A. I. Konovalov

Supramolecular systems based on dicationic pyrimidine-containing surfactants and polyethyleneimine

Aggregates based on a novel pyrimidine-containing amphiphile containing three uracil fragments were quantitatively characterized. The critical micelle concentration (CMC) is 2 mmol L–1 and the degree of binding of counterions is β = 0.95, which is consistent with the low zeta potential of the micelles equal to +5 mV. Aggregates with a diameter of 45 nm are formed in the CMC region, and in the region of higher concentrations the aggregates are rearranged to micelle-like particles. In the presence of hydrophilic polymer polyethyleneimine, the CMC significantly decreases (to 0.2 mmol L–1), the degree of binding of counterions decreases, and the electrokinetic potential increases. The size of the aggregates in the binary system is 6—7 nm.

Alkylated 1,4-diazabicyclo[2.2.2]octanes: self-association, catalytic properties, and biological activity

Aggregation of 1-hexadecyl-4-aza-1-azoniabicyclo[2.2.2]octane bromide in the presence of diethyl 4-nitrophenyl phosphate was studied using 1H NMR spectroscopy. The quantitative characteristics of the aggregation were determined. The data obtained were used to explain the catalytic effect of micelles on the hydrolysis of the phosphate. It was found that the aggregation properties and biological activity of alkylated mono- and dicationic 1,4-diazabicyclo-[2.2.2]octanes are correlated.

Cooperative intramolecular hydrogen bond and conformations of thiocalix[4]arene molecules

The joint FTIR spectroscopic study and ab initio quantum-chemical calculations (HF/3-21G and PBE/TZ2P methods) showed that thiocalix[4] arene molecules adopt the cone conformation in CCl4 solutions. The weakening of the cooperative intramolecular H bond in thiocalix[4]arenes compared to the corresponding calix[4]arenes can be due to the larger thiocalixarene macrocycle, bifurcated hydrogen bond in it, and electron density transfer from the bridging S atom to the benzene ring.

THE NATURE OF LITHIUM PERCHLORATE AND GALLIUM CHLORIDE SALT EFFECT IN CYCLOADDITION REACTIONS

Abstract Comparing the acceleration effects of (4+2)-, (3+2)- and (2+2)-cycloaddition reactions in the presence of the salts of two types: gallium chloride in inert solvents and lithium perchlorate (LP) in diethyl ether (DE) it was observed that in the presence of GaCl3 the acceleration effect is approximately the same (104 times) for the studied reactions, while in LPDE medium for the same reactions strong increase (up to 104 times), weak increase or even decrease of the rate and equilibrium constants take place even with the common dienophile depending on the nature of the second reagent. It was suggested that the acceleration effect of cycloaddition reactions in the presence of such Lewis acids as aluminum, gallium or boron halides is due to the sharp increase of π-acceptor properties of dienophiles and therefore increasing energy of orbital interaction, whereas LPDE medium demonstrates strong stabilization of static and/or dynamic polar forms and favors reactions with charge control.

Formation of nanoassociates as a key to understanding of physicochemical and biological properties of highly dilute aqueous solutions

On the grounds of experimental data obtained by a set of physicochemical methods (dynamic light scattering, microelectrophoresis, conductometry, tensiometry, pH-metry, dielcometry, polarimetry, atomic force microscopy, and UV and ESR spectroscopy), a previously unknown fundamental phenomenon was discovered, namely, the formation nanosized molecular assemblies, so-called nanoassociates, in aqueous solutions of low concentrations prepared by successive serial dilutions. The formation and concentration rearrangements of nanoassociates may be responsible for physicochemical and biological properties of highly dilute aqueous solutions. The formation of nanoassociates is initiated by a solute under certain conditions, most essential among them being the presence of external physical fields (geomagnetic and low-frequency electromagnetic fields) and particular structure of the substance.

Diels—Alder reaction. Effect of internal and external factors on the reactivity of diene—dienophile systems

The key factors influencing the Diels—Alder reaction rate at ambient and elevated pressures were elucidated using data on the reactivity of various diene—dienophile systems in usual and Lewis acid-catalyzed Diels—Alder reactions, the reaction enthalpy, complex formation, dissolution, and solvation, and the donor-acceptor properties of the reactants. It was found that taking account of both the orbital interaction energy and the balance of bond rupture and formation energies allows correct prediction of the reaction rate in the absence or in the presence of Lewis acids.

Molecular tectonics: control of the dimensionality in tetramercaptothiacalixarenes based coordination networks.

Combinations of tetramercaptotetrathiacalix[4]arene pyridyl-appended positional isomers with HgCl2 lead to the formation of neutral coordination networks with their dimensionality imposed by the position of the N atom on the pyridyl group.

Methyl viologen and tetraviologen calix[4]resorcinol as mediators of the electrochemical reduction of [PdCl4]2− with formation of finely dispersed Pd0

Methyl viologen and tetraviologen calix[4]resorcinol with decyl substituents in the resorcinol cycles (MVCA-C108+) are mediators of the electrochemical reduction of complex dianion [PdCl4]2− facilitating its reduction on the glassy carbon electrode at 0.5–0.6 V. The reduction product of Pd2+ salt is finely dispersed metallic palladium, and its structure and some properties are determined by the mediator nature. When using methyl viologen, palladium is deposited on the electrode and dispersed as flakes in a solution, whereas in the case of MVCA-C108+ palladium is completely deposited on the electrode as nanoparticles together with calixresorcinol.

Quantum-Chemical Study on Reactions of Isocyanates with Linear Methanol Associates: III.* Reaction of Methyl Isocyanate with Linear Methanol Associates

Addition of linear methanol associates at the C=N and C=O bonds of methyl isocyanate was studied in terms of the B3LYP/6-311++G(df,p) hybrid quantum-chemical method. The addition at the C=N bond is more favorable than the reaction at the carbonyl group. All reactions involve late asymmetric cyclic transition states. The activity of the reacting system increases in parallel with the degree of methanol association. Isomerization of methyl hydrogen methylcarbonimidate into carbamate is catalyzed by methanol associates. Thermal decomposition of carbamates with formation of isocyanates can occur in autocatalytic mode.

Catalysis of nucleophilic substitution reactions in supramolecular systems

The factors determining the catalytic effect of supramolecular systems on the nucleophilic substitution reactions are analyzed. The role of the structural and phase transitions of nanoaggregates in the catalytic mechanism are determined. The substrate specificity is shown for different structures of the supramolecular composition.