O. I. Gnezdilov

The first mesogenic derivative of boron difluoride β-diketonate

Boron difluoride β-diketonate exhibiting liquid crystalline as well as photoluminescence properties was prepared for the first time. It is the promising material for creating supramolecular organized luminescent media.

Time-resolved EPR study of electron spin polarization and spin exchange in mixed solutions of porphyrin stable free radicals

The time-resolved electron paramagnetic resonance (EPR) spectra are studied in the temperature range of 110–300 K for two mixed solutions of porphyrins, ZnTPP and H2TPP, in toluene and the stable free radical 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO). The EPR spectra and their kinetic behavior were studied for concentrations of TEMPO varied in the interval from 0.51 to 7.68 mM, while the porphyrin concentration was fixed as 1 mM. The EPR spectra of triplet-state porphyrins and free radicals manifest the chemically induced spin polarization. For the relatively short-lived radical-triplet pairs, with the perturbation theory up to the fourth order, the theoretical expressions are obtained for the triplet and radical spin polarization induced by the enhanced intersystem crossing (ISC) due to the interaction of excited singlet-state porphyrins with free radicals and by the triplet quenching by free radicals. The time-dependent EPR spectra of the triplets are simulated taking into account the spin-lattice relaxation. It is shown that the variation of the triplet EPR spectra shape, when the time of observation increases, arises from the spin-lattice relaxation kinetics. The kinetic behavior of the TEMPO EPR spectrum was simulated on the basis of the kinetic scheme suggested earlier in the literature. The triplet spin-lattice relaxation time, the rate of the ISC and the lifetime of the excited singlet state were estimated by fitting the kinetic curves for the triplet EPR spectra intensity. For the mixed porphyrin-TEMPO solutions, a possible set of the rate constants of important bimolecular processes were determined. For this set of parameters, it turns out that the spin polarization transfer has a smaller rate constant than the rate constant of the diffusion collisions of the triplet and radical. It appears that the rate constant of the ISC catalyzed by radicals is relatively high in the solutions close to the melting point of the solvent and in the soft-glassy state. In the triplet porphyrins the initial spin polarization induced by the spin-selective ISC was found to exceed the equilibrium spin polarization by up to two orders of magnitude.

Micellization in sodium deoxycholate solutions

NMR self-diffusion, tensiometry, and measurement of solubilization capacity are employed to comparatively study micellization in aqueous solutions of a facial amphiphilic compound, sodium deoxycholate (NaDC), and a conventional micelle-forming sodium dodecyl sulfate. Based on the two-state model, which is commonly used to analyze the data of NMR diffusometry, a method is proposed for determining variable sizes of NaDC micelles. It is shown that, in the concentration range from the critical micelle concentration to 0.1 M, the sizes of NaDC micelles monotonically increase. At comparable sizes of molecules of the examined surfactants, NaDC micelles are characterized by noticeably smaller aggregation numbers and solubilization capacity than sodium dodecyl sulfate due to the rigid structure of NaDC molecules, their facial amphiphilicity, and a low value of hydrophilic-lipophilic balance.

Effective self-diffusion coefficients of ions in sodium dodecyl sulfate micellar solutions

The effective self-diffusion coefficients of ions in premicellar and micellar solutions of sodium dodecyl sulfate are measured by the NMR self-diffusion method at 40°C. The obtained regularities are explained using a proposed model that takes into account the possible surface diffusion of counterions bound with micelles. This effect is shown to markedly influence the charge transfer in micellar solutions. Based on the results obtained, the self-diffusion coefficients of bound Na+ counterions are estimated and the causes and ranges of their variations are indicated.

Phase diagram of the liquid crystal system of water-decanol-lanthanum nitrate-decaethylene glycol monododecyl ether

The phase behavior of a self-organizing system based on the nonionic surfactant of decaethylene glycol monodecyl ether-lanthanum nitrate hexahydrate-water and decanol is presented. A system phase diagram was constructed. The concentration, temperature ranges of existence and types of liquid crystal phases were established. Analysis of structural changes during the phase transitions hexagonal phase-lamellar phase-isotropic liquid was made on the basis of data obtained by viscosimetry and self-diffusion NMR.

First mesogenic derivative of boron difluoride β-enaminoketonate

Boron difluoride complexes possessing liquid crystalline and luminescent properties were synthesized for the first time on the basis of non-mesogenic β-enaminoketones.

Synthesis and photoisomerization of mesogenic 4-alkoxystyrylpyridines

Introduction of long-chain alkoxy substituents into molecules of styrylpyridines as potential ligands for photosensitive metal complexes endows them with liquid crystalline properties over a wide temperature range. trans-cis Photoisomerization of 4-alkoxystyrylpyridines in solution was revealed by NMR and electronic absorption spectroscopy, and the kinetics of transformations of their molecular forms after irradiation were estimated. Photoinduced trans→cis isomerization of 4-alkoxystyrylpyridines is characterized by a higher rate, and intramolecular cyclization of their cis isomers after irradiation is slower, as compared to unsubstituted analog.

ESR study of the nitric oxide production in tissues of animals under an external influence on the functioning of the cardiovascular and nervous systems

Electron spin resonance (ESR) of the ternary (DETC)2-Fe2+-NO complex has been applied to determine the nitric oxide production in tissues of rats and snails. A preliminary ESR study of the NO content in tissues of rats before and after artificially induced acute myocardial infarct was performed. The analysis of the obtained results shows that the nitric oxide production during the first hour after the moment of inducing myocardial infarct decreases. It is also demonstrated that ESR may be useful in the study of the influence of the long-term sensitization of snails on the nitric oxide production in their body. The changes in the NO production after the external influences in both cases are discussed.

MRI study of spatial distribution of photochemical reaction products

Spatial distribution of molecules with chemically induced dynamic nuclear polarization has been studied by nuclear magnetic resonance imaging. It is shown that heating of a system during the photolysis can cause highly nonuniform distribution of reaction products due to a convective effect.

Structure of the product of interaction of N-vinylcaprolactam with 3-chlorophenylisocyanate

The [2+2]-cycloaddition reaction of N-vinylcaprolactam with 3-chlorophenylcyanate yielding 1-(3-chlorophenyl)-4-[1H-perhydroazepinone-2]-azetidinone-2 is studied. The structure of the obtained compound is determined by single crystal XRD.