Supramolecular complexes: Determination of stability constants on the basis of various experimental methods

Stability constants and formation enthalpies of supramolecular complexes of crown ethers and their cyclic and acyclic analogues are determined on the basis of experimental data obtained by different physicochemical methods in the terms of a general approach developed and implemented in the ChemEqui software package. The established regularities of variation of stability of complexes are discussed as dependent on the ligand structure, nature of the cation, solvent, and anion. The applicability of the suggested method of determining complexation selectivity is shown for multicomponent equilibria in solutions.

     

Determination of the Life Cycle of Heat-Exchange Tubes of Vapor Condensers on the Basis of Statistical Analysis of Local Pitting Corrosion According to Data of Eddy Current Testing

Protection of Metals and Physical Chemistry of Surfaces - The possibility is shown of creating a chart of local corrosion damage in the walls of heat-exchange tubes on the basis of the data of...     

A new type of polymer-polymer PVC systems with surface layers converted into hydroxyethylcyclam nanofilms of the type “hard coating on soft substrate”

With the aim of classifying PVC materials in which surface layers are converted into interpenetrated network cyclam nanofilms among polymer-polymer systems, comparative studies of their properties were carried out with consideration for the specific conditions for the preparation of the material. The density and structures of near-surface layers, the bulk ratio of the ordered and disordered forms, the dynamics of swelling in water, and the effective partial volume occupied by water molecules were studied for PVC plates prior to and after hydrothermal treatment. The conversion of the surface layers changes the structural self-organization of PVC: the polymer structure becomes more compact and ordered both in the area adjacent to the nanofilm and in the polymer bulk, which is characteristic of systems of the type “hard coating on soft substrate”. Original Russian Text ? A.Ya. Fridman, E.M. Morozova, A.Yu. Tsivadze, N.P. Sokolova, I.I. Bardyshev, A.M. Gorbunov, O.P. Shapokhina, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 5, pp. 498–502.     

Removal of <Superscript>90</Superscript>Sr from nitric acid solutions with sorbents based on di-<Emphasis Type="Italic">tert</Emphasis>-butyldicyclohexyl-18-crown-6

A series of impregnated sorbents based on di-tert-butyldicyclohexyl-18-crown-6 (DTBDCH18C6), various diluents (1-octanol, nitrobenzene, telomeric alcohol n3), and supports (Porolas-Т, LPS-500, hydrophobized silica gel) for removing tracer and weighable amounts of Sr ions from nitric acid solutions were prepared. The distribution coefficient of tracer amounts of ⁹⁰Sr on all the synthesized sorbents increases with an increase in the HNO₃ concentration in the range 1–7 M. The most pronounced increase in the sorption occurs with an increase in the HNO₃ concentration to 3 M. The maximal distribution coefficient of ⁹⁰Sr (K _d = 158 cm³ g^–1) is reached for the sorbent based on DTBDCH18C6 and 1-octanol in 7 M HNO₃. Experiments on sorption of weighable amounts of Sr²⁺ ions show that the static capacity of all the prepared sorbents for Sr in nitric acid solutions amounts to 4.3, 9.2, and 8.4 mg g^–1 for the sorbents based on 1-octanol, nitrobenzene, and telomeric alcohol n3, respectively. The synthesized sorbents are suitable for radioanalytical determination of Sr radionuclides in liquid radioactive waste and in radioactively contaminated natural objects.     

Magnesium octa[(4′-benzo-15-crown-5)oxy]phthalocyaninate in water micellar solutions of sodium deoxycholate

Aggregation of magnesium octa-[(4′-benzo-15-crown-5)oxy]phthalocyaninate (Mgcr₈Pc) in solutions of biocompatible anionic surfactant, sodium deoxycholate (SDC), was studied. It was shown using the electron absorption spectra that formation of Mgcr₈Pc monomers in micellar solutions of SDC is affected by both increased surfactant concentration and by changes in the ionic strength of solution after sodium chloride is added. The effect of the chemical structure of biocompatible anionic surfactant on monomerization of crown-containing phthalocyanines was identified; this fact opens new possibilities for using this family of compounds for fluorescent diagnosis and photodynamic therapy.     

The effect of self-organizing vinyl siloxane nanolayers on the corrosion behavior of aluminum in neutral chloride-containing solutions

The methods of quartz crystal microbalance, atomic force microscopy (AFM), scanning electron microscopy (SEM), Fourier-transform IR spectroscopy, and X-ray structural microanalysis were is used to show that adsorption of vinyl silane on an aluminum surface from an aqueous solution results in formation of a uniform, self-organizing protective vinyl siloxane nanolayer covalently bound with surface metal groups. Its thickness can be controlled by variation of application conditions. The effect of a vinyl siloxane nanolayer on dissolution of aluminum is studied in chloride-containing solutions. It is found that an ordered vinyl siloxane nanolayer with a thickness of up to 5 molecular layers causes efficient inhibition of uniform and local corrosion of aluminum. It is shown that the vinyl siloxane nanolayer is preserved on the surface of aluminum after 10 days of corrosion tests, which indicates its stability at exposure to water and corrosive components.     

Photorefractive and nonlinear optical properties of indium(III) tetra(15-crown-5)phthalocyaninate-based composites

Photoelectric, nonlinear optical, and photorefractive properties of hybrid composite materials based on polyvinylcarbazole (PVK) and indium(III) 2,3,9,10,16,17,23,24-tetra(15-crown-5)phthalocyaninate [(15C5)₄Pc]In(OH) are studied in detail. Field dependence of the quantum efficiency in a 7.8 μm-thick layer containing 5 at % [(15C5)₄Pc]In(OH) is measured. The best approximation of the quantum efficiency with Onsager’s equation corresponds to a quantum yield of thermalized electron-hole pairs φ₀ = 0.01 at initial separation r ₀ = 9.8 Å. Z-scan measurements in a nanosecond range showed that the electric susceptibility of [(15C5)₄Pc]In(OH) solution in tetrachloroethane (TCE) with a concentration of 7 × 10^?4 mol/L is χ⁽³⁾ = 1.34 × 10^?9 esu. The maximum coupling gain coefficient found for the material composed of PVK and 5 wt % [(15C5)₄Pc]In(OH) at an electric-field intensity of 200 V/μm is Γ = 80 cm^?1, and the difference between the coupling gain and absorption coefficients is Γ ? α = 70 cm^?1. The dependence of the coupling gain coefficient on the intensity ratio of interfering beams 1 and 2 (β = I ₁(0)/I ₂(0)) in a composite containing 3 wt % [(15C5)₄Pc]In(OH) is measured. An increase in β was attained by decreasing intensity of the signal beam I ₂(0) at constant intensity of the pump beam I ₁(0) = 0.15 W/cm² and E ₀ = 214 V/μm. Within the initial segment of the curve, the coupling gain coefficient increases from 30 to 60 cm^?1; then, the coefficient drops almost to the initial value. The data obtained show that the composite materials studied can be used in practice for correcting faded images. The combined analysis of the results obtained and similar data for gallium and ruthenium tetra-15-crown-5-phthalocyaninate complexes revealed the regularities in the change of the quantum yield of thermalized electron-hole pairs and the photorefractive coupling gain coefficient in a series of complexing metals: gallium(III), ruthenium(II), and indium(III). An increase in the molecular weight of the central metal atom is found to result in a substantial decrease in Γ and φ₀ due to the increase in the spin-orbit coupling constant.     

Improving the Anticorrosion Characteristics of Polymer Coatings in the Case of Their Modification with Compositions Based on Organosilanes

Protection of Metals and Physical Chemistry of Surfaces - The effect of a series of organosilanes and their mixtures with corrosion inhibitors on the anticorrosion properties of polymer and paint...     

New Octopus-like Phthalocyanines as Fullerene Receptors: Synthesis and Photophysical Investigation

Octopus-like zinc and magnesium phthalocyaninates bearing eight flexible benzylated diethylene glycol chains were synthesized and their interaction with fullerenes C₆₀ and C₇₀ was investigated by UV-Vis spectrophotometric titration, as well as by steady-state and time-resolved fluorescence spectroscopy in chloroform and toluene media. These measurements revealed a high affinity of receptors for C₆₀ and C₇₀, with selectivity to C₇₀: binding constants for C₇₀ are almost two times higher than for C₆₀. These results are interpreted by means of quantum-chemical calculations using the PM6-DH2 Hamiltonian. The binding constants also depend on both the nature of the metal ion in the receptor and the solvent. It is expected that the obtained molecules and supramolecular complexes can be used for further elaboration of optoelectronic donor-acceptor materials.     

The Effect of a Nanosize TiO<Subscript> <Emphasis Type="Italic">x</Emphasis> </Subscript> Layer on the Performance of an Organic Solar Cell

This work studies the role of a cathodic TiO_x buffer layer in operation of a photovoltaic organic solar cell (OSC) based on a photoactive layer with a bulk heterojunction. Using a liquid solution to obtain a TiO_x layer is of current interest for simplification of process technologies of successive formation of OSC layers. It is found that the optimum thickness of the TiO_x layer is 10 nm; at this thickness, the efficiency of the OSC reaches the value of 4.36%. The effect of air oxygen on the OSC samples is studied and it is found that samples with a TiO_x buffer layer undergo degradation to a lesser extent as compared to the samples with no such layer. The effect of oxygen on operation of the photovoltaic device is discussed.