Photo- and electroluminescent properties of zinc(II) complexes with tetradentate Schiff bases,derivatives of salicylic aldehyde

It is studied how the introduction of various substituents into the composition of organic ligands affects the photoluminescence spectra of new zinc(II) complexes with tetradentate Schiff bases H₂L (derivatives of salicylic aldehyde (H₂SAL1, H₂SAL2) and o-vanillin (H₂MO1, H₂MO2) with ethylenediamine and o-phenylenediamine) in the form of bulk solids and thin films. It is demonstrated that the emission spectra of bulk solid complexes without o-phenylenediamine bridges (ZnSAL1 and ZnMO1) contain additional long-wavelength bands compared to the spectra of corresponding thin films. In the case of films obtained from [ZnSAL1]₂ dimer complexes, the long-wavelength band is dominant. At the same time, the photoluminescence spectra of ZnSAL2 and ZnMO2 complexes with o-phenylenediamine bridges are similar in the case of solid samples and thin films. The electroluminescent properties of organic light-emitting diodes (OLEDs) with the ITO/α-NPD/ZnL/Ca:Al structure are studied. The bathochromic shift of the electroluminescence peaks of OLEDs with respect to the photoluminescence spectra of bulk solid samples and thin films is probably related to the formation of exciplexes at the α-NPD/ZnL interface. The electroluminescence spectra of OLEDs based on [ZnSAL1]₂ show a hypsochromic shift of the emission maximum, which can be caused by a shift of the recombination region into the α-NPD layer.     

Thinning of wetting films formed from aqueous solutions of non-ionic surfactant

We investigated the thinning of wetting films formed from aqueous solution of non-ionic triblock copolymer Pluronic F127 on the surface of silica using a home-made thin film balance and time-resolved ellipsometry. Imaging ellipsometry was used to visualize the film structures at subsequent stages of their development. The results unambiguously show that the time required for the formation of steady films strongly depends on the electrolyte concentration. When increasing the latter from 10(-4) to 0.1 M, this time typically increases with several orders of magnitude, from a few minutes to several hours. Moreover, for sufficiently large amounts of salt, two characteristic relaxation regimes can be clearly identified. After initial quick thinning, further thinning slows down enormously. These typical kinetic regimes are thought to result from the coupled dependencies of the bulk and interfacial properties of F127 on salt concentration. Possible explanations of the phenomenon are discussed.     

Sorption of methanal by a weak basic anion exchanger

Peculiarities of the sorption of methanal on a polyfunctional anion exchanger are investigated. Based on the sorption isotherm, it is established that the distribution coefficient of the aldehyde in the ion exchanger-solution system depends exponentially on the concentration of the external solution. From breakthrough curves of sorption, the rate-determining stage of the absorption of the aldehyde in dynamic conditions is estimated. Structural changes in the sorbent phase saturated with methanal are supported by IR spectroscopy.     

Films of polyamides with phenylpyridine units in the backbone

New polyamides derived from 2-(4-aminophenyl)-5-aminopyridine, 4,4-diaminodiphenyl ether, and 4,4′-terephthaloyloxybis(3-methoxybenzoic) acid dichloride were prepared. These polyamides are of interest as macromolecular ligands. The deformation-strength, thermomechanical, and thermal properties of films of polyamides with various content of phenylpyridine fragments were studied.     

Synthesis and study of the structure of o-hydroxyaryl-1,2,4-oxadiazoles

The reaction of 4-oxo-1,3-benz- and -naphthoxazinium perchlorates with hydroxylamine leads to 5-(o-hydroxyaryl)-1,2,4-oxadiazoles rather than to 3-(o-hydroxyaryl)-1,2,4-oxadiazoles, as was previously assumed. The structure of the compounds obtained was proved by alternative synthesis, as well as by mass spectrometry and comparison of the experimentally found and calculated dipole moments and Kerr constants of the possible structures of the o-hydroxyaryl-1,2,4-oxadiazoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 540–549, April, 1992.     

Synthesis and structure of 1-benzoyl-2,5-dimethyl- and 1,2,5-trimethyl-4-arylpiperideins

Isomeric 1-benzoyl-2,5-dimethyl-³-piperidein and 1-benzoyl-2,5-dimethyl-⁴-piperidein were prepared from disubstituted -piperidols and were hydroxylated with osmium tetroxide. The isomeric 1,2,5-trimethyl-4-(p-nitrophenyl)-³- and-⁴-piperideins were obtained from trisubstituted -piperidols.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1200–1206, September, 1986.In conclusion, the authors would like to thank Yu. T. Struchkov and N. I. Lebedev for carrying out the x-ray structural study.     

Synthesis starting from 3-methyl-2-phenyl-5-(3-methyl-2-phenyl-3,4-dehydropiperidyl-6)pyridine. 2-phenyldinicotinic and 4-azafluorenone-2-carboxylic acids

N-Methyl (ethyl, benzoyl, trifluoroacetyl)-substituted 3-methyl-2-phenyl-5-(3-methyl-2-phenyl-3,4-dehydropiperidyl-6) pyridines and di(N-oxide) of the correspondingly substituted ,ß-dipyridyl were prepared. A method for synthesizing 2-phenyldinicotinic acid was developed. Cyclodehydration of this acid gave 4-azafluorenone-2-carboxylic acid. Transformations of this acid were carried out with respect to two functional groups.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 813–817, June, 1986.     

Near-Wall Aggregation of Amyloidogenic Aβ 1-40 Peptide: Direct Observation by the FRET

The formation of amyloid fibrils is one of the variants of the self-organization of polypeptide chains. For the amyloid aggregation, the solution must be oversaturated with proteins. The interface of the liquid (solution) and solid (vessel walls) phases can trigger the adsorption of protein molecules, and the resulting oversaturation can initiate conformational transitions in them. In any laboratory experiment, we cannot exclude the presence of surfaces such as the walls of vessels, cuvettes, etc. However, in many works devoted to the study of amyloid formation, this feature is not considered. In our work, we investigated the behavior of the Aβ 1-40 peptide at the water–glass, water–quartz, and water–plastic interface. We carried out a series of simple experiments and showed that the Aβ 1-40 peptide is actively adsorbed on these surfaces, which leads to a significant interaction and aggregation of peptides. This means that the interface can be the place where the first amyloid nucleus appears. We suggest that this effect may also be one of the reasons for the difficulty of reproducing kinetic data when studying the aggregation of the amyloid of the Aβ 1-40 peptide and other amyloidogenic proteins     

Synthesis and Pharmacological Evaluation of Novel 2,3,4,5-tetrahydro[1,3]diazepino[1,2-a]benzimidazole Derivatives as Promising Anxiolytic and Analgesic Agents

A number of novel 2,3,4,5-tetrahydro[1,3]diazepino[1,2-a]benzimidazole derivatives 2 were obtained by alkylation mainly in the 1H-tautomeric form of 2,3,4,5-tetrahydro[1,3]diazepino[1,2-a]benzimidazole or its 8,9-dimethyl-substituted analog 4-chlorobenzyl bromide, 4-chloroacetic acid fluoroanilide, and 4-tert-butylphenacyl bromide in neutral medium. Compounds 3 were cyclized and synthesized earlier with 11-phenacyl-substituted diazepino[1,2-a]benzimidazoles upon heating in conc. HBr. The chemical structures of the compounds were clarified by using the ¹H Nuclear Magnetic Resonance Spectroscopy (¹H-NMR) technique. Anxiolytic properties were evaluated using the elevated plus maze (EPM) and open field (OF) tests. The analgesic effect of compounds was estimated with the tail flick (TF) and hot plate (HP) methods. Besides, possible the influence of the test compounds on motor activities of the animals was examined by the Grid, Wire, and Rotarod tests. Compounds 2d and 3b were the most active due to their prominent analgesic and anxiolytic potentials, respectively. The results of the performed in silico analysis showed that the high anxiolytic activity of compound 3b is explained by the combination of a pronounced interaction mainly with the benzodiazepine site of the GABA_A receptor with a prominent interaction with both the specific and allosteric sites of the 5-HT_2A receptor.     

Effects of circulation and facilitated electromigration of amino acids in electrodialysis with ion-exchange membranes

Dependences of fluxes of the mass of amino acids and mineral ions on the density of a direct electrical current in an electrodialysis process are obtained experimentally. Mutual influence of components on transport at low strengths of the electric field in membranes is discussed. Effects of circulation and facilitated electromigration of amino acids are considered. At a small excess of the limiting current density, the effects lead to a decrease in fluxes of amino acids through membranes. At a large excess of the limiting current, the effects result in an intensive conjugated transport of bipolar ions with the medium ions through membranes.