V. Yu. Kotov

Cation transport during ion exchange on acid phosphates of multivalent metals

The kinetics of an exchange of a proton for alkali metal cations in such layered acid phosphates of multivalent elements as HxY(PO4)2 · nH2O (Y = Ti, Zr, x = 2; or Y = Ta, x = 1), where cations are rather mobile, is studied by a potentiostatic-titration method. The kinetics of the ion exchange in the phosphates is controlled by a two-dimensional cation diffusion through the layer of the forming exchange product. Coefficients of the cation diffusion in the exchange products and basic mechanisms of the defect formation in the phosphates are determined. The nonequilibrium phases with a large substitution degree, which form on the sample surface during the first stage of an exchange, substantially affect the process kinetics.

Ion association in the Na[CoEdta]-KI-sucrose system

X-Ray diffraction study of Na [CoEdta] · 4H2O was carried out. The stability constants of the [CoEdta]−, I− ion pairs in aqueous sucrose solutions were measured. The results were interpreted in terms of the “excluded volume effect”.

1D-Bromobismuthates of Dipyridinoalkane Derivatives

The following bromobismuthates of organic cations (dipyridinoalkane derivatives) are synthesized and characterized: (4-NH2PyC5)BiBr5 (I), (2-MePyC2)BiBr5 (II), (2-NH2PyC10)BiBr5 · 0.65H2O (III), (2-NH2PyC10)4H5O2(BiBr6)3 (IV), (2-NH2PyС6)2KBi2Br11 (V), (2-NH2PyC6)H3OBiBr6 · 2.33H2O (VI), and (2-NH2PyC6)3(BiBr6)2 · CH3CN (VII). Three compounds obtained (I–III) contain the zigzag 1D chain (BiBr5)n. A new type of 1D chains, (KBi2Br11)n, is found in the structure of compound V. Pseudo-1D chains of BiBr63− anions can be observed in the 3D structures of compounds IV, VI, and VII. The crystallographic data were deposited with the Cambridge Crystallographic Data Centre (CIF files CCDC 1569478 (I)–1569484 (VII), respectively).

Ion aggregation of methylpyrazinium iodide and its derivatives in crystals and in solutions of nonpolar solvents

Aggregation of methylpyrazinium iodide and its derivatives in chloroform and dichloromethane solutions was studied by EAS and 1H NMR spectroscopy. The isopentylpyrazinium iodide ion quadruple formation constants in solutions were evaluated. Formal extinction coefficient in the outer-sphere charge transfer band maxima does not depend on the degree of aggregation in the system. A model suggested for the formation of ion quadruples in solutions was discussed in terms of the density functional theory and using the X-ray diffraction data for crystalline methylpyrazinium iodides and its derivatives.

Icelike (H2O)12 Fragment in the Structure of Potassium Ethylviologen Hexacyanometallates

Arrangement of water clusters in the structure of potassium ethylviologen hexacyanometallate hydrates is discussed. An icelike fragment of 12 water molecules corresponding to the cell of hexagonal Ih ice is isolated in the structures.

Lead bipyridyl hexacyanoferrate complex

A low-solubility complex [PbBipy2]6[Fe(CN)6]4 · Bipy · 14H2O was prepared and characterized by physicochemical methods. Although containing [PbBipy2]2[Fe(CN)6] discrete species and a {[PbBipy2][Fe(CN)6]}n infinite chain in the crystal structure, the complex has weak antiferromagnetic properties over a wide temperature range. The irreversible thermal destruction of the complex, which starts at 192°C, is preceded by complete dehydration.

Electrode processes involving associates of CoNTA- and CoEDTA2- with hexacyanoferrate ions in aqueous solutions

Ionic association in K3Fe(CN)6solutions containing cobalt(II) ethylenediaminetetraacetate and nitrilotriacetate is studied by voltammetry, spectrophotometry, and Mössbauer, IR, and 59Co NMR spectroscopy techniques. Situations where the inner-sphere association leads to the formation of solid products on electrodes (conducting films among them) are revealed.

Calculation of activation-controlled reaction rate constants from parameters of electronic absorption spectra of ion pairs

An equation relating the rate constants of a bimolecular activation-controlled redox reaction to the parameters directly determined from the electronic absorption spectra was obtained in the framework of the Marcus-Hush theory. Applicability of the equation for the prediction of redox reaction rate constants was shown.

OUTER-SPHERE INTERACTIONS BETWEEN ANIONS

The properties of anion associates are reviewed. Experimental electronic absorption spectra of anion-anion and anion-cation pairs were analyzed and compared with calculated data. Stability constants of ion pairs were determined in the framework of the theory of outer-sphere association of ions. Anion association was shown to be a specific case of typical cation-anion association, in which associates of the 2Na+,[Coedta]− type play the role of a complex cation.