolium brush (PimB)‐modified nanopipettes is presented. The rectification inversion degree is strongly dependent on the concentration and species of monovalent anions. For chaotropic anions (for example, ClO₄^?), the rectification inversion is easily observed at a low concentration (5 mm ), while there is no rectification inversion observed for kosmotropic anions (Cl^?) even at a high concentration (1 m ). Moreover, at the specific concentration (for example, 10 mm ), the variation of rectification ratio on the type of anions is ranged by Hofmeister series (Cl^?≥NO₃^?>BF₄^?>ClO₄^?>PF₆^?>Tf₂N^?). Estimation of the electrokinetic charge density (σ^ek) demonstrates that rectification inversion originates from the charge inversion owing to the over‐adsorption of chaotropic monovalent anion. To qualitatively understand this phenomenon, a concentration‐dependent adsorption mechanism is proposed.     

Investigation of Chloride Ion Substitution Equilibria in AuCl<Stack><Subscript>4</Subscript><Superscript>−</Superscript></Stack> with Ethylenediamine and 1,3-Diaminopropane Using Capillary Zone Electrophoresis

Substitution of chloride ions in AuCl ₄ ^? with ethylenediamine (en) and propylenediamine (tn) is studied by capillary zone electrophoresis at I = 0.05 M and T = 25°C. The substitution constants are determined: AuenCl ₂ ⁺ + en = Auen ₂ ³⁺ + 2Cl^–, logK₂ = 10.4; AuCl ₄ ^? + tn = AutnCl ₂ ⁺ + 2Cl^–, logK₁ = 16.1; AutnCl ₂ ⁺ + tn = Autn³⁺₂ + 2Cl^–, logK₂ = 12.0.     

Crystal structure,optical and magnetic properties of the bis(perchlorate) of 3,4-diaminopyridine

3,4-diaminopyridinium bis(perchlorate) has been synthesized and its crystal structure has been solved by single crystal X-ray diffraction. The optical and magnetic properties of the N1, N4 protonated 3,4-diaminopyridinium dication have been elucidated in solution and in the solid-state by means of linear-polarized solid state IR-spectroscopy (IR-LD), UV-spectroscopy, TGA, DSC, and positive and negative ESI MS. Quantum chemical calculations were used to obtain the electronic structure, vibrational data, and electronic spectra of the dication. The studied compound crystallizes in the noncentrosymmetric space group Cc and exhibits infinite molecular chains formed by 3,4-diaminopyridinium dications and ClO ₄ ^? anions along the c-axis by moderate intermolecular NH ₃ ⁺ ···OClO ₃ ^? interactions with bond lengths of 3.031, 3.024, 2.825, and 2.875 Å. The NH group participates in intermolecular NH···OClO ₃ ^? contacts with bond lengths of 3.220 and 3.172 Å, respectively. The effect of N1, N4 diprotonation on the optical and magnetic properties of the 3,4-diaminopyridinium dication is discussed.     

Calculation of equilibrium in anion-exchange extractive systems

Anion-exchange extractive systems based on solutions of higher quaternary ammonium salts in the presence of solvating additives, derivatives of trifluoroacetophenone, were considered. A mathematical model of the extractive system was developed and average solvation numbers and constants of solvation of ClO ₄ ^? , SCN^?, Br^?, and NO ₃ ^? ions by variously structured derivatives of trifluoroacetophenone were calculated from experimental data.     

Nucleophilic activity of peroxyhydrocarbonate and peroxocarbonate ions relative to 4-nitrophenyl diethyl phosphonate

Peroxocarbonate ions HCO ₄ ^? and CO ₄ ^2? , which are formed in the H₂O₂/NH₄HCO₃/HO^? system, react with 4-nitrophenyl diethyl phosphonate (I) through a nucleophilic mechanism with rate constants \(k_{HCO_4^ - } = 0.008\) and \(k_{CO_4^{2 - } } = 0.13 L/mol \cdot s\). Comparison of these constants with the corresponding constants of other inorganic anions in their reaction with I in the framework of the Brönsted equation indicates that HCO ₄ ^? and CO ₄ ^2? are typical α-nucleophiles.     

The solubility of ozone and kinetics of its chemical reactions in aqueous solutions of sodium chloride

The solubility of ozone and the kinetics of its decomposition and interaction with chloride ions in a 1 M aqueous solution of NaCl at 20°C and pH 8.4–10.8 were studied. The ratio between the concentration of O₃ in solution and the gas phase was found to be 0.16 at pH 8.4–9.8. The concentration of dissolved ozone decreased sharply as pH increased to 10.8 because of a substantial increase in the rate of its decomposition. It was observed for the first time that the interaction of O₃ with Cl^? in alkaline media resulted in the formation of ClO ₃ ^? chlorate ions. The dependence of the rate of formation of ClO ₃ ^? on pH was determined; its maximum value was found to be 9.6 × 10^?6 mol l^?1 min^?1 at pH 10.0 and the concentration of ozone at the entrance of the reactor 30.0 g/m³. A spectrophotometric method for the determination of chlorate ions (concentrations 1 × 10^?5?3 × 10^?4 M) in aqueous solutions was suggested.