Search

New antioxidants are commonly evaluated via two main approaches, i.e., the ability to donate an electron and the ability to intercept free radicals. We compared these approaches by evaluating the properties of 11 compounds containing both antioxidant moieties (mono- and polyphenols) and auxiliary pharmacophores (pyrrolidone and caprolactam). Several common antioxidants, such as butylated hydroxytoluene (BHT), 2,3,5-trimethylphenol (TMP), quercetin, and dihydroquercetin, were added for comparison. The antioxidant properties of these compounds were determined by their rates of reaction with 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and their oxidation potentials from cyclic voltammetry. Although these methods test different chemical properties, their results correlate reasonably well. However, several exceptions exist where the two methods give opposite predictions! One of them is the different behavior of mono- and polyphenols: polyphenols can react with DPPH more than an order of magnitude faster than monophenols of a similar oxidation potential. The second exception stems from the size of a "bystander" lactam ring at the benzylic position. Although the phenols with a seven-membered lactam ring are harder to oxidize, the sterically nonhindered compounds react with DPPH about 2× faster than the analogous five-membered lactams. The limitations of computational methods, especially those based on a single parameter, are also evaluated and discussed.

International audience; Primary products of single-electron transfer to/from organogermanium compounds (anion radicals and cation radicals issued from reduction and oxidation, respectively) and their chemistry are considered through different approaches to the generation and study of organogermanium ion radicals; the relationship between the data obtained by various methods, including voltammetry, UV-Vis and photoelectron spectroscopy, and the possibilities of modern computational methods in this field are discussed. The chapter provides a systematized overview of literature data on the ion radicals of tetravalent organogermanium compounds, including germanium catenates, low-valent (germylenes, digermenes, phosphagermene) and hypercoordinated germanium derivatives, including germatranes. General aspects of the ion radical chemistry of organogermanium compounds, as well as its premise for the actively developing area of germylene catalysis in organic and organoelement synthesis are considered along with the possible prospects for the development of this field. © 2023 John Wiley and Sons, Inc. All rights reserved.

International audience; For the first time, the possibility of obtaining porous germanium from both single-crystal and polycrystalline starting materials using environmentally friendly (in contrast to the commonly used HF and HCl) imidazolium ionic liquids (IL) was shown. It was demonstrated that pore formation depended significantly on the viscosity of the IL, on the etching current density and etching time, and on defects and imperfections of the substrate surface. By varying these parameters, the rates of two competing processes - formation and growth of pores and electropolishing - could be adjusted, consequently allowing germanium with a various structured surface, including a porous surface. In particular, using a more viscous IL (for example, [BMIM][PF6] versus [BMIM][BF4]) made it possible to reduce the rate of dissolution of the germanium dioxide surface layer; as a result, the formation and growth of pores became a dominant process. At the same time, the dissolution rate of the already formed porous layer (electropolishing) increased with the etching current density and the number of defects and imperfections of the germanium surface.

Electrocatalytic cascade assembly of benzylidenebarbiturates and cyclohexane-1,3-diones in methanol in the presence of sodium bromide as mediator in an undivided cell results in the formation of dihydro-2'H,3H-spiro[1-benzofuran-2,5'-pyrimidines] in 72–85% yields. This electrochemical process occurs under mild conditions, and the isolation procedure after the reaction is simple. The structures of the final compounds were confirmed by 1H–13C HMBC spectroscopy.

The new electrochemical multicomponent assembling has been found: the electrolysis of arylaldehydes, malononitrile, and pyrazolin-5-ones in alcohols in an undivided cell in the presence of sodium bromide as mediator results in the formation of substituted 4-methyl-7-oxo-2-phenyl-5,6-diazaspiro[2.4]hept-4-ene-1,1-dicarbonitriles in 60–80% yields. The optimized reaction conditions and a mechanistic rationale for this electrocatalytic multicomponent assembling are presented.

A continuously growing interest in convenient and ‘green’ reaction techniques encourages organic chemists to elaborate on new synthetic methodologies. Nowadays, organic electrochemistry is a new useful method with important synthetic and ecological advantages. The employment of an electrocatalytic methodology in cascade reactions is very promising because it provides the combination of the synthetic virtues of the cascade strategy with the ecological benefits and convenience of electrocatalytic procedures. In this research, a new type of the electrocatalytic cascade transformation was found: the electrochemical cyclization of 1,3-dimethyl-5-[[3-hydroxy-6-(hydroxymethyl)-4-oxo-4H-pyran-2-yl](aryl)methyl]pyrimidine-2,4,6(1H,3H,5H)-triones was carried out in alcohols in an undivided cell in the presence of sodium halides with the selective formation of spiro[furo[3,2-b]pyran-2,5′-pyrimidines] in 59-95% yields. This new electrocatalytic process is a selective, facile, and efficient way to create spiro[furo[3,2-b]pyran-2,5′-pyrimidines], which are pharmacologically active heterocyclic systems with different biomedical applications. Spiro[furo[3,2-b]pyran-2,5′-pyrimidines] were found to occupy the binding pocket of aldose reductase and inhibit it. The values of the binding energy and Lead Finder’s Virtual Screening scoring function showed that the formation of protein–ligand complexes was favorable. The synthesized compounds are promising for the inhibition of aldose reductase. This makes them interesting for study in the treatment of diabetes or similar diseases.

The article is devoted to considering the use of the decision tree method, defects at a machine-building enterprise, the reasons for having defects in the product and proposals for amending the normative and technical documentation. At the moment, non-destructive diagnostics methods have become widespread, which make it possible to determine the places of fault localization and predict the object state without the need for research which requires making object inoperative or its dismantling. The construction of the diagnostic models is implemented using the methods and tools of regression analysis, the theory of artificial neural networks, etc. However, they do not have a high level of generalization, and neural networks are difficult to interpret, which complicates their application in practice.

A 1: 1 photostable complex between dichlorosilylene and CO2 was detected using matrix-isolation FTIR spectroscopy. The photostability can be attributed to the existence of photochemical equilibria between this complex and products of its isomerization, first of all, a complex of dichlorosilanone with CO, which are strongly shifted to the complex. A detailed computational study of the potential energy surface of the SiCl2 + CO2 system was carried out.

Electrocatalytic transformation of aldehydes with two equivalents of 1,3-diethyl-2-thiobarbituric acid has been carried out in alcohols in an undivided cell in the presence of sodium halides with the selective formation of the substituted 5,5'-(arylmethylene)bis(1,3-diethyl-2-thiobarbituric acids) in 87–98% yields and with 870–980% current efficiency. This new one-pot electrochemically induced tandem Knoevenagel–Michael process is a simple and efficient approach to substituted 5,5'-(arylmethylene)bis(1,3-diethyl-2-thiobarbituric acids) containing two 1,3-diethyl-2-thiobarbituric acid fragments separated by C-aryl-substituted spacer, which are promising compounds for different biomedical applications, including anticonvulsant, antiAIDS agents and anti-inflammatory remedies. Theoretical studies were carried out to investigate the interaction of the synthesized compounds with beef and human catalases.

New N-Boc-alkyl(2-alkynylcyclopropyl)amines were synthesized from 1-alkynyl-1-chlorocyclopropanes and N-Boc- alkylamines under the action of ButOK in DMSO, the intermediates having been the corresponding conjugated alkynylcyclopropenes. The Boc-derivatives can be converted into free secondary 2-alkynylcyclopropylamines, as well as ββ-lithiated with subsequent alkylation.

The concept of using redox-active ligands, which has become extremely widespread in organometallic chemistry, is often considered from ‘their effect on the metal center properties’ point of view and ‘how to modify the ligands’. In this paper, we present the reverse side of this effective approach – a dramatic change of redox properties of ligands under the influence of a redox-inert metal. Germanium derivatives based on 2,3-dihydroxynaphthalene (1) and N,N′-bidentate ligands, namely 2,2′-bipyridine (2) and 1,10-phenanthroline (3), were obtained and characterized by CV, UV-vis spectroscopy, DFT calculations and in the case of 3 X-ray diffraction. It was shown that the HOMO of the complexes is almost completely located on the naphthalene fragment while the LUMO is on the N,N-ligands. At the same time, there are no boundary molecular orbitals on the germanium atom, but it forms the axial part of the molecule holding two opposite motifs together. Moreover, it sharply affects the level of HOMO and LUMO. Derivatives 2 and 3 are more easily oxidized compared to 2,3-dihydroxynaphthalene by 0.31–0.34 V (7–8 kcal mol−1) and are more easily reduced compared to N,N-donors by 1.08–1.15 V (25–26.5 kcal mol−1). All this together makes it possible to form a system with a narrow HOMO/LUMO gap (∼2 eV). The crystal structure of 3 consists of alternating monomolecular easily oxidizing and easily reducing layers formed due to intermolecular interactions, in particular π-stacking. In addition, in contrast to 1 that starts to decompose noticeably at the temperatures from 200 °C, 2 and 3 have an extremely high thermal stability. They remain stable with no signs of decomposition and melting up to 400 °С. We believe that this approach to the formation of the supramolecular structure may present prospects for obtaining new functional materials.

Multicomponent reactions employ three or more reactants to obtain heterocycles containing fragments of all starting materials in a onepot process. All new bonds are formed at once, hence multicomponent reactions are characterized by high bond-forming index. A new multicomponent, one-pot reaction yielding previously unknown 5-(4-hydroxy-2-oxo-2H-chromen-3-yl)-5H-chromeno[2,3-b]pyridines in 52–94% yield has been found. This multicomponent approach allows to construct four new bonds to synthesize some 5H-chromeno[2,3-b]-pyridines under mild conditions. Molecular docking and dynamics studies of the synthesized structures were carried out to identify their interaction with the binding pocket of the neuropeptide Y1 receptor.

New Schiff base germanate derivative containing the chain Ar–C=N→Ge←N=C–Ar was synthesized and characterized by physical methods including X-ray diffraction. The stability of the corresponding radical anion obtained electrochemically was confirmed by cyclic voltammetry, the results were compared with UV-VIS data and quantum chemical calculations.

International audience; Anodic etching of n-type {111} silicon in ionic liquid (IL) systems ([RMIM] [X], R = H, Bu; X = BF4-, PF6-), realized under galvanostatic conditions and at room temperature, allowed the formation of porous silicon surfaces with different pore morphology depending on the etching time, current density, and the IL used. The study of the effect of water content in IL on the etching process has shown a water content of 1% to be optimal. The role of the anion on the etching process was elucidated using 1-methylimidazolium tetrafluoroborate ([HMIM][BF4]) and 1-methylimidazolium hexafluorophosphate ([HMIM] [PF6]) IL systems. [HMIM] [BF4] was found to be most efficient for the formation of a silicon nanostructured array with a pore size of 30-80 nm. The thusprepared porous silicon samples show fluorescence in blue light (475 nm). The NMR spectra of [HMIM] [BF4] ionic liquid before and after etching do not show noticeable changes, which makes it possible to consider this IL as a potentially recyclable etching agent.

International audience; Various forms of germanium and germanium-containing compounds and materials are actively investigated as energy-intensive alternatives to graphite as the anode of lithium-ion batteries. The most accessible form-germanium dioxide-has the structure of a 3D polymer, which accounts for its rapid destruction during cycling, and requires the development of further approaches to the production of nanomaterials and various composites based on it. For the first time, we propose here the strategy of using 2-carboxyethylgermanium sesquioxide ([O GeCH CH CO H] , 2-CEGS), in lieu of GeO , as a promising, energy-intensive, and stable new source system for building lithium-ion anodes. Due to the presence of the organic substituent, the formed polymer has a 1D or a 2D space organization, which facilitates the reversible penetration of lithium into its structure. 2-CEGS is common and commercially available, completely safe and non-toxic, insoluble in organic solvents (which is important for battery use) but soluble in water (which is convenient for manufacturing diverse materials from it). This paper reports the preparation of micro- (flower-shaped agglomerates of ≈1 μm thick plates) and nanoformed (needle-shaped nanoparticles of ≈500×(50-80) nm) 2-CEGS using methods commonly available in laboratories and industry such as vacuum and freeze-drying of aqueous solutions of 2-CEGS. Lithium half-cell anodes based on 2-CEGS show a capacity of ≈400 mAh g for microforms and up to ≈700 mAh g for nanoforms, which is almost two times higher than the maximal theoretical capacity of graphite. These anodes are stable during the cycling at various rates. The results of DFT simulations suggest that Li atoms form the stable Li O with the oxygen atoms of 2-CEGS, and actual charge-discharge cycles involve deoxygenated GeC H molecules. Thus, C chains loosen the anode structure compared to pure Ge, improving its ability to accommodate Li ions.

The new electrochemically induced multicomponent assembling was found: the electrocatalytic transformation of benzaldehydes, N,N′-dimethylbarbituric acid, and kojic acid has been carried out in alcohols in an undivided cell in the presence of sodium halides with the selective formation of the earlier unknown substituted 5-[[3-hydroxy-6-(hydroxymethyl)-4-oxo-4H-pyran-2-yl](phenyl)methyl]-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-triones in 65–88% yields and with 325–440% current efficiency. This new multicomponent process provides facile and efficient way to the novel type of separated by C-aryl-substituted spacer both 4-oxo-4H-pyran and 1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione pharmacology active systems, which are promising compounds for different biomedical applications.

International audience; In this paper, we propose a halogen-free process for the preparation of germanium micro-scale particles with a nano-structured surface morphology from germanium citrate, an easily accessible and environment-friendly precursor formed from germanium dioxide and citric acid in an aqueous medium. Electrodeposition of nanostructured Ge anodes on copper foil was performed via electrolysis of 1-5% germanium citrate solution in propylene glycol with addition of 5% acetic acid. Cyclic voltammetry data suggested that germanium citrate is an electrochemically inactive compound, but readily undergoes reduction by cathodic hydrogen released in the electrolysis. Such behaviour allows one to run the electrolysis under simple galvanostatic conditions without any need for controlling the potential. Furthermore, no diaphragm is required to separate the cathodic and anodic cell compartments. The electrodeposition produces black and compact films composed of similar to 200 nm germanium particles, which, in turn, consist of nanoparticles no larger than 25 nm in size (SEM and TEM data). XRD and Raman spectroscopy data lead to the conclusion that germanium precipitates in the amorphous phase; however, with an increase in the power of the He-Ne laser (632.8 nm) during Raman spectra recording, it transforms into a nanocrystalline form. Testing germanium anodes in lithium-ion half-cells showed a specific capacity of similar to 600 mA h g(-1) at 1-2C current rates, which is comparable to the best results achieved for Ge anodes produced using more sophisticated and less environment-friendly techniques.

The general electrocatalytic cascade approach was found to medicinally relevant spirobarbituric 2,3-dihydro-4H-furo[2,3-c]chromen-4-one scaffold. This new electrocatalytic fast and efficient reaction of benzylidenebarbiturates and 4-hydroxycoumarin in alcohols in the presence of alkali metal halides as mediators in an undivided cell results in the formation of the substituted unsymmetric spirobarbituric 2,3-dihydro-4H-furo[2,3-с]chromen-4-ones in 72–83% yields. This general and efficient approach avoids traditional recrystallization and chromatographic purification stages. According to screening molecular docking data, all synthesized compounds may be prominent for different medical applications, such as control pain, breast cancer therapies, and treatment of obesity, epilepsy, hypertension, cardiovascular disease and diabetes.

Electrocatalytic cyclization of 6-hydroxy-5-[(2-hydroxy-6-oxocyclohex-1-en-1-yl)(aryl)methyl]-1,3-dimethylpyrimidine-2,4-(1H,3H)-diones in alcohols in an undivided cell in the presence of sodium halides results in selective formation of substituted spirobarbituric dihydrofurans in 82–93% yields. Crystal structure of 3-(3-bromophenyl)-1′,3′,6,6-tetramethyl-3,5,6,7-tetrahydro-2′,4-dihydrospiro[benzofuran-2,5′-pyrimidine]-2′,4,4′,6′(1′H,3′H)-tetraone has been confirmed by X-ray diffraction data.

The effect of biodegradable polysaccharides – sodium (NaCMC) and ethanolammonium salts of carboxymethylcellulose, dextran and arabinogalactan on the process of gas hydrate formation was studied in order to search for new "green" inhibitors of low-concentration gas hydrate formation. The ability of polysaccharides to inhibit gas hydrate formation was studied in a quasi-equilibrium thermodynamic experiment. A mixture of hydrocarbon gases with a composition typical of the composition of petroleum gas and containing 78% methane was used as a gas-hydrate-forming model medium. It was found that in concentrations of 0.005, 0.0065 and 0.008%, dextran, NaCMC and arabinogalactan as thermodynamic inhibitors exceed methanol by 170-270 times in inhibitory properties. Dextran is superior to NaCMC and arabinogalactan in terms of inhibition efficiency, reduction of gas hydrate formation rate and induction time. Since with an increase in the concentration of polysaccharides, the pressure drop of gas hydrate formation increases and the rate of formation of gas hydrates decreases according to the mechanism of action, the studied polysaccharides can be attributed to both thermodynamic and kinetic inhibitors. It is established that the molecular weight of water-soluble polysaccharides has a significant effect on their inhibitory properties. A polysaccharide with a molecular weight of 250,000 demonstrated the highest inhibitory activity among the studied samples of NaCMC, which is 400 times more effective than methanol. NaCMC with a mass of 700 thousand did not have any effect on the formation of hydrates. Among the ethanolammonium salts, the monoethanolammonium salt CMC showed the greatest effectiveness in inhibiting the formation of tetrahydrofuran hydrates. An increase in its concentration from 0.02 to 0.1% leads to an increase in the induction time required for the nucleation and subsequent growth of crystals by 10 times. When switching from mono - to di - and triethanolammonium salts of carboxymethylcellulose, the inhibition efficiency decreases. It is shown that sodium and ethanolammonium salts of carboxymethylcellulose, arabinogalactan and dextran are promising for creating new "green" highly effective inhibitors of gas hydrate formation on their basis. The results of laboratory and field tests of the preparative form of the "green" gas hydrate formation inhibitor at the fields of Western Siberia are presented. It was found that at dosages of 500 g/m3 or less, there is no formation of hydrate plugs in the annulus of wells.