Том 67, № 12 (2018)
- Год: 2018
- Статей: 31
- URL: https://journals.rcsi.science/1066-5285/issue/view/15042
Full Articles
Nonradiative energy transfer in mixed Langmuir monolayers and Langmuir–Blodgett films of compounds of different chemical composition and structure
Аннотация
The efficiency of the Förster resonance energy transfer (FRET) in a monolayer film containing the energy donor and energy acceptor fluorophores is low since the energy transfer process occurs in one plane only. As the number of layers increases to five, the energy transfer efficiency increases due to the interlayer energy transfer occurring in three dimensions. Further increase in the number of layers (up to 10) causes no significant increase in the efficiency since in this case the total film thickness exceeds an optimum value for the FRET process.
Reactivity of an aluminum hydride complex with a redox-active diimine ligand
Аннотация
The reaction of the hydride [(dpp-bian)Al(H)Cl] (1) containing the 1,2-bis[(2,6-diisopropylphenyl) imino]acenaphthene (dpp-bian) radical anion with MeLi affords the compound [(dpp-bian)Al(H)Me] (2). The reaction of complex 1 with two equivalents of PhC≡CNa involves the replacement of chlorine along with oxidative substitution of hydrogen accompanied by the reduction of dpp-bian to the dianion to form the compound [(dpp-bian)Al(C≡CPh)2Na(Et2O)2] ({sn3}). This reaction gives the complex [{dpp-bian(H)}Al(C≡CPh)3Na(Et2O)2] (4) as the second product, which is apparently generated in the reaction of compound 3 with PhC≡CH. The reaction of compound 1 with Cp*Na (Cp* is pentamethylcyclopentadiene) in dimethoxyethane is also accompanied by the reduction of redox-active dpp-bian to the dianion, giving the complex [(dpp-bian)Al(H)Cl][Na(DME)3] (5). Diamagnetic derivatives 3–5 were characterized by 1H NMR spectroscopy; paramagnetic compound 2, by EPR spectroscopy. The molecular structures of compounds 2–5 were determined by X-ray diffraction.
Regulation of a phase structure at the interface in epoxy–polysulfone systems
Аннотация
The influence of technological parameters on the formation of an interfacial diffusion region and a gradient heterogeneous structure during a curing reaction of epoxy–polysulfone system was studied. It was established that the three–step temperature curing process of the modified system allows regulating both the width of the interphase zone and the sizes of the dispersed phases in it.
Thermal stability of the complex of pyrene–β-cyclodextrin dimer with aromatic amino acids
Аннотация
Using the method of adsorption spectroscopy, the temperature dependence of the electronic absorption spectra of the fluorescent chemosensor (CS), based on the supramolecular pyrene–2β-cyclodextrin complex (Pyr@2βCD, PCD), was studied in the absence and in the presence of phenylalanine (Phe). The application of CS, where pyrene serves as a fluorescent probe, is based on the ability of CS to form the inclusion complexes with small organic molecules as well as with aromatic amino acids (AA) such as Phe, tryptophan (Trp), tyrosine (Tyr), and histidine (His) in aqueous solutions. Upon heating to 55 °C, the PCD complex in the presence of Phe shows a higher stability as compared to that in the absence of Phe. The molecular dynamics simulation was applied to study the thermal stability of PCD and its complexes with the above AAs in water. The PCD complex exists in two configurations. In configuration 1 the planar Pyr molecule lies in the equatorial plane of the βCD dimer, the plane of Pyr is nearly perpendicular to the vertical axis of the dimer 2βCD, and water fills up the empty part of the cavity. In configuration 2, the plane of Pyr is inclined with respect to the axis of the 2βCD dimer by ~30°. The PCD complex initially prepared in state 1 is spontaneously transformed into state 2 and remains stable up to the boiling temperature. The transition of PCD from the form 1 to 2 is provided by fluctuations in water content in its cavities. The inclusion complexes of amino acids 2AA@PCD exist in a single conformation 1. Complexes of PCD with Trp and Phe are stable up to the boiling temperature, i.e., these AAs are preserved within the PCD cavities even at the elevated temperature. The complex with Tyr decays at 60 °C, and the complex with His is unstable at room temperature and above.
Complexation of gallium(III) nitrate with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakis(methylenephosphonic acid)
Аннотация
Eight dissociation constants of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakis (methylene phosphonic acid) (DOTMP, H8L) were determined for the first time by potentiometric titration in water using the CHEMEQUI program. The stability constants of Ga3+ complexes with deprotonated forms of DOTMP were determined. The stability constant of the Ga3+ complex with the fully deprotonated DOTMP ligand, lg KML equal to 27.8, is higher than the corresponding constant for the Ga3+ complex with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), the ligand most widely used in radiopharmacy; it is also higher than the constant for the Ga3+ complex with plasma protein transferrin, which makes the DOTMP ligand very promising for the use in radiopharmacy.
Behavior of Na and K in the extraction process of lithium isotope separation
Аннотация
The extraction behavior of Na and K during lithium isotope separation using benzo-15-crown-5 (B15C5) in chloroform as the extractant was investigated. It was found that potassium was extracted better than sodium and lithium, the metal: B15C5 ratio in the extracted compound was 1: 1 for all metals. It was shown that in the extraction systems with a LiCl concentration higher than 5 mol L-1, B15C5 was noticeably transferred into aqueous solutions, while concentrated LiCl solutions had a salting-out effect with respect to Na and K.
Complexation of tetrafluoroboric acid with benzo-15-crown-5
Аннотация
The extraction of tetrafluoroboric acid from aqueous solutions to a solution of benzo-15-crown-5 (B15С5, 1 mol L-1) in chloroform is shown to occur due to complexation with the ratio of components HBF4: B15С5 = 1: 1.5. It was revealed by IR spectroscopy that the whole crown ether in the extract is coordinated. The 1: 1 HBF4•В15С5 complex was isolated and characterized using IR spectroscopy and X-ray diffraction analysis. The O(2) and O(4) atoms of the crown ether ring participate in the coordination.
Spectrophotometric study of the cation-induced dimerization of heteroleptic terbium(III) tetra-15-crown-5-bisphthalocyaninate
Аннотация
We proposed a new approach to the synthesis of heteroleptic crown-substituted terbium(III) bisphthalocyaninate, [(15C5)4Pc]Tb(Pc) (1) based on the reaction of unsubstituted lanthanum bisphthalocyaninate (La(Pc)2) with tetra-15-crown-5-phthalocyanine (H2[(15C5)4Pc]) and terbium(III) acetate in a mixture of octanol and chloronaphthalene in the presence of 1,8-diazabicyclo[ 5.4.0]undec-7-ene as an organic base. For the first time, we carried out a comparative spectrophotometric titration of compound 1 with MBPh4 solutions (M = K, Rb, Cs) and demonstrated the formation of isostructural cofacial supramolecular dimers. Spectral-structural correlations were developed for evaluation of the distances between phthalocyanine ligands in new supramolecular assemblies, which can be used for the development of polynuclear suprasingle-molecule magnetic materials.
Synthesis and spectral luminescent properties of 4,4´,4´´,4´´´-tetra(tert-butyl)-5,5´,5´´,5´´´-tetrakis(phenylsulfanyl)phthalocyanines and their sulfo acids
Аннотация
Magnesium and zinc complexes of 4,4´,4´´,4´´´-tetra(tert-butyl)-5,5´,5´´,5´´´-tetra kis-(phenylsulfanyl)phthalocyanine were synthesized. The corresponding sulfo acids were prepared by sulfochlorination and further hydrolysis. Spectral luminescent properties of the synthesized phthalocyanine derivatives were studied. Introduction of sulfo groups resulted in a bathochromic shift of Q-band in the spectra recorded in DMF and pyridine regardless of the metal nature as well as in a hypsochromic shift in sulfuric acid.
Supramolecular organization of crown- and phosphoryl-containing magnesium and zinc phthalocyaninates in solutions of synthetic and natural surfactants
Аннотация
The behavior of crown- and phosphoryl-containing magnesium and zinc phthalocyaninates in solutions of synthetic and natural surfactants is studied. In a phosphate buffer (рН 7.4), zinc phthalocyaninate bearing oxy(pentyloxy)phosphoryl groups in peripheral substituents of the macrocycle is in aggregated state. According to absorption and fluorescence spectroscopy data, adding oppositely charged synthetic and natural surfactants leads to monomerization of this compound. The degree of monomerization of magnesium octa[(4´-benzo-15-crown-5)oxy]-phthalocyaninate in a microheterogeneous medium is affected by the concentration of sodium cholate and ionic strength. Fluorescence-active supramolecular gels based on sodium deoxycholate were prepared using phosphoryl-containing zinc phthalocyaninate.
Supramolecular structuring of aqueous solutions of strong acids: manifestations in light scattering, NMR, and oxidation kinetics. Does liquid have a drop-like nature?
Аннотация
The properties of large (~100 nm) aggregates, that is, solvate associates formed in aqueous solutions of perchloric acid, including their stability in time, dependence of their structure on the solution composition and preparation procedure, and effects of temperature and mechanical impacts were studied by light scattering methods. The slow supramolecular structuring in aqueous solutions of perchloric acid was compared with the previously studied structuring in aqueous solutions of nitric acid. A number of regularities and features that can significantly affect the chemical processes in these solutions were revealed.
Effect of promotion of nickel sulfide catalyst with silver on kinetics of decarbonilation of stearic acid
Аннотация
The kinetics of liquid-phase decarbonylation of stearic acid in n-dodecane on γ-Al2O3 supported nickel sulfide catalyst promoted with silver was experimentally studied at 350 °C. The parameters of the reaction steps were determined and a structural kinetic model was developed. The model was compared with an earlier developed kinetic model for the unpromoted catalyst. It was suggested that an increased reaction selectivity in the presence of silver promoted catalyst was caused by a change in the composition of the adsorption complexes formed by the active sites of the catalyst. This change in the composition of the complexes is probably associated with an increase in the average size of the surface active particles of the catalyst.
Ultrathin films based on luminescent complexes of 4-n-octyloxybenzoic acid with lanthanides
Аннотация
Europium(III) and terbium(III) complexes with 4-n-octyloxybenzoic acid of the composition LnL3 were synthesized and their luminescent properties were studied. It was established that the luminescence intensity of the TbL3 complex in the visible region is much higher than that of EuL3. Langmuir monolayers of these compounds on the water subphase and Langmuir–Blodgett films on solid substrates were prepared. The morphological characteristics of the latter were studied. The results obtained indicate good prospects for application of these compounds in the design and fabrication of planar photonic and optoelectronic devices.
Hydride transfer mechanism in the catalytic allylation of norbornadiene with allyl formate
Аннотация
Allylation of norbornadiene with allyl formate in the presence of the palladium catalytic systems is characterized by several peculiarities associated with the new reaction route: hydroallylation (reductive allylation) occurs along with the traditional allylation (oxidative allylation). Both processes are considered from the single point of view, and the mechanism assuming different routes of the hydride transfer in the key intermediates was proposed. It was proved by using deuterated reactants that the hydride transfer can involve the allyl, norbornenyl, or formyl moieties. In all cases, the hydrogen atom bound to the carbon atom in the β-position relative to palladium is eliminated in this step.
Reactions of the N-isopropyl-α-chloroketimines with PIV dithioacids
Аннотация
A primary iminium salt formed in the reaction of PIV dithioacids with N-isopropyl-α-chloroketimines is transformed into products of nucleophilic substitution of the chlorine atom by dithiophosphorus group (SN pathway), if the imine carbon atom is bonded to the donor and small-volume methyl group, or undergoes reduction of the CCl bond (C-Cl→C-H) (Red pathway), when it is bonded with the bulky acceptor phenyl group. The same effect of substituents was discovered, when replacing methyl group with phenyl one in the position 2 of N-tert-butyl-2-chloraldimines: SN: Red ratio is 1: 0 in the case of Me and 1: 9 in the case of Ph. The iminium salts were transformed into new type ketones containing a phosphor functionality.
Perfluorinated porphyrazines
Аннотация
Nucleophilic substitution of fluorine atoms in the phenyl rings by alkoxy groups was performed in perfluorosubstituted zinc(II) octaphenylporphyrazine [ZnPAF40]. Up to 12 fluorine atoms are substituted in the reaction with sodium butoxide in boiling butanol leading to the formation of [ZnPAF40-n(OBu)n] (n = 6–12). Up to eight monosaccharide groups are introduced in the reaction with 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose (Gal´) in toluene in the presence of sodium hydride leading to the formation of [ZnPaF(40-n)(Gal´)n] (n = 6–8). It was possible to obtain a water-soluble glycoconjugated zinc(II) porphyrazine [ZnPaF(40-n)(Gal)n] after removal of the isopropylidene protecting groups by treatment with trifluoroacetic acid. Substitution products are characterized by electron absorption spectroscopy, NMR spectroscopy, and mass spectrometry. Substituting the fluorine atoms with monosaccharide residues leads to an increase in the fluorescence quantum yield from ФF = 0.19 for [ZnPAF40] to 0.29 for [ZnPA(Gal´)nF40-n] (n = 6–8).
Synthesis and spectral properties of isomers of cobalt tetrakis(dicyanophenoxy)phthalocyaninate
Аннотация
4,4´-[1,3-Phenylenebis(oxy)]- and 4,4´-(1,4-phenylenebis(oxy)]diphthalonitriles and the corresponding tetrasubstituted cobalt phthalocyaninates were synthesized. The spectral properties of the synthesized complexes in various organic solvents were studied.
Methyl esters of 2-aminotetrahydrobenzothiophene-3-carboxylic acids decorated with trifluoromethyl-containing heterocycles
Аннотация
Methyl 2-aminothiophene-3-carboxylates were modified with trifluoromethyl-containing five-membered heterocycles by cyclocondensation of methyl trifluoropyruvate N-thiophen-2-ylimines with 1,3-N,N-binucleophiles (2-aminothiazoline and benzamidines) to obtain the corresponding 5-oxo-6-trifluoromethyl-2,3,5,6-tetrahydroimidazoles and 5-oxo-2-phenyl-4-trifluoromethyl-4,5-dihydro-1H-imidazoles. Radioligand binding was used to study the in fluence of the synthesized compounds on the neuronal NMDA receptors.
Complexation of a crown-substituted naphthalimide derivative with heavy metals in Langmuir monolayers
Аннотация
It was demonstrated that, in contrast to a solution in an organic solvent, the relaxation of the excited state of a fluorophore moiety proceeds mainly radiationless upon the formation of naphthalimide fluoroionophore complexes with complementary cations in a monolayer on a water surface. Apparently, this is due to the fact that the distribution of the energy levels of molecular orbitals in the fluoroionophore complexes with cations at the air-water interfaces changes in such a way that relaxation of the excited state via charge transfer within the complex molecule remains possible.
Microwave-assisted synthesis of macroheterocyclic compounds using 1-alkyl-1,2,4-triazoles
Аннотация
Microwave-assisted synthesis of new representatives of triazole-containing macroheterocycles bearing 1-alkyl-1,2,4-triazole moieties was described. The developed procedure is advantageous over the conventional method as it allows significant reduction of the reaction time from 72 h to 20 min and leads to higher yields (up to 53–57%).
Photochromic transformations of amphiphilic spiropyran in acetonitrile solutions and at the air/water interface
Аннотация
The results of a study of the photochromic properties of 1´-hexadecyl-3´,3´-dimethyl-6-nitro-1´,3´-dihydrospiro[chromene-2,2´-indole] (SP) are presented. The kinetic characteristics of photophysical processes occurring in acetonitrile solution of SP upon irradiation with UV light and during dark relaxation are determined. It is shown that spiropyran modified at the nitrogen atom by a long-chain hydrocarbon radical exhibits photochromic properties in the dissolved state, with the rate of the direct photocoloration exceeding the rate of dark relaxation by an order of magnitude. Comparative studies of SP photoreaction in dissolved and 2D states are carried out. The obtained results open up broad prospects for application of such photochromes in thin-film devices obtained using the Langmuir monolayer technique.
Condensation products of Betti base and pyridinecarboxaldehydes
Аннотация
Previously unknown condensation products were obtained by the reaction of the racemic Betti base with 2-, 3- and 4-pyridinecarboxaldehydes. It was established that they have a naphthoxazine structure in solid state. In the solution, a three-component ring-chain equilibrium is established between the imine form and cis- and trans-oxazines. Over time or under heating, these compounds are prone to 2-azaallylic prototropic tautomerism, involving 1-(phenyl- (pyridinylmethylimino)methyl)naphthalen-2-ols in equilibrium.
Impregnated type sorbents based on benzo-15-crown-5 for gold(III) extraction from hydrochloric solutions
Аннотация
A series of sorbents based on benzo-15-crown-5, various supports (styrene-divinylbenzene LPS-500, hydrophobized silica gel), and diluents (octan-1-ol, nitrobenzene, 1,1,7-trihydrododecafluoroheptanol (FHA), ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (С4mim+Tf2N-)) and without diluents was obtained. The sorbents without diluents with the benzo-15-crown-5 content 20–30% have the maximum sorption characteristics (recovery of gold higher than 90%). The influence of the diluent and support nature, procedure of support pretreatment, impregnation time and temperature, and the solvent for impregnation on the sorption characteristics was studied. The maximum sorption characteristics were found for the sorbents based on the styrene-divinylbenzene support LPS-500. A high selectivity of the obtained sorbents toward gold was established, and the recovery of gold higher than 95% was achieved by the optimization of the synthesis procedure of the sorbents.
Synthesis of telehelic oligodimethylsiloxanes with 4-carboxypyrrolidone fragments: rheological and thermal properties
Аннотация
Telehelic oligodimethylsiloxanes containing 4-carboxypyrrolidone fragments were synthesized by the reactions of oligodimethylsiloxanes bearing terminal 3-aminopropyl groups with itaconic acid. The thermal and rheological properties of the obtained polymers were studied. The activation energies of viscous flow of the oligomers obtained and the previously synthesized oligodimethylsiloxanes containing terminal fragments of undecenoic or benzoic acid are compared.
Formulation of perspective hepatoprotector polymeric forms based on silybin and ursodeoxycholic acid
Аннотация
Silybin (Slb) and ursodeoxycholic acid (UDCA) are hepatoprotectors used in the pathogenetic therapy of liver and biliary tract. However, low bioavailability of these drugs restricts their application. In order to solve this problem, Slb and UDCA were incorporated into polymer carriers based on polylactic acid and poly(lactic-co-glycolic acid) by nanoprecipitation. The polymeric forms obtained according to the developed and optimized method are nanoparticles with a size from 100 to 200 μm. In vitro experiments showed a 1.5–2-fold higher hepatoprotective activity of Slb- and UDCA-containing polymeric nanoparticles compared to free substances.
New approaches to analogs of α-linked galactosylceramides based on functionalized serinol
Аннотация
New derivatives of serinol, 3-[4-(2-chloroethoxy)benzyloxy]-2-phthalimidopropan-1-ol and 3-[4-(2-azidoethoxy)phenoxy]-2-phthalimidopropan-1-ol, were synthesized and tested as glycosyl acceptors in stereoselective 1,2-cis-galactosylation in the benzyl-free synthesis of analogs of α-linked galactosylceramides. It was found that NIS/AgOTf-promoted glycosylation of 3-[4-(2-chloroethoxy)benzyloxy]-2-phthalimidopropan-1-ol with ethyl 4,6-O-(di-tert-butylsilylene)-1-thio-β-D-galactoside resulted in both the expected α-linked diastereomeric glycosides and the product of iodination of the benzyl group of the aglycon. This process was avoided by using the corresponding galactosyl imidate under Et3SiOTf promotion to give exclusively α-linked diastereometic serinol glycosides.
The effect of ELOVL6 fatty acid elongase inhibition on the expression of genes associated with the metastasis of breast cancer
Аннотация
The paper addresses the effect of a new fatty acid elongase 6 (ELOVL6) inhibitor on the migration of breast cancer cells (estrogen receptor positive MCF7 cells and estrogen receptor negative MDA-MB-231 cells) and expression of genes associated with the epithelial-mesenchymal transition, the first stage of tumor metastasis. It was shown that inhibition of the synthesis of C18 fatty acids does not change the migration activity or expression of transcription factors regulating the epithelial-mesenchymal transition. At the same time, the inhibition of ELOVL6 resulted in overexpression of genes associated with breast cancer development and metastasis in vivo (EGFR, CASP4 and VEGFA).
Brief Communications
Efficient synthesis of 3,4-diarylpyrrole-2-carboxylates, the key fragments of natural antimitotic agents
Аннотация
Barton-Zard reaction of nitrostilbenes with ethyl isocyanoacetate carried out in EtOH in the presence of K2CO3 allowed us to minimize the formation of side products and to obtain 3,4-diarylpyrrole-2-carboxylates in high yields.
Antihypoxic activity of adaptaquin enantiomers
Аннотация
Adaptaquin, 7-{(4-chlorophenyl)[(3-hydroxypyridin-2-yl)amino]methyl}quinolin-8-ol (1), was identified in our earlier study as a hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitor by high-throughput screening of cell lines, which stably express the reporter construct encoding a fusion protein composed of the HIF oxygen degradable domain and firefly luciferase (HIF1 ODD-luc). Adaptaquin is a specific inhibitor of this enzyme and exhibits neuroprotective properties in cell models of oxidative stress and in vivo models of hemorrhagic stroke. The role of the chiral carbon atom in the inhibitor molecule was studied in order to further improve the adaptaquin structure. The separation into two enantiomers was performed. Both enantiomers were shown to equally activate the HIF1 ODD-luc reporter. The adaptaquin structure can be significantly modified and made more sophisticated in order to improve specificity toward this group of enzymes and subsequently toward individual isozymes.